Rev. 0.9 10/16 Copyright © 2016 by Silico n Laboratories AN543
Silicon Laboratories Confidential. Information contained herein is covered under non-disclosure agreement (NDA).
AN543
Si475X PROGRAMMING GUIDE
1. Introduction
This document provides an overview of the programming requirements for the Si475x-A10/A20/A30/A40/A55 and
Si475xC-A55 AM/FM receiver. The hardware control interface and software commands are detailed along with
several examples of the required steps to configure the device for various modes of operation. Table 1 provides a
programming guide cross-reference for each Si475x part released by Silicon Labs to date. This programming guide
focuses on the Si475x/5xC-A55 release; however, features, properties, ranges, and defaults that differ from the
Si475x-A10 to Si475x-A40 are noted as well. Refer to previous versions of this document for earlier firmware
revisions.
2. Overview
This devices in this product family are programmed using commands and responses. To perform an action, the
system controller writes a command byte and associated arguments, which cause the device to execute the given
command. The device will, in turn, provide a response depending on the type of command that was sent.
The device has a slave control interface that allows the system controller to send commands to and receive
responses from the device using 2-wire mode (I2C compatible).
3. Terminology
CTS—Clear to send
STC—Seek/Tune Complete
NVM—Non-volatile internal device memory
Device—Refers to the AM/FM Receiver
System Controller —Refers to the system microcontroller
CMD—Command byte
ARGn—Argument byte (n = 1 to 7)
STATUS—Status byte
RESPn—Response byte (n = 1 to 15)
Table 1. Si475x Firmware Revisions
Part # Part Revision FMRX Component AMRX Component
Si475x-A10 1.0 3.2.3 3.2.3
Si475x-A20 2.0 8.0.8 7.0.5
Si475x-A30 3.0 10.0.8 9.0.6
Si475x-A40 4.0 13.0.11 12.0.10
Si475x-A55 5.5 15.0.2 14.0.1
Si475xC-A55 5.5 15.0.2 14.0.1
AN543
2 Rev. 0.9
4. Control Interface
The Si475x provides an I2C-compatible, 2-wire control interface.
In powerdown mode, all circuitry is disabled except for the device control interface. The device comes out of
powerdown mode when the POWER_UP command is written to the command register. Once in powerup mode,
the device accepts additional commands such as tuning. The device will not accept commands while in
powerdown mode, with the exception of the powerup command. If the system controller writes a command other
than POWER_UP when in powerdown mode, the device does not respond, and the command is ignored.
Setting the RSTB pin low places the device in reset mode. In reset mode, all circuitry is disabled including the
device control interface; registers are set to their default settings, and the control bus is disabled.
4.1. 2-Wire Control Interface
Figure 1 and Figure 2 show the 2-wire control interface read and write timing parameters and diagrams,
respectively. Refer to the Si475x data sheet for timing parameter values.
Figure 1. I2C Control Interface Read and Write Timing Parameters
Figure 2. I2C Control Interface Read and Write Timing Diagram
SCL 70%
30%
SDA 70%
30%
START STARTSTOP
tf:IN
tr:IN
tLOW tHIGH
tHD:STA
tSU:STA tSU:STO
tSP tBUF
tSU:DAT
tr:IN tHD:DAT tf:IN,
tf:OUT
tPD:DAT
SCL
SDA
(Write)
START STOPADDRESS + R/W ACK DATA ACK DATA ACK
A6-A0, 0 Command
7-0 Arg1
7-0
SDA
(Read)
START STOPADDRESS + R/W ACK DATA ACK DATA ACK
A6-A0, 1 Status
7-0 Response
7-0
AN543
Rev. 0.9 3
Two-wire bus mode uses the SCL and SDA pins for signaling. A transaction begins with the START condition,
which occurs when SDA falls while SCL is high. Next, the system controller drives an 8-bit control word serially on
SDA, which is captured by the device on rising edges of SCL. The control word consists of a seven-bit device
address followed by a read/write bit (read = 1, write = 0). The device acknowledges the control word by driving
SDA low on the next falling edge of SCL.
For write operations, the system controller next sends a data byte on SDA, which is captured by the device on
rising edges of SCL. The device acknowledges each data byte by driving SDA low for one cycle on the next falling
edge of SCL. For each write transaction, the first byte is a command and the following bytes are arguments.
For read operations, after the device has acknowledged the control byte, it will drive an eight-bit data byte on SDA,
changing the state of SDA on the falling edges of SCL. The system controller acknowledges each data byte by
driving SDA low for one cycle on the next falling edge of SCL. If a data byte is not acknowledged by the system
controller, the transaction will end. For each read transaction, the first byte is the status byte and the following bytes
are the response data from the receiver.
A 2-wire transaction ends with the STOP condition, which occurs when SDA rises while SCL is high.
5. Powerup and Powerdown
There are two procedures for powering up a receiver to move it from powerdown mode to the powerup mode. The
first is a powerup from internal receiver memory. The second is a powerup from a firmware component patch that is
stored in system controller memory. Patches can be applied to a firmware component by the system controller via
a download mechanism to address field issues, errata, or adjust device behavior. Patches are encrypted and
unique to a particular device firmware version, cannot be generated by customers, and can be used to replace a
portion of the component (to address errata, for example) or to download an entirely new component. The user
must verify that the device contains the correct base firmware to support the patch as described later in this
section.
It has been noted that some crystals require greater startup current and settling times than others. The procedure
below is meant to apply to a wide variety of such crystals, providing maximum current and 40 ms for crystal
oscillation to stabilize. If there are still difficulties with POWER-UP that may be related to your choice of crystal,
please refer to the settings and hardware options in “AN750: Si475x 4 MHz Crystal Compatibility Power-Up
Procedure”.
AN543
4 Rev. 0.9
5.1. Powerup Receiver from Internal Memory
1. Supply VA, VD, and VIO while keeping the RSTB = 0. Power supplies may be sequenced in any order.
2. After a minimum of 100 µs, set RSTB = 1.
3. After a minimum of 100 µs, continue to the next step.
4. Send the POWER_UP command for the desired function (AM, FM).
Supply VA, VD, and VIO while
keeping the RSTB = 0
START
After a minimum of 100 µs,
set RSTB = 1
After a minimum of 100 µs,
continue to the next step
Send second POWER_UP
command for the desired
function (AM, FM)
Commence normal operation
Send POWER_DOWN
command
Send the POWER_UP
command for desired function
(AM, FM)
Wait at least 100 ms
Send command
to force CTS = 1
AN543
Rev. 0.9 5
Example (with crystal 4 MHz, FM function):
1. Provide the initial POWER_UP Command:
2. Apply a wait time of at least 100 ms.
3. Apply the following command:
4. Apply the following command:
Note: For more details on the external circuit for the 4 MHz crystal, see “AN750: Si475x 4 MHz Crystal Circuit and Power-Up
Procedure”.
5. The device is ready to commence normal operation and accept additional commands. Refer to Figure 3.
Action Data Description
CMD 0x01 POWER_UP
ARG1 0X77 NORMAL OPERATION, 4 MHz Crystal
ARG2 0x1F SETS CRYSTAL LOAD CAPACITANCE
Note: Change this value to the capacitance that matches the crystal in use.
ARG3 0x27 SETS CRYSTAL BIAS = 7 w/ FASTBOOT
ARG4 0x00
0x10
0x20
BOOT LOADER
FM Receive, 4 MHz Crystal
AM Receive, 4 MHz Crystal
ARG5 0x00 DIGITAL CORE DISABLED/CRYSTAL OSCILLATOR DISABLED
STATUS NO CTS bit returned
Action Data Description
CMD 0xFB CONTROL REGISTER WRITE COMMAND
ARG1 0X06 CONTROL REGISTER ADDRESS
ARG2 0x80 FORCES CTS = 1
STATUS NO CTS bit returned
Action Data Description
CMD 0x01 POWER_UP
ARG1 0X77 NORMAL OPERATION, 4 MHz Crystal
ARG2 0x1F SETS CRYSTAL LOAD CAPACITANCE
Note: Change this value to the capacitance that matches the crystal in use.
ARG3 0x23 SETS CRYSTAL BIAS = 3 w/ FASTBOOT
ARG4 0x00
0x10
0x20
BOOT LOADER
FM Receive, 4 MHz Crystal
AM Receive, 4 MHz Crystal
ARG5 0x11 DIGITAL CORE ENABLED/CRYSTAL OSCILLATOR ENABLED
STATUS CTS = 1
AN543
6 Rev. 0.9
Figure 3. Powerup Timing
6. If desired, send the POWER_DOWN command.
Example:
7. It is now possible to move to the powerup state by returning to step 4.
POWER_DOWN Command
Action Data Description
CMD 0x11 POWER_DOWN
ARG1 0x00 Disable oscillator (ARG1 may be omitted with the same result)
STATUS →0x80 CTS = 1
VIO
VD
VA
RSTB
SCL
SDA POWER_UP Command
100 µs min
100 µs min
> 10 µs
AN543
Rev. 0.9 7
5.2. Powerup Receiver from a Patch
1. Supply VA, VD, and VI0 while keeping the RSTB = 0. Power supplies may be sequenced in any order.
2. After a minimum of 100 µs, set RSTB = 1.
3. After a minimum of 100 µs, proceed to the next step.
4. (Optional – step 1 of 3 to verify part firmware revision and ROM revision.) Both part firmware revision and ROM
revision must be compatible with a partial patch and ROM revision must be compatible with a full patch. Send
the POWER_UP command for the desired function (AM, FM).
Supply VA, VD, and VIO
while keeping the RSTB = 0
START
After a minimum of 100 µs,
set RSTB = 1
After a minimum of 100 µs,
continue to the next step
Send the POWER_UP
command for the desired
function (AM, FM)
Send POWER_DOWN
command
A
B
Verify Firmware and ROM
revision? A
B
Send PART_INFO command
Wait at least 100 ms
Send second POWER_UP
command for the desired
function (AM, FM)
C
Send the POWER_UP
command with boot loader
function
Send patch data.
Send the POWER_UP
command for the desired
function (AM, FM)
Commence normal operation.
Send POWER_DOWN
command.
Wait at least 100 ms
Send second POWER_UP
command with bootloader
function
B
C
Send com m and to force
CTS = 1 Send command to force
CTS = 1
AN543
8 Rev. 0.9
Example (with crystal 4 MHz, FM function):
1. Provide the initial POWER_UP Command:
2. Apply a wait time of at least 100 ms.
3. Apply the following command:
4. Apply the following command:
Note: For more details on the external circuit for the 4 MHz crystal, see “AN750: Si475x 4 MHz Crystal Circuit and Power-Up
Procedure”.
5. (Optional – step 2 of 3 to verify part firmware revision and ROM revision). Verify part firmware revision and
ROM revision. Send the PART_INFO command.
Action Data Description
CMD 0x01 POWER_UP
ARG1 0X77 NORMAL OPERATION, 4 MHz Crystal
ARG2 0x1F SETS CRYSTAL LOAD CAPACITANCE
Note: Change this value to the capacitance that matches the crystal in use.
ARG3 0x27 SETS CRYSTAL BIAS = 7 w/ FASTBOOT
ARG4 0x00
0x10
0x20
BOOT LOADER
FM Receive, 4 MHz Crystal
AM Receive, 4 MHz Crystal
ARG5 0x00 DIGITAL CORE DISABLED/CRYSTAL OSCILLATOR DISABLED
STATUS NO CTS bit returned
Action Data Description
CMD 0xFB CONTROL REGISTER WRITE COMMAND
ARG1 0X06 CONTROL REGISTER ADDRESS
ARG2 0x80 FORCES CTS = 1
STATUS NO CTS bit returned
Action Data Description
CMD 0x01 POWER_UP
ARG1 0X77 NORMAL OPERATION, 4 MHz Crystal
ARG2 0x1F SETS CRYSTAL LOAD CAPACITANCE
Note: Change this value to the capacitance that matches the crystal in use.
ARG3 0x23 SETS CRYSTAL BIAS = 3 w/ FASTBOOT
ARG4 0x00
0x10
0x20
BOOT LOADER
FM Receive, 4 MHz Crystal
AM Receive, 4 MHz Crystal
ARG5 0x11 DIGITAL CORE ENABLED/CRYSTAL OSCILLATOR ENABLED
STATUS CTS = 1
AN543
Rev. 0.9 9
Example:
In this example, the part revision is 2.0.0 and the ROM ID is 4. Ensure that partial patches received from Silicon
Labs are intended for use with the part firmware revision and ROM, and that full patches are intended for use with
the ROM ID as shown in Table 2. It is possible to verify the FM and AM component firmware revisions with the
FUNC_INFO command, however, this is not necessary because there is always a unique mapping of component
revision to part revision.
6. (Optional—step 3 of 3 to verify part firmware revision and ROM revision.) Send the POWER_DOWN
command. This step is required before proceeding with the patching procedure if steps 4 and 5 have been
followed.
Example
7. Send the POWER_UP command for boot loader function.
PART_INFO Command
Action Data Description
CMD 0x02 PART_INFO
STATUS →0x80 CTS = 1
RESP1 →0x06 Chip revision, 6
RESP2 →0x35 Part number (last two digits) 0x35 = 53, or Si4753
RESP3 →0x32 Firmware major revision = ASCII character “2”
RESP4 →0x30 Firmware minor revision = ASCII character “0”
RESP5 →0x00 Firmware build version = 0
RESP6 →0x00 Reserved, values will vary
RESP7 →0x00 Reserved, values will vary
RESP8 →0x04 ROM ID
Table 2. Si475x Firmware and ROM Compatibility
Part # Part Revision ROM ID FM Revision AM Revision
Si475x-A10 1.0 2 3.2.3 3.2.3
Si475x-A20 2.0 4 8.0.8 7.0.5
Si475x-A30 3.0 5 10.0.8 9.0.6
POWER_DOWN Command
Action Data Description
CMD 0x11 POWER_DOWN
ARG1 0x00 Disable oscillator (ARG1 may be omitted with the same result)
STATUS →0x80 CTS = 1
AN543
10 Rev. 0.9
Example (with crystal 4 MHz, boot loader function):
1. Provide the initial POWER_UP Command:
2. Apply a wait time of at least 100 ms.
3. Apply the following command:
4. Apply the following command:
5. Send the patch data.
The patch file provided by Silicon Labs typically has a .sg extension. The system controller must send each line of
8 bytes, wait for a CTS, then send the next line of 8 bytes, etc., until the entire patch has been sent. An example
showing the first few lines and final line of a patch file is shown below. Note that the “#” character indicates a
comment and the patch file indicates the required ROM ID for a partial or full download. If the checksum fails, the
part issues an error code, ERR (bit 6 of the STATUS byte received after each 8-byte transfer), and halts. The part
must be reset to recover from this error condition.
Action Data Description
CMD 0x01 POWER_UP
ARG1 0X77 NORMAL OPERATION, 4 MHz Crystal
ARG2 0x1F SETS CRYSTAL LOAD CAPACITANCE
Note: Change this value to the capacitance that matches the crystal in use.
ARG3 0x27 SETS CRYSTAL BIAS = 7 w/ FASTBOOT
ARG4 0x00
0x10
0x20
BOOT LOADER
FM Receive, 4 MHz Crystal
AM Receive, 4 MHz Crystal
ARG5 0x00 DIGITAL CORE DISABLED/CRYSTAL OSCILLATOR DISABLED
STATUS NO CTS bit returned
Action Data Description
CMD 0xFB CONTROL REGISTER WRITE COMMAND
ARG1 0X06 CONTROL REGISTER ADDRESS
ARG2 0x80 FORCES CTS = 1
STATUS NO CTS bit returned
Action Data Description
CMD 0x01 POWER_UP
ARG1 0X77 NORMAL OPERATION, 4 MHz Crystal
ARG2 0x1F SETS CRYSTAL LOAD CAPACITANCE
Note: Change this value to the capacitance that matches the crystal in use.
ARG3 0x23 SETS CRYSTAL BIAS = 3 w/ FASTBOOT
ARG4 0x00
0x10
0x20
BOOT LOADER
FM Receive, 4 MHz Crystal
AM Receive, 4 MHz Crystal
ARG5 0x11 DIGITAL CORE ENABLED/CRYSTAL OSCILLATOR ENABLED
STATUS CTS = 1
AN543
Rev. 0.9 11
The following is an example of a patch file:
# COPYRIGHT=2011 Silicon Laboratories, Inc.
# GENERATED=13:53 May 23 2011
# ROMID=0x04
# PATCHID=0x228C
# REQUIRES=NONE
# SIZE=8272
# FUNCTION=FMRX
# MAJOR=8
# MINOR=0
# BUILD=8
# CRCT=0x81CF
# CRCM=0x0A6C
# CRCP=0xEC8D
# CRCX=0x66EE
# CRCY=0x6381
# CRCZ=0xA805
0x04,0x11,0x81,0xCF,0x00,0x00,0x0D,0xC6
0x05,0xAE,0xE1,0xBD,0xB4,0x90,0x07,0x33
0x06,0xD9,0x3D,0x11,0xF7,0x25,0xCB,0x06
0x17,0x7A,0xF8,0xD0,0x71,0x10,0x3F,0xB7
0x1F,0xBF,0xFF,0x7E,0x42,0xE7,0x53,0x05
…
[Additional Lines]
…
0x08,0x21,0xAB,0xB5,0xF1,0x7A,0xD6,0x5A
0x08,0x10,0x0E,0x9E,0x3B,0xD1,0x01,0xF4
0x08,0xBF,0x8D,0x94,0xB0,0x2D,0xCF,0xFF
0x05,0x8D,0xB1,0x22,0xF2,0x8D,0x22,0x8C
# END
AN543
12 Rev. 0.9
Example:
6. Send the POWER_UP command for the desired function (AM, FM).
Example (with crystal 4 MHz, FM function):
Example (with external clock 4 MHz, FM function):
First line of the patch file example
Action Data Description
CMD 0x04
ARG1 0x11
ARG2 0x81
ARG3 0xCF
ARG4 0x00
ARG5 0x00
ARG6 0x0D
ARG7 0xC6
STATUS →0x80 CTS = 1
Second line of the patch file example
CMD 0x05
ARG1 0xAE
ARG2 0xE1
ARG3 0xBD
ARG4 0xB4
ARG5 0x90
ARG6 0x07
ARG7 0x33
STATUS →0x80 CTS = 1
POWER_UP Command
Action Data Description
CMD 0x01 POWER_UP
ARG1 0x77 Normal operation
ARG2 0x27 Crystal load capacitance = 15.803 pF each pin
ARG3 0x23 Disables CTS interrupt, crystal bias = 3, enable fastboot
ARG4 0x10 FM function, crystal frequency 4 MHz
ARG5 0x11 Crystal
STATUS →0x80 CTS = 1
AN543
Rev. 0.9 13
7. The device is ready to commence normal operation and accept additional commands.
8. If desired, send the POWER_DOWN command.
Example:
9. It is now possible to move to the powerup state by returning to step 7.
POWER_UP Command
Action Data Description
CMD 0x01 POWER_UP
ARG1 0x77 Normal operation
ARG2 0x00 Crystal load capacitance = 5 pF each pin
ARG3 0x23 Disables CTS interrupt, crystal bias = 3, enable fastboot
ARG4 0x10 FM function, clock frequency 4 MHz
ARG5 0x12 External clock
STATUS →0x80 CTS = 1
POWER_DOWN Command
Action Data Description
CMD 0x11 POWER_DOWN
ARG1 0x00 Disable oscillator (ARG1 may be omitted with the same result)
STATUS →0x80 CTS = 1
AN543
14 Rev. 0.9
6. Timing
6.1. Command and Property Timing
When the user reads a response over the I2C bus, the first 8 bits returned are the STATUS register. Bit 7 of the
STATUS register is the CTS bit (Clear to Send). When CTS is 1, it indicates that the chip is ready to receive a new
command. Seek and Tune commands may take longer to complete than most other commands, so they also use
the STC bit (Seek/Tune Complete) to indicate they have completed. STC is bit 0 of the STATUS register.
When the user sends any command, the CTS bit will immediately reset to 0. CTS will remain 0 while the chip
processes the command. When the chip is finished processing the command, the CTS bit will be set back to 1.
Before sending another command, the user may poll CTS by reading the first byte of response until CTS = 1. If the
user has enabled the optional CTS interrupt, then the INTB pin will pulse low immediately after CTS has been set
to 1, to notify the user that the previous command has completed. For information on how to enable the CTS
interrupt, see the INT_CTL_ENABLE property and CTSIEN bit in the arguments for the POWER_UP command.
The commands for seek and tune (FM_TUNE_FREQ, FM_SEEK_START, etc.) will cause CTS to reset to 0 for a
short time, but they will set CTS back to 1 after the seek or tune has started. The seek or tune is progressing even
though CTS has been set back to 1. Although the user is free to send another command at this time, it is highly
recommended to wait until the STC (Seek/Tune Complete) bit has been set to 1 before sending another command.
The only exception is the AM/FM_RSQ_STATUS command, which may be sent at any time because it can be used
to cancel the seek/tune in progress and check the status of which station seek is currently on.
When the seek/tune completes, the STC bit will be set to 1. The user may poll STC by reading the first byte of
response until STC = 1. If the user has enabled the optional STC interrupt, then the INTB pin will pulse low
immediately after STC has been set to 1, to notify the user that the seek or tune has completed. For information on
how to enable the STC interrupt, see the INT_CTL_ENABLE property.
After the seek or tune has completed, the user may acknowledge the completion by sending the AM/
FM_RSQ_STATUS command with the STCACK bit set to 1. This will reset the STC bit back to 0. After this, the
user may send another seek or tune command. Alternatively a new seek or tune command will also clear the STC
bit when it begins.
Figure 4 shows a seek or tune command with the optional CTS and STC interrupts enabled. The timing parameters
are shown in Table 3.
Figure 4. CTS and STC Timing Model
Command
FM_TUNE_FREQ
Control
Bus
tSTC
tINT
CTS
Bit
STC
Bit
Command
FM_RSQ_STATUS
INTB
tCTS
AN543
Rev. 0.9 15
Table 3. Command Timing Parameters for Common Commands
Command tCTS tSTC tINT
POWER_UP 100ms — 3µs
POWER_DOWN <1000 µs — 3 µs
FUNC_INFO <200 µs — 3 µs
SET_PROPERTY <200 µs — 3 µs
GET_PROPERTY <200 µs — 3 µs
GET_INT_STATUS <200 µs — 3 µs
AGC_STATUS <200 µs — 3 µs
ANA_AUDIO_PIN_CFG <200 µs — 3 µs
Table 4. Command Timing Parameters for FM Receiver
Command tCTS tSTC tINT
FM_TUNE_FREQ <200 µs 21 ms 3 µs
FM_TUNE_FREQ (fast tune) <200 µs 5 ms 3 µs
FM_SEEK_START <200 µs See Note below. 3 µs
FM_RSQ_STATUS <200 µs — 3 µs
FM_ACF_STATUS <200 µs — 3 µs
FM_RDS_STATUS <200 µs — 3 µs
FM_RDS_BLOCKCOUNT <200 µs — 3 µs
*Note: tSTC is seek time per channel. Total seek time depends on bandwidth, channel spacing, and
number of channels to next valid channel.
Worst case seek time complete for FM_SEEK_START is:
For Si475x-A30, the seek time will require an additional tSTC + tSTC(FAST) for channel
spacings other than 200 kHz.
Table 5. Command Timing Parameters for AM Receiver
Command tCTS tSTC tINT
AM_TUNE_FREQ 100 µs 40 ms 3 µs
AM_SEEK_START 100 µs See Note below. 3 µs
AM_RSQ_STATUS 100 µs — 3 µs
AM_ACF_STATUS 100 µs — 3 µs
*Note: tSTC is seek time per channel. Total seek time depends on bandwidth, channel spacing, and
number of channels to next valid channel.
FM_SEEK_BAND_TOP FM_SEEK_BAND_BOTTOM–
FM_SEEK_FREQ_SPACING
--------------------------------------------------------------------------------------------------------------------------------------------------
1+
tSTC
AN543
16 Rev. 0.9
6.2. Alternate Frequency (AF) Timing
The Si4754/55/56/57 features a flexible FM tune command that allows for a number of operational choices. While
tuned to the current station, the receiver can quickly tune to candidate FM stations and perform one of three
operations.
1. Tune to the FM station and stay tuned.
2. Tune to the FM station; check the selected signal metrics, and jump back to the original station (AF check).
3. Tune to the FM station; check the selected signal metrics, and decide if the receiver is kept tuned to the FM
station (AF Jump) or re-tuned to the original station.
The timing diagrams for AF tune and AF check are shown in Figure 5 and Figure 6, respectively.
Figure 5. AF Tune Diagram
AF Tune
command
issued
AF Tune
Initiated
F1F1 F2
AF station metrics qualified:
Above thresholds
Tuner stays on AF station
Audio Audio
F2
}
F2
T2T3
T1T1
T1 ~ 0.5 ms
T2 ~ 1 ms
T3 ~ 4.8 ms
AN543
Rev. 0.9 17
Figure 6. AF Check Timing Diagram
AF Check
command
issued
AF Check
Initiated
F1F1 F2F2 F1F1
AF Station metrics
measured and qualified.
Tuner jumps back to F1
Audio Audio
F2
}
}
T2T4T2
T1T1
T1 ~ 0.5 ms
T2 ~ 1 ms
T4 ~ 7 ms
AN543
Rev. 0.9 19
7. Commands and Properties
7.1. Common Commands and Properties
The following properties and commands are common to all receiver modes.
Table 6. Common Receiver Command Summary
Number Name Summary
0x01 POWER_UP Power-up device and mode selection. Modes include operational
function (AM, FM) and audio interface configuration.
0x02 PART_INFO Returns the part information of the device.
0x11 POWER_DOWN Power-down the device.
0x12 FUNC_INFO Returns the firmware revision and patch revision.
0x13 SET_PROPERTY Sets the value of a property.
0x14 GET_PROPERTY Retrieve a property's value.
0x15 GET_INT_STATUS Read interrupt status bits.
0x17 AGC_STATUS Reports the status of the AGC.
0x1B ANA_AUDIO_PIN_CFG Configures the analog audio pins.
0x1C INTB_PIN_CFG Configures behavior of INTB and A1 pins.
Table 7. Common Receiver Property Summary
Number Name Default Summary
A10 A20 A30 A40 A55
0x0000 INT_CTL_ENABLE 0x0000 0x0000 0x0000 0x0000 0x0000 Interrupt enable prop-
erty.
0 0 000
0x0300 AUDIO_ANALOG_VOLUME 0x003F 0x003F 0x003F 0x003F 0x003F Sets the analog audio
volume.
63 63 63 63 63
0x0301 AUDIO_MUTE 0x0000 0x0000 0x0000 0x0000 0x0000 Audio mute property.
0 0 000
AN543
20 Rev. 0.9
Table 8. Status Response for the FM Receiver
Bit 76543210
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
Bit Name Function
7CTS
Clear to Send.
0 = Wait before sending next command.
1 = Clear to send next command.
6ERR
Error.
0=No error.
1=Error.
5:4 Reserved Values may vary.
3RSQINT
Received Signal Quality Interrupt.
0 = Received Signal Quality measurement has not been triggered.
1 = Received Signal Quality measurement has been triggered.
2RDSINT
Radio Data System Interrupt.
0 = Radio data system interrupt has not been triggered.
1 = Radio data system interrupt has been triggered.
1ACFINT
Automatically Controlled Features Interrupt.
0 = ACF measurement has not been triggered.
1 = ACF measurement has been triggered.
0STCINT
Seek/Tune Complete Interrupt.
0 = Tune complete has not been triggered.
1 = Tune complete has been triggered.
AN543
Rev. 0.9 21
Table 9. Status Response for the AM Receiver
Bit 76543210
STATUS CTS ERR XX RSQINT X ACFINT STCINT
Bit Name Function
7CTS
Clear to Send.
0 = Wait before sending next command.
1 = Clear to send next command.
6ERR
Error
0=No error.
1=Error.
5:4 Reserved Values may vary.
3RSQINT
Received Signal Quality Interrupt
0 = Received Signal Quality measurement has not been triggered.
1 = Received Signal Quality measurement has been triggered.
2 Reserved Value may vary.
1ACFINT
Automatically Controlled Features Interrupt.
0 = ACF measurement has not been triggered.
1 = ACF measurement has been triggered.
0STCINT
Seek/Tune Complete Interrupt.
0 = Tune complete has not been triggered. Do not send a new TUNE/SEEK
command.
1 = Tune complete has been triggered. It is safe to send a new TUNE/
SEEK command.
AN543
22 Rev. 0.9
If the ERR bit in the STATUS response is set for a command or property, the response is redefined as follows:
Table 10. Response When ERR Bit is Set
Bit 7 6 5 4 3 2 1 0
STATUS CTS 1 XX RSQINT RDSINT ACFINT STCINT
RESP1 ERROR
RESP Bit Name Function
17:0ERROR
Error definitions.
0x10 = Bad command.
0x11 = Bad ARG1.
0x12 = Bad ARG2.
0x13 = Bad ARG3.
0x14 = Bad ARG4.
0x18 = Command busy.
0x20 = Bad internal memory.
0x30 = Bad patch.
0x31 = Bad boot mode.
0x40 = Bad property.
AN543
Rev. 0.9 23
7.1.1. Common Receiver Commands
Command 0x01 POWER_U P
The POWER_UP command initiates the boot process to move the device from powerdown to powerup mode. The
boot can occur from internal device memory or a system controller downloaded patch. This command powers up
the device with the specified function (FM Receive and AM Receive). Power-up is complete when the CTS bit is
set. This is the only command that may be sent while the device is powered down. Due to variation of the 4 MHz
crystal from vendor to vendor, two power up commands are required for reliably powering up: a 4 MHz crystal pre-
boot POWER_UP command, and a POWER_UP command to boot the part with the desired function (AM, FM).
Command
Bit 7 6 5 4 3 2 1 0
CMD 0x01
ARG1 XSTART[7:0]
ARG2 00 XCLOAD[5:0]
ARG3 CTSIEN INTSEL FASTBOOT 00 XIBIAS[2:0]
ARG4 FUNC[3:0] 0000
ARG5 CTEN[4:0] XMODE[2:0]
ARG Bit Name Function
1 7:0 XSTART[7:0]
Oscillator startup
01110101 = 4 MHz crystal pre-boot (first command in 4 MHz crystal
sequence)
01110111 = boot (normal operation with external clock, or the second
command in a 4 MHz crystal sequence)
2 7:6 Reserved Always write 00.
2 5:0 XCLOAD[5:0]
Selects the amount of additional on-chip capacitance to be connected
between XTAL1 and gnd and between XTAL2 and gnd. One half of the
capacitance value shown here is the additional load capacitance pre-
sented to the xtal. The minimum step size is 0.25 pF. The required value
will be layout-dependent. Range is 0–0x3F (i.e. 5–20.75 pF) The EVB
sets XCLOAD = 0x27.
3 7 CTSIEN
CTS interrupt enable
0 = Disable.
1 = Enable.
3 6 INTSEL
CTS interrupt pin select
0=A1 pin.
1=INTB pin.
3 5 FASTBOOT Speeds boot time when set. It is required to set this bit with Si475x-A20
and later only.
3 4:3 Reserved Always write 00.
3 2:0 XBIAS[2:0]
Crystal bias current
3 = 4 MHz crystal or external clock
7 = 4 MHz crystal for boot-up
AN543
24 Rev. 0.9
4 7:4 FUNC[3:0]
Selects the boot function of the device.
0 = Boot Loader.
1=FM Receive.
2=AM Receive.
Note: Values other than those listed may result in unpredictable behavior.
4 3:0 Reserved Always write 0000.
5 7:3 CNTEN[4:0]
Enable counter
00000 = 4 MHz crystal pre-boot (first command in 4 MHz crystal
sequence)
00010 = boot (normal operation with external clock, or the second com-
mand in a 4 MHz crystal sequence)
5 2:0 XMODE[2:0]
Crystal mode
1 = Crystal
2 = External clock
ARG Bit Name Function
AN543
Rev. 0.9 25
Command 0x02 PART_IN FO
The PART_INFO command returns the chip revision, part firmware major, minor, and build revision, and ROM ID.
The command is complete when the CTS bit (and optional interrupt) is set. The command may only be sent in
powerup mode.
Command
Response
Bit76543210
CMD 0x02
Bit 7 6 5 4 3 2 1 0
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
RESP1 CHIPREV[7:0]
RESP2 PART[7:0]
RESP3 PMAJOR[7:0]
RESP4 PMINOR[7:0]
RESP5 PBUILD[7:0]
RESP6 Reserved
RESP7 Reserved
RESP8 ROMID[7:0]
RESP Bit Name Function
17:0 CHIPPREV Chip Revision
27:0 PART Part Number, last two digits of part number
37:0 PMAJOR Part Major Revision (ASCII Character Value)
47:0 PMINOR Part Minor Revision (ASCII Character Value)
57:0 PBUILD Part Build Version
67:0 Reserved Values may vary.
77:0 Reserved Values may vary.
87:0 ROMID ROM ID
AN543
26 Rev. 0.9
Command 0x11 POWER_DOWN
The POWER_DOWN command moves the device from powerup to powerdown mode. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This command may only be sent when in powerup
mode. Note that only the POWER_UP command is accepted in powerdown mode. If the system controller writes a
command other than POWER_UP when in powerdown mode, the device will not respond. The device will only
respond when a POWER_UP command is written. It is possible to power down a device and leave the oscillator
running.
Command
Response
Bit76543210
CMD 0x11
ARG1 0000000 XOSC
ARG Bit Name Function
1 7:1 Reserved Always write 0000000.
10XOSC
0 = Full powerdown.
1 = Powerdown and leave oscillator running.
Bit76543210
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
Note: The above response shows status bits for FM Receive mode (see Table 8). See Table 9 for status bits for AM Receive
mode.
AN543
Rev. 0.9 27
Command 0x12 FUN C_ INFO
The FUNC_INFO command returns the firmware revision and patch revision for currently-loaded functional mode
firmware (AM and FM). The command is complete when the CTS bit (and optional interrupt) is set. This command
may only be sent in powerup mode.
Command
Response
Bit76543210
CMD 0x12
Bit 76543210
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
RESP1 FWMAJOR[7:0]
RESP2 FWMINOR1[7:0]
RESP3 FWMINOR2[7:0]
RESP4 PATCHH[7:0]
RESP5 PATCHL[7:0]
RESP6 FUNC[7:0]
Note: The above response shows status bits for FM Receive mode (see Table 8 on page 20). See Table 9 on page 21 for
status bits for AM Receive mode.
RESP Bit Name Function
1 7:0 FWMAJOR[7:0] Firmware Major Revision.
2 7:0 FWMINOR1[7:0] Firmware Minor1 Revision.
3 7:0 FWMINOR2[7:0] Firmware Minor2 Revision.
4 7:0 PATCHH[7:0] Patch ID High Byte (HEX).
5 7:0 PATCHL[7:0] Patch ID Low Byte (HEX).
6 7:0 FUNC[7:0]
Returns the current functional mode:
1 = FM Receive
2=AM Receive
AN543
28 Rev. 0.9
Command 0x13 SET_PROPERTY
The SET_PROPERTY command sets the value of a property. The CTS bit (and optional interrupt) is set when it is
safe to send the next command. This command may only be sent in powerup mode.
Command
Response
Bit76543210
CMD 0x13
ARG1 00000000
ARG2 PROPH[7:0]
ARG3 PROPL[7:0]
ARG4 PROPDH[7:0]
ARG5 PROPDL[7:0]
ARG Bit Name Function
1 7:0 Reserved Always write to 0.
27:0
PROPH
[7:0]
Property Address High Byte
This byte, in combination with PROPL, is used to specify the property to modify.
37:0
PROPL
[7:0]
Property Address Low Byte
This byte, in combination with PROPH, is used to specify the property to modify.
47:4
PROPDH
[7:0]
Property Data High Byte
This byte, in combination with PROPDL, is used to set the property value.
57:0
PROPDL
[7:0]
Property Data Low Byte
This byte, in combination with PROPDH, is used to set the property value.
Bit76543210
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
Note: The above response shows status bits for FM Receive mode (see Table 8 on page 20). See Table 9 on page 21 for
status bits for AM Receive mode.
AN543
Rev. 0.9 29
Command 0x14 GET _P ROP ERT Y
The GET_PROPERTY command retrieves a property's value. The CTS bit (and optional interrupt) is set when it is
safe to send the next command. This command may only be sent in powerup mode
Command
Response
Bit76543210
CMD 0x14
ARG1 00000000
ARG2 PROPH[7:0]
ARG3 PROPL[7:0]
ARG Bit Name Function
1 7:0 Reserved Always write 0.
27:0PROP
H[7:0]
Property Address High Byte.
This byte, in combination with PROPL, is used to specify
the property to get.
37:0PROP
L[7:0]
Property Address Low Byte.
This byte, in combination with PROPH, is used to specify
the property to get.
Bit 76543210
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
RESP1 XXXXXXXX
RESP2 PROPDH[7:0]
RESP3 PROPDL[7:0]
Note: The above response shows status bits for FM Receive mode (see Table 8 on page 20). See Table 9 on page 21 for
status bits for AM Receive mode.
RESP Bit Name Function
1 7:0 Reserved Response values may vary.
27:0PROPD
H[7:0] Property Data High Byte.
This byte, in combination with PROPDL, represents
the requested property value.
37:0PROPD
L[7:0] Property Data Low Byte.
This byte, in combination with PROPDH, represents
the requested property value.
AN543
30 Rev. 0.9
Command 0x15 GET_INT_STATUS
The GET_INT_STATUS command updates the bits of the status byte. This command should be called after any
command that sets the STCINT, ACFINT, RDSINT, ASQINT, or RSQINT bits. When polling, this command should
be periodically called to monitor the STATUS byte, and, when using interrupts, this command should be called after
the interrupt is set to update the STATUS byte. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This command may only be set in powerup mode.
Command
Response
Command 0x17 AGC_STATUS
The AGC_STATUS command reports the current status of the AGC for FM mode. AM_AGC_STATUS (command
0x47) is used in AM/LW/SW modes. The command is complete when the CTS bit (and optional interrupt) is set.
This command may only be sent when in powerup mode.
Bit76543210
CMD 0x15
Bit 76543210
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
Note: The above response shows status bits for FM Receive mode (see Table 8 on page 20). See Table 9 on page 21 for
status bits for AM Receive mode.
Bit76543210
CMD 0x17
RESP76543210
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
RESP1 XX MIXHI MIXLO LNAHI LNALO X X
RESP2 FMAGC1
RESP3 FMAGC2
RESP4 PGAGAIN
RESP5 FMLNAG
Note: The above response shows status bits for FM Receive mode (see Table 8 on page 20). See Table 9 on page 21 for
status bits for AM Receive mode.
AN543
Rev. 0.9 31
RESP Bit Name Function
1 7:6 Reserved Values may vary.
15MIXHI
0 = FM Mixer PD high threshold is not tripped.
1 = FM Mixer PD high threshold is tripped.
14MIXLO
0 = FM Mixer PD low threshold is not tripped.
1 = FM Mixer PD low threshold is tripped.
13LNAHI
0 = FM LNA PD high threshold is not tripped.
1 = FM LNA PD high threshold is tripped.
12LNALO
0 = FM LNA PD low threshold is not tripped.
1 = FM LNA PD low threshold is tripped.
1 1:0 Reserved Values may vary.
27:0FMAGC1
The parallel combination of these resistors indicates
the current FMAGC1 attenuator resistance. The total
resistance value at the pin is 800/FMAGC1.
0=10k
—no attenuation
1=800
2=400
4=200
8=100
16 = 50
32 = 25
64 = 12.5
128 = 6.25
37:0FMAGC2
The parallel combination of these resistors indicates
the current FMAGC2 attenuator resistance. The total
resistance value at the pin is 800/FMAGC2.
0=10k
—no attenuation
1=800
2=400
4=200
8=100
16 = 50
32 = 25
64 = 12.5
128 = 6.25
4 7:0 PGAGAIN PGA gain in dB
Range: 8–33
57:0FMLNAG
FM LNA Gain in dB
Range: 2–14
AN543
32 Rev. 0.9
Command 0x1B AN A_AUDIO_PIN_CFG
The ANA_AUDIO_PIN_CFG command configures the analog audio pins. Writing an argument byte to 0 will not
change the state of the pin and is useful when using this command to query the state of the pins. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This command may only be sent in powerup
mode.
Note: Available in Si475x-A20 and later only.
Command
Response
Bit76543210
CMD 0x1B
ARG1 0 LROUT[6:0]
ARG Bit Name Function
1 7 Reserved Always write 0.
1 6:0 LROUT[6:0]
0= Do not modify the behavior of this pin.
1= Disable the output drivers, so the pins are completely inac-
tive and can be left floating.
2= Configure the LOUT/ROUT pins to output audio.
3 = Configure LOUT for MPX and disable ROUT
(Si4755/57 only).
Bit 7 6 5 4 3 2 1 0
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
RESP1 X LROUT[6:0]
Note: The above response shows status bits for FM Receive mode (see Table 8 on page 20). See Table 9 on page 21 for
status bits for AM Receive mode.
RESP Bit Name Function
1 7 Reserved Values may vary.
1 6:0 LROUT[6:0]
1 = The output drivers are disabled, so the pins are com-
pletely inactive and can be left floating.
2 = LOUT/ROUT pins configured to output audio.
3 = LOUT is configured for MPX out (Si4755/57 only) and
ROUT is disabled.
AN543
Rev. 0.9 33
Command 0x1C IN TB _PI N _C FG
The INTB_PIN_CFG command configures INTB and A1 pins. Writing an argument byte to 0 will not change the
state of the pin and is useful when using this command to query the state of the pins. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This command may only be sent in powerup mode.
Command
Response
Bit76543210
CMD 0x1C
ARG1 0 INTB[6:0]
ARG2 0 A1[6:0]
ARG Bit Name Function
1 7 Reserved Always write to 0.
1 6:0 INTB[6:0]
0 = Do not modify the behavior of this pin.
1 = Disable both the output and input drivers so the pin is
completely inactive and can be left floating.
40 = Configure this pin as the interrupt.
2 7 Reserved Always write to 0.
26:0A1[6:0]
0 = Do not modify the behavior of this pin.
1 = Disable both the output and input drivers so the pin is
completely inactive and can be left floating.
40 = Configure this pin as the interrupt.
Bit76543210
Status CTS ERR xx RSQINT RDSINT ACFINT STCINT
RESP1 X INTB[6:0]
RESP 2 X A1[6:0]
Note: The above response shows status bits for FM Receive mode (see Table 8 on page 20). See Table 9 on page 21 for
status bits for AM Receive mode.
RESP Bit Name Function
1 7 Reserved Values may vary.
1 6:0 INTB[6:0] 1 = Disabled.
40 = Configured as the interrupt.
2 7 Reserved Values may vary.
26:0A1[6:0]
1 = Disabled.
40 = Configured as the interrupt.
AN543
34 Rev. 0.9
7.1.2. Common Receiver Properties
Property 0x0000 INT_CTL_ENABLE
The INT_CTL_ENABLE property enables top-level interrupt sources. The CTS bit (and optional interrupt) is set
when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 0x0000
INT_CTL_ENABLE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0000 RSQREP RDSREP ACFREP STCREP CTSIEN ERRIEN 00 RSQIEN RDSIEN ACFIEN STCIEN
0000 0 0 0 0 0 0 00 0 0 0 0
Bit Name Function
15:12 Reserved Always write 0.
11 RSQREP Repeat interrupt pulse when RSQINT is set, even if a previous interrupt was
generated but not acknowledged.
10 RDSREP Repeat interrupt pulse when RDSINT is set, even if a previous interrupt was
generated but not acknowledged.
9 ACFREP Repeat interrupt pulse when ACFINT is set, even if a previous interrupt was
generated but not acknowledged.
8 STCREP Repeat interrupt pulse when STCIEN is set, even if a previous interrupt was
generated but not acknowledged.
7 CTSIEN Interrupt when CTS is set.
6 ERRIEN Interrupt when ERR is set.
5:4 Reserved Always write 0.
3 RSQIEN Interrupt when RSQIEN is set.
2 RDSIEN Interrupt when RDSINT is set.
1 ACFIEN Interrupt when ACFINT is set.
0 STCIEN Interrupt when STCIEN is set.
AN543
Rev. 0.9 35
Property 0x0300 AUDIO_ANALOG_VOLUME
The AUDIO_ANALOG_VOLUME property sets the analog audio volume. A value of 0 will mute the audio; a value
of 1 applies 62 dB of attenuation, and a value of 63 applies no attenuation. Each step accounts for 1 dB of change
in the output. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property
may only be set or read in powerup mode.
Default: 63
Property 0x0301 AUDIO_MUTE
The AUDIO_MUTE property mutes/unmutes each audio output (analog left or analog right).The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read when in
the powerup mode.
Default: 0x0000
AUDIO_ANALOG_VOLUME
1514131211109876543210
0x000 VOL[5:0]
0x000 0x3F
Bit Name Function
15:6 Reserved Always write 0.
5:0 VOL[5:0] Sets the analog audio volume. Default is 63. Range is 0–63.
AUDIO_MUTE
15141312111098765432 1 0
0x0000 RIGHTMUTE LEFTMUTE
0x0000 0 0
Bit Name Function
15:2 Reserved Always write 0.
1 RIGHTMUTE 0 = Right audio is not muted.
1 = Right audio is muted.
0 LEFTMUTE 0 = Left audio is not muted.
1 = Left audio is muted.
AN543
36 Rev. 0.9
7.2. Commands and Properties for FM Receiver
Table 11 . FM Receiver Command Summary
Number Name Summary
0x30 FM_TUNE_FREQ Tunes the FM receiver to a frequency in 10 kHz steps.
0x31 FM_SEEK_START Initiates a seek for a channel that meets the validation criteria for
FM.
0x32 FM_RSQ_STATUS Returns status information about the received signal quality.
0x35 FM_ACF_STATUS Returns status information about automatically-controlled features
for the tuned station.
0x36 FM_RDS_STATUS Returns RDS information for current channel and reads an entry
from the RDS FIFO (Si4751/53/55/57 only).
0x37 FM_RDS_BLOCKCOUNT Returns RDS expected, received, and uncorrectable block statistic
information (Si4751/53/55/57 only).
AN543
Rev. 0.9 37
Table 12. FM Receiver Properties Summary
Address Name Default Summary
A10 A20 A30 A40 A55
0x0302 AUDIO_DE_EMPHASIS 0x0000 0x0000 0x0000 0x0000 0x0000 Sets the FM Receive de-emphasis.
00000
0x0400 FM_SOFT_MUTE_MAX_ATTENUATION 0x0008 0x0008 0x0008 0x0008 0x0008 Sets the maximum soft mute attenuation for
RSSI/SNR softmute engine.
88888
0x0401 FM_SOFT_MUTE_TRIGGER_THRESHOLD 0x0008 0x0008 0x0008 0x0008 0x0002 Sets the trigger threshold for RSSI/SNR
softmute engine.
88882
0x0402 FM_SOFT_MUTE_END_THRESHOLD 0x0000 0x0000 0x0000 0x0000 0x00FA Sets the end threshold for RSSI/SNR soft-
mute engine.
0000–6
0x0403 FM_SOFT_MUTE_RELEASE_TIME 0x01F4 0x01F4 0x01F4 0x01F4 0x01F4 Sets the maximum soft mute release time
in
ms for RSSI/SNR softmute engine.
500 500 500 500 500
0x0404 FM_SOFT_MUTE_ATTACK_TIME 0x0078 0x0078 0x0078 0x0078 0x0078 Sets the maximum soft mute attack time in
ms for RSSI/SNR softmute engine.
120 120 120 120 120
0x0405 FM_SOFT_MUTE_MAX_ATTENUATION_AGC N/A N/A 0x0080 0x0080 0x0080 Sets the maximum soft mute attenuation for
RSSI/SNR+AGC softmute engine.
128 128 128
0x0406 FM_SOFT_MUTE_TRIGGER_THRESHOLD_AGC N/A N/A
0x0008 0x0008 0x0008 Sets the trigger threshold for RSSI/
SNR+AGC softmute engine.
888
0x0407 FM_SOFT_MUTE_END_THRESHOLD_AGC N/A N/A 0x0000 0x0000 0x0000 Sets the end threshold for RSSI/SNR+AGC
softmute engine.
000
0x0408 FM_SOFT_MUTE_RELEASE_TIME_AGC N/A N/A
0x01F4 0x01F4 0x01F4 Sets the maximum soft mute release time in
ms for RSSI/SNR+AGC softmute engine.
500 500 500
0x0409 FM_SOFT_MUTE_ATTACK_TIME_AGC N/A N/A 0x0078 0x0078 0x0078 Sets the maximum soft mute attack time in
ms for RSSI/SNR+AGC softmute engine.
120 120 120
0x040A FM_SOFT_MUTE_USN_LIMITS N/A N/A 0x060E N/A N/A Set the limits for the USN input metric on
the soft mute mitigation engine.
1550
38 Rev. 0.9
AN543
0x040B FM_SOFT_MUTE_USN_ATTENUATION N/A N/A
0x0000
N/A N/A
Set the limits for the attenuation when
driven by USN on the soft mute mitigation
engine.
0
0x040C FM_SOFT_MUTE_USN_ATTACK_TIME N/A N/A
0x0080
N/A N/A USN-based soft mute attack time in ms.
128
0x040D FM_SOFT_MUTE_USN_RELEASE_TIME N/A N/A
0x0100
N/A N/A USN-based soft mute release time in ms.
256
0x040E FM_SOFT_MUTE_ASSI200_DEV_LIMITS N/A N/A
0x335A 0x335A 0x335A Sets the trigger and end thresholds for
ASSI200DEV softmute engine.
13146 13146 13146
0x040F FM_SOFT_MUTE_ASSI200_DEV_ATTENUATION N/A N/A
0x0000 0x0000 0x0000 Sets the maximum soft mute attenuation for
ASSI200DEV softmute engine.
000
0x0410 FM_SOFT_MUTE_ASSI200_DEV_ATTACK_TIME N/A N/A
0x0080 0x0080 0x0080 Sets the maximum soft mute release time
in
ms for ASSI200DEV softmute engine.
128 128 128
0x0411 FM_SOFT_MUTE_ASSI200_DEV_RELEASE_TIME N/A N/A
0x100 0x100 0x100 Sets the maximum soft mute attack time in
ms for ASSI200DEV softmute engine.
256 256 256
0x0700 FM_AGC_FE_CONFIG
0x0080 0x0080 0x0080 0x0080 0x0080 Specified the input path for RF signal and
other FE configuration options.
128 128 128 128 128
0x0701 FM_AGC_PD_CONFIG
0x0270 0x0270 0x0270 0x0270 0x0270 Specifies the behavior of the FM peak
detectors and attenuators.
624 624 624 624 624
0x0702 FM_LNA_AGC_ATTACK_MS
0x0004 0x0004 0x0004 0x0004 0x0004 Sets the number of milliseconds the wide-
band RF high-peak
detector must be
exceeded before
attenuating the appropri-
ate block.
44444
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 39
0x0703 FM_LNA_AGC_RELEASE_MS
0x0050 0x0050 0x0050 0x0050 0x0050 Sets the number of milliseconds the wide-
band RF low-peak detector must not be
exceeded before increasing the gain of the
80 80 80 80 80
0x0704 FM_LNA_AGC_PD_THRESHOLD 0x4F05 0x4F05 0x4F05 0x4F05 0x4F05 Sets the high threshold and hysteresis for
the LNA peak detector.
20229 20229 20229 20229 20229
0x0705 FM_MIXER_AGC_ATTACK_MS
0x0004 0x0004 0x0004 0x0004 0x00F8 Sets the number of milliseconds the wide-
band mixer high-peak detector must be
exceeded before attenuating the
appropri-
ate block.
4444248
0x0706 FM_MIXER_AGC_RELEASE_MS
0x0050 0x0050 0x0050 0x0050 0x0050 Sets the number of milliseconds the wide-
band mixer low-peak detector must not be
exceeded before increasing the gain of the
appropriate block.
80 80 80 80 80
0x0707 FM_MIXER_AGC_PD_THRESHOLD 0x5103 0x5103 0x5103 0x5103 0x5103 Sets the high threshold and hysteresis for
the mixer peak detector.
20739 20739 20739 20739 20739
0x0710 FM_AGC_OVERRIDE 0x0000 0x0000 0x0000 0x0000 0x0000 Overrides the AGC setting by disabling the
AGC and forcing the gain to be maximum.
00000
0x071B FM_AGC_RSSI_OFFSET N/A 0x0000 0x0000 0x0000 0x0000 Offsets the RSSI value so that it can take
into account front-end gain/loss.
0000
0x071C FM_MIXER_AGC_PD_THRESHOLD_MAX N/A N/A 0x0055 0x0055 0x0059 Sets the maximum threshold for the mixer
peak detector.
85 85 89
0x071D FM_AGC_RSSI_MIXER_KEY N/A N/A 0x140E 0x140E 0x140E Sets the RSSI threshold and hysteresis to
enable keyed AGC.
5134 5134 5134
0x1006 FM_SEEK_TUNE_CHBW_HOLD_TIME N/A Do not
Write
0x0050 0x0050 0x0050 Sets the length of time CHBW is held in unit
of ms.
80 80 80
0x1007 FM_TUNE_CHBW N/A N/A 0x0050 0x0050 0x0050 Sets the maximum CHBW allowed during
the normal tune.
80 80 80
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
40 Rev. 0.9
AN543
0x1008 FM_TUNE_AF_CHBW N/A N/A 0x0096 0x0096 0x0096 Sets the CHBW during the AF tune/check.
150 150 80
0x1100 FM_SEEK_BAND_BOTTOM 0x222E 0x222E 0x222E 0x222E 0x222E Sets the lower seek boundary of the FM
band in multiples of 10 kHz.
8750 8750 8750 8750 8750
0x1101 FM_SEEK_BAND_TOP 0x2A26 0x2A26 0x2A26 0x2A26 0x2A30 Sets the upper seek boundary for the FM
band in multiples of 10 kHz.
10790 10790 10790 10790 10800
0x1102 FM_SEEK_FREQUENCY_SPACING
0x000A 0x000A 0x000A 0x000A 0x000A Sets the frequency spacing for the FM band
in multiples of 10 kHz when performing a
seek.
10 10 10 10 10
0x1104 FM_SEEK_CHBW N/A N/A 0x006E 0x006E 0x0050 Sets the CHBW during the seek.
110 110 80
0x1200 FM_RSQ_INTERRUPT_SOURCE
0x0000 0x0000 0x0000 0x0000 0x0000 Configures interrupt related to Received
Signal Quality metrics (FM_RSQ_STA-
TUS).
00000
0x1201 FM_RSQ_SNR_HIGH_THRESHOLD 0x007F 0x007F 0x007F 0x007F 0x007F Sets high threshold which triggers the RSQ
interrupt if the SNR is above this threshold.
127 127 127 127 127
0x1202 FM_RSQ_SNR_LOW_THRESHOLD 0xFF80 0xFF80 0xFF80 0xFF80 0xFF80 Sets low threshold which triggers the RSQ
interrupt if the SNR is below this threshold.
–128 –128 –128 –128 –128
0x1203 FM_RSQ_RSSI_HIGH_THRESHOLD 0x007F 0x007F 0x007F 0x007F 0x007F Sets high threshold which triggers the RSQ
interrupt if the RSSI is above this threshold.
127 127 127 127 127
0x1204 FM_RSQ_RSSI_LOW_THRESHOLD 0xFF80 0xFF80 0xFF80 0xFF80 0xFF80 Sets low threshold which triggers the RSQ
interrupt if the RSSI is below this threshold.
–128 –128 –128 –128 –128
0x1205 FM_RSQ_ISSI_HIGH_THRESHOLD
0x007F 0x007F 0x007F 0x007F 0x007F Sets high threshold, which triggers the
RSQ
interrupt if image signal strength is above
this threshold.
127 127 127 127 127
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 41
0x1206 FM_RSQ_ISSI_LOW_THRESHOLD
0xFF80 0xFF80 0xFF80 0xFF80 0xFF80 Sets low threshold which triggers the RSQ
interrupt if image signal strength is below
this threshold.
–128 –128 –128 –128 –128
0x1207 FM_RSQ_MULTIPATH_HIGH_THRESHOLD 0x007F 0x007F 0x007F 0x007F 0x007F Sets high threshold which triggers the RSQ
interrupt if Multipath is above this threshold.
127 127 127 127 127
0x1208 FM_RSQ_MULTIPATH_LOW_THRESHOLD 0x0000 0x0000 0x0000 0x0000 0x0000 Sets low threshold which triggers the RSQ
interrupt if Multipath is below this threshold.
00000
0x1300 FM_ACF_INTERRUPT_SOURCE 0x0000 0x0000 0x0000 0x0000 0x0000 Enables the ACF interrupt sources.
00000
0x1301 FM_ACF_SM_THRESHOLD 0x001F 0x001F 0x001F 0x001F 0x001F Sets the softmute interrupt threshold in dB.
31 31 31 31 31
0x1302 FM_ACF_CHBW_THRESHOLD 0x0000 0x0000 0x0000 0x0000 0x0000 Sets the Channel Filter Bandwidth interrupt
threshold in units of kHz.
00000
0x1303 FM_ACF_HICUT_THRESHOLD 0x0000 0x0000 0x0000 0x0000 0x0000 Sets the HICUT interrupt threshold in units
of 100 Hz.
00000
0x1304 FM_ACF_HIBLEND_THRESHOLD 0x0000 0x0000 0x0000 0x0000 0x0000 Sets the HIBLEND interrupt threshold in
units of 100 Hz.
00000
0x1305 FM_ACF_BLEND_THRESHOLD 0x0000 0x0000 0x0000 0x0000 0x0000 Sets the Stereo Blend interrupt threshold in
units of percent L–R gain.
00000
0x1306 FM_ACF_CONTROL_SOURCE 0x0001 0x0001 0x0001 0x0001 0x0003 Sets the controlling metric for ACF fea-
tures.
11113
0x1307 FM_ACF_HOLD_TIME N/A N/A N/A N/A 0x0064 Sets the ACF hold time after tune.
100
0x2000 FM_VALID_MAX_TUNE_ERROR
0x004B 0x004B 0x004B 0x004B 0x004B Sets the maximum frequency error in 2
ppm allowed before setting the AFCRL indi-
cator.
75 75 75 75 75
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
42 Rev. 0.9
AN543
0x2001 FM_VALID_RSSI_TIME
0x0006 0x0006 0x0006 0x0006 0x0006 Sets the amount of time in milliseconds to
allow the RSSI metric to settle before eval-
uating.
66666
0x2002 FM_VALID_SNR_TIME
0x0012 0x0012 0x0012 0x0012 0x0012 Sets the amount of time in milliseconds to
allow the SNR metric to settle before evalu-
ating.
18 18 18 18 18
0x2003 FM_VALID_SNR_THRESHOLD 0x0008 0x0008 0x0008 0x0008 0x0008 Sets the SNR threshold for a valid FM Seek
Tune.
88888
0x2004 FM_VALID_RSSI_THRESHOLD 0x000C 0x000C 0x000C 0x000C 0x000C Sets the RSSI threshold for a valid FM
Seek Tune.
12 12 12 12 12
0x2005 FM_VALID_ISSI_THRESHOLD Do not
write
Do not
write
0x001E 0x001E 0x001E Sets the ISSI threshold for injection side
switch during FM Seek Tune.
30 30 30
0x2006 FM_VALID_MULT_THRESHOLD N/Z 0x0064 0x0064 0x0064 0x0064 Sets the multipath threshold for a valid FM
Seek/Tune.
100 100 100 100
0x2007 FM_VALID_AF_TIME N/A
0x0005 0x0005 0x0002 0x0002 Sets the amount of time in milliseconds to
allow the RSSI and SNR metrics to settle
before evaluating during an AF check/tune.
5522
0x2008 FM_VALID_AF_RDS_TIME N/A N/A
0x0078 0x0078 0x0078 Sets the amount of time in milliseconds to
allow the PI code to be captured before
evaluating.
120 120 120
0x2009 FM_VALID_AF_PI N/A N/A 0x0000 0x0000 0x0000 Sets the PI code to match during AF tune.
000
0x200A FM_VALID_ASSI_THRESHOLD N/A N/A 0x503C 0x503C 0x503C Sets the ASSI/ASSI200 threshold for valid
FM Seek/Tune.
20540 20540 20540
0x200B FM_VALID_AF_PI_MASK N/A N/A 0xFFFF 0xFFFF 0xFFFF Sets the mask on PI code match during AF
tune.
65535 65535 65535
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 43
0x200C FM_VALID_FREQOFF_SCALE N/A N/A N/A 0x0000 0x0000 Changes FREQOFF from bppm units to
some multiple of Hz.
00
0x200D FM_VALID_FREQOFF_FILTER N/A N/A N/A 0x0064 0x0064 Changes the amount that FREQOFF is fil-
tered.
100 100
0x2100 FM_NB_DETECT_THRESHOLD 0x0012 0x0012 0x0012 0x0012 0x0012 Sets the threshold for detecting impulses in
dB above the noise floor.
18 18 18 18 18
0x2101 FM_NB_INTERVAL 0x0005 0x0005 0x0005 0x0005 0x0005 Sets the interval that original samples are
replaced by interpolated clean samples.
55555
0x2103 FM_NB_SECONDARY_DETECT_THRESHOLD N/A N/A N/A N/A 0x0000 Sets the threshold for detecting impulses in
percentage of average to peak
0
0x2105 FM_NB_WEAK_DETECT_THRESHOLD N/A N/A 0x3500 0x3500 0x1D71 Sets the threshold for detecting impulses
with the weak signal noise blanker.
13568 13568 7537
0x2106 FM_NB_STRONG_SIGNAL_SHUTOFF
0x0032 0x0032 0x0032 0x0032 0x0023 The RSSI based shutoff threshold. Used to
turn off the noise blanker under strong sig-
nal conditions.
50 50 50 50 35
0x2109 FM_NB_MODE_CONTROL N/A N/A
0x0000 0x0000 0x0000
Sets options of the noise blankers.
000
0x210A FM_NB_WEAK_BLANK_INTERVAL N/A N/A
0x0005 0x0005 0x0005 Number of samples that are replaced by
interpolated clean samples.
555
0x210B FM_NB_STRONG_WEAK_SWITCH N/A N/A 0x0B09 0x0B09 0x0B09 Sets the SNR/RSSI thresholds for deter-
mining whether strong or weak blanker is
used.
2825 2825 2825
0x2111 FM_NB_CIMP_HICUT_LIMIT N/A N/A N/A N/A
0x0A14 Sets the HiCut multipath threshold when
continuous impulses are detected.
2580
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
44 Rev. 0.9
AN543
0x2112 FM_NB_CIMP_HICUT_FREQ N/A N/A N/A N/A 0x6401 Sets the HiCut cut-off frequency when con-
tinuous impulses are detected.
25601
0x2113 FM_NB_CIMP_HICUT_ATTACK N/A N/A N/A N/A 0x0001 Sets the HiCut attack time when continuous
impulses are detected.
1
0x2114 FM_NB_CIMP_HICUT_RELEASE N/A N/A N/A N/A 0x0008 Sets the HiCut release time when continu-
ous impulses are detected.
8
0x2115 FM_NB_CIMP_DETCNTR N/A N/A N/A N/A 0x0402 Continuous impulse detection counter set-
ting.
1026
0x2116 FM_NB_CIMP_A2PTH N/A N/A N/A N/A 0x0800 Independent IQ impulse detection thresh-
old for continuous impulse detection.
2048
0x2117 FM_NB_CIMP_IMPDET N/A N/A N/A N/A
0x400A Aggressive noise blanker impulse detection
threshold when continuous impulses
detected.
16394
0x2118 FM_NB_CIMP_MPX_INTV N/A N/A N/A N/A
0x0A0A Aggressive MPX blanker interval when
continuous impulses detected replacing
property 0x2101.
2570
0x2200 FM_CHBW_SQ_MIN_MAX
0x9637 0x9637 0x9637 0x9637 0x9637 Sets the maximum and minimum channel
filter bandwidth in units of kHz based on
RSSI/STRONGDEV (or SNR) in weak sig-
nal condition.
38455 38455 38455 38455 38455
0x2201 FM_CHBW_SQ_HIGH_THRESHOLD
0x000C 0x000C 0x000C 0x000C 0x000C Sets the RSSI/STRONGDEV (or SNR)
threshold for maximum channel filter band-
width in weak signal condition.
12 12 12 12 12
0x2202 FM_CHBW_SQ_LOW_THRESHOLD
0xFFFC 0xFFFC 0xFFFC 0xFFFC 0x0002 Sets the RSSI/STRONGDEV (or SNR)
threshold for minimum channel filter band-
width in weak signal condition.
–4 –4 –4 –4 2
0x2203 FM_CHBW_SQ_WIDENING_TIME
0x0010 0x0010 0x0010 0x0010 0x0010 Sets the channel filter bandwidth widening
time based on RSSI/STRONGDEV (or
SNR) in weak signal condition.
16 16 16 16 16
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 45
0x2204 FM_CHBW_SQ_NARROWING_TIME
0x0800 0x0800 0x0800 0x0800 0x0800 Sets the channel filter bandwidth narrowing
time based on RSSI/STRONGDEV (or
SNR) in weak signal condition.
2048 2048 2048 2048 2048
0x2205 FM_CHBW_ASSI_MIN_MAX
0x9623 0x9623 0x9623 0x9623 0x9623 Sets the delta (HASSI,LASSI) threshold for
maximum and minimum channel filter
bandwidth in units of kHz.
38435 38435 38435 38435 38435
0x2206 FM_CHBW_ASSI_LOW_THRESHOLD 0x0007 0x0007 0x0007 0x0007 0x0007 Sets the delta (HASSI,LASSI) threshold for
maximum channel filter bandwidth
77777
0x2207 FM_CHBW_ASSI_HIGH_THRESHOLD 0x0014 0x0014 0x0014 0x0014 0x0014 Sets the delta (HASSI,LASSI) threshold for
minimum channel filter bandwidth.
20 20 20 20 20
0x2208 FM_CHBW_ASSI_WIDENING_TIME 0x0001 0x0001 0x0C80 0x0C80 0x0C80 Sets the channel filter bandwidth widening
time based on the delta (HASSI,LASSI).
1 1 3200 3200 3200
0x2209 FM_CHBW_ASSI_NARROWING_TIME 0x0140 0x0140 0x0140 0x0140 0x0140 Sets the channel filter bandwidth narrowing
time based on the delta (HASSI,LASSI).
320 320 320 320 320
0x220A FM_CHBW_ASSI200_MIN_MAX 0x9632 0x9650 0x9650 0x9650 0x964B Sets the ASSI200 maximum and minimum
channel filter bandwidth in units of kHz.
38450 38480 38480 38480 38475
0x220B FM_CHBW_ASSI200_LOW_THRESHOLD 0xFFF6 0xFFF6 0xFFF6 0xFFF6 0x0000 Sets the ASSI200 threshold for maximum
channel filter bandwidth.
–10 –10 –10 –10 0
0x220C FM_CHBW_ASSI200_HIGH_THRESHOLD
0x000A 0x000A 0x000A 0x000A 0x000A Sets the ASSI200 threshold for minimum
channel filter bandwidth.
10 10 10 10 10
0x220D FM_CHBW_ASSI200_WIDENING_TIME 0x0001 0x0001 0xC80 0xC80 0xFA0 Sets the channel filter bandwidth widening
time based on ASSI200.
1 1 3200 3200 4000
0x220E FM_CHBW_ASSI200_NARROWING_TIME 0x0140 0x0140 0x0140 0x0140 0x0140 Sets the channel filter bandwidth narrowing
time based on ASSI200.
320 320 320 320 320
0x220F FM_CHBW_WEAKSIG_THR N/A 0x100D 0x100D 0x100D 0x100D Sets the hysteresis window for the weak
signal channel filter bandwidth engine.
4109 4109 4109 4109
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
46 Rev. 0.9
AN543
0x2210 FM_CHBW_BLOCKER_THR N/A Do not
Write
0x140A 0x140A 0x140A Sets the threshold and hysteresis to enable
channel filter bandwidth based on
ASSI200DEV.
5130 5130 5130
0x2214 FM_CHBW_ASSI_B_CONTROL N/A N/A 0x0000 0x0200 0x0200 Selects the behavior of ASSI-B channel fil-
ter bandwidth control engine.
0 512 512
0x2215 FM_CHBW_STRONGDEV_MIN_MAX N/A
0x9680 0x9680 0x9680 0x9664 Sets the maximum and minimum channel
filter bandwidth in units of kHz based on
STRONGDEV.
38528 38528 38528 38500
0x2216 FM_CHBW_STRONGDEV_LOW_THRESHOLD N/A 0x0008 0x0008 0x0008 0x0008 Sets the STRONGDEV threshold for maxi-
mum channel filter bandwidth.
8888
0x2217 FM_CHBW_STRONGDEV_HIGH_THRESHOLD N/A 0x0013 0x0013 0x0013 0x0013 Sets the STRONGDEV threshold for mini-
mum channel filter bandwidth.
19 19 19 19
0x2218 FM_CHBW_STRONGDEV_WIDENING_TIME N/A 0x1000 0x1000 0x1000 0x1000 Sets the channel filter bandwidth widening
time based on STRONGDEV.
4096 4096 4096 4096
0x2219 FM_CHBW_STRONGDEV_NARROWING_TIME N/A 0x0200 0x0200 0x0200 0x0200 Sets the channel filter bandwidth narrowing
time based on STRONGDEV.
512 512 512 512
0x221A FM_CHBW_ASSI200DEV_MIN_MAX N/A N/A
0x5020 0x9646 0x9646 Sets the maximum and minimum channel
filter bandwidth in units of kHz based on
ASSI200DEV.
20512 38470 38470
0x221B FM_CHBW_ASSI200DEV_LOW_THRESHOLD N/A N/A 0x0032 0x0032 0x0032 Sets the ASSI200DEV threshold for maxi-
mum channel filter bandwidth.
50 50 50
0x221C FM_CHBW_ASSI200DEV_HIGH_THRESHOLD N/A N/A 0x005A 0x005A 0x005A Sets the ASSI200DEV threshold for mini-
mum channel filter bandwidth.
90 90 90
0x221D FM_CHBW_ASSI200DEV_WIDENING_TIME N/A N/A 0x0800 0x0800 0x0800 Sets the channel filter bandwidth widening
time based on ASSI200DEV.
2048 2048 2048
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 47
0x221E FM_CHBW_ASSI200DEV_NARROWING_TIME N/A N/A 0x0080 0x0080 0x0080 Sets the channel filter bandwidth narrowing
time based on ASSI200DEV.
128 128 128
0x221F FM_CHBW_ASSI_B_MIN_MAX N/A N/A
0x9696 0x9696 0x9696 Sets the maximum and minimum channel
filter bandwidth in units of kHz based on
max (HASSI,LASSI).
38550 38550 38550
0x2220 FM_CHBW_ASSI_B_LOW_THRESHOLD N/A N/A 0x0000 0x0000 0xFFFB Sets the max (HASSI,LASSI) threshold for
maximum channel filter bandwidth.
00-5
0x2221 FM_CHBW_ASSI_B_HIGH_THRESHOLD N/A N/A 0x0000 0x0000 0x0005 Sets the max (HASSI,LASSI) threshold for
minimum channel filter bandwidth.
005
0x2222 FM_CHBW_ASSI_B_WIDENING_TIME N/A N/A 0x0001 0x0001 0x0FA0 Sets the channel filter bandwidth widening
time based on max (HASSI,LASSI).
1 1 4000
0x2223 FM_CHBW_ASSI_B_NARROWING_TIME N/A N/A 0x0001 0x0001 0x0190 Sets the channel filter bandwidth narrowing
time based on max (HASSI,LASSI).
1 1 400
0x3105 FM_LOWCUT_MIN_FREQ Do Not
Write N/A 0x0000 0x0000 0x0000 Sets the minimum LowCut cutoff frequency.
000
0x3106 FM_LOWCUT_MAX_FREQ Do Not
Write N/A 0x0000 0x0000 0x0000 Sets the maximum LowCut cutoff fre-
quency.
000
0x3200 FM_POP_NOISE_FADE_HYST Do not
Write
Do not
Write
0x0A06 0x0A06 0x0604 Sets the thresholds for FM pop filter fading
hysteresis
2566 2566 1540
0x3207 FM_POP_NOISE_MODE 0x0001 0x0001 0x0001 0x0001 0x0002 Sets the pop mitigation mode.
11112
0x3208 FM_POP_NOISE_RSSI_THRESHOLDS N/A
0xECE7 0xECE7 0xECE7 0xFDF9 Sets the change in RSSI thresholds for
maximum and minimum MPX limiting (set
by property 0x3209).
60647 60647 60647 65017
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
48 Rev. 0.9
AN543
0x3209 FM_POP_NOISE_RSSI_MPX_LIMIT N/A 0x1009 0x1009 0x1009 0x0502 Sets the minimum and maximum limit for
MPX limiter based on change in RSSI.
4105 4105 4105 1282
0x320A FM_POP_NOISE_RSSI_MPX_ATTACK N/A 0x0001 0x0001 0x0001 0x001E Sets the attack rate for MPX limiter pop mit-
igation.
11130
0x320B FM_POP_NOISE_RSSI_MPX_RELEASE N/A 0x0001 0x0001 0x0001 0x0BB8 Sets the release rate for pop mitigation.
1 1 1 3000
0x320C FM_POP_NOISE_MPX_USN_THRESHOLDS N/A
0x03FE 0x03FE 0x03FE 0x0501 Sets the ratio of MPX to USN thresholds for
maximum and minimum MPX limiting (set
by property 0x320D).
1022 1022 1022 1281
0x320D FM_POP_NOISE_MPX_USN_LIMITS N/A 0x1009 0x1009 0x1009 0x0502 Sets the maximum and minimum limit for
MPX limiter based on ratio of MPX to USN.
4105 4105 4105 1282
0x320E FM_POP_NOISE_MPX_USN_ATTACK N/A 0x0001 0x0001 0x0001 0x001E Sets the attack rate for MPX limiter pop mit-
igation.
11130
0x320F FM_POP_NOISE_MPX_USN_RELEASE N/A 0x0001 0x0001 0x0001 0x0BB8 Sets the release rate for pop mitigation.
1 1 1 3000
0x3210 FM_POP_NOISE_SCALE 0x007F 0x007F 0x007F 0x007F 0x007F Sets the scale for the FM pop filter.
127 127 127 127 127
0x3400 FM_MULT_EQ_CTL N/A N/A 0x0601 0x0601 0x8001 Controls the multipath channel equalizer.
1537 1537 32769
0x3401 FM_MULT_EQ_NOISE_DISABLE N/A N/A
0xFC81 0xFCFA 0xFCFA Sets the RSSI threshold below which the
channel equalizer will use noise measure-
ment to enable/disable channel equalizer.
64641 64762 64762
0x3402 FM_MULT_EQ_CTL_STEP N/A N/A 0x0000 0x0000 0x0000 Sets the channel equalizer tap updating
rate.
000
0x3409 FM_EQ_CTL_AUTOTAP N/A N/A N/A N/A 0x03FB Sets the threshold for channel equalizer
auto tap control.
1019
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 49
0x3500 FM_BLEND_RSSI_THRESHOLDS 0x3719 0x3719 0x3719 0x3719 0x3719 Sets the thresholds for the RSSI metric for
the stereo blend mitigation engine.
14105 14105 14105 14105 14105
0x3501 FM_BLEND_RSSI_STEREO_SEP
0x2D00 0x2D00 0x2D00 0x2D00 0x2D00 Set the limits for the stereo separation
when driven by RSSI on the stereo blend
mitigation engine.
11520 11520 11520 11520 11520
0x3502 FM_BLEND_RSSI_ATTACK_TIME 0x0010 0x0010 0x0010 0x0010 0x0010 Sets the stereo blend attack time in ms.
16 16 16 16 16
0x3503 FM_BLEND_RSSI_RELEASE_TIME 0x0FA0 0x0FA0 0xFA0 0xFA0 0xFA0 Sets the stereo blend release time in ms.
4000 4000 4000 4000 4000
0x3508 FM_BLEND_MULTIPATH_THRESHOLDS 0x1E3C 0x1E3C 0x1E3C 0x1E3C 0x0A14 Sets the thresholds for the multipath metric
for the stereo blend mitigation engine.
7740 7740 7740 7740 2580
0x3509 FM_BLEND_MULTIPATH_STEREO_SEP
0x2D00 0x2D00 0x2D00 0x2D00 0x2D00 Sets the limits for the stereo separation
when driven by multipath on the stereo
blend mitigation engine.
11520 11520 11520 11520 11520
0x350A FM_BLEND_MULTIPATH_ATTACK_TIME 0x0010 0x0010 0x0010 0x0010 0x0010 Sets the stereo blend attack time in ms.
16 16 16 16 16
0x350B FM_BLEND_MULTIPATH_RELEASE_TIME 0x0FA0 0x0FA0 0x0FA0 0x0FA0 0x0FA0 Sets the stereo blend release time in ms.
4000 4000 4000 4000 4000
0x3510 FM_BLEND_USN_THRESHOLDS 0x341B 0x341B 0x341B 0x341B 0x341B Set the thresholds for the USN metric for
the stereo blend mitigation engine.
13339 13339 13339 13339 13339
0x3511 FM_BLEND_USN_STEREO_SEP
0x2D00 0x2D00 0x2D00 0x2D00 0x2D00 Sets the limits for the stereo separation
when driven by USN on the stereo blend
mitigation engine.
11520 11520 11520 11520 11520
0x3512 FM_BLEND_USN_ATTACK_TIME 0x0010 0x0010 0x0010 0x0010 0x0010 Sets the stereo blend attack time in ms.
16 16 16 16 16
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
50 Rev. 0.9
AN543
0x3513 FM_BLEND_USN_RELEASE_TIME 0x0FA0 0x0FA0 0x0FA0 0x0FA0 0x0FA0 Sets the stereo blend release time in ms.
4000 4000 4000 4000 4000
0x3518 FM_BLEND_CHBW_LIMITS 0x0000 0X0000 0x0000 0x0000 0x0000 Set the limits for CHBW input metric on the
stereo blend mitigation engine
00000
0x3519 FM_BLEND_CHBW_STEREO_SEP
0x2D2D 0x2D2D 0x2D2D 0x2D2D 0x2D2D Set the limits for the stereo separation
when driven by CHBW on the stereo blend
mitigation engine
11565 11565 11565 11565 11565
0x351A FM_BLEND_CHBW_ATTACK_TIME 0x0001 0x0001 0x0001 0x0001 0x0001 Set stereo blend attack time in ms
11111
0x351B FM_BLEND_CHBW 0x0001 0x0001 0x0001 0x0001 0x0001 Set stereo blend release time in ms
11111
0x3600 FM_HICUT_RSSI_THRESHOLDS 0x230F 0x230F 0x230F 0x230F 0x230F Sets the thresholds for the RSSI metric for
the L+R high cut mitigation engine.
8975 8975 8975 8975 8975
0x3601 FM_HICUT_RSSI_CUTOFF_FREQ
0xB428 0xB428 0xB428 0xB428 0xB419 Sets the limits for the cutoff frequency when
driven by RSSI on the L+R high cut mitiga-
tion engine.
46120 46120 46120 46120 46105
0x3602 FM_HICUT_RSSI_ATTACK_TIME 0x0010 0x0010 0x0010 0x0010 0x0064 Sets the L+R high cut attack time in ms.
16 16 16 16 100
0x3603 FM_HICUT_RSSI_RELEASE_TIME 0x0FA0 0x0FA0 0x0FA0 0x0FA0 0x0FA0 Sets the L+R high cut release time in ms.
4000 4000 4000 4000 4000
0x3608 FM_HICUT_MULTIPATH_THRESHOLDS 0x3250 0x3250 0x3250 0x3250 0x0A14 Sets the thresholds for the multipath metric
for the L+R high cut mitigation engine.
12880 12880 12880 12880 2580
0x3609 FM_HICUT_MULTIPATH_CUTOFF_FREQ
0xB428 0xB428 0xB428 0xB428 0x6419 Set the limits for the cutoff frequency when
driven by multipath on the L+R high cut mit-
igation engine.
46120 46120 46120 46120 25625
0x360A FM_HICUT_MULTIPATH_ATTACK_TIME 0x0010 0x0010 0x0010 0x0010 0x0064 Sets the L+R high cut attack time in ms.
16 16 16 16 100
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 51
0x360B FM_HICUT_MULTIPATH_RELEASE_TIME 0x0FA0 0x0FA0 0x0FA0 0x0FA0 0x0FA0 Sets the L+R high cut release time in ms.
4000 4000 4000 4000 4000
0x3610 FM_HICUT_USN_THRESHOLDS 0x250F 0x250F 0x250F 0x250F 0x250F Sets the thresholds for the USN metric for
the L+R high cut mitigation engine.
9487 9487 9487 9487 9487
0x3611 FM_HICUT_USN_CUTOFF_FREQ
0xB428 0xB428 0xB428 0xB428 0xB419 Sets the limits for the cutoff frequency when
driven by USN on the L+R high cut mitiga-
tion engine.
46120 46120 46120 46120 46105
0x3612 FM_HICUT_USN_ATTACK_TIME 0x0010 0x0010 0x0010 0x0010 0x0064 Sets the L+R high cut attack time in ms.
16 16 16 16 100
0x3613 FM_HICUT_USN_RELEASE_TIME 0x0FA0 0x0FA0 0x0FA0 0x0FA0 0x0FA0 Sets the L+R high cut release time in ms.
4000 4000 4000 4000 4000
0x3618 FM_HICUTN_CHBW_LIMITS 0x0000 0x0000 0x0000 0x0000 0x0000 Set the limits for the CHBW input metric on
L+R high cut mitigation engine
00000
0x3619 FM_HICUTN_CHBW_CUTOFF_FREQ
0xB4B4 0xB4B4 0xB4B4 0xB4B4 0xB4B4 Set the limits for the cutoff frequency when
driven by CHBW on the L+R high cut miti-
gation engine
46260 46260 46260 46260 46260
0x361A FM_HICUTN_CHBW_ATTACK_TIME 0x0001 0x0001 0x0001 0x0001 0x0001 Set L+R high cut attack time in ms
11111
0x361B HM_HICUTN_CHBW_RELEASE_TIME 0x0001 0x0001 0x0001 0x0001 0x0001 Set L+R high cut release time in ms
11111
0x3700 FM_HIBLEND_RSSI_THRESHOLDS 0x371B 0x371B 0x371B 0x371B 0x371B Sets the thresholds for the RSSI metric for
the L–R high cut mitigation engine.
14107 14107 14107 14107 14107
0x3701 FM_HIBLEND_RSSI_CUTOFF_FREQ
0xB41E 0xB41E 0xB41E 0xB41E 0xB419 Sets the limits for the cutoff frequency when
driven by RSSI on the L–R high-blend miti-
gation engine.
46110 46110 46110 46110 46105
0x3702 FM_HIBLEND_RSSI_ATTACK_TIME 0x0004 0x0004 0x0004 0x0004 0x0064 Sets the L–R high-blend attack time in ms.
4444100
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
52 Rev. 0.9
AN543
0x3703 FM_HIBLEND_RSSI_RELEASE_TIME 0x1F40 0x1F40 0x1F40 0x1F40 0x0FA0 Sets the L–R high-blend release time in ms.
8000 8000 8000 8000 4000
0x3708 FM_HIBLEND_MULTIPATH_THRESHOLDS
0x193C 0x193C 0x193C 0x193C 0x080F Sets the thresholds for the multipath metric
for the L–R high-blend mitigation engine.
6460 6460 6460 6460 2063
0x3709 FM_HIBLEND_MULTIPATH_CUTOFF_FREQ
0xB41E 0xB41E 0xB41E 0xB41E 0x6419 Sets the limits for the cutoff frequency when
driven by multipath on the L–R high-blend
mitigation engine.
46110 46110 46110 46110 25625
0x370A FM_HIBLEND_MULTIPATH_ATTACK_TIME 0x0004 0x0004 0x0004 0x0004 0x0064 Sets the L–R high-blend attack time in ms.
4444100
0x370B FM_HIBLEND_MULTIPATH_RELEASE_TIME 0x1F40 0x1F40 0x1F40 0x1F40 0x0FA0 Sets the L–R high-blend release time in ms.
8000 8000 8000 8000 4000
0x3710 FM_HIBLEND_USN_THRESHOLDS 0x371E 0x371E 0x371E 0x371E 0x371E Sets the thresholds for the USN metric for
the L–R high-blend mitigation engine.
14110 14110 14110 14110 14110
0x3711 FM_HIBLEND_USN_CUTOFF_FREQ
0xB41E 0xB41E 0xB41E 0xB41E 0x9619 Sets the limits for the cutoff frequency when
driven by USN on the L–R high-blend miti-
gation engine.
46110 46110 46110 46110 38425
0x3712 FM_HIBLEND_USN_ATTACK_TIME 0x0004 0x0004 0x0004 0x0004 0x0064 Sets the L–R high-blend attack time in ms.
4444100
0x3713 FM_HIBLEND_USN_RELEASE_TIME 0x1F40 0x1F40 0x1F40 0x1F40 0x0FA0 Sets the L–R high-blend release time in ms.
8000 8000 8000 8000 4000
0x3718 FM_HIBLEND_CHBW_LIMITS
0x0000 0x0000 0x0000 0x0000 0x0000 Set the limits for the CHBW input metric on
the hi-blend (L-R high cut) mitigation
engine.
00000
0x3719 FM_HIBLEND_CHBW_CUTOFF_FREQ
0xB4B4 0xB4B4 0xB4B4 0xB4B4 0xB4B4 Set the limits for the cutoff frequency when
driven by CHBW on the hi-blend (L-R high
cut) mitigation engine.
46260 46260 46260 46260 46260
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 53
0x371A FM_HIBLEND_CHBW_ATTACK_TIME 0x0001 0x0001 0x0001 0x0001 0x0001 Set hi-blend (L-R high cut) attack time in
ms
11111
0x371B FM_HIBLEND_CHBW_RELEASE_TIME 0x0001 0x0001 0x0001 0x0001 0x0001 Set hi-blend (L-R high cut) release time in
ms.
11111
0x4000 FM_RDS_INTERRUPT_SOURCE 0x0000 0x0000 0x0000 0x0000 0x0000 Configures interrupt related to RDS.
00000
0x4001 FM_RDS_INTERRUPT_FIFO_COUNT
0x0000 0x0000 0x0000 0x0000 0x0000 Sets the minimum number of RDS groups
stored in the RDS FIFO before RDSRECV
is set.
00000
0x4002 FM_RDS_CONFIG
0x0000 0x0000 0x0000 0x0000 0x0000 Configures RDS settings to enable RDS
processing (RDSEN) and set RDS block
error thresholds.
00000
0x4003 FM_RDS_CONFIDENCE 0x1111 0x1111 0x1111 0x1111 0x1111 Sets the confidence level requirement for
each RDS block.
4369 4369 4369 4369 4369
Table 12. FM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
54 Rev. 0.9
7.2.1. FM Receiv er Co mman d s
Command 0x30 FM_T U NE_ FREQ
The FM_TUNE_FREQ command sets the FM Receiver to tune to a frequency between 64 and 108 MHz in 10 kHz
units. The CTS bit (and optional interrupt) is set when it is safe to send the next command. The ERR bit (and
optional interrupt) is set if an invalid argument is sent. Note that only a single interrupt occurs if both the CTS and
ERR bits are set. The optional STC interrupt is set when the command completes. This command may only be sent
in powerup mode. The command clears the STC bit if it is already set.
Command
Bit 7 6 5 4 3 2 1 0
CMD 0x30
ARG1 00 TUNEMODE[1:0] 0 SMOOTHMETRICS INJSIDE[1:0]
ARG2 FREQH[7:0]
ARG3 FREQL[7:0]
ARG Bit Name Function
17:6Reserved
Always write 0.
1 5:4 TUNEMODE[1:0]
Sets the Desired Tuning Mode.
0 = Validated normal tune: Unconditionally stay on the new
channel after tune, tune status is valid.
1 = Invalidated fast tune: Unconditionally stay on the new
channel after tune, tune status invalid.
2 = Validated AF Tune: Jump back to previous channel if
metric thresholds are not met (Si4755/57 only).
3 = Validated AF Check: Unconditionally jump back to the
previous channel (Si4755/57 only).
13Reserved
Always write 0.
12
SMOOTH-
METRICS
Smoothly transition audio state after tune.
0 = Initialize audio state to match this new channel.
1 = Transition audio state from previous channel values to
the new channel values.
Note: This is the recommended setting when performing an AF
check.
1 1:0 INJSIDE[1:0]
Selects Injection Side.
0 = Automatic injection side selection by the tuner.
1 = Force low-side injection.
2 = Force high-side injection.
AN543
Rev. 0.9 55
Response
27:0FREQ
H[7:0]
Tune Freque ncy High Byte.
This byte in combination with FREQL selects the tune
frequency in units of 10 kHz. In FM mode the valid range is
from 6400 to 10800 (64–108 MHz).
37:0FREQ
L[7:0]
Tune Frequency Low Byte.
This byte in combination with FREQH selects the tune
frequency in units of 10 kHz. In FM mode, the valid range is
from 6400 to 10800 (64–108 MHz).
Bit76543210
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
ARG Bit Name Function
AN543
56 Rev. 0.9
Command 0x31 FM_S EEK_ S TART
The FM_SEEK_START command begins searching for a valid station. In order for a station to be considered valid,
each of the following thresholds must be met:
FM_VALID_SNR_THRESHOLD, FM_VALID_RSSI_THRESHOLD,
FM_VALID_ASSI_THRESHOLD, FM_VALID_ISSI_THRESHOLD, and FM_VALID_MAX_TUNE_ERROR. Clears
any pending STCINT, RSQINT, or RDSINT interrupt status. Seek can be cancelled through setting the CANCEL bit
in the FM_RSQ_STATUS command. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. The ERR bit (and optional interrupt) is set if an invalid argument is sent. Note that only a single interrupt
occurs if both the CTS and ERR bits are set. The optional STC interrupt is set when the command completes. This
command may only be sent in powerup mode. The command clears the STCINT bit if it is already set.
Command
Response
Bit76543210
CMD 0x31
ARG1 0000 SEEKUP WRAP 00
ARG Bit Name Function
1 7:4 Reserved Always write 0000.
1 3 SEEKUP
Seek Up/Down.
Determines the direction of the search, either UP = 1, or
DOWN = 0.
12WRAP
Wrap/Halt.
Determines whether the seek should Wrap = 1, or Halt = 0 when
it hits the band limit.
1 1:0 Reserved Always write 00.
Bit76543210
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
AN543
Rev. 0.9 57
Command 0x32 FM _R SQ_ STATUS
The FM_RSQ_STATUS command returns status information about the received signal quality. This command
returns the Received Signal Strength Indicator (RSSI), Signal to Noise Ratio (SNR), Adjacent Channel Strength for
200 kHz (ASSI200), Adjacent Channel Strength for 100 kHz (LASSI and HASSI), frequency offset (FREQOFF),
Multipath (MULT), Ultrasonic Noise (USN), Pilot Deviation (PILOTDEV), RDS Deviation (RDSDEV), Adjacent
Channel Deviation for 200 kHz (ASSI200DEV), Deviation (DEV and STRONGDEV), and RDS PI code (RDSPI)
associated with the desired channel. It also indicates valid channel (VALID) and AFC rail status (AFCRL). This
command can be used to check if the received signal is above the RSSI high threshold as reported by RSSIHINT
or below the RSSI low threshold as reported by RSSILINT. It can also be used to check if the signal is above the
SNR high threshold as reported by SNRHINT or below the SNR low threshold as reported by SNRLINT. It can be
used to check if the detected multipath is above the Multipath high threshold as reported by MULTHINT or below
the Multipath low threshold as reported by MULTLINT.
The command clears the RSQINT, SNRHINT, SNRLINT, RSSIHINT, RSSILINT, MULTHINT, and MULTLINT
interrupt bits when the RSQACK bit of ARG1 is set. If the condition is still true after the interrupt is cleared, another
interrupt will fire assuming that bit is enabled in FM_RSQ_INTERRUPT_SOURCE. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This command may only be sent when in powerup
mode.
FM_RSQ_
STATUS
Command
76543210
CMD 0x32
ARG1 0000 RSQACK ATTUNE CANCEL STCACK
ARG Bit Name Function
1 7:4 Reserved Always write 0000.
1 3 RSQACK Clears RSQINT, SNRHINT, SNRLINT, RSSIHINT, RSSILINT,
MULTHINT, and MULTLINT if set.
1 2 ATTUNE
Returns the values of metrics as of tune time. When the
ATTUNE bit is set, values returned for RSQ_STATUS are the
values calculated at tune and do not change unless another
FM_TUNE_FREQ or FM_SEEK_START command is called.
This feature can be used to determine why seek stopped at the
current station.
1 1 CANCEL
Aborts a seek or tune currently in progress.
0 = Don't abort.
1 = Abort.
1 0 STCACK Clears the STC interrupt status indicator if set.
AN543
58 Rev. 0.9
Response
Bit 7 6 5 4 3 2 1 0
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
RESP1 MULTHINT MULTLINT ISSIHINT ISSILINT SNRHINT SNRLINT RSSIHINT RSSILINT
RESP 2 BLTF X SNRREADY RSSIREADY X INJSIDE AFCRL VALID
RESP 3 READFREQ[15:8]
RESP 4 READFREQ[7:0]
RESP 5 FREQOFF[7:0]
RESP 6 RSSI[7:0]
RESP 7 SNR[7:0]
RESP 8 ISSI[7:0]
RESP 9 LASSI[7:0]
RESP 10 HASSI[7:0]
RESP 11 MULT[7:0]
RESP 12 DEV[7:0]
RESP 13 XXXXXXXX
RESP 14 XXXXXXXX
RESP 15 ASSI200[7:0]
RESP 16 USN[7:0]
RESP 17 PILOTDEV[7:0]
RESP 18 RDSDEV[7:0]
RESP 19 ASSI200DEV[7:0]
RESP 20 STRONGDEV[7:0]
RESP 21 RDSPI[15:8]
RESP 22 RDSPI[7:0]
AN543
Rev. 0.9 59
RESP Bit Name Function
17MULTHINT
Multipath Detect High.
0 = Indicates that multipath value has not exceeded the
Multipath high threshold set by
FM_RSQ_MULTIPATH_HIGH_THRESHOLD.
1 = Indicates that multipath value has exceeded the
Multipath high threshold set by
FM_RSQ_MULTIPATH_HIGH_THRESHOLD.
16MULTLINT
Multipath Detect Low.
0 = Indicates that multipath value has not fallen below the
Multipath low threshold set by
FM_RSQ_MULTIPATH_LOW_THRESHOLD.
1 = Indicates that multipath value has fallen below the
Multipath low threshold set by
FM_RSQ_MULTIPATH_LOW_THRESHOLD.
1 5 ISSIHINT ISSI Detect High.
(Available in Si475x-A30 only)
0 = Indicates that ISSI has not exceeded the ISSI high
threshold set by
FM_RSQ_ISSI_HIGH_THRESHOLD.
1 = Indicates that ISSI has exceeded the ISSI high
threshold set by
FM_RSQ_ISSI_HIGH_THRESHOLD.
14ISSILINT
ISSI Detect Low.
(Available in Si475x-A30 only)
0 = Indicates that ISSI has not fallen below the ISSI low
threshold set by
FM_RSQ_ISSI_LOW_THRESHOLD.
1 = Indicates that ISSI has fallen below the ISSI low
threshold set by
FM_RSQ_ISSI_LOW_THRESHOLD.
1 3 SNRHINT SNR Detect High.
0 = Indicates that the received signal SNR has not
exceeded the SNR high threshold set by
FM_RSQ_SNR_HIGH_THRESHOLD
1 = Indicates that the received signal SNR has exceeded
the SNR high threshold set by
FM_RSQ_SNR_HIGH_THRESHOLD.
1 2 SNRLINT SNR Detect Low.
0 = Indicates that the received signal SNR has not fallen
below the SNR low threshold set by
FM_RSQ_SNR_LOW_THRESHOLD.
1 = Indicates that the received signal SNR has fallen
below the SNR low threshold set by
FM_RSQ_SNR_LOW_THRESHOLD.
AN543
60 Rev. 0.9
1 1 RSSIHINT RSSI Detect High.
0 = Indicates that the received signal RSSI has not
exceeded the RSSI high threshold set by
FM_RSQ_RSSI_HIGH_THRESHOLD.
1 = Indicates that the received signal RSSI has exceeded
the RSSI high threshold set by
FM_RSQ_RSSI_HIGH_THRESHOLD.
1 0 RSSILINT RSSI Detect Low.
0 = Indicates that the received signal RSSI has not fallen
below the RSSI low threshold set by
FM_RSQ_RSSI_LOW_THRESHOLD.
1 = Indicates that the received signal RSSI has fallen
below the RSSI low threshold set by
FM_RSQ_RSSI_LOW_THRESHOLD.
27BLTF Band Limit.
Reports if a seek hits the band limit (WRAP = 0 in
FM_START_SEEK) or wrapped to the original frequency
(WRAP = 1).
26
Reserved Values may vary.
2 5 SNRREADY The SNRREADY and RSSIREADY bits indicate that the
RSSI/SNR have been read as a result of a tune command.
If either one of these bits are 0 this indicates that either the
metric is being measured (because a tune is in progress)
or that the metric was not measured during tune because
the station was invalidated before the metric could be
measured. In the case where a metric was not measured
during tune, the tune time RSQ status will read back as 0
for the unmeasured metric. The normal running time sta-
tus for these metrics is not affected and will report nor-
mally.
0 = SNR measurement in progress (tune in progress) or
not taken (tune completed).
1 = SNR measurement ready.
2 4 RSSIREADY The SNRREADY and RSSIREADY bits indicate that the
RSSI/SNR have been read as a result of a tune command.
If either one of these bits are 0 this indicates that either the
metric is being measured (because a tune is in progress)
or that the metric was not measured during tune because
the station was invalidated before the metric could be
measured. In the case where a metric was not measured
during tune, the tune time RSQ status will read back as 0
for the unmeasured metric. The normal running time sta-
tus for these metrics is not affected and will report nor-
mally.
0 = RSSI measurement in progress (tune in progress) or
not taken (tune completed).
1 = RSSI measurement ready.
RESP Bit Name Function
AN543
Rev. 0.9 61
2 3 Reserved Values may vary.
2 2 INJSIDE Injection side used.
0 = Low-side injection is being used
1 = High-side injection is being used
2 1 AFCRL Set if the AFC rails. AFC gets railed if FREQOFF >
FM_VALID_MAX_TUNE_ERROR.
2 0 VALID (Si475x-A20 and earlier)
Reports if the channel is valid based on the settings of:
FM_VALID_RSSI_THRESHOLD,
FM_VALID_SNR_THRESHOLD,
FM_VALID_MAX_TUNE_ERROR
(Si475x-A30 and later)
Reports if the channel is valid based on the settings of:
FM_VALID_RSSI_THRESHOLD,
FM_VALID_SNR_THRESHOLD,
FM_VALID_MAX_TUNE_ERROR,
FM_VALID_ASSI_THRESHOLD,
FM_VALID_ISSI_THRESHOLD
3,4 15:0 READFREQ[15:0] Returns the currently tuned frequency.
5 7:0 FREQOFF[7:0] Signed frequency offset in units set by
FM_VALID_FREQOFF_SCALE (–128 to 126)
6 7:0 RSSI[7:0] Received Signal Strength indicator in dBµV
(–128 to 127)
7 7:0 SNR[7:0] RF SNR indicator in dB (–128 to 127).
8 7:0 ISSI[7:0] Image Signal Strength Indicator reports the image power
relative to carrier (–128 to 127). This metric is only valid
when ATTUNE = 1.
Only applicable to Si475x-A30 and later.
9 7:0 LASSI[7:0] Low side Adjacent (100 kHz) Channel Strength Indicator
reports the (Signal + Noise) power relative to the
carrier.(–128 to 127)
10 7:0 HASSI[7:0] High side Adjacent (100 kHz) Channel Strength Indicator
reports the (Signal + Noise) power relative to the
carrier.(–128 to 127)
11 7:0 MULT[7:0] Multipath Indicator.
(For Si475x-A20 and later)
Range: 0–100%
(ForSi475x-A10)
Multipath = MULT/127 x 100%
Range: 0–127
12 7:0 DEV[7:0] Frequency Deviation metric in kHz.
13, 14 15:0 Reserved Values may vary.
RESP Bit Name Function
AN543
62 Rev. 0.9
Command 0x35 FM _A CF _S TATUS
The FM_ACF_STATUS command returns status information about automatically-controlled features. This
command returns the Soft Mute Attenuation, Channel Filter Bandwidth, HICUT cutoff frequency, HIBLEND cutoff
frequency, and Stereo Separation associated with the desired channel. Stereo Separation will only be non-zero if
the pilot indicator is set. If SMUTE bit is high, it indicates that audio is soft-muted. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This command may only be sent in powerup mode.
Command
15 7:0 ASSI200[7:0] Adjacent Channel (±200 kHz) Strength Indicator reports
the (Signal + Noise) power relative to the carrier. This
metric reports the sum of high and low adjacent channel
strengths. (–128 to 127)
16 7:0 USN[7:0] Ultrasonic Noise Indicator in –dBFS (0 to 127). 127
corresponds to 127 dB down from full scale.
17 7:0 PILOTDEV[7:0]
(Only applicable to Si475x-A30 and later) Pilot deviation in
units of 100 Hz.
Range:0-127
18 7:0 RDSDEV[7:0] (Only applicable to Si475x-A30 and later) RDS deviation
in units of 100 Hz.
19 7:0 ASSI200DEV[7:0]
(Only applicable to Si475x-A30 and later) Adjacent
Channel (±200 kHz) Deviation. Deviation is equal to
ASSI200DEV x 1.5 kHz minus 12 kHz.
20 7:0 STRONGDEV[7:0]
(Only applicable to Si475x-A30 and later) Deviation of
very strong desired signals. This is an alternative to DEV,
which can become erroneous in the presence of very
strong signals. STRONGDEV is the weighted sum of FM
mono/stereo (L + R) and stereo (L – R) deviation.
Approximately, deviation in kHz = STRONGDEV x f(mod),
where f(mod) is 5.55 kHz for mono signals, or 2.75 kHz for
stereo signals.
21,22 15:0 RDSPI[15:0] (Only applicable to Si475x-A30 and later) RDS PI code.
Bit76543210
CMD 0x35
ARG1 0000000 ACFACK
ARG Bit Name Function
1 7:1 Reserved Always write 0000000.
1 0 ACFACK If set clears ACFINT and any ACF interrupts bits.
RESP Bit Name Function
AN543
Rev. 0.9 63
Response
Bit 7 6 5 4 3 2 1 0
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
RESP1 XX CHBWH_
INT
BLEND_
INT
HIBLEND_
INT
HICUT_
INT
CHBW_
INT
SOFTMUTE_
INT
RESP2 XXXXXXX SMUTE
RESP3 XXX SMATTN[4:0]
RESP4 CHBW[7:0]
RESP5 HICUT[7:0]
RESP6 HIBLEND[7:0]
RESP7 PILOT STBLEND[6:0]
RESP8 LOWCUT[7:0]
AN543
64 Rev. 0.9
RESP Bit Name Function
1 7:6 Reserved Values may vary.
1 5 CHBWH_INT
(Available on Si475x-A40 only.)
If set, indicates that the channel filter bandwidth is greater than
the threshold set by FM_ACF_CHBW_THRESHOLD.
1 4 BLEND_INT If set, indicates that stereo separation has crossed below the
blend threshold set by FM_ACF_BLEND_THRESHOLD.
1 3 HIBLEND_INT If set, indicates that the HIBLEND cutoff frequency is lower than
the threshold as set by FM_ACF_HIBLEND_THRESHOLD.
1 2 HICUT_INT If set, indicates that the HICUT cutoff frequency is lower than the
threshold set by FM_ACF_HICUT_THRESHOLD.
11CHBW_INT
If set, indicates that the Channel Filter Bandwidth is less than
the threshold set by FM_ACF_CHBW_THRESHOLD.
1 0 SOFTMUTE_INT If set, indicates that softmute attenuation has increased above
the softmute threshold as set by ACF_SM_THRESHOLD.
2 7:1 Reserved Values may vary.
20 SMUTE
0 = Audio is not soft muted.
1 = Audio is soft muted.
3 7:5 Reserved Values may vary.
34:0SMATTN[7:0]
Soft mute attenuation level in dB.
Range: 0–31.
4 7:0 CHBW[7:0] Channel filter bandwidth in kHz.
Range: 0–150.
57:0HICUT[7:0]
LPR cutoff frequency in units of 100 Hz.
Range: 10–180.
6 7:0 HIBLEND[7:0] LMR cutoff frequency in units of 100 Hz.
Range: 10–180.
77 PILOT
0 = Stereo pilot is not present.
1 = Stereo pilot is present.
7 6:0 STBLEND[6:0] Indicates stereo separation. STBLEND will only be non-zero if
PILOT = 1. Range 0–100.
8 7:0 LOWCUT[7:0]
(Available in Si475x-A30 and later.)
Lowcut cutoff frequency in units of 10 Hz. Only available if low-
cut is enabled by the FM_LOWCUT_MIN_FREQ property.
Range 1–100.
AN543
Rev. 0.9 65
Command 0x36 FM_RDS_STATUS (Si4751/53/55/57 Only)
The FM_RDS_STATUS command returns RDS information for current channel and reads an entry from the RDS
FIFO. RDS information includes synch status, FIFO status, group data (blocks A, B, C, and D), and block errors
corrected. Maximum RDS FIFO size is 25 groups. This command clears the RDSINT interrupt bit when INTACK bit
in ARG1 is set, and, if MTFIFO is set, the entire RDS receive FIFO is cleared (FIFO is always cleared during
FM_TUNE_FREQ or FM_SEEK_START). The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This command may only be sent in powerup mode.
Command
Bit76543 2 1 0
CMD 0x36
ARG1 00000 STATUS_ONLY MTFIFO INTACK
ARG Bit Name Function
1 7:3 Reserved Always write 00000.
12STATUS_ONLY
Status Only.
Determines if data should be removed from the RDS FIFO.
0 = Data is removed from RDS FIFO, and RDSFIFOUSED decre-
ments by one. Data in BLOCKA, BLOCKB, BLOCKC, BLOCKD,
and BLE contain the oldest data in the RDS FIFO.
1 = Data is not removed from RDSFIFO, and the RDSFIFOUSED
value stays the same. Data in BLOCKA, BLOCKB, BLOCKC,
BLOCKD, BLE, PI, TP, PTY, and status contain the last valid data
received for the current station.
1 1 MTFIFO
Empty FIFO.
The FIFO will always be cleared during FM_TUNE_FREQ and
FM_SEEK_START.
0 = If FIFO not empty, read and remove oldest FIFO entry.
1 = Clear RDS Receive FIFO.
10 INTACK
Interrupt Acknowledge.
0 = RDSINT status preserved.
1 = Clears RDSINT.
AN543
66 Rev. 0.9
Response
Bit 7 6 5 4 3 2 1 0
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
RESP1 XXX RDSTPPTYINT RDSPIINT X RDSSYNCINT RDSFIFOINT
RESP2 XXX TPPTYVALID PIVALID X RDSSYNC RDSFIFOLOST
RESP3 XX TP PTY[4:0]
RESP4 PI[15:8]
RESP5 PI[7:0]
RESP6 RDSFIFOUSED[7:0]
RESP7 BLEA[1:0] BLEB[1:0] BLEC[1:0] BLED[1:0]
RESP8 BLOCKA[15:8]
RESP9 BLOCKA[7:0]
RESP10 BLOCKB[15:8]
RESP11 BLOCKB[7:0]
RESP12 BLOCKC[15:8]
RESP13 BLOCKC[7:0]
RESP14 BLOCKD[15:8]
RESP15 BLOCKD[7:0]
RESP16 IQSNR[7:0]
AN543
Rev. 0.9 67
RESP Bit Name Function
1 7:5 Reserved Values may vary.
14RDSTPPTYINT
1 = TP (Traffic Program) flag and/or PTY (Program Type) code
has changed.
1 3 RDSPIINT 1 = PI (Program Identification) code has changed.
1 2 Reserved Values may vary.
1 1 RDSSYNCINT 1 = RDS synchronization has changed.
1 0 RDSFIFOINT 1 = RDS was received and the RDS FIFO is full or has atleast
FM_RDS_INTERRUPT_FIFO_COUNT entries.
2 7:5 Reserved Values may vary.
2 4 TPPTYVALID 1 = Indicates that TP flag and PTY code are valid.
2 3 PIVALID 1 = Indicates that PI code is valid.
2 2 Reserved Values may vary.
2 1 RDSSYNC 1 = RDS is currently synchronized.
2 0 RDSFIFOLOST 1 = Indicates that one or more RDS groups have been discarded
due to FIFO overrun since last call to FM_RDS_STATUS.
3 7:6 Reserved Values may vary.
3 5 TP Current channel’s TP flag if TPPTYVALID is set to 1.
3 4:0 PTY[4:0] Current channel's PTY code if TPPTYVALID is 1.
4,5 15:0 PI[15:0] Current channel’s PI code if PIVALID is set to 1.
6 7:0 RDSFIFOUSED[7:0]
RDS FIFO Used.
Number of groups remaining in the RDS FIFO (0 if empty). If
non-zero, BLOCKA-BLOCKD contain the oldest FIFO entry and
RDSFIFOUSED decrements by one on the next call to RDS_FI-
FO_STATUS (assuming no RDS data received in the interim).
7 7:6 BLEA[1:0]
RDS Block A Corrected Errors.
0 = No errors.
1 = 1–2 bit errors detected and corrected.
2 = 3–5 bit errors detected and corrected.
3 = Uncorrectable.
7 5:4 BLEB[1:0]
RDS Block B Corrected Errors.
0 = No errors.
1 = 1–2 bit errors detected and corrected.
2 = 3–5 bit errors detected and corrected.
3 = Uncorrectable.
7 3:2 BLEC[1:0]
RDS Block C Corrected Errors.
0 = No errors.
1 = 1–2 bit errors detected and corrected.
2 = 3–5 bit errors detected and corrected.
3 = Uncorrectable.
AN543
68 Rev. 0.9
7 1:0 BLED[1:0]
RDS Block D Corrected Errors.
0 = No errors.
1 = 1–2 bit errors detected and corrected.
2 = 3–5 bit errors detected and corrected.
3 = Uncorrectable.
8,9 15:0 BLOCKA[15:0] Block A group data from oldest FIFO entry if STATUSONLY is 0.
Last valid Block A data if STATUSONLY is 1.
10,11 15:0 BLOCKB[15:0] Block B group data from oldest FIFO entry if STATUSONLY is 0.
Last valid Block B data if STATUSONLY is 1.
12,13 15:0 BLOCKC[15:0] Block C group data from oldest FIFO entry if STATUSONLY is 0.
Last valid Block C data if STATUSONLY is 1.
14,15 15:0 BLOCKD[15:0] Block D group data from oldest FIFO entry if STATUSONLY is 0.
Last valid Block D data if STATUSONLY is 1.
16 7:0 IQSNR[7:0]
(Available in Si475x-A40 and later.)
RDS I/Q SNR.
Range: –128 to 127
RESP Bit Name Function
AN543
Rev. 0.9 69
Command 0x37 FM_RDS_BLOCKCOUNT (Si4751/53/55/57 Only)
The FM_RDS_BLOCKCOUNT command returns RDS expected, received, and uncorrectable block statistic
information. Reset info by setting CLEAR bit or sending FM_TUNE_FREQ or FM_SEEK_START commands. Once
EXPECTED saturates at 65535, all other block count statistics will be frozen until the counts are cleared. The CTS
bit (and optional interrupt) is set when it is safe to send the next command. This command may only be sent when
in powerup mode.
Command
Response
Bit76543210
CMD 0x37
ARG1 0000000 CLEAR
ARG Bit Name Function
1 7:1 Reserved Always write 0000000.
1 0 CLEAR Clears the block counts if set. The current block counts will be
reported before they are cleared.
Bit76543210
STATUS CTS ERR XX RSQINT RDSINT ACFINT STCINT
RESP1 XXXXXXXX
RESP 2 EXPECTED[15:8]
RESP 3 EXPECTED[7:0]
RESP 4 RECEIVED[15:8]
RESP 5 RECEIVED[7:0]
RESP 6 UNCORRECTABLE[15:8]
RESP 7 UNCORRECTABLE[7:0]
AN543
70 Rev. 0.9
RESP Bit Name Function
1 7:0 Reserved Values may vary.
2,3 15:0 EXPECTED[15:0] Number of expected RDS blocks.
4,5 15:0 RECEIVED[15:0]
Number of received RDS blocks. Under ideal condi-
tions, EXPECTED and RECEIVED would be identi-
cal. The difference between these two numbers is
the number of blocks lost.
6,7 15:0 UNCORRECTABLE[15:0]
Number of uncorrectable RDS blocks. These blocks
have been received, but were found to have uncor-
rectable errors. The block error rate (BLER) is cal-
culated by: BLER = (UNCORRECTABLE +
(EXPECTED-RECEIVED)) / EXPECTED
AN543
Rev. 0.9 71
7.2.2. FM Rece iv er Pro p e rt ie s
Property 0x0302 AUDIO_DE_EMPHASIS
The AUDIO_DE_EMPHASIS property sets the FM Receive deemphasis to 50 or 75 μs. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
The default is 75 μs.
Default: 0
Property 0x0400 FM_ SOFT_MUTE_MAX_ATTENUATION
The FM_SOFT_MUTE_MAX_ATTENUATION property sets the maximum attenuation in dB that will be applied by
the softmute feature. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: 8
Units: dB
AUDIO_DE_EMPHASIS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x0000 DE_EMPH
0x0000 0
Bit Name Function
15:1 Reserved Always write 0.
0 DE_EMPH
Sets the FM Receive de-emphasis to 50 or 75 μs. Default is 75 µs.
0=75µsec
1=50µsec
FM_SOFT_MUTE_MAX_ATTENUATION
1514131211109876543210
0x000 SMATTN[6:0]
0x000 0x08
Bit Name Function
15:7 Reserved Always write 0.
6:0 SMATTN[6:0]
Sets the maximum attenuation in dB that will be applied by the softmute
feature. Default is 8 dB.
(Si475x-A20 and earlier)
Range is 0-31.
(Si475x-A30 and later)
Range is 0–63 dB.
AN543
72 Rev. 0.9
Property 0x0401 FM_ SOFT_MUTE_TRIGGER_THRESHOLD
The FM_SOFT_MUTE_TRIGGER_THRESHOLD property sets the RSSI/SNR threshold in dB to engage softmute.
If USE_RSSI is set in FM_ACF_CONTROL_SOURCE property, then property 0x0401 refers to RSSI threshold. If
USE_RSSI is not set, this property refers to SNR threshold. The CTS bit (and optional interrupt) is set when it is
safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 8
Si475x/5xC-A55, Default: 2
Units: dB
FM_SOFT_MUTE_TRIGGER_THRESHOLD
1514131211109876543210
SNR_SMTRGTH[7:0] RSSI_SMTRGTH[7:0]
0x00 0x02
Bit Name Function
15:8 SNR_SMTRGTH[7:0]
Sets the SNR threshold in dB to engage softmute, default is 0.
Range is -127 ~ 127.
This field is only available in Si475x/5xC-A55.
7:0 RSSI_SMTRGTH[7:0]
Sets the RSSI threshold in dB to engage softmute.
Si475x/5xC-A55, Default is 2 dB
Range is 0 to 15 dB for Si475x-A10 and –127 to 127 dB for
Si475x-A20 or
later.
AN543
Rev. 0.9 73
Property 0x0402 FM_SOFT_MUTE_END_THRESHOLD
The FM_SOFT_MUTE_END_THRESHOLD property sets the SNR threshold in dB at which softmute attenuation
will be set to its maximum value. When the SNR is at this level or lower, the audio attenuation will be set to
FM_SOFT_MUTE_MAX_ATTENUATION. If USE_RSSI is set in the FM_ACF_CONTROL_SOURCE property,
then property 0x0402 refers to the RSSI threshold. If USE_RSSI is not set, this property refers to SNR threshold.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Si475x-A40 and earlier, Default: 0
Si475x/5xC-A55, Default: -6
Units:dB
Property 0x0403 FM_SOFT_MUTE_RELEASE_TIME
The FM_SOFT_MUTE_RELEASE_TIME property sets the maximum time in ms it takes to unmute the audio. The
CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or
read in powerup mode.
Default: 500
Units: ms
FM_SOFT_MUTE_END_THRESHOLD
1514131211109876543210
SNR_SMENDTH[7:0] RSSI_SMENDTH[7:0]
0x00 0xFA
Bit Name Function
15:8 SNR_SMENDTH[7:0]
Sets SNR threshold in dB to end the softmute, default is 0.
Range is –127 ~ 127
This field is only available in Si475x/5xC-A55.
7:0 RSSI_SMENDTH[7:0]
Sets the RSSI threshold in dBuV to end the softmute.
Si475x/5xC-A55, Default is –6 dB. Si475x-A40 and earlier, default is 0.
Range is 0 to 15 dB for Si475x-A10, and –127 to127 dB for Si475x-A20 or
later.
FM_SOFT_MUTE_RELEASE_TIME
1514131211109876543210
RELEASE[15:0]
0x01F4
AN543
74 Rev. 0.9
Property 0x0404 FM_SOFT_MUTE_ATTACK_TIME
The FM_SOFT_MUTE_ATTACK_TIME property sets the maximum time in ms it takes to mute the audio. The CTS
bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A20 and earlier, Si475x-A40 and later: This property is not available
Units: ms
Property 0x0405 FM_SOFT_MUTE_MAX_ATTENUATION_AGC (Si4754/55/56/57 Only)
When AGC is engaged, the FM_SOFT_MUTE_MAX_ATTENUATION_AGC property sets the maximum
attenuation in dB that will be applied by the RSSI/SNR softmute feature. The CTS bit (and optional interrupt) is set
when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0x0080
Bit Name Function
15:0 RELEASE[15:0]
Sets the maximum time in ms it takes to unmute the audio. Note that there
will be 16 ms of filter delay for RSSI/SNR metric before softmute can
engage/disengage.
Default is 500 ms. Range is 1–32767 ms.
FM_SOFT_MUTE_ATTACK_TIME
1514131211109876543210
ATTACK[15:0]
0x0078
Bit Name Function
15:0 ATTACK[15:0]
Sets the maximum time in ms it takes to mute the audio. Note that there will
be 16 ms of filter delay for RSSI/SNR metric before softmute can engage/
disengage.
Default is 120 ms. Range is 1–32767 ms.
FM_SOFT_MUTE_MAX_ATTENUATION_AGC
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x00 IGNORE_AGC SMATTN[6:0]
0x00 1 0x00
AN543
Rev. 0.9 75
Property 0x0406 FM_SOFT_MUTE_TRIGGER_THRESHOLD_AGC (Si4754/55/56/57 Only)
When AGC is engaged, the FM_SOFT_MUTE_TRIGGER_THRESHOLD_AGC property sets the RSSI/SNR
threshold in dB to engage softmute. If USE_RSSI bit is set in FM_ACF_CONTROL_SOURCE property (0x1306),
then this property refers to RSSI threshold. If USE_RSSI bit is not set, this property refers to SNR threshold. The
CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or
read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 8
Units: dB
Bit Name Function
15:8 Reserved Always write to 0.
7 IGNORE_AGC
Selects which set of properties control softmute when AGC is engaged.
0 = Use properties 0x0405-0x0409 when the AGC is engaged, and proper-
ties 0x0400-0x0404 otherwise.
1 = Always use only properties 0x0400-0x0404.
6:0 SMATTN[6:0]
When AGC is engaged, sets the maximum attenuation in dB that will be
applied by the RSSI/SNR softmute feature. Default is 0 dB. Range is 0–
63 dB.
FM_SOFT_MUTE_TRIGGER_THRESHOLD_AGC
1514131211109876543210
0x00 SMTRGTH_AGC[7:0]
0x00 0x08
Bit Name Function
15:8 Reserved Always write to 0.
7:0 SMTRGTH_AGC[7:0] When AGC is engaged, sets the RSSI/SNR threshold in dB to engage soft-
mute. Default is 8 dB. Range is –127 to 127 dB.
AN543
76 Rev. 0.9
Property 0x0407 FM_S OFT_MUTE_END_THRESHOLD_AGC (Si4754/55/56/57 Only)
When AGC is engaged, the FM_SOFT_MUTE_END_THRESHOLD_AGC property sets the RSSI/SNR threshold
in dB at which softmute attenuation will be set to its maximum value. When the RSSI/SNR is at this level or lower,
the audio attenuation will be set to FM_SOFT_MUTE_MAX_ATTENUATION_AGC. If USE_RSSI bit is set in
FM_ACF_CONTROL_SOURCE property (0x1306), then this property refers to RSSI threshold. If USE_RSSI bit is
not set, this property refers to SNR threshold. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0
Units: dB
Property 0x0408 FM_SOFT_MUTE_RELEASE_TIME_AGC (Si4754/55/56/57 Only)
When AGC is engaged, the FM_SOFT_MUTE_RELEASE_TIME_AGC property sets maximum time in ms it takes
to unmute the audio. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 500
Units: ms
FM_SOFT_MUTE_END_THRESHOLD_AGC
1514131211109876543210
0x00 SMTRGTH_AGC[7:0]
0x00 0x08
Bit Name Function
15:8 Reserved Always write to 0.
7:0 SMTRGTH_AGC[7:0] When AGC is engaged, sets the RSSI/SNR threshold in dB to engage soft-
mute. Default is 8 dB. Range is –127 to 127 dB.
FM_SOFT_MUTE_RELEASE_TIME_AGC
1514131211109876543210
RELEASE_AGC[15:0]
0x01F4
Bit Name Function
15:0 RELEASE_AGC[15:0]
Sets the maximum time in ms it takes to unmute the audio. Note that there
will be 16 ms of filter delay for RSSI/SNR metric before softmute can
engage/disengage.
Default is 500 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 77
Property 0x0409 FM_SOFT_MUTE_ATTACK_TIME_AGC (Si4754/55/56/57 Only)
When AGC is engaged, the FM_SOFT_MUTE_ATTACK_TIME_AGC property sets maximum time in ms it takes to
mute the audio. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property
may only be set or read in powerup mode.
Si475x-A20 and earlier, Si475x-A40 and later: This property is not available
Si475x-A30, Default: 120
Units: ms
Property 0x040A FM_SOFT_MUTE_USN_LIMITS
The FM_SOFT_MUTE_USN_LIMITS property sets the values of USN for which audio is minimally and maximally
muted by USN-based soft mute. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Note: USN will generally be negative under signal conditions where soft mute is desirable. The recommended setting is
0xCEE2 (YMIN = –50, YMAX = –30).
Si475x-A20 and earlier, Si475x-A40 and later: This property is not available
Si475x-A30, Default: 0x060E
Units: ms
FM_SOFT_MUTE_ATTACK_TIME_AGC
1514131211109876543210
ATTACK_AGC[15:0]
0x0078
Bit Name Function
15:0 ATTACK_AGC[15:0]
Sets the maximum time in ms it takes to unmute the audio. Note that
there will be 16 ms of filter delay for RSSI/SNR metric before softmute
can engage/disengage.Default is 120 ms. Range is 1–32767 ms.
FM_SOFT_MUTE_USN_LIMITS
1514131211109876543210
YMIN[7:0] YMAX[7:0]
0x06 0x0E
Bit Name Function
15:8 YMIN[7:0] Sets the value of USN that causes minimum attenuation for USN-
based soft mute. Default is 6. Range is –127 to 127.
7:0 YMAX[7:0] Sets the value of USN that causes maximum attenuation for
USN-based soft mute. Default is 14. Range is –127 to 127.
AN543
78 Rev. 0.9
Property 0x040B FM_SOFT_MUTE_USN_ATTENUATION
The FM_SOFT_MUTE_USN_ATTENUATION property sets the limits for soft mute attenuation when driven by
USN. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only
be set or read in powerup mode.
Si475x-A20 and earlier, Si475x-A40 and later: This property is not available.
Si475x-A30, Default: 0x0000
Units: dB
Property 0x040C FM_SOFT_MUTE_USN_ATTACK_TIME
The FM_SOFT_MUTE_USN_ATTACK_TIME property sets maximum time in ms it takes to mute the audio based
on USN. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Si475x-A20 and earlier, Si475x-A40 and later: This property is not available.
Si475x-A30, Default: 0x0080
Units: ms
FM_SOFT_MUTE_USN_ATTENUATION
1514131211109876543210
YMIN[7:0] YMAX[7:0]
0x00 0x00
Bit Name Function
15:8 YMIN[7:0] Sets the minimum attenuation in dB for USN-based soft mute.
Default is 0. Range is 0–63.
7:0 YMAX[7:0] Sets the maximum attenuation in dB for USN-based soft mute.
Default is 0. Range is 0–63.
FM_SOFT_MUTE_USN_ATTACK_TIME
1514131211109876543210
ATTACK[15:0]
0x0080
Bit Name Function
15:0 ATTACK[15:0]
Sets the USN-based soft mute attack time in ms. Note that there
will be 16 ms of filter delay for USN metric before softmute can
engage/disengage. Default is 128. Range is 1–32767.
AN543
Rev. 0.9 79
Property 0x040D FM_SOFT_MUTE_ USN_RELEASE_TIME
The FM_SOFT_MUTE_USN_RELEASE_TIME property sets maximum time in ms it takes to unmute the audio
based on USN. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property
may only be set or read in powerup mode.
Si475x-A20 and earlier, Si475x-A40 and later: This property is not available
Si475x-A30, Default: 0x0100
Units: ms
Property 0x040E FM_SOFT_MUTE_ASSI20 0DEV_LIMITS
The FM_SOFT_MUTE_ASSI200DEV_LIMITS property sets the ASSI200DEV threshold to engage softmute and
sets the ASSI200DEV threshold at which softmute attenuation will be set to its maximum value. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A10 and earlier: Range: 4–248 ms.
Si475x-A20 and later: Range is 4–4096 ms.
FM_SOFT_MUTE_USN_RELEASE_TIME
1514131211109876543210
RELEASE[15:0]
0x0004
Bit Name Function
15:0 RELEASE[15:0]
Sets the USN-based soft mute release time in ms. Note that
there will be 16 ms of filter delay for USN metric before softmute
can engage/disengage.
Default is 256.
Range is 1–32767.
FM_SOFT_MUTE_ASSI200DEV_LIMITS
1514131211109876543210
SMTRGTH_ASSI200DEV[7:0] SMENDTH_ASSI200DEV[7:0]
0x33 0x5A
Bit Name Function
15:8 SMTRGTH_ASSI200DEV[7:0] Sets the ASSI200DEV threshold to engage softmute. Default is
51. Range is 0 to 150.
7:0 SMENDTH_ASSI200DEV[7:0] Sets the ASSI200DEV threshold at which softmute attenuation
will be set to its maximum value. Default is 90. Range is 0 to 150.
AN543
80 Rev. 0.9
Property 0x040F FM_SOFT_MUTE_ASSI2 00DEV_ATTENUATION
The FM_SOFT_MUTE_ASSI200DEV_ATTENUATION property sets the maximum attenuation in dB that will be
applied by the ASSI200DEV softmute feature. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0
Units: dB
Property 0x0410 FM_SOFT_MUTE_ASSI200DEV_ATTACK_TIME
The FM_SOFT_MUTE_ASSI200DEV_ATTACK_TIME property sets maximum time in ms it takes to mute the
audio. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only
be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 128
Units: ms
FM_SOFT_MUTE_ASSI200DEV_ATTENUATION
1514131211109876543210
0x00 SMATTN_ASSI200DEV[6:0]
0x00 0x00
Bit Name Function
15:8 Reserved Always write to 0.
7:0 SMATTN_ASSI200DEV[6:0]
Sets the maximum attenuation in dB that will be applied by the
ASSI200DEV softmute feature. Default is 0 dB. Range is 0–
63 dB.
FM_SOFT_MUTE_ASSI200DEV_ATTACK_TIME
1514131211109876543210
ATTACK_ASSI200DEV[15:0]
0x0080
Bit Name Function
15:0 ATTACK_ASSI200DEV[15:0]
Sets the maximum time in ms it takes to mute the audio.
Note that there will be 16 ms of filter delay for the ASSI200DEV
metric before softmute can engage/disengage.
Default is 128 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 81
Property 0x0411 FM_SOFT_MUTE_ASSI200DEV_RELEASE_TIME
The FM_SOFT_MUTE_ASSI200DEV_RELEASE_TIME property sets maximum time in ms it takes to unmute the
audio. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only
be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 256
Units: ms
Property 0x0700 FM_AGC_FE_CONFIG
The FM_AGC_FE_CONFIG property specifies the input path for the RF signal and other FE configuration options.
This property should only be set before the first tune. The CTS bit (and optional interrupt) is set when it is safe to
send the next command. This property may only be set or read in powerup mode. Changes to this property take
effect after the next tune is completed.
Default: 0x0080
FM_SOFT_MUTE_ASSI200DEV_RELEASE_TIME
1514131211109876543210
RELEASE_ASSI200DEV[15:0]
0x0100
Bit Name Function
15:0 RELEASE_ASSI200DEV[15:0]
Sets the maximum time in ms it takes to unmute the audio.
Note that there will be 16 ms of filter delay for the ASSI200DEV
metric before softmute can engage/disengage.
Default is 256 ms. Range is 1–32767 ms.
FM_AGC_FE_CONFIG
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x00 FMLNAZ 1000 INPUTSELECT[3:0]
0x00 0 1000 0x0
Bit Name Function
15:9 Reserved Always write 0.
8FMLNAZ
0 = LNA input impedance is 50 .(Normal Operation)
1 = LNA input impedance is 100 (Loop-through mode: two receiv-
ers splitting a single antenna signal) (Si4754/55/56/57 only)
7:4 Reserved Always write 1000.
3:0 INPUTSELECT[3:0]
0 = Received signal comes into FMI pin, out FMO and then the
mixer pin.
1 = Received signal comes directly into the mixer at the FMXIP/
FMIN pins.
AN543
82 Rev. 0.9
Property 0x0701 FM_AGC_PD_CONFIG
The FM_AGC_PD_CONFIG property specifies behavior of the FM peak detectors and attenuators. This property
should only be set before the first tune. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This command may only be sent in powerup mode. Changes to this property take effect after the next
tune is completed.
Default: 0x0270
FM_AGC_PD_CONFIG
151413 12 1110 9 8 765432 1 0
0x0 LNA_MODE 00100 MIXER_PD[2:0] 0x00 LNA_PD[1:0]
0x0 0 00100 0x7 0x00 0x00
Bit Name Function
15:13 Reserved Always write 0.
12 LNA_MODE
LNA_MODE default: 0 This property only used when the LNA gain
and one or both of the attenuators are controlled by the same peak
detector.
0 = Reduce LNA gain and then attenuate with FMAGC1/2.
1 = Attenuate with FMAGC1/2 and then reduce LNA gain.
11:7 Reserved Always write 00100.
6:4 MIXER_PD[2:0]
MIXER_PD[2:0] default: 0x7.
0 = Peak detector not used.
1 = Controls FMAGC1.
2 = Controls FMAGC2.
3 = Controls FMAGC1 and FMAGC2.
4 = Controls LNA gain.
5 = Controls LNA gain and FMAGC1.
6 = Controls LNA gain and FMAGC2.
7 = Controls LNA gain, FMAGC1 and FMAGC2.
3:2 Reserved Always write 0.
1:0 LNA_PD[1:0]
LNA_PD[1:0] default: 0x0
0 = Peak detector not used
1 = Controls FMAGC1
2 = Controls FMAGC2
3 = Controls FMAGC1 and FMAGC2
AN543
Rev. 0.9 83
Property 0x0702 FM_LNA_AGC_ATTACK_MS
The FM_LNA_AGC_ATTACK_MS property sets the number of milliseconds the wide-band RF high-peak detector
must be exceeded before attenuating the appropriate block. The peak detectors are only sampled once every 3 to
5 ms. If the peak detector trips, the internal counter is incremented by 4 ms.The CTS bit (and optional interrupt) is
set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 4
Units: ms
FM_LNA_AGC_ATTACK_MS
1514131211109876543210
RF_AGC_ATTACK_MS[15:0]
0x0004
Bit Name Function
15:0 RF_AGC_ATTACK_MS[15:0]
Number of milliseconds the wideband RF high-
peak detector must be exceeded before atten-
uating the appropriate block.
Default is 4 ms.
Si475x-A10 and earlier: Range: 4–248 ms.
Si475x-A20 and later: Range is 4–4096 ms.
AN543
84 Rev. 0.9
Property 0x0703 FM_LNA_AGC_RELEASE_MS
The FM_LNA_AGC_RELEASE_MS property sets the number of milliseconds the wideband RF low-peak detector
must not be exceeded before increasing the gain of the appropriate block. The peak detectors are only sampled
once every 3 to 5 ms. If the peak detector trips, the internal counter is incremented by 4 ms. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 80
Units: ms
FM_LNA_AGC_RELEASE_MS
1514131211109876543210
RF_AGC_RELEASE_MS[15:0]
0x0050
Bit Name Function
15:0 RF_AGC_RELEASE_MS[15:0]
Number of milliseconds the wideband RF low-peak detector must not
be exceeded before increasing the gain of the appropriate block.
Default is 80 ms
Si475x-A10 and earlier: Range: 4–248 ms.
Si475x-A20 and later: Range is 4–4096 ms.
AN543
Rev. 0.9 85
Property 0x0704 FM_LNA_AGC_PD_THRESHOLD
The FM_LNA_AGC_PD_THRESHOLD property sets the high threshold and hysteresis for the LNA peak detector.
The high threshold sets the level at which the AGC increases attenuation. The hysteresis is how many dB below
the high threshold the level must drop before the AGC decreases attenuation. It is possible to decrease the
likelihood of intermod break-in by decreasing the peak detector threshold from the default and it is possible to
decrease the likelihood of desensitization by increasing the peak detector threshold. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 0x4F05
FM_LNA_AGC_PD_THRESHOLD
1514131211109876543210
HIGH[7:0] HYST[7:0]
0x4F 0x05
Bit Name Function
15:8 HIGH[7:0]
Sets the level in dBµV at which AGC increases attenuation
HIGH[7:0] Range: 73–87
73 = 73 dBµV
75 = 75 dBµV
77 = 77 dBµV
79 = 79 dBµV
81 = 81 dBµV
83 = 83 dBµV
85 = 85 dBµV
87 = 87 dBµV
7:0 HYST[7:0]
Sets how many dB below the high threshold the level must drop
before the AGC decreases attenuation.
HYST[7:0] Range: 3–6
3 = 3 dB
4 = 4 dB
5 = 5 dB
6 = 6 dB
AN543
86 Rev. 0.9
Property 0x0705 FM_MIXER_AGC_ATTACK_MS
The FM_MIXER_AGC_ATTACK_MS property sets the number of milliseconds the wideband mixer high-peak
detector must be exceeded before attenuating the appropriate block. The peak detectors are only sampled once
every 3–5 ms. If the peak detector trips, the internal counter is incremented by 4 ms. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 4
Si475x/5xC-A55, Default: 248
Units: ms
FM_MIXER_AGC_ATTACK_MS
1514131211109876543210
MIX_AGC_ATTACK_MS[15:0]
0x00F8
Bit Name Function
15:0 MIX_AGC_ATTACK_MS[15:0]
Number of milliseconds the wideband RF high-
peak detector must be exceeded before atten-
uating the appropriate block.
Si475x/5xC-A55, Default is 248 ms
Si475x-A10 and earlier: Range: 4–248 ms
Si475x-A20 and later: Range is 4–4096 ms
AN543
Rev. 0.9 87
Property 0x0706 FM_MIXER_AGC_RELEASE_MS
The FM_MIXER_AGC_RELEASE_MS property sets the number of milliseconds the wideband mixer low-peak
detector must not be exceeded before increasing the gain of the appropriate block. The peak detectors are only
sampled once every 3–5 ms. If the peak detector trips, the internal counter is incremented by 4 ms. The CTS bit
(and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 80
Units: ms
FM_MIXER_AGC_RELEASE_MS
1514131211109876543210
MIX_AGC_RELEASE_MS[15:0]
0x0050
Bit Name Function
15:0 MIX_AGC_RELEASE_MS[15:0]
Number of milliseconds the wideband RF low-peak detector must not
be exceeded before increasing the gain of the appropriate block.
Default is 80 ms
Si475x-A10 and earlier: Range: 4–248 ms.
Si475x-A20 and later: Range is 4–4096 ms.
AN543
88 Rev. 0.9
Property 0x0707 FM_MIXER_AGC_PD_THRESHOLD
The FM_MIXER_AGC_PD_THRESHOLD property sets the high threshold and hysteresis for the mixer peak
detector. The high threshold sets the level at which the AGC increases attenuation. The hysteresis is how many dB
below the high threshold the level must drop before the AGC decreases attenuation. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 0x5103
FM_MIXER_AGC_PD_THRESHOLD
1514131211109876543210
HIGH[7:0] HYST[7:0]
0x51 0x03
Bit Name Function
15:8 HIGH[7:0]
Sets the level in dBµV at which AGC increases attenuation.
HIGH[7:0]: Range 79–93.
79 = 79 dBµV.
81 = 81 dBµV.
83 = 83 dBµV.
85 = 85 dBµV.
87 = 87 dBµV.
89 = 89 dBµV.
91 = 91 dBµV.
93 = 93 dBµV.
7:0 HYST[7:0]
Sets how many dB below the high threshold the level must drop
before the AGC decreases attenuation.
HYST[7:0] - Range: 3–6.
3 = 3 dB.
4 = 4 dB.
5 = 5 dB.
6 = 6 dB.
AN543
Rev. 0.9 89
Property 0x0710 FM_AGC_OVERRIDE
The FM_AGC_OVERRIDE property overrides the AGC setting by disabling the AGC and forcing the gain to be
maximum. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Note: In Si475x-A30 only, property FM_AGC_PD_CONFIG should be set to 0x0000 when overriding the AGC with the
FM_AGC_OVERRIDE property. Doing so removes the automatic AGC from peak detector control. Failure to set
FM_AGC_PD_CONFIG when using FM_AGC_OVERRIDE could lead to a conflict which locks the tuner following an
FM_TUNE_FREQ command.
Default: 0x0000
Property 0x071B FM_AGC_RSSI_OFFSET
The FM_AGC_RSSI_OFFSET property sets the value of the offset applied to the RSSI value in order to account
for the front-end gain/loss due to the AGC. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read in powerup mode.
Si475x-A10 and before: This property is not available
Si475x-A20 and later, Default: 0
Units: dB
FM_AGC_OVERRIDE
1514131211109876543210
0x000 AGC_OVERRIDE[5:0]
0x000 0x000
Bit Name Function
15:6 Reserved Always write 0.
5:0 AGC_OVERRIDE[5:0]
AGC_OVERRIDE selects whether the AGC is
enabled or disabled.
0 = AGC is enabled.
0x3F = AGC is disabled and set to maximum
gain.
FM_AGC_RSSI_OFFSET
1514131211109876543210
OFFSET[7:0] RSVD[7:0]
0x00 0x00
Bit Name Function
15:8 OFFSET[7:0]
Sets the RSSI offset value to take into account front-end gain/loss.
Default is 0.
Range is –128 to 127.
7:0 Reserved Always write 0.
AN543
90 Rev. 0.9
Property 0x071C FM_MIXER_AGC_PD_THRESHOLD_MAX (Si4754/55/5 6/57 Only)
The FM_MIXER_AGC_PD_THRESHOLD_MAX property sets the maximum threshold for the mixer peak detector
when keyed AGC is engaged. The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30/A40, Default: 85
Si475x/5xC-A55, Default: 89
FM_MIXER_AGC_PD_THRESHOLD_MAX
1514131211109876543210
0x00 MAX_KEY[7:0]
0x00 0x59
Bit Name Function
15:8 Reserved Always write to 0.
7:0 MAX_KEY[7:0]
Sets the maximum level in dBuV at which AGC increases attenu-
ation.
MAX_KEY [7:0]: Range 79–93
79 = 79 dBµV.
81 = 81 dBµV.
83 = 83 dBµV.
85 = 85 dBµV.
87 = 87 dBµV.
89 = 89 dBµV.
91 = 91 dBµV.
93 = 93 dBµV
Si475x/5xC-A55, Default is 89 dBµV.
AN543
Rev. 0.9 91
Property 0x071D FM_AGC_RSSI_MIXER_KEY (Si4754/55/56/57 Only)
The FM_AGC_RSSI_MIXER_KEY property sets the RSSI threshold at which the mixer keyed AGC begins to lower
or raise the peak detector threshold. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0x140E
Property 0x1006 FM_SEEK_TUNE_CHBW_HOLD_TIME
The FM_SEEK_TUNE_CHBW_HOLD_TIME property sets the length of time Channel Filter Bandwidth is held at
specified value after Seek or Tune. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Si475x-A10: This property is not available.
Si475x-A20: This feature is not available. Do not write to this property.
Si475x-A30 and later, Default: 80
Units: ms
FM_AGC_RSSI_MIXER_KEY
1514131211109876543210
KEY_HIGH_THR[7:0] KEY_LOW_THR[7:0]
0x14 0x0E
Bit Name Function
15:8 KEY_HIGH_THR[7:0]
Sets the RSSI threshold at which the mixer keyed AGC begins to
lower the peak detector threshold.
Default is 20 dB. Range: –128 to 127 dB.
7:0 KEY_LOW_THR[7:0]
Sets the RSSI threshold at which the mixer keyed AGC begins to
raise the peak detector threshold.
Default is 14 dB. Range: –128 to 127 dB.
FM_SEEK_TUNE_CHBW_HOLD_TIME
1514131211109876543210
CHBW_HOLD_TIME[15:0]
0x0050
Bit Name Function
15:0 CHBW_HOLD_TIME[15:0] Sets the length of time Channel Filter Bandwidth is held at speci-
fied value after Seek or Tune. Default is 80ms. Range is 4-1000.
AN543
92 Rev. 0.9
Property 0x1007 FM_TUNE_CHBW
The FM_TUNE_CHBW property sets the maximum Channel Filter Bandwidth to allow during normal tune.
Narrower Channel Filter Bandwidth could be used based on RSSI, HASSI, LASSI, and ASSI200. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 80
Units: kHz
Property 0x1008 FM_TUNE_AF_CHBW (Si4754/55/56/57 Only)
The FM_TUNE_AF_CHBW property sets the Channel Filter Bandwidth during the AF tune/check. The CTS bit
(and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Note: With Si475x-A40 defaults, the RSSI metric value for AF Check settles within 2 ms. To qualify additional metrics (SNR,
Multipath, USN, LASSI, HASSI, ASSI200) users should set Property 0x2007 FM_VALID_AF_TIME to 0x0005 (5 ms) and
Property 0x1008 FM_TUNE_AF_CHBW to 0x0050 (80 kHz).
Si475x-A20 and earlier: This property is not available Si475x-A30 and A40, Default: 150
Si475x/5xC-A55, Default: 80
Units: kHz
FM_TUNE_CHBW
1514131211109876543210
0x00 TUNE_CHBW[7:0]
0x00 0x50
Bit Name Function
15:8 Reserved Always write to 0.
7:0 TUNE_CHBW[7:0]
Sets the maximum Channel Filter Bandwidth to allow during nor-
mal tune. Narrower Channel Filter Bandwidth could be used
based on RSSI, HASSI, LASSI, and ASSI200. Default is 80 kHz.
Range is 0–150.
FM_TUNE_AF_CHBW
1514131211109876543210
0x00 TUNE_AF_CHBW[7:0]
0x00 0x50
Bit Name Function
15:8 Reserved Always write to 0.
7:0 TUNE_AF_CHBW[7:0] Sets the maximum Channel Filter Bandwidth to allow during AF
tune.
Si475x/5xC-A55, Default is 80 kHz. Range is 0–150.
AN543
Rev. 0.9 93
Property 0x1100 FM_SEEK_BAND_BOTTOM
The FM_SEEK_BAND_BOTTOM property sets the bottom of the FM band for seek. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 8750
Units: 10 kHz
Property 0x1101 FM_SEEK_BAND_TOP
The FM_SEEK_BAND_TOP property sets the top of the FM band for seek. The CTS bit (and optional interrupt) is
set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 10790
Si475x/5xC-A55, Default:10800
Units: 10 kHz
FM_SEEK_BAND_BOTTOM
1514131211109876543210
FMSKFREQL[15:0]
0x222E
Bit Name Function
15:0 FMSKFREQL[15:0]
Sets the bottom of the FM band for seek. Default is 8750.
Range: 6400–10800, 64.0 MHz to 108.0 MHz.
Range: 8750–10790, Worldwide FM excluding Japan.
Range: 6580–7400, OIRT FM.
Range: 7600–9000, Japan FM.
FM_SEEK_BAND_TOP
1514131211109876543210
FMSKFREQH[15:0]
0x2A30
Bit Name Function
15:0 FMSKFREQH[15:0]
Sets the top of the FM band for seek.
Si475x/5xC-A55 Default is 10800.
Range: 6400–10800, 64.0 MHz to 108.0 MHz.
Range: 8750–10790, Worldwide FM excluding Japan. Range: 6580–7400,
OIRT FM.
Range: 7600–9000, Japan FM.
AN543
94 Rev. 0.9
Property 0x1102 FM_SEEK_FREQUENCY_SPACING
The FM_SEEK_FREQUENCY_SPACING property selects frequency spacing for FM seek. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode. The default is 100 kHz.
Default: 10
Units: 10 kHz
Property 0x1104 FM_SEEK_CHBW
The FM_SEEK_CHBW property sets the Channel Filter Bandwidth during seek. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available. Si475x-A30 and A40, Default: 110
Si475x/5xC-A55, Default: 80
Units: kHz
FM_SEEK_FREQUENCY_SPACING
1514131211109876543210
0x000 FMSKSPACE[4:0]
0x000 0x0A
Bit Name Function
15:5 Reserved Always write 0.
4:0 FMSKSPACE[4:0] Selects frequency spacing for FM
seek. Default is 10. Range is 1–31.
FM_SEEK_CHBW
1514131211109876543210
0x00 SEEK_CHBW[7:0]
0x00 0x50
Bit Name Function
15:8 Reserved Always write to 0.
7:0 SEEK_CHBW[7:0]
Sets the maximum Channel Filter Bandwidth to allow during seek.
Si475x/5xC-A55,
Default is 80 kHz. Range is 0–150.
Recommended value for 50 or 100 kHz spacing is 80 kHz.
Recom-
mended value for 200 kHz spacing is 110 kHz.
AN543
Rev. 0.9 95
Property 0x1200 FM_RSQ_INTERRUPT_SOURCE
The FM_RSQ_INTERRUPT_SOURCE property configures interrupt related to Received Signal Quality metrics.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Default: 0
FM_RSQ_INTERRUPT_SOURCE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x00 MULTHINT MULTLINT ISSIHINT ISSILINT SNRHINT SNRLINT RSSIHINT RSSILINT
0x00 0 0 0 000 0 0
Bit Name Function
15:8 Reserved Always write 0.
7MULTHINT
0: Disable Interrupt.
1:Enable interrupt if Multipath level goes above the threshold set by FM_RSQ_-
MULTIPATH_HIGH_THRESHOLD.
6MULTLINT
0: Disable Interrupt.
1: Enable interrupt if Multipath level falls below the threshold set by FM_RSQ_-
MULTIPATH_LOW_THRESHOLD.
5 ISSIHINT
0: Disable Interrupt.
1: Enable interrupt if ISSI goes above the threshold set by
FM_RSQ_ISSI_HIGH_THRESHOLD.
4 ISSILINT
0: Disable Interrupt.
1: Enable interrupt if ISSI falls below the threshold set by
FM_RSQ_ISSI_LOW_THRESHOLD.
3 SNRHINT
0: Disable Interrupt.
1: Enable interrupt if SNR goes above the threshold set by FM_RSQ_SN-
R_HIGH_THRESHOLD.
2SNRLINT
0: Disable Interrupt.
1: Enable interrupt if SNR falls below the threshold set by FM_RSQ_SN-
R_LOW_THRESHOLD.
1 RSSIHINT
0: Disable Interrupt.
1: Enable interrupt if RSSI goes above the threshold set by FM_R-
SQ_RSSI_HIGH_THRESHOLD.
0 RSSILINT
0: Disable Interrupt.
1: Enable interrupt if RSSI falls below the threshold set by FM_R-
SQ_RSSI_LOW_THRESHOLD.
AN543
96 Rev. 0.9
Property 0x1201 FM_ RSQ_SNR_HIGH_THRESHOLD
The FM_RSQ_SNR_HIGH_THRESHOLD property sets the high threshold, which triggers the RSQ interrupt if the
SNR is above this threshold. The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Default: 127
Units: dB
Property 0x1202 FM_RSQ_SNR_LOW_THRESHOLD
The FM_RSQ_SNR_LOW_THRESHOLD property sets low threshold, which triggers the RSQ interrupt if the SNR
is below this threshold. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: –128
Units: dB
FM_RSQ_SNR_HIGH_THRESHOLD
1514131211109876543210
0x00 SNRH[7:0]
0x00 0x7F
Bit Name Function
15:8 Reserved Write 0 for (+) values and 0xFF for (–) values.
7:0 SNRH [7:0] Sets the high threshold, which triggers the RSQ interrupt if the SNR is above this
threshold. Default is 127 dB. Range is –128 to 127 in steps of 1 dB.
FM_RSQ_SNR_LOW_THRESHOLD
1514131211109876543210
0xFF SNRL[7:0]
0xFF 0x80
Bit Name Function
15:8 Reserved Write 0 for (+) values and 0xFF for (–) values.
7:0 SNRL [7:0] Sets low threshold, which triggers the RSQ interrupt if the SNR is below this
threshold. Default is –128 dB. Range is –128 to 127 in steps of 1 dB.
AN543
Rev. 0.9 97
Property 0x1203 FM_RSQ_RSSI_HIGH_THRESHOLD
The FM_RSQ_RSSI_HIGH_THRESHOLD property sets the high threshold, which triggers the RSQ interrupt if
RSSI is above this threshold. The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Default: 127
Units: dBµV
Property 0x1204 FM_RSQ_RSSI_LOW_THRESHOLD
The FM_RSQ_RSSI_LOW_THRESHOLD property sets low threshold, which triggers the RSQ interrupt if the RSSI
is below this threshold. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: –128
Units: dBµV
FM_RSQ_RSSI_HIGH_THRESHOLD
1514131211109876543210
0x00 RSSIH[7:0]
0x00 0x7F
Bit Name Function
15:8 Reserved Write 0 for (+) values and 0xFF for (–) values.
7:0 RSSIH [7:0] Sets high threshold, which triggers the RSQ interrupt if the RSSI is above
this threshold. Default is 127 dBµV. Range is –128 to 127 in steps of 1 dB.
FM_RSQ_RSSI_LOW_THRESHOLD
1514131211109876543210
0xFF RSSIL[7:0]
0xFF 0x80
Bit Name Function
15:8 Reserved Write 0 for (+) values and 0xFF for (–) values.
7:0 RSSIL [7:0] Sets low threshold, which triggers the RSQ interrupt if the RSSI is below this
threshold. Default is –128 dBµV. Range is –128 to 127 in steps of 1 dB.
AN543
98 Rev. 0.9
Property 0x1205 FM_RSQ_ISSI_HIGH_THRESHOLD
The FM_RSQ_ISSI_HIGH_THRESHOLD property sets the Image Signal Strength Indicator high threshold, which
triggers the RSQ interrupt if the ISSI is above this threshold. The CTS bit (and optional interrupt) is set when it is
safe to send the next command. This property may only be set or read in powerup mode.
Default: 127
Property 0x1206 FM_RSQ_ISSI_LOW_THRESHOLD
The FM_RSQ_ISSI_LOW_THRESHOLD property sets the Image Signal Strength Indicator low threshold, which
triggers the RSQ interrupt if the ISSI is below this threshold. The CTS bit (and optional interrupt) is set when it is
safe to send the next command. This property may only be set or read in powerup mode.
Default: –128
FM_RSQ_RSSI_LOW_THRESHOLD
1514131211109876543210
0x00 HIGH[7:0]
0x00 0x7F
Bit Name Function
15:8 Reserved Always write 0.
7:0 HIGH[7:0] High threshold for ISSI interrupt in dBr relative to the desired signal.
Default is 127 dBr. Range is –128 to 127.
FM_RSQ_ISSI_LOW_THRESHOLD
1514131211109876543210
0x00 LOW[7:0]
0x00 0x80
Bit Name Function
15:8 Reserved Always write 0.
7:0 LOW[7:0] Low threshold for ISSI interrupt in dBr relative to the desired signal.
Default is –128 dBr. Range is –128 to 127.
AN543
Rev. 0.9 99
Property 0x1207 FM_RSQ_MULTIPATH_HIGH_THRESHOLD
The FM_RSQ_MULTIPATH_HIGH_THRESHOLD property sets the high threshold, which triggers the RSQ
interrupt if Multipath is above this threshold. Multipath is a measure of AM modulation and can exceed 100%. The
CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or
read in powerup mode.
Default: 127
Property 0x1208 FM_RSQ_MULTIPATH_LOW_THRESHOLD
The FM_RSQ_MULTIPATH_LOW_THRESHOLD property sets low threshold, which triggers the RSQ interrupt if
Multipath is below this threshold. Multipath is a measure of AM modulation and can exceed 100%. The CTS bit
(and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 0
FM_RSQ_MULTIPATH_HIGH_THRESHOLD
1514131211109876543210
0x000 MULTH[6:0]
0x000 0x7F
Bit Name Function
15:7 Reserved Always write 0.
6:0 MULTH [6:0] Sets the high threshold, which triggers the RSQ interrupt if Multipath is
above this threshold. Default is 127. Range is 0–127.
FM_RSQ_MULTIPATH_LOW_THRESHOLD
1514131211109876543210
0x000 MULTL[6:0]
0x000 0x00
Bit Name Function
15:7 Reserved Always write 0.
6:0 MULTL[6:0] Sets low threshold, which triggers the RSQ interrupt if Multipath is below this
threshold. Default is 0. Range is 0–127.
AN543
100 Rev. 0.9
Property 0x1300 FM_ACF_INTERRUPT_SOURCE
The FM_ACF_INTERRUPT_SOURCE property enables the ACF interrupt sources. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 0
FM_ACF_INTERRUPT_SOURCE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x000 CHBWH_INT BLEND_INT HIBLEND_INT HICUT_INT CHBW_INT SOFTMUTE_INT
0x000 00 0 00 0
Bit Name Function
15:6 Reserved Always write 0.
5 CHBWH_INT
(Available on Si475x-A40 only)
When set, enables the Channel Filter Bandwidth High interrupt. Default is 0.
0 = The Channel Bandwidth interrupt is disabled
1 = The Channel Bandwidth interrupt is enabled
4BLEND_INT
When set, enables the blend interrupt. Default is 0.
0 = The blend interrupt is disabled.
1 = The blend interrupt is enabled.
3 HIBLEND_INT
When set, enables the HIBLEND interrupt. Default is 0.
0 = The HIBLEND interrupt is disabled.
1 = The HIBLEND interrupt is enabled.
2 HICUT_INT
When set, enables the HICUT interrupt. Default is 0.
0 = The HICUT interrupt is disabled.
1 = The HICUT interrupt is enabled.
1 CHBW_INT
When set, enables the Channel Filter Bandwidth Interrupt. Default is 0.
0 = The Channel Filter Bandwidth interrupt is disabled.
1 = The Channel Filter Bandwidth interrupt is enabled.
0 SOFTMUTE_INT
When set, enables the softmute interrupt. Default is 0.
0 = The softmute interrupt is disabled.
1 = The softmute interrupt is enabled.
AN543
Rev. 0.9 101
Property 0x1301 FM_ACF_S M_THRESHOLD
The FM_ACF_SM_THRESHOLD property sets the softmute interrupt threshold in dB. When softmute attenuation
rises above the level set by this property and the SOFTMUTE_INT interrupt is enabled through the
FM_ACF_INTERRUPT_SOURCE property, the SOFTMUTE_INT interrupt will be asserted. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in the
powerup mode.
Default: 31
Units: dB
FM_ACF_SM_THRESHOLD
1514131211109876543210
0x000 SMATTN_THRESH[4:0]
0x000 0x1F
Bit Name Function
15:5 Reserved Always write 0.
4:0 SMATTN_THRESH[4:0]
Softmute interrupt threshold in dB, which triggers the softmute interrupt
when the softmute attenuation rises above this level.
Default is 31 dB
Range is 0–31 dB.
AN543
102 Rev. 0.9
Property 0x1302 FM_ACF_C HBW_THRESHOLD
The FM_ACF_CHBW_THRESHOLD property sets the Channel Filter Bandwidth interrupt threshold in units of kHz.
When the Channel Filter Bandwidth falls below this threshold and the CHBW_INT interrupt is enabled through the
FM_ACF_INTERRUPT_SOURCE property, the CHBW_INT interrupt will be asserted. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 0
Units: kHz
FM_ACF_CHBW_THRESHOLD
1514131211109876543210
CHBW_THRESH_HIGH[7:0] CHBW_THRESH_LOW[7:0]
0x00 0x00
Bit Name Function
15:8 CHBW_THRESH_HIGH[7:0]
(Available in Si475x-A40 and later)
Channel Filter Bandwidth High interrupt threshold in units of kHz, which
triggers the Channel Filter Bandwidth High Interrupt when the channel fil-
ter bandwidth rises above this threshold.
Default is 0 kHz.
Range is 0–255 kHz
7:0 CHBW _THRESH_LOW[7:0]
Channel Filter Bandwidth interrupt threshold in units of kHz, which trig-
gers the Channel Filter Bandwidth Low interrupt when the Channel Filter
Bandwidth falls below this threshold.
Default is 0 kHz
Range is 0–255 kHz.
AN543
Rev. 0.9 103
Property 0x1303 FM_ACF_H ICUT_THRESHOLD
The FM_ACF_HICUT_THRESHOLD property sets the HICUT interrupt threshold in units of 100 Hz. When the
HICUT cutoff frequency falls below this threshold and the HICUT_INT interrupt is enabled through the
FM_ACF_INTERRUPT_SOURCE property, the HICUT_INT interrupt will be asserted. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 0
Units: 100 Hz
FM_ACF_HICUT_THRESHOLD
1514131211109876543210
0x00 HICUT_THRESH[7:0]
0x00 0x00
Bit Name Function
15:8 Reserved Always write 0.
7:0 HICUT_THRESH[7:0]
HICUT interrupt threshold in units of 100 Hz, which triggers the HICUT
Interrupt when the HICUT cutoff frequency falls below this threshold.
Default is 0.
Range is 0–200.
AN543
104 Rev. 0.9
Property 0x1304 FM_ACF_HIBLEND_THRESHOLD
The FM_ACF_HIBLEND_THRESHOLD property sets the HIBLEND interrupt threshold in units of 100 Hz. When
the HIBLEND cutoff frequency falls below this threshold and the HIBLEND_INT interrupt is enabled through the
FM_ACF_INTERRUPT_SOURCE property, the HIBLEND_INT interrupt will be asserted. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 0
Units: 100 Hz
FM_ACF_HIBLEND_THRESHOLD
1514131211109876543210
0x00 HIBLEND_THRESH[7:0]
0x00 0x00
Bit Name Function
15:8 Reserved Always write 0.
7:0 HIBLEND_THRESH[7:0]
HIBLEND interrupt threshold in units of 100 Hz, which triggers the
HIBLEND Interrupt when the HIBLEND cutoff frequency falls below this
threshold.
Default is 0.
Range is 0–200.
AN543
Rev. 0.9 105
Property 0x1305 FM_ACF_BLEND_THRESHOLD
The FM_ACF_BLEND_THRESHOLD property sets the interrupt trigger threshold for stereo blend. The threshold is
expressed as a percentage in terms of L minus R (L – R) gain factor K. When the L–R gain falls below this
threshold and the BLEND_INT is enabled through the FM_ACF_INTERRUPT_SOURCE property, the BLEND_INT
will be asserted. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property
may only be set or read in powerup mode.
Note: Stereo Separation S = (1 + K) / (1 – K), where K is the L minus R gain factor. Stereo separation of 1 implies mono mode
and stereo separation of >1 implies that the part is in stereo with up to 20 log(S) dB of stereo separation. This property
expresses the threshold value of K as a percentage. For example, value 0x0032 = a K of 50%, or a stereo separation of
S = (1.5 / 0.5) = 3. The interrupt would then trigger at 20 log(3) = 9.5 dB of stereo separation.
Default: 0
Units: % L–R gain
FM_ACF_BLEND_THRESHOLD
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x000 BLEND_THRESH[6:0]
0x000 0x00
Bit Name Function
15:7 Reserved Always write 0.
6:0
BLEND_
THRESH
[6:0]
Stereo Blend Interrupt threshold in units of % L–R gain, which triggers the Blend threshold
interrupt when L–R gain falls below this threshold.
Default is 0%.
Range is 0–100%.
AN543
106 Rev. 0.9
Property 0x1306 FM_ACF_CONTROL_SOURCE
The FM_ACF_CONTROL_SOURCE property determines the controlling metric for ACF features. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A40 and earlier, Default: 1
Si475x/5xC-A55, Default: 3
FM_ACF_CONTROL_SOURCE
1514131211109876543 2 1 0
0x0000 AFC_SM DEV_CHBW USE_MULT-
PATH
0x0000 00 1
Bit Name Function
15:1 Reserved Always write 0.
2AFC_SM
(Only applicable to Si475x-A20 and later)
When set, softmute will be triggered by an AFC rail. Default is 0.
0 = Do not use AFC rail to force a softmute.
1 = Use AFC rail to force maximum softmute attenuation set by
FM_SOFT_MUTE_MAX_ATTENUATION property (0x400).
1 DEV_CHBW
(Only applicable to Si475x-A20 and later)
When set, STRONGDEV will be used instead of RSSI as the controlling metric for
Channel Filter Bandwidth. Default is 0.
0 = Use RSSI as the controlling metric for weak signal Channel Filter Bandwidth
control.
1 = Use STRONGDEV as the controlling metric for weak signal Channel Filter
Bandwidth control.
0 USE_MULTPATH
(Only applicable to Si475x/5xC-A55 and later)
When cleared to 0, ASSI200DEV will be used instead of Multipath as the controlling
metric for softmute. Default is 1.
0 = Use ASSI200DEV as the controlling metric for softmute.
1 = Use MultiPath as the controlling metric for softmute.
AN543
Rev. 0.9 107
Property 0x1307 FM_ACF_HOLD_TIME
The FM_ACF_HOLD_TIME property sets the ACF hold time after tune. The CTS
bit (and optional interrupt) is set
when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A40 and earlier, this property is not available.
Si475x/5xC-A55, Default: 0x0064
Units: ms
FM_ACF_HOLD_TIME
1514131211109876543210
0x00 DELAY[7:0]
0x00 0x64
Bit Name Function
15:8 Reserved Always write 0.
7:0 DELAY [7:0]
Sets the ACF hold time after tune in millisecond. Default
is 100 ms, Range is 4 ~ 255 ms.
Recommended minimum value is 8 ms.
AN543
108 Rev. 0.9
Property 0x2000 FM_VALID_MAX_TUNE_ERROR
The FM_VALID_MAX_TUNE_ERROR property sets the maximum freq error allowed in units of 2 ppm before
setting the AFC rail indicator (AFCRL). The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Default: 75 (150 ppm)
Units: 2 ppm
Property 0x2001 FM_VALID_RSSI_TIME
The FM_VALID_RSSI_TIME property sets the amount of time in milliseconds to allow the RSSI metric to settle
before evaluating.
This parameter is valid only if TUNEMODE[1:0] (FM_TUNE_FREQ) is set to 0. The minimum RSSI settling delay is
3 milliseconds. The reliability of the valid bit for identifying valid stations relies on this parameter being set properly.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Default: 6
Units: ms
FM_VALID_MAX_TUNE_ERROR
1514131211109876543210
0x00 FMMAXTUNEERR[7:0]
0x00 0x4B
Bit Name Function
15:8 Reserved Always write 0.
7:0 FMMAXTUNEERR
[7:0]
Sets the maximum freq error allowed in units of 2 ppm before setting the AFC
rail indicator (AFCRL). Range is 0–126.
FM_VALID_RSSI_TIME
1514131211109876543210
0x00 SSIVALTIME[5:0]
0x00 0x06
Bit Name Function
15:6 Reserved Always write 0.
5:0 SSIVALTIME[5:0]
Validation time in milliseconds. Default is 6 ms.
Range is 3–63 ms in Si475x-A30 and earlier.
Range is 3–127 ms in Si475x-A40 and later.
AN543
Rev. 0.9 109
Property 0x2002 FM_VALID_SNR_T IME
The FM_VALID_SNR_TIME property sets the amount of time in milliseconds to allow the SNR metric to settle
before evaluating.
This parameter is valid only if TUNEMODE[1:0] (FM_TUNE_FREQ) is set to 0. The minimum SNR settling delay is
4 ms. The reliability of the valid bit for identifying valid stations relies on this parameter being set properly. The CTS
bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 18
Units: ms
FM_VALID_SNR_TIME
1514131211109876543210
0x00 SNRVALTIME[5:0]
0x00 0x12
Bit Name Function
15:6 Reserved Always write 0.
5:0 SNRVALTIME[5:0]
Validation time in milliseconds. Default is
18 ms.
Range is 4–63 ms in Si475x-A30 and earlier.
Range is 4–127 ms in Si475x-A40 and later.
AN543
110 Rev. 0.9
Property 0x2003 FM_VALID_SNR_THRESHOLD
The FM_VALID_SNR_THRESHOLD property sets the SNR threshold for a valid FM Seek/Tune. If the desired
channel SNR is above this threshold, then it is considered valid. The CTS bit (and optional interrupt) is set when it
is safe to send the next command. This property may only be set or read in powerup mode.
Default: 8
Units: dB
FM_VALID_SNR_THRESHOLD
1514131211109876543210
FMVALUSN[7:0] FMVALSNR[7:0]
0x00 0x08
Bit Name Function
15:8 FMVALUSN[7:0]
(Available in Si475x-A40 and later)
Sets the USN threshold for a valid FM Seek/Tune. Default is 0 dBFS.
Range is 0 to 127 in units of negative –dBFS. (0 is full scale, 127 is 127 dB
down from full scale.)
0 = USN is not used as a criterion in determining the validity of a station.
(In Si475x-A30 and earlier, this field should be the continued SIGN of FMVAL-
SNR. That is, it should be 0x00 for positive (+) values and 0xFF for negative
(–) values.)
7:0 FMVALSNR [7:0]
Sets the SNR threshold for a valid FM Seek/Tune. Default is 8 dB.
Range is –128 to 127 in steps of 1 dB.
–128 = SNR is not used as a criterion in determining the validity of a station.
AN543
Rev. 0.9 111
Property 0x2004 FM_VALID_RSSI_THRESHOLD
The FM_VALID_RSSI_THRESHOLD property sets the RSSI threshold for a valid FM Seek/Tune. If the desired
channel RSSI is above this threshold, then it is considered valid. The CTS bit (and optional interrupt) is set when it
is safe to send the next command. This property may only be set or read in powerup mode.
Default: 12
Units: dBµV
Property 0x2005 FM_VALID_ISSI_THRESHOLD (Si4754/55/56/57 Only)
The FM_VALID_ISSI_THRESHOLD property sets the ISSI threshold for valid FM Seek/Tune. If the desired
channel ISSI is below this threshold, then it is considered valid. If the desired channel ISSI is above this threshold,
then the tuner will retune after switching the injection side and revalidate the station. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A30, Default: 30
All others: This feature is not available.Units: dB
FM_VALID_RSSI_THRESHOLD
1514131211109876543210
0x00 FMVALRSSI[7:0]
0x00 0x0C
Bit Name Function
15:8 Reserved Always write 0.
7:0 FMVALRSSI[7:0]
Sets the RSSI threshold for a valid FM Seek/Tune. Default is 12 dBµV.
Range is –128 to 127 in steps of 1 dB.
–128 = RSSI is not used as a criterion in determining the validity of a station.
FM_VALID_ISSI_THRESHOLD
1514131211109876543210
0x00 FMVALISSI[7:0]
0x00 0x1E
Bit Name Function
15:8 Reserved Always write to 0.
7:0 FMVALISSI[7:0] Sets the ISSI threshold for valid FM Seek/Tune. Default is 30 dB.
Range is –128 to 127 dB.
AN543
112 Rev. 0.9
Property 0x2006 FM_VALID_MULT_THRESHOLD
The FM_VALID_MULT_THRESHOLD sets the multipath threshold for a valid FM Seek/Tune. If the desired channel
multipath is below this threshold, then it is considered valid. The CTS bit (and optional interrupt) is set when it is
safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A10 and earlier: This property is not available.
Si475x-A20 and later, Default: 100
FM_VALID_MULT_THRESHOLD
1514131211109876543210
0x00 FMVALMULT[7:0]
0x00 0x64
Bit Name Function
15:8 Reserved Always write 0.
7:0 FMVALMULT[7:0] FM Seek/Tune Received Multipath Threshold.
Default is 100%. Range is 0–100%.
AN543
Rev. 0.9 113
Property 0x2007 FM_VALID_AF_TIME (Si4754/55/56/57 Only)
The FM_VALID_AF_TIME property sets the amount of time in milliseconds to allow the RSSI and SNR metrics to
settle before evaluating during an AF check/tune. This parameter is valid only if TUNEMODE[1:0]
(FM_TUNE_FREQ) is set to 2 or 3. The reliability of the valid bit for identifying valid stations relies on this
parameter being set properly. Setting this property to a value lower than 4 will result in the metric not being
measured correctly at tune time. To disable metric as a tune qualifier set the validation time to 0 and set the
validation threshold to the minimum value. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read in powerup mode.
Note: With Si475x-A40 defaults, the RSSI metric value for AF Check settles within 2 ms. To qualify additional metrics (SNR,
Multipath, USN, LASSI, HASSI, ASSI200) users should set Property 0x2007 FM_VALID_AF_TIME to 0x0005 (5 ms)
and Property 0x1008 FM_TUNE_AF_CHBW to 0x0050 (80 kHz).
Si475x-A10, it is not available.
Si475x-A20 and Si475x-A30, Default: 5
Si475x-A40 and later, Default: 2
Units: ms
FM_VALID_AF_TIME
1514131211109876543210
Reserved AFVALTIME[5:0]
0x000 0x02
Bit Name Function
15:6 Reserved Always write 0.
5:0 AFVALTIME[5:0]
Validation time for AF tune.
For RSSI only check, range is 3–63 ms. For RSSI and SNR check, range is
0–63 ms.
AN543
114 Rev. 0.9
Property 0x2008 FM_VALID_AF_RDS_TIME (Si4754/55/56/57 Only)
The FM_VALID_AF_RDS_TIME property sets the maximum amount of time in milliseconds to allow RDS to
acquire PI code when performing AF tune with non-zero FM_VALID_AF_PI property (0x2009). The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 120
Units: ms
Property 0x2009 FM_ VALID_AF_PI (Si4754/55/56/57 Only)
The FM_VALID_AF_PI property sets PI code used for validating an AF tune. If set to 0x0000, then PI code check is
not performed. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property
may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0x0000
FM_VALID_AF_RDS_TIME
1514131211109876543210
AFVALPITIME[15:0]
0x0078
Bit Name Function
15:0 AFVALPITIME[15:0] Validation time for AF tune with PI code check. Default is 120 ms. Range is
0–32767 ms.
FM_VALID_AF_PI
1514131211109876543210
AFVALPI[15:0]
0x0000
Bit Name Function
15:0 AFVALPI[15:0] Sets PI code used for validating an AF tune. If set to 0x0000, then PI code
check is not performed. Default is 0x0000.
AN543
Rev. 0.9 115
Property 0x200A FM_VALID_ASSI_THRESHOLD (Si4754/55/56/57 Only)
The FM_VALID_ASSI_THRESHOLD property sets the ASSI threshold for valid FM Seek/Tune. If the desired
channel ASSI is below this threshold, then it is considered valid. The CTS bit (and optional interrupt) is set when it
is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0x503C
Units: dB
Property 0x200B FM_VALID_AF_PI_MASK (Si4754/55/56/57 Only)
The FM_VALID_AF_PI_MASK property sets the bit mask for comparing the PI code to the FM_VALID_AF_PI
property (0x2009). The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0xFFFF
FM_VALID_ASSI_THRESHOLD
1514131211109876543210
0 FMVALASSI200[6:0] 0 FMVALASSI100[6:0]
00x5000x3C
Bit Name Function
15 Reserved Always write to 0.
14:8 FMVALASSI200[6:0] Sets the ASSI200 threshold for valid FM Seek/Tune. Default is 80 dB.
Range is 0 to 127 dB.
7 Reserved Always write to 0.
6:0 FMVALASSI100[6:0] Sets the max(HASSI,LASSI) threshold for valid FM Seek/Tune. Default is
60 dB. Range is 0 to 127 dB.
FM_VALID_AF_PI_MASK
1514131211109876543210
AFVALPIMASK[15:0]
0xFFFF
Bit Name Function
15:0 AFVALPIMASK[15:0] Sets the bit mask for comparing the PI code to the FM_VALID_AF_PI prop-
erty (0x2009). Default is 0xFFFF.
AN543
116 Rev. 0.9
Property 0x200C FM_VALID_FREQOFF_SCALE
The FM_VALID_FREQOFF_SCALE sets the units in Hz for the FM_RSQ_STATUS response FREQOFF metric, as
well as FM_VALID_MAX_TUNE_ERROR. (For example, if FM_VALID_FREQOFF_SCALE is set to 100, then
FM_VALID_MAX_TUNE_ERROR will have units of 100 Hz per property value step.) The default is to use units of
binary ppm instead of any number of Hz. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode. In Si475x-A30 and earlier, FREQOFF is always
in units of bppm (binary ppm, or 2 ppm).
Si475x-A30 and earlier: This property is not available.
Si475x-A40 and later, Default: 0
Units: Hz
Property 0x200D FM_VALID_FREQOFF_FILTER
The FM_VALID_FREQOFF_FILTER sets the number of FREQOFF samples averaged by the metric filter before
reporting FREQOFF as part of FM_RSQ_STATUS. The CTS bit (and optional interrupt) is set when it is safe to
send the next command. This property may only be set or read in powerup mode.
Si475x-A30 and earlier: This property is not available.
Si475x-A40 and later, Default: 100
FM_VALID_FREQOFF_SCALE
1514131211109876543210
SCALE[15:0]
0x0000
Bit Name Function
15:8 SCALE[15:0]
Sets the units in Hz for the frequency offset metric and the
FM_VALID_MAX_TUNE_ERROR. The recommended value for FM is
1000 Hz.
Default is 0.
0 = Use units of bppm.
FM_VALID_FREQOFF_FILTER
1514131211109876543210
0x00 FILTER[7:0]
0x00 0x64
Bit Name Function
15:8 Reserved Always write 0.
7:0 FILTER[7:0]
The number of FREQOFF values that are averaged when reporting the value in
FM_RSQ_STATUS. (Values below 10 will begin to track audio and are not recom-
mended. If low-cut is being used then the minimum value will need to be
increased accordingly to avoid tracking low frequency audio.)
Default is 100 samples. Range is 0–127.
AN543
Rev. 0.9 117
Property 0x2100 FM_NB_DETECT_THRESHOLD
The FM_NB_DETECT_THRESHOLD property sets the threshold for detecting impulses in dB above the noise
floor. The noise blanker can be disabled by setting the noise blanker detect threshold to 0.The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 18
Units: dB
Property 0x2101 FM_NB_INTERVAL
The FM_NB_INTERVAL property sets the interval that original samples are replaced by interpolated clean
samples. The noise blanker can be disabled by setting the noise blanker detect threshold to 0.The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 5
Units: none
FM_NB_DETECT_THRESHOLD
1514131211109876543210
DETECT_THRESHOLD[15:0]
0x0012
Bit Name Function
15:0 DETECT_THRESHOLD[15:0]
Sets the threshold for detecting impulses in dB above the
noise floor.
Default is 18 dB
Range is 0–90 dB.
To disable the noise blanker, set the DETECT_THRESH-
OLD to 0.
FM_NB_INTERVAL
1514131211109876543210
NB_INTERVAL[15:0]
0x0005
Bit Name Function
15:0 NB_INTERVAL[15:0]
Sets the interval in number of audio samples that original sam-
ples are replaced by interpolated clean samples.
Default is 5.
Range is 1–20.
AN543
118 Rev. 0.9
Property 0x2103 FM_NB_SECONDARY_DETECT_THRESHOLD
The FM_NB_SECONDARY_DETECT_THRESHOLD property sets the threshold for secondary (IF) noise blanker.
The noise blanker is triggered when the IF signal’s average-to-peak ratio is no more than
FM_NB_SECONDARY_DETECT_THRESHOLD / 32767. The recommended average-to-peak ratio 10%, which is
equivalent to setting this property to 32767. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read when in the powerup mode.
Si475x-A40 and earlier, this property is not available.
Si475x/5xC-A55, Default: 0
Units: None
FM_NB_SECONDARY_DETECT_THRESHOLD
1514131211109876543210
SECONDARY_DETECT_THRESHOLD[15:0]
0x0000
Bit Name Function
15:0 SECONDARY_DETECT_
THRESHOLD[15:0]
The percentage is a fractional Q15 number. Recommended
setting is 14%, which is equivalent to setting this property to
0x11EC.
Default is 0.
Range is 0–32767.
0 = Disable the secondary noise blanking (IF) engine.
AN543
Rev. 0.9 119
Property 0x2105 FM_NB_WEAK_DETECT_THRESHOLD
The FM_NB_WEAK_DETECT_THRESHOLD property sets the threshold for detecting impulses. The threshold is
set in Q15 format as a linear scaling factor between the average (noise floor) and the pulse peak. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 13568,
Si475x/5xC-A55, Default: 7537
Property 0x2106 FM_NB_STRONG_SIGNAL_SHUTOFF
The RSSI based shutoff threshold. Used to turn off the noise blanker under strong signal conditions.
Default: 50
Units: dBuV
FM_NB_WEAK_DETECT_THRESHOLD
1514131211109876543210
WEAK_DETECT_THRESHOLD[15:0]
0x3500
Bit Name Function
15:0 WEAK_DETECT_THRESHOLD[15:0]
Sets the detection threshold for the weak signal blanker. If
(measured audio level average/peak audio level)
< WEAK_DETECT_THRESHOLD/32767, then the blanker is
engaged. Higher settings blank more aggressively.
Si475x/5xC-A55; Default is 7537. Range is 0–32767
FM_NB_STRONG_SIGNAL_SHUTOFF
1514131211109876543210
0x00 RSSI_THRESH [6:0]
0x00 0x32
Bit Name Function
15:7 Reserved Always write 0.
6:0 RSSI_THRESH[6:0]
default: 0x32 RSSI level at which the noise blanker is effectively
off.
Range: 0–127 RSSI level in dB.
AN543
120 Rev. 0.9
Property 0x2109 FM_NB_ MODE_CONTROL
The FM_NB_MODE_CONTROL property sets high-level control for the FM noise blanker. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0
Property 0x210A FM_NB_WEAK_BLANK_INTERVAL
The FM_NB_WEAK_BLANK_INTERVAL sets the number of samples to be blanked by the weak-signal blanker
upon detection of a noise pulse. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 5
FM_NB_MODE_CONTROL
151413121110987654321 0
0x0000 USE_RSSI
0x0000 0
Bit Name Function
15:1 Reserved Always write 0.
0 USE_RSSI
When set, selects noise blanker to use based on RSSI instead of SNR.
0 = SNR metric controls automatic noise blanker selection.
1 = RSSI metric controls automatic noise blanker selection.
FM_NB_WEAK_BLANK_INTERVAL
1514131211109876543210
WEAK_BLANK_INTERVAL[15:0]
0x0005
Bit Name Function
15:0 WEAK_BLANK_INTERVAL[15:0]
Number of samples that are replaced by interpolated clean
samples in the weak noise blanker.
Default is 5.
Range is 0–32767.
AN543
Rev. 0.9 121
Property 0x210B FM_NB_STRONG_WEAK_SWITCH
The FM_NB_STRONG_WEAK_SWITCH sets the threshold for switching between the weak signal and strong
signal noise blanker. (Particularly strong noise pulses can interfere with signal metrics, which can in turn interfere
with noise pulse detection. The weak signal blanker operates under most signal conditions, while the strong signal
blanker operates under conditions that would normally disturb signal quality metrics and prevent proper pulse
detection.) The difference between HIGH and LOW is the hysteresis of the switch. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0x0B09
FM_NB_STRONG_WEAK_SWITCH
1514131211109876543210
0HIGH[6:0] 0LOW[6:0]
00x0B 00x09
Bit Name Function
15 Reserved Always write 0.
14:8 HIGH[6:0]
SNR/RSSI level above which the strong noise blanker is used.
Default is 11 dB/dBuV.
Range is –127 to 127 dB/dBµV.
7 Reserved Always write 0.
6:0 LOW[6:0]
SNR/RSSI level below which the weak noise blanker is used.
Default is 9 dB/dBµV.
Range is –127 to 127 dB/dBuV.
AN543
122 Rev. 0.9
Property 0x2111 FM_NB_CIMP_HICUT_LIMIT
The FM_NB_CIMP_HICUT_LIMIT property sets the HICUT multipath threshold when continuous impulses are
detected. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Si475x-A40 and earlier: this property is not available.
Si475x/5xC-A55, Default: 0x0A14
FM_CHBW_SQ_MIN_MAX
1514131211109876543210
XMAX[7:0] XMIN[7:0]
0x0A 0x14
Bit Name Function
15:8 XMAX [7:0]
Sets the Multipath level at which HICUT reaches max band limiting on the
L+R channel based on cutoff frequency set by property 0x2112.
Si475x/5xC-A55, Default is 10. Range is 0–127%.
7:0 XMIN [7:0]
Sets the Multipath level at which HICUT begins to band limit on the L+R
channel based on cutoff frequency set by property 0x2112.
Si475x/5xC-A55, Default is 20. Range is 0–127%.
AN543
Rev. 0.9 123
Property
0
x2112
FM_NB_CIMP_HICUT_FREQ
Th
e
F
M_NB_CIMP_HICUT_FREQ proper
ty
sets the HiCut cut-off frequency settings when continuous impulses
are detected.
The
CTS
bit
(and
optional
interrupt)
is
set
when
it
is
safe
to
send
the
next
comman
d. T
his proper
ty
may only be se
t
or read in powerup mode.
Si475x-A40 and earlier: This property is not available.
Si475x/5xC-A55, Default: 0x6401
Unit: 100 Hz
FM_NB_CIMP_HICUT_FREQ
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
YMAX[7:0] YMIN[7:0]
0x64 0x01
Bit Name Function
15:8 YMAX[7:0] Sets the maximum cutoff frequency. Range is 0–18 kHz.
Si475x/5xC-A55, Default is 10 kHz.
7:0 YMIN[7:0] Sets the minimum stereo separation. Range is 0–18 kHz.
Si475x/5xC-A55,
Default is 100 Hz.
AN543
124 Rev. 0.9
Property
0
x2113
FM_NB_CIMP_HICUT_ATTACK
The FM_NB_CIMP_HICUT_ATTACK property sets the transition time for which the HICUT mitigation engine
lowers the cutoff frequency based on Multipath when continuous impulses are detected. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier: This property is not available.
Si475x/5xC-A55, Default: 0x0001
Unit: ms
Property
0
x2114
FM_NB_CIMP_HICUT_RELEASE
The FM_NB_CIMP_HICUT_RELEASE property sets the transition time for which the HICUT mitigation engine
increases the cutoff frequency based on Multipath when continuous impulses are detected. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A40 and earlier: This property is not available.
Si475x/5xC-A55 Default: 0x0008
Unit: ms
FM_NB_CIMP_HICUT_FREQ
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0001
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the HICUT mitigation engine lowers the
cutoff frequency based on Multipath.
Si475x/5xC-A55 Default is 1 ms. Range is 1–32767 ms.
FM_NB_CIMP_HICUT_RELEASE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0008
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the HICUT mitigation engine increases the
cutoff frequency based on Multipath.
Si475x/5xC-A55 Default is 8 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 125
Property 0x2115 FM_NB_CIMP_DETCNTR
The FM_NB_CIMP_DETCNTR property sets the continuous impulse detection counter setting. NCONT sets how
many continuous 1ms timeslots with impulse detected will trigger continuous flag, NSTEP sets accumulative step,
this determines release time for continuous flag if no impulses was detected, the release time is NCONT*NSTEP.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Si475x-A40 and earlier: this property is not available.
Si475x/5xC-A55, Default is: 0x0402.
Property
0
x2116 FM_NB_CIMP_A2PTH
Th
e
F
M_NB_CIMP_A2PTH proper
ty
sets the Independent IQ impulse detection threshold for continuous impulse
detection.
The
CTS
bit
(and
optional
interrupt)
is
set
when
it
is
safe
to
send
the
next
comman
d. T
his proper
ty
may
only be se
t
or read in powerup mode.
Si475x-A40 and earlier: This property is not available.
Si475x/5xC-A55, Default: 0x0800.
FM_NB_CIMP_DETCNTR
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
NSTEP[7:0] NCONT[7:0]
0x04 0x02
Bit Name Function
15:8 NSTEP[7:0]
The continuous impulses counter will be increased by this step size when
impulse detected in last 1ms time window.
Si475x/5xC-A55, Default is 4. Range is 0 to 255.
7:0 NCONT[7:0]
For this given number of continuous impulses detected in every conse-
quent 1ms time window, the detector will assert.
Si475x/5xC-A55, Default is 2. Range is 0 to 255.
FM_NB_CIMP_HICUT_FREQ
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RATIO[15:0]
0x0800
Bit Name Function
15:0 RATIO[15:0]
Sets the Continuous impulse detector threshold of average to peak ratio.
The ratio is RATIO[15:0]/32768, range is 0–1.0.
Si475x/5xC-A55, Default is 0x0800.
AN543
126 Rev. 0.9
Property 0x2117 FM_NB_CIMP_IMPDET
The FM_NB_CIMP_IMPDET property sets the noise blanker impulse detection threshold to replace property
0x2100 and 0x2105 when continuous impulses are detected. The CTS bit (and optional interrupt) is set when it is
safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier: this property is not available.
Si475x/5xC-A55, Default is: 0x400A.
Property
0
x2118 FM_NB_CIMP_MPX_INTV
Th
e
F
M_NB_CIMP_MPX_INTV proper
ty
sets the MPX noise blanker interval when continuous impulses are
detected replacing property 0x2101.
The
CTS
bit
(and
optional
interrupt)
is
set
when
it
is
safe
to
send
the
next
comman
d. T
his proper
ty
may only be se
t
or read in powerup mode.
Si475x-A40 and earlier: This property is not available
Si475x/5xC-A55, Default: 0x0A0A
Unit: ms
FM_NB_CIMP_IMPDET
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
WEAK[7:0] NORM[7:0]
0x40 0x0A
Bit Name Function
15:8 WEAK[7:0]
Sets the MPX noise blanker threshold at weak signal case replacing prop-
erty 0x2105 when continuous impulses are detected. the scale of this field
is property 0x2105>>8.
Si475x/5xC-A55, Default is 0x40. Range is 0 ~ 255.
7:0 NORM[7:0]
Sets the MPX noise blanker threshold at normal signal case replacing prop-
erty 0x2100 when continuous impulses are detected.
Si475x/5xC-A55, Default is 0x0A. Range is 0 ~ 255.
FM_NB_CIMP_HICUT_FREQ
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
INTV[15:0]
0x0A0A
Bit Name Function
15:0 INTV[15:0]
MPX blanker interval when continuous impulses are detected, high Byte is
for strong signal case, low Byte is for weak signal case.
Si475x/5xC-A55, Default is 0x0A0A, Range is 0 ~ 32767.
AN543
Rev. 0.9 127
Property 0x2200 FM_ CHBW_SQ_MIN_MAX
The FM_CHBW_SQ_MIN_MAX property sets the maximum and minimum Channel Filter Bandwidth in kHz based
on RSSI/STRONGDEV (for Si475x-A20 and later) or RSSI/SNR (for Si475x-A10), as selected with through
property 0x1306, FM_ACF_CONTROL. For Si475x-A20 and later, this engine is only enabled when RSSI is below
the FM_CHBW_WEAKSIG_THR (property 0x220F). To force a given Channel Filter Bandwidth, set the min and
max to the same value. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Notes:
1. The Si4750/51/52/53 do not support dynamic bandwidth control, hence MIN[7:0] = MAX[7:0]. The minimum of MAX[7:0]
of properties 0x2200, 0x2205, and 0x220A determines the Channel Filter Bandwidth. Default for Si4750/51/52/53-A10 is
110 kHz; default for Si4750/51/52/53-A20/A30 is 150 kHz.
2. RSSI/SNR can be used to control this engine for Si475x-A10. RSSI/STRONGDEV can be used to control this engine for
Si475x-A20 and later.
Si4754/55/56/57 Default: 0x9637
Si4750/51/52/53 Default: 0x6E6E
Units: kHz
FM_CHBW_SQ_MIN_MAX
1514131211109876543210
MAX[7:0] MIN[7:0]
0x96 0x37
Bit Name Function
15:8 MAX [7:0]
Sets the maximum Channel Filter Bandwidth in kHz.
Si4754/55/56/57 default is 150 kHz.
Si4750/51/52/53 default is 110 kHz.
Range is 1–150 kHz.
7:0 MIN [7:0]
Sets the minimum Channel Filter Bandwidth in kHz.
Si4754/55/56/57 default is 55 kHz.
Si4750/51/52/53 default is 110 kHz.
Range is 1–150 kHz.
AN543
128 Rev. 0.9
Property 0x2201 FM_CHBW_SQ_HIGH_THRESHOLD (Si4754/55/56/57 Only)
The FM_CHBW_SQ_HIGH_THRESHOLD property sets the threshold for maximum Channel Filter Bandwidth
based on RSSI/STRONGDEV (for Si475x-A20 and later) or RSSI/SNR (for Si475x-A10), as selected with through
property 0x1306, FM_ACF_CONTROL. For Si475x-A20 and later, this engine is only enabled when RSSI is below
the FM_CHBW_WEAKSIG_THR (property 0x220F). If the instantaneous RSQ value is greater than or equal to the
programmed RSSI high threshold, then the Channel Filter Bandwidth will be set to the maximum value
programmed through Property 0x2200. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Note: RSSI/SNR can be used to control this engine for Si475x-A10. RSSI/STRONGDEV can be used to control this engine for
Si475x-A20 and later.
Default: 12
Units: dB for RSSI/SNR metrics, kHz for STRONGDEV metric
FM_CHBW_SQ_HIGH_THRESHOLD
1514131211109876543210
SQMAX[15:0]
0x000C
Bit Name Function
15:0 SQMAX[15:0]
Sets the RSSI threshold for maximum Channel Filter Bandwidth.
Default is 12 dBµV
Range is –128 to 127 dBµV for Si475x-A20 and later; Range is
0–127 for Si475x-A10.
AN543
Rev. 0.9 129
Property 0x2202 FM_CHBW_SQ_LOW_THRESHOLD (Si4754/55/56/57 Only)
The FM_CHBW_SQ_LOW_THRESHOLD property sets the threshold for minimum Filter Channel Bandwidth
based on RSSI/STRONGDEV (for Si475x-A20 and later) or RSSI/SNR (for Si475x-A10), as selected with through
property 0x1306, FM_ACF_CONTROL. For Si475x-A20 and later, this engine is only enabled when RSSI is below
the FM_CHBW_WEAKSIG_THR (property 0x220F). If the instantaneous RSQ value is less than or equal to the
programmed RSSI low threshold, then the Channel Filter Bandwidth will be set to the minimum value programmed
through Property 0x2200. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Note: RSSI/SNR can be used to control this engine for Si475x-A10. RSSI/STRONGDEV can be used to control this engine for
Si475x-A20 and later.
Si475x-A40 and earlier, Default: –4
Si475x/5xC-A55, Default: 2
Units: dB for RSSI/SNR metrics, kHz for STRONGDEV metric
FM_CHBW_SQ_LOW_THRESHOLD
1514131211109876543210
SQMIN[15:0]
0x0002
Bit Name Function
15:0 SQMIN[15:0]
Sets the RSSI threshold for minimum Channel Filter Bandwidth.
Si475x/5xC-A55, Default is 2 dBµV
Range is –127 to 128 dBµV for Si475x-A20 and later.
Range is 0–127 for
Si475x-A10.
AN543
130 Rev. 0.9
Property 0x2203 FM_ CHBW_SQ_WIDENING_TIME (Si4754/55/56/57 Only)
The FM_CHBW_SQ_WIDENING_TIME property sets the Channel Filter Bandwidth widening time based on RSSI/
STRONGDEV (for Si475x-A20 and later) or RSSI/SNR (for Si475x-A10), as selected with through property
0x1306, FM_ACF_CONTROL. For Si475x-A20 and later, this engine is only enabled when RSSI is below the
FM_CHBW_WEAKSIG_THR (property 0x220F). The CTS bit (and optional interrupt) is set when it is safe to send
the next command. This property may only be set or read in powerup mode.
Note: RSSI/SNR can be used to control this engine for Si475x-A10. RSSI/STRONGDEV can be used to control this engine for
Si475x-A20 and later.
Default: 16
Si475x-A10, Units: ms
Si475x-A20, Units: 0.2 ms
Si475x-A30 and later, Units: 0.4 ms
FM_CHBW_SQ_WIDENING_TIME
1514131211109876543210
WIDENING_TIME[15:0]
0x0010
Bit Name Function
15:0 WIDENING_TIME[15:0]
Sets the RSSI based Channel Filter Bandwidth widening
time.
Default is 16.
Range is 1–32767.
AN543
Rev. 0.9 131
Property 0x2204 FM_CHBW_SQ_NARROWING_TIME (Si4754/55/56/57 Only)
The FM_CHBW_SQ_NARROWING_TIME property sets the Channel Filter Bandwidth narrowing time based on
RSSI/STRONGDEV (for Si475x-A20 and later) or RSSI/SNR (for Si475x-A10), as selected with through property
0x1306, FM_ACF_CONTROL. For Si475x-A20 and later, this engine is only enabled when RSSI is below the
FM_CHBW_WEAKSIG_THR (property 0x220F). The CTS bit (and optional interrupt) is set when it is safe to send
the next command. This property may only be set or read in powerup mode.
Note: RSSI/SNR can be used to control this engine for Si475x-A10. RSSI/STRONGDEV can be used to control this engine for
Si475x-A20 and later.
Default: 2048
Si475x-A10, Units: ms
Si475x-A20, Units: 0.2 ms
Si475x-A30 and later, Units: 0.4 ms
FM_CHBW_SQ_NARROWING_TIME
1514131211109876543210
NARROWING_TIME[15:0]
0x0800
Bit Name Function
15:0 NARROWING_TIME[15:0]
Sets the RSSI based Channel Filter Bandwidth narrowing
time.
Default is 2048.
Range is 1–32767.
AN543
132 Rev. 0.9
Property 0x2205 FM_CHBW_ASSI_MIN_MAX
The FM_CHBW_ASSI_MIN_MAX property sets the maximum and minimum Channel Filter Bandwidth in kHz
based on delta (HASSI,LASSI). To force a given Channel Filter Bandwidth, set the min and max to the same value.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Notes:
1. The Si4750/51/52/53 do not support dynamic bandwidth control, hence MIN[7:0] = MAX[7:0]. The minimum of MAX[7:0]
of properties 0x2200, 0x2205, and 0x220A determines the Channel Filter Bandwidth. Default for Si4750/51/52/53 is
150 kHz.
2. Delta (HASSI,LASSI) is the absolute difference between HASSI and LASSI. In Si475x-A30 and later, at least one of
HASSI or LASSI must be greater than –15 dB in order for these settings to be observed. Otherwise, the adjacent
channels are considered empty, and the Filter Channel Bandwidth will not be limited based on ASSI.
Si4754/55/56/57 Default: 0x9623
Si4750/51/52/53 Default: 0x9696
Units: kHz
FM_CHBW_ASSI_MIN_MAX
1514131211109876543210
MAX[7:0] MIN[7:0]
0x96 0x23
Bit Name Function
15:8 MAX [7:0]
Sets the maximum Channel Filter Bandwidth in kHz.
Si4754/55/56/57 default is 150 kHz.
Si4750/51/52/53 default is 150 kHz.
Range is 1–150 kHz.
7:0 MIN [7:0]
Sets the minimum Channel Filter Bandwidth in kHz.
Si4754/55/56/57 default is 35 kHz.
Si4750/51/52/53 default is 150 kHz.
Range is 1–150 kHz.
AN543
Rev. 0.9 133
Property 0x2206 FM_CHBW_ASSI_LOW_THRESHOLD (Si4754/55/56/57 Only)
Sets the 100 kHz blocker delta (difference between HASSI and LASSI) threshold for maximum Channel Filter
Bandwidth. If the 100 kHz blocker delta is less than or equal to the programmed ASSI low threshold, then the
Channel Filter Bandwidth will be set to the maximum value programmed through Property 0x2205. The CTS bit
(and optional interrupt) is set when it is safe to send the next command. This command may only be sent in
powerup mode.
Note: Delta (HASSI,LASSI) is the absolute difference between HASSI and LASSI. In Si475x-A30 and later, at least one of
HASSI or LASSI must be greater than –15 dB in order for these settings to be observed. Otherwise, the adjacent chan-
nels are considered empty, and the Filter Channel Bandwidth will not be limited based on ASSI.
Default: 7
Units: dB
FM_CHBW_ASSI_LOW_THRESHOLD
1514131211109876543210
ASSIMIN[15:0]
0x0007
Bit Name Function
15:0 ASSIMIN[15:0]
Sets the 100 kHz blocker delta threshold for maximum channel filter
bandwidth.
Default is 7 dB.
Range is –128 to 127 dB.
AN543
134 Rev. 0.9
Property 0x2207 FM_CHBW_ASSI_HIGH_THRESHOLD (Si47 54/55/56/57 Only)
Sets the 100 kHz blocker delta (difference between HASSI and LASSI) threshold for minimum Channel Filter
Bandwidth. If the 100 kHz blocker delta is greater than the programmed ASSI high threshold, then the Channel
Filter Bandwidth will be set to the minimum value programmed through Property 0x2205. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This command may only be sent in powerup mode.
Note: Delta (HASSI,LASSI) is the absolute difference between HASSI and LASSI. In Si475x-A30 and later, at least one of
HASSI or LASSI must be greater than –15 dB in order for these settings to be observed. Otherwise, the adjacent chan-
nels are considered empty, and the Filter Channel Bandwidth will not be limited based on ASSI.
Default: 20
Units: dB
FM_CHBW_ASSI_HIGH_THRESHOLD
1514131211109876543210
ASSIMAX[15:0]
0x0014
Bit Name Function
15:0 ASSIMAX[15:0]
Sets the 100 kHz blocker delta threshold for minimum channel filter
bandwidth.
Default is 20 dB.
Range is –128 to 127 dB.
AN543
Rev. 0.9 135
Property 0x2208 FM_CHBW_ASSI_WIDENING_TIME (Si4754/55/56/57 Only)
Sets the Channel Filter Bandwidth widening time based on the 100 kHz blocker delta (difference between HASSI
and LASSI). The CTS bit (and optional interrupt) is set when it is safe to send the next command. This command
may only be sent in powerup mode.
Si475x-A20 and earlier, Default: 1
Si475x-A30 and later, Default: 3200
Si475x-A10, Units: ms
Si475x-A20, Units: 0.2 ms
Si475x-A30 and later, Units: 0.4 ms
FM_CHBW_ASSI_WIDENING_TIME
1514131211109876543210
WIDENING_TIME[15:0]
0x0C80
Bit Name Function
15:0 WIDENING_TIME[15:0]
Sets the 100 kHz blocker delta based Channel Filter Bandwidth widening
time.
Default is 1 (Si475x-A20 and earlier) or 3200 (Si475x-A30 and later).
Range is 1–32767.
AN543
136 Rev. 0.9
Property 0x2209 FM_CHBW_ASSI_NARROWING_TIME (Si4754/55/56/57 Only)
Sets the Channel Filter Bandwidth narrowing time based on the 100 kHz blocker delta (difference between HASSI
and LASSI). The CTS bit (and optional interrupt) is set when it is safe to send the next command. This command
may only be sent in powerup mode.
Default: 320
Si475x-A10, Units: ms
Si475x-A20, Units: 0.2 ms
Si475x-A30 and later, Units: 0.4 ms
FM_CHBW_ASSI_NARROWING_TIME
1514131211109876543210
NARROWING_TIME[15:0]
0x0140
Bit Name Function
15:0 NARROWING_TIME[15:0]
Sets the 100 kHz blocker delta based Channel Filter Band-
width narrowing time.
Default is 320.
Range is 1–32767.
AN543
Rev. 0.9 137
Property 0x220A FM_CHBW_ASSI200_MIN_MAX
The FM_CHBW_ASSI200_MIN_MAX property sets the maximum and minimum Channel Filter Bandwidth in kHz
based on ASSI200. To force a given Channel Filter Bandwidth, set the min and max to the same value. The CTS bit
(and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Note: The Si4750/51/52/53 do not support dynamic bandwidth control, hence MIN[7:0] = MAX[7:0]. The minimum of MAX[7:0]
of properties 0x2200, 0x2205, and 0x220A determines the Channel Filter Bandwidth. Default for Si4750/51/52/53 is 150
kHz.
Si4754/55/56/57-A10 Default: 0x9632
Si4754/55/56/57-A20/A30/A40, Default: 0x9650
Si4750/51/52/53 Default: 0x9696
Si475x/5xC-A55, Default: 0x964B
Units: kHz
FM_CHBW_ASSI200_MIN_MAX
1514131211109876543210
MAX[7:0] MIN[7:0]
0x96 0x4B
Bit Name Function
15:8 MAX[7:0]
Sets the maximum Channel Filter Bandwidth in kHz.
Si4754/
55/56/57 default is 150 kHz.
Si4750/51/52/53 default is 150 kHz.
Si475x/5xC-A55, Default is 150 kHz
Range is 1–150 kHz.
7:0 MIN[7:0]
Sets the minimum Channel Filter Bandwidth in kHz.
Si4754/55/56/57-A20/A30/A40, Default is 80 kHz.
Si4754/55/56/57-A10, Default is 55 kHz.
Si4750/51/52/53, Default is 150 kHz.
Si475x/5xC-A55, Default is 75 kHz
Range is 1–150 kHz
AN543
138 Rev. 0.9
Property 0x220B FM_CHBW_ASSI200_LOW_THRESHOLD (Si4754/55/56/57 Only)
The FM_CHBW_ASSI200_LOW_THRESHOLD property sets the ASSI200 threshold for maximum Channel Filter
Bandwidth. If the ASSI200 is less than or equal to the programmed ASSI200 low threshold, then the Channel Filter
Bandwidth will be set to the maximum value programmed through Property 0x220A. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This command may only be sent in powerup mode.
Si475x-A40 and earlier, Default: –10
Si475x/5xC-A55, Default: 0
Units: dB relative to desired channel RSSI
Property 0x220C FM_CHBW_ASSI200_HIGH_THRESHOLD (Si4754/55/56/57 Only)
The FM_CHBW_ASSI200_HIGH_THRESHOLD property sets the ASSI200 threshold for minimum Channel Filter
Bandwidth. If the ASSI200 is greater than the programmed ASSI200 high threshold, then the Channel Filter
Bandwidth will be set to the minimum value programmed through Property 0x220A. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This command may only be sent in powerup mode.
Default: 10
Units: dB relative to desired channel RSSI
FM_CHBW_ASSI200_LOW_THRESHOLD
1514131211109876543210
ASSI200MIN[15:0]
0x0000
Bit Name Function
15:0 ASSI200MIN[15:0]
Sets the 200 kHz blocker strength threshold for maximum
Channel Filter Bandwidth.
Si475x/5xC-A55, Default is 0 dB (relative to desired channel
RSSI) Range is –128 to 127 dBr.
FM_CHBW_ASSI200_HIGH_THRESHOLD
1514131211109876543210
ASSI200MAX[15:0]
0x000A
Bit Name Function
15:0 ASSI200MAX[15:0]
Sets the 200 kHz blocker strength threshold for maximum
Channel Filter Bandwidth.
Default is 10 dB (relative to desired channel RSSI)
Range is –128 to 127 dBr.
AN543
Rev. 0.9 139
Property 0x220D FM_CHBW_ASSI200_WIDENING_TIME (Si4754/55/56/57 Only)
The FM_CHBW_ASSI200_WIDENING_TIME property sets the Channel Filter Bandwidth widening time based on
the ASSI200. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This command
may only be sent in powerup mode.
Si475x-A20 and before, Default: 1
Si475x-A30 and A40: Default: 3200
Si475x/5xC-A55, Default: 4000
Si475x-A10, Units: ms
Si475x-A20, Units: 0.2 ms
Si475x-A30 and later, Units: 0.4 ms
FM_CHBW_ASSI200_WIDENING_TIME
1514131211109876543210
WIDENING_TIME[15:0]
0x0FA0
Bit Name Function
15:0 WIDENING_TIME[15:0]
Sets the 200 kHz blocker strength based channel filter
bandwidth widening time.
Si475x/5xC-A55 Default is 4000.
Range is 1–32767.
AN543
140 Rev. 0.9
Property 0x220E FM_CHBW_ASSI200_NARROWING_TIME (Si4754/55/56/57 Only)
The FM_CHBW_ASSI200_NARROWING_TIME property sets the Channel Filter Bandwidth narrowing time based
on the ASSI200. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
command may only be sent in powerup mode.
Default: 320
Si475x-A10, Units: ms
Si475x-A20, Units: 0.2 ms
Si475x-A30 and later, Units: 0.4 ms
FM_CHBW_ASSI200_NARROWING_TIME
1514131211109876543210
NARROWING_TIME[15:0]
0x0140
Bit Name Function
15:0 NARROWING_TIME[15:0]
Sets the 200 kHz blocker strength based Channel Filter
Bandwidth narrowing time.
Default is 320.
Range is 1–32767.
AN543
Rev. 0.9 141
Property 0x220F FM_CHBW_W EAKSIG_THR (Si4754/55/56/57 Only)
The FM_CHBW_WEAKSIG_THR property sets the RSSI value at which the weak signal Channel Filter Bandwidth
engine will engage (LOW) and disengage (HIGH). The CTS bit (and optional interrupt) is set when it is safe to send
the next command. This property may only be set or read in powerup mode.
Si475x-A10: This property is not available
Si475x-A20 and later, Default: 0x100D
Units: dBµV
FM_CHBW_WEAKSIG_THR
15 14 13 12 11 10 9876543210
HIGH[7:0] LOW[7:0]
0x10 0x0D
Bit Name Function
15:8 HIGH[7:0]
When RSSI is above this value, the weak signal Channel Filter Bandwidth engine
disengages. Default: 0x10.
Range: –128–127 dBµV
7:0 LOW[7:0]
When RSSI is below this value, the weak signal Channel Filter Bandwidth engine
engages. Default: 0x0D.
Range: –128–127 dBµV
AN543
142 Rev. 0.9
Property 0x2210 FM_CHBW_BLOCKER_THR
The FM_CHBW_BLOCKER_THR property sets the ASSI200 value at which the ASSI200DEV channel filter
bandwidth engine will engage (HIGH) and disengage (LOW). The CTS bit (and optional interrupt) is set when it is
safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A10 and earlier: This property is not available.
Si475x-A20: This feature is not available. Do not write to this property.
Si475x-A30 and later, Default: 0x140A
Units: dB
FM_CHBW_BLOCKER_THR
1514131211109876543210
HIGH[7:0] LOW[7:0]
0x14 0x0A
Bit Name Function
15:8 HIGH[7:0]
When ASSI200 is above this value, the ASSI200DEV chan-
nel filter bandwidth engine engages. Default is 20 dB. Range
is -128 to 127 dB.
7:0 LOW[7:0]
When ASSI200 is below this value, the ASSI200DEV chan-
nel filter bandwidth engine disengages. Default is 10 dB.
Range is –128 to 127 dB.
AN543
Rev. 0.9 143
Property 0x2214 FM_CHBW_ASSI_B_CONTROL
The FM_CHBW_ASSI_B_CONTROL property selects the behavior of ASSI_B (max ASSI) channel filter bandwidth
engine. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30, Default: 0
Si475x-A40 and later, Default: 0x2000
Units: dB
FM_CHBW_ASSI_B_CONTROL
151413121110 9 8 7654321 0
0x00 FREQOFF_CHBW_MODE[1:0] 0x00 ASSI_B_MODE
0x00 10 0x00 0
Bit Name Function
15:10 Reserved Always write to 0.
9:8 FREQOFF_CHBW_MODE[1:0]
(Available in Si4754/55/56/57-A40 only.)
Configures the behavior of Channel Filter Bandwidth based on fre-
quency offset/200kHz blocker deviation.
Default:0x2
0 = Use ASSI200DEV to control BW.
1 = Use post-channel filter carrier frequency offset to control BW.
2 = Use the average of pre-channel filter, pre-equalizer and post-equal-
izer frequency offset to control BW.
(For Si475x-A30 and earlier, always write to 0.)
7:1 Reserved Always write to 0.
0 ASSI_B_MODE
Selects the behavior of ASSI_B (max ASSI) channel filter bandwidth
engine. Default is 0.
0 = Only engage when blockers are detected at both HASSI and LASSI
through beat_detector.
1 = Always engage.
AN543
144 Rev. 0.9
Property 0x2215 FM_CHBW_STRONGDEV_MIN_MAX
The FM_CHBW_STRONGDEV_MIN_MAX property sets the maximum and minimum Channel Filter Bandwidth in
kHz based on STRONGDEV. To force a given Channel Filter Bandwidth, set the min and max to the same value.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Note: The Si4750/51/52/53 do not support dynamic bandwidth control; hence, MIN[7:0] = MAX[7:0]. The minimum of MAX[7:0]
of properties 0x2200, 0x2205, and 0x220A determines the Channel Filter Bandwidth. Default for Si4750/51/52/53-A20/
A30 is 150 kHz.
Si475x-A10: This property is not available
Si4754/55/56/57-A40 and before Default: 0x9680
Si4750/51/52/53-A40 and before, Default: 0x9696
Si475x/5xC-A55, Default: 0x9664
Units: kHz
FM_CHBW_STRONGDEV_MIN_MAX
1514131211109876543210
MAX[7:0] MIN[7:0]
0x96 0x64
Bit Name Function
15:8 MAX[7:0]
Sets the maximum Channel Filter Bandwidth in kHz.
Si4754/55/56/57, Default is 150 kHz.
Si4750/51/52/53, Default is 150 kHz.
Si475x/5xC-A55, Default is 150 kHz
Range is 1–150.
7:0 MIN[7:0]
Sets the maximum Channel Filter Bandwidth in kHz.
Si4754/55/56/57, Default is 128 kHz.
Si4750/51/52/53, Default is 150 kHz.
Range is 1–150.
AN543
Rev. 0.9 145
Property 0x2216 FM_CHBW_STRONGDEV_LOW_THRESHOLD (Si4754/55/56/57 Only)
The FM_CHBW_STRONGDEV_LOW_THRESHOLD property sets the STRONGDEV threshold for minimum
Channel Filter Bandwidth. If the STRONGDEV is less than or equal to the programmed STRONGDEV low
threshold, then the Channel Filter Bandwidth will be set to the minimum value programmed through Property
0x2215. The value used here is the result of the formula:
For mono: programmed value = desired deviation/5.5 kHz (i.e., 8 corresponds to approximately 44 kHz
deviation)
For stereo: programmed value = desired deviation/2.75 kHz (i.e., 8 corresponds to approximately 22 kHz
deviation).
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Si475x-A10: This property is not available
Si475x-A20 and later, Default: 8
Units: None
FM_CHBW_STRONGDEV_LOW_THRESHOLD
1514131211109876543210
STRONGDEVMIN[15:0]
0x0008
Bit Name Function
15:0 STRONGDEVMIN [15:0]
Sets the STRONGDEV threshold for minimum Channel Filter
Bandwidth.
Default is 8.
Range is 0–127.
AN543
146 Rev. 0.9
Property 0x2217 FM_CHBW_STRONGDEV_HIGH_THRESHOLD (Si4754/55/56/57 Only)
The FM_CHBW_STRONGDEV_HIGH_THRESHOLD property sets the STRONGDEV threshold for maximum
Channel Filter Bandwidth. If the STRONGDEV is greater than the programmed STRONGDEV high threshold, then
the Channel Filter Bandwidth will be set to the maximum value programmed through Property 0x2215. The value
used here is the result of the formula:
For mono: programmed value = desired deviation/5.5 kHz (i.e., 19 corresponds to approximately 104 kHz
deviation)
For stereo: programmed value = desired deviation/2.75 kHz (i.e., 19 corresponds to approximately 52 kHz
deviation).
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Si475x-A10: This property is not available
Si475x-A20 and later, Default: 19
Units: None
FM_CHBW_STRONGDEV_HIGH_THRESHOLD
1514131211109876543210
STRONGDEVMIN[15:0]
0x0013
Bit Name Function
15:0 STRONGDEVMIN [15:0]
Sets the STRONGDEV threshold for maximum Channel Fil-
ter Bandwidth.
Default is 19.
Range is 0–127.
AN543
Rev. 0.9 147
Property 0x2218 FM_CHBW_STRONGDEV_WIDENING_TIME (Si4754/55/56/57 Only)
The FM_CHBW_STRONGDEV_WIDENING_TIME property sets the STRONGDEV based Channel Filter
Bandwidth widening time. The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Si475x-A10: This property is not available
Si475x-A20 and later, Default: 4096
Si475x-A20 Units: 0.2 ms
Si475x-A30 and later, Units: 0.4 ms
Units: ms
FM_CHBW_STRONGDEV_WIDENING_TIME
1514131211109876543210
WIDENING_TIME[15:0]
0x1000
Bit Name Function
15:0 WIDENING_TIME [15:0]
Sets the STRONGDEV based Channel Filter Bandwidth wid-
ening time.
Default is 4096.
Range is 1–32767.
AN543
148 Rev. 0.9
Property 0x2219 FM_CHBW_STRONGDEV_NARROWING_TIME (Si4754/55/56/57 Only)
The FM_CHBW_STRONGDEV_NARROWING_TIME property sets the STRONGDEV based Channel Filter
Bandwidth narrowing time. The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Si475x-A10: This property is not available
Si475x-A20 and later, Default: 512
Si475x-A20, Units: 0.2 ms
Si475x-A30 and later, Units: 0.4 ms
FM_CHBW_STRONGDEV_NARROWING_TIME
1514131211109876543210
NARROWING_TIME[15:0]
0x0200
Bit Name Function
15:0 NARROWING_TIME[15:0]
Sets the STRONGDEV based Channel Filter Bandwidth nar-
rowing time.
Default is 512.
Range is 1–32767.
AN543
Rev. 0.9 149
Property 0x221A FM_CHBW_ASSI200DEV_ MIN_MAX
The FM_CHBW_ASSI200DEV_MIN_MAX property sets the maximum and minimum channel filter bandwidth in
kHz based on ASSI200DEV. To force a given Channel Filter Bandwidth, set the min and max to the same value.
This engine is only enabled when ASSI200 is above the FM_CHBW_BLOCKER_THR. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Note: The Si4750/51/52/53 do not support dynamic bandwidth control, hence MIN[7:0] = MAX[7:0]. Default for Si4750/51/52/
53-A10 is 110 kHz. The default for Si4750/51/52/53-A30 is 150 kHz.
Si475x-A20 and earlier: This property is not available.
Si475x-A30, Default: 0x5020
Si475x-A40 and later: Default: 0x9646
FM_CHBW_ASSI200DEV_MIN_MAX
1514131211109876543210
MAX[7:0] MIN[7:0]
0x96 0x46
Bit Name Function
15:8 MAX[7:0] Sets the maximum Channel Filter Bandwidth in kHz.
Range is 1–150 kHz.
7:0 MIN[7:0] Sets the minimum Channel Filter Bandwidth in kHz.
Range is 1–150 kHz.
AN543
150 Rev. 0.9
Property 0x221B FM_CHBW_ASSI200DEV_LOW_THRESHOLD (Si475 4/55/56/57 Only)
The FM_CHBW_ASSI200DEV_LOW_THERSHOLD property sets the ASSI200DEV threshold for maximum
Channel Filter Bandwidth. This engine is only enabled when ASSI200DEV is above the
FM_CHBW_BLOCKER_THR. If the ASSI200DEV is less than or equal to the programmed ASSI200DEV low
threshold then the Channel Filter Bandwidth will be set to maximum value programmed through Property 0x221A.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 50
FM_CHBW_ASSI200DEV_LOW_THRESHOLD
1514131211109876543210
ASSI200DEVMAX[15:0]
0x0032
Bit Name Function
15:0 ASSI200DEVMAX[15:0]
Sets the ASSI200DEV threshold for maximum Channel Filter Bandwidth.
The minimum such deviation is equal to ASSI200DEVMAX*1.5 kHz minus
12 kHz.
Default is 50.
Range is 0–127.
AN543
Rev. 0.9 151
Property 0x221C FM_CHBW_ASSI200DEV_HIGH_THRESHOLD (Si4754/55/56/57 Only)
The FM_CHBW_ASSI200DEV_HIGH_THERSHOLD property sets the ASSI200DEV threshold for minimum
Channel Filter Bandwidth. This engine is only enabled when ASSI200DEV is above the
FM_CHBW_BLOCKER_THR. If the ASSI200DEV is greater than the programmed ASSI200DEV high threshold
then the Channel Filter Bandwidth will be set to minimum value programmed through Property 0x221A. The CTS
bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 90
Property 0x221D FM_CHBW_ASSI200DEV_WIDENING_TIME (Si4754/55/56/57 Only)
The FM_CHBW_ASSI200DEV_WIDENING_TIME property sets the channel filter bandwidth widening time based
on the ASSI200DEVThe CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 2048
Units: 0.4 ms
FM_CHBW_ASSI200DEV_HIGH_THRESHOLD
1514131211109876543210
ASSI200DEVMIN[15:0]
0x005A
Bit Name Function
15:0 ASSI200DEVMIN[15:0]
Sets the ASSI200DEV threshold for minimum Channel Filter Bandwidth.
The maximum such deviation is equal to ASSI200DEVMIN*1.5 kHz minus
12 kHz.
Default is 90.
Range is 0-127.
FM_CHBW_ASSI200DEV_WIDENING_TIME
1514131211109876543210
WIDENING_TIME[15:0]
0x0800
Bit Name Function
15:0 WIDENING_TIME[15:0]
Sets the ASSI200DEV based Channel Filter Bandwidth widening time.
Default is 2048 (819 ms).
Range is 1–32767.
AN543
152 Rev. 0.9
Property 0x221E FM_CHBW_ASSI200DEV_NARROWING_TIME (Si4754/55/56/57 Only)
The FM_CHBW_ASSI200DEV_WIDENING_TIME property sets the channel filter bandwidth narrowing time based
on the ASSI200DEVThe CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 128
Units: 0.4 ms
Property 0x221F FM_CHBW_A SSI_B_MIN_MAX
The FM_CHBW_ASSI_B_MIN_MAX property sets the maximum and minimum channel filter bandwidth in kHz
based on max (HASSI,LASSI). To force a given Channel Filter Bandwidth, set the min and max to the same value.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Note: The Si4750/51/52/53 do not support dynamic bandwidth control, hence MIN[7:0] = MAX[7:0]. Default for Si4750/51/52/
53 is 150 kHz.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0x9696
FM_CHBW_ASSI200DEV_NARROWING_TIME
1514131211109876543210
NARROWING_TIME[15:0]
0x0080
Bit Name Function
15:0 NARROWING_TIME[15:0]
Sets the ASSI200DEV based Channel Filter Bandwidth narrowing time.
Default is 128 (51 ms).
Range is 1–32767.
FM_CHBW_ASSI_B_MIN_MAX
1514131211109876543210
MAX[7:0] MIN[7:0]
0x96 0x96
Bit Name Function
15:8 MAX[7:0]
Sets the maximum Channel Filter Bandwidth in kHz.
Default is 150 kHz.
Range is 1–150 kHz.
7:0 MIN[7:0]
Sets the minimum Channel Filter Bandwidth in kHz.
Default is 150 kHz.
Range is 1–150 kHz.
AN543
Rev. 0.9 153
Property 0x2220 FM_CHBW_ASSI_B_LOW_THRESHOLD (Si4754/55/56/57 Only)
The FM_CHBW_ASSI_B_LOW_THERSHOLD property sets the max (HASSI,LASSI) threshold for maximum
Channel Filter Bandwidth. If the max (HASSI,LASSI) is less than or equal to the programmed max (HASSI,LASSI)
low threshold then the channel Filter Bandwidth will be set to maximum value programmed through Property
0x221F. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and A40, Default: 0
Si475x/5xC-A55, Default: –5
Units: dB
Property 0x2221 FM_CHBW_ASSI_B_HIGH_THRESHOLD (Si4754/55/56/57 Only)
The FM_CHBW_ASSI_B_HIGH_THERSHOLD property sets the max (HASSI,LASSI) threshold for minimum
Channel Filter Bandwidth. If the max (HASSI,LASSI) is greater than the programmed max (HASSI,LASSI) high
threshold then the Channel Filter Bandwidth will be set to minimum value programmed through Property 0x221A.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Si475x-A20 and earlier: This property is not available
Si475x-A30 and A40, Default: 0
Si475x/5xC-A55, Default: 5
Units: dB
FM_CHBW_ASSI_B_LOW_THRESHOLD
1514131211109876543210
ASSI_B_MAX[15:0]
0xFFFB
Bit Name Function
15:0 ASSI_B_MAX[15:0]
Sets the max (HASSI,LASSI) threshold for maximum channel Filter Band-
width.
Si475x/5xC-A55, Default is –5.
Range is –128 to 127 dB.
FM_CHBW_ASSI_B_HIGH_THRESHOLD
1514131211109876543210
ASSI_B_MIN[15:0]
0x0005
Bit Name Function
15:0 ASSI_B_MIN[15:0]
Sets the max (HASSI,LASSI) threshold for minimum Channel Filter Band-
width.
Si475x/5xC-A55, Default is 5.
Range is –128 to 127 dB.
AN543
154 Rev. 0.9
Property 0x2222 FM_CHBW_ASSI_B_WIDENING_TIME (Si4754/55/56/57 Only)
The FM_CHBW_ASSI_B_WIDENING_TIME property sets the channel filter bandwidth widening time based on the
max (HASSI,LASSI). The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-
A
30 and A40
,
Defaul
t: 1
Si475x/5xC-A55, Default: 4000
Unit: 0.4 ms
Property 0x2223 FM_CHBW_ASSI_B_NARROWING_TIME (Si4754/55/56/57 Only)
The
FM_CHBW_ASSI_B_WIDENING_TIME
property
sets
the
channel
filter
bandwidth
narrowing
time
based
on
the max
(HASSI,LASSI).
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property
may
only
be
set
or
read
in
powerup
mode.
Si475x-
A
20 and earlier
:
T
his proper
ty
is no
t
availabl
e.
Si475x
-
A3
0
and
A40,
Default:
1
Si475x/5xC-A55, Default: 400
Unit
s:
0.4 ms
FM_CHBW_ASSI_B_WIDENING_TIME
1514131211109876543210
WIDENING_TIME[15:0]
0x0FA0
Bit Name Function
15:0 WIDENING_TIME[15:0]
Sets the max (HASSI,LASSI) based Channel Filter Bandwidth widening
time.
Si475x/5xC-A55, Default is 4000 (0.4 ms).
Range is 1–32767.
FM_CHBW_ASSI_B_NARROWING_TIME
1514131211109876543210
NARROWING_TIME[15:0]
0x0190
Bit Name Function
15:0 NARROWING_TIME[15:0]
Sets the max (HASSI,LASSI) based Channel Filter Bandwidth narrowing
time.
Si475x/5xC-A55, Default is 400 (0.4 ms).
Range is 1–32767.
AN543
Rev. 0.9 155
Property 0x3105 FM_LOWCUT_MIN_FREQ
The FM_LOWCUT_MIN_FREQ property sets the minimum cutoff frequency. The LowCut tracks the HICUT
engine; therefore, thresholds are programmed in HICUT threshold properties (0x3600, 0x3608, 0x3610) and the
HIBLEND threshold properties (0x3700, 0x3708, 0x3710). Setting the property to 0 disables LowCut. The CTS bit
(and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Note: This setting requires a re-tune before it can come into effect.
Si475x-A20 and earlier: This feature is not available. Do not write to this property.
Si475x-A30 and later, Default: 0
Units: Hz
Property 0x3106 FM_LOWCUT_MAX_FREQ
The FM_LOWCUT_MAX_FREQ property sets the maximum cutoff frequency. The LowCut tracks the HICUT
engine, therefore thresholds are programmed in HICUT threshold properties (0x3600, 0x3608, 0x3610) and the
HIBLEND threshold properties (0x3700, 0x3708, 0x3710). The CTS bit (and optional interrupt) is set when it is safe
to send the next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This feature is not available. Do not write to this property.
Si475x-A30 and later, Default: 0
Units: Hz
FM_LOWCUT_MIN_FREQ
1514131211109876543210
FREQ_MIN[15:0}
0x0000
Bit Name Function
15:0 FREQ_MIN[15:0]
Sets the minimum LOW-CUT cutoff frequency in Hz. Default is disabled.
Range is 0 (disable) or 8–1000 Hz.
0 = Disabled.
FM_LOWCUT_MAX_FREQ
1514131211109876543210
FREQ_MAX[15:0]
0x0000
Bit Name Function
15:0 FREQ_MAX[15:0]
Sets the maximum LOW-CUT cutoff frequency in Hz. Note that if property
0x3105 (FM_LOWCUT_MIN_FREQ) is non-zero, this property must be
set to a value no less than property 0x3105.
Default is 0 Hz.
Range is 8–1000 Hz.
AN543
156 Rev. 0.9
Property 0x3200 FM_POP_NOISE_FADE_HYST (Si4754/55/56/57 Only)
The FM_POP_NOISE_FADE_HYST property sets the thresholds for FM pop filter fading hysteresis. The pop noise
filter will engage once fade is at least equal to the HIGH setting. Once engaged, the pop filter will remain engaged
until the fade becomes as low as the LOW setting. The CTS bit (and optional interrupt) is set when it is safe to send
the next command. This property may only be set or read in powerup mode.
Note: Fade is an internal metric, and is not available to the user for inspection. Units are in dB
Si475x-
A
20 and earlier
:
T
his fea
t
ure is no
t
available
.
Do no
t
write to this proper
ty
.
Si475x-
A
30 and A40
,
Defaul
t:
0x0A06
Si475x/5xC-A55, Default: 0x0604
Property 0x3207 FM_POP_NOISE_MODE (Si4754/55/56/57 Only)
Th
e FM_POP_NOISE_M
O
DE proper
ty
sets the mitigation mode for the
FM
POP
filter
.
T
he CTS bit (and optional
in
terr
up
t)
is set when it is safe to send the next command
.
This proper
ty
may only be se
t
or read in powerup mode
.
Si475x-A40 and earlier, Defaul
t:
0x0001
Si475x/5xC-A55, Default: 0x0002
FM_POP_NOISE_FADE_HYST
1514131211109876543210
HIGH[7:0] LOW[7:0]
0x06 0x04
Bit Name Function
15:8 HIGH[7:0] If the fade this greater than this value, the FM pop filter is turned on.
Si475x/5xC-A55, Default is 6.
Range is –127 to 127.
7:0 LOW[7:0] If the fade this less than this value, the FM pop filter is turned off.
Si475x/5xC-A55, Default is 4. Range is –127 to 127.
FM_POP_NOISE_MODE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x0000 MODE[1:0]
0x0000 02
Bit Name Function
1:0 MODE[1:0]
Sets the mitigation mode for FM POP filter.
Si475x/5xC-A55,
Default is 2.
0 = Pop mitigation off.
1 = Pop mitigation at MPX on.
2 = Pop mitigation at MPX on, but MPX RMS level sets the mitigation limit (only
applicable to Si475x-A30 and later).
AN543
Rev. 0.9 157
Property 0x3208 FM_POP_NOISE_RSSI_THRESHOLDS (Si4754/55/56/57 Only)
The FM_POP_NOISE_RSSI_THERSHOLDS property sets the change in RSSI thresholds for maximum and
minimum MPX limiting (set by property 0x3209). The CTS bit (and optional interrupt) is set when it is safe to send
the next command. This property may only be set or read when in the powerup mode.
Si475x-A10: This property is not available.
Si475x-A20/A30/A40, Default: 0xECE7
Si475x/5xC-A55, Default: 0xFDF9
Property 0x3209 FM_POP_NOISE_RSSI_MPX_LIMIT (Si4754/55/56/57 Only)
Th
e
F
M_POP_N
OISE_
R
SSI_MPX_
L
IMIT
proper
ty
sets the minimum and maximum limit for MPX limiter based on
change in RSSI.
T
o force a given setting (i
.
e
.
either completely on or completely of
f)
set YMIN = YMAX.
T
o disable
the
MPX
limiter
based
on
change
in
RSSI,
set
YMIN = YMAX = 127
.
The
CTS
bit
(and
optional
interrupt)
is
set
when it is sa
fe to
send the ne
xt
command. This prop
erty may
only be set or read when in the powerup mode
.
Si475x
-
A10:
This
property
is
not
available.
Si475x-
A
20/A30/A40
,
Defaul
t:
0x1009
Si475x/5xC-A55, Default: 0x0502
FM_POP_NOISE_RSSI_THRESHOLDS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
XMAX[7:0] XMIN[7:0]
0xFD 0xF9
Bit Name Function
15:8 XMAX[7:0]
Sets the maximum change in RSSI threshold. If the change in RSSI is above this
threshold maximum MPX limiting will be achieved as set by property 0x3209.
Range is –127 to 127 (dB).
7:0 XMIN[7:0]
Sets the minimum change in RSSI threshold. If the change in RSSI is below this
threshold minimum MPX limiting will be achieved as set by property 0x3209.
Range is –127 to 127 (dB).
FM_POP_NOISE_RSSI_MPX_LIMIT
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
YMAX[7:0] YMIN[7:0]
0x05 0x02
Bit Name Function
15:8 YMAX[7:0] Sets the upper limit. Si475x/5xC-A55, Default: 0x05. Range 0–127.
7:0 YMIN[7:0] Sets the lower limit. Si475x/5xC-A55, Default: 0x02. Range 0–127.
AN543
158 Rev. 0.9
Property 0x320A FM_POP_NOISE_RSSI_MPX_ATTACK (Si4754/55/56/57 Only)
The FM_POP_NOISE_RSSI_MPX_ATTACK property sets the attack rate for MPX pop limiter mitigation. The
attack time is in milliseconds. The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Si475x/5xC-A55, Default: 0x001E
Si475x-A40 and earlier, Default: 0x0001
Si475x-A10: This property is not available.
Si475x-A20, Units: 0.05 ms
Si475x-A30 and later, Units: 0.4 ms
Property 0x320B FM_POP_NOISE_RSSI_MPX_RELEASE (Si4754/55/56/57 Only)
The FM_P
O
P_NOISE_RSSI_MPX_RELEASE proper
ty
sets the release rate for pop limiter mitigation. The release
time
is
in
milliseconds.
The
CTS
bit
(and
optional
interrupt)
is
set
when
it
is
safe
to
send
the
next
command.
This
proper
ty
may only be se
t
or read in powerup mode.
Si475x/5xC-A55, Default: 3000
Si475x-A40 and earlier, Default:
1
Si475x-
A
10
:
This proper
ty
is not available.
Si475x
-
A2
0,
Units:
0.05 ms
FM_POP_NOISE_RSSI_MPX_ATTACK
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0001E
Bit Name Function
15:0 ATTACK[15:0] Sets the attack rate for MPX pop limiter mitigation. Range is 1 –32767.
FM_POP_NOISE_RSSI_MPX_RELEASE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0BB8
Bit Name Function
15:0 RELEASE[15:0] Sets the release rate for MPX pop limiter mitigation. Range is 1–32767.
AN543
Rev. 0.9 159
Property 0x320C FM_POP_NOISE_MPX_USN_THRESHOLDS (Si4754/55/56/57 Only)
The FM_POP_NOISE_MPX_USN_THRESHOLDS property sets the ratio of MPX to USN thresholds for maximum
and minimum MPX limiting (set by property 0x320D). The CTS bit (and optional interrupt) is set when it is safe to
send the next command. This property may only be set or read when in the powerup mode.
Si475x-A10 is not available
Si475x-A40 and before, Default: 0x03FE
Si475x/5xC-A55, Default: 0x0501
Property 0x320D FM_POP_NOISE_MPX_USN_LIMITS (Si4754/55/56/57 Only)
The
FM_POP_NOISE_MPX_USN_LIMIT
property
sets
the
maximum
and
minimum
limit
for
MPX
limiter
based
on
ratio of MPX to U
SN
.
T
o force a given setting (i.e. either completely on or completely of
f)
set YMIN = YMAX. The
CTS
bit
(and
optional
interrupt)
is
set
when
it
is
safe
to
send
the
next
command.
This
property
may
only
be
set
or
read
when
in
the
powerup
mode
.
Si475x-A1
0
is
not
available
Si475x-
A
40 and before
,
Defaul
t:
0x1009
Si475x/5xC-A55, Default: 0x0502
FM_POP_NOISE_MPX_USN_THRESHOLDS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
XMAX[7:0] XMIN[7:0]
0x05 0x01
Bit Name Function
15:8 XMAX[7:0]
Sets the maximum MPX limiting based on ratio of MPX to USN. If the ratio of MPX to
USN is above this threshold maximum MPX limiting will be achieved as set by
FM_POP_NOISE_MPX_USN_LIMIT. Range is –127 to127.
7:0 XMIN[7:0]
Sets the minimum MPX limiting based on ratio of MPX to USN. If the ratio of MPX to
USN is below this threshold minimum MPX limiting will be achieved as set by
FM_POP_NOISE_MPX_USN_LIMIT. Range is –127 to 127.
FM_POP_NOISE_MPX_USN_LIMIT
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
YMAX[7:0] YMIN[7:0]
0x05 0x02
Bit Name Function
15:8 YMAX[7:0] Maximum limiting for MPX_NOISE based limiter. Range is 0–127.
7:0 YMIN[7:0] Minimum limiting for MPX_NOISE based limiter. Range is 0–127.
AN543
160 Rev. 0.9
Property 0x320E FM_POP_NOISE_MPX_USN_ATTACK (Si4754/55/56/57 Only)
The FM_POP_NOISE_MPX_USN_ATTACK property sets the attack rate for MPX pop limiter mitigation. The attack
time is in milliseconds.
Si475x-A10 is not available
Si475x-A20/A30/A40, Default: 1
Si475x/5xC-A55, Default: 30
Si475x-A20, Units: 0.05 ms
Si475x-A30 and later, Units: 0.4 ms
Property 0x320F FM_POP_NOISE_MPX_USN_RELEASE (Si4754/55/56/57 Only)
The FM_POP_NOISE_MPX_USN_RELEASE property sets the release rate for MPX pop limiter mitigation. The
release time is in milliseconds. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read in powerup mode.
Si475x-A10 is not available
Si475x-A20/A30/A40, Default: 1
Si475x/5xC-A55, Default: 3000
Si475x-A20, Units: 0.05 ms
Si475x-A30 and later, Units: 0.4 ms
FM_POP_NOISE_MPX_USN_ATTACK
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x001E
Bit Name Function
15:0 ATTACK[15:0] Maximum limiting for MPX_NOISE based limiter. Range is 1–32767.
FM_POP_NOISE_MPX_USN_RELEASE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0BB8
Bit Name Function
15:0 RELEASE[15:0] Sets release rate for MPX pop limiter mitigation. Range is 1–32767.
AN543
Rev. 0.9 161
Property 0x3210 FM_POP_NOISE_SCALE
The FM_POP_NOISE_SCALE property sets the scale for the FM pop filter. The CTS bit (and optional interrupt) is
set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 127
Property 0x3400 FM_MULT_EQ_CTL (Si4754/55/56/57 Only)
The FM_MULT_EQ_CTL property controls the multipath channel equalizer. The CTS bit (and optional interrupt) is
set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0x0601
Si475x/5xC-A55, Default: 0x8001
FM_POP_NOISE_SCALE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x00 SCALE[7:0]
0x00 0x7F
Bit Name Function
15:8 Reserved Always write to 0.
7:0 SCALE[7:0]
Sets the scale for the FM pop filter. This allows users to scale back the pop
filter. Default is 127. Range is 0–127, which scales the pop filter from full on
(127) to full off (0)
FM_MULT_EQ_CTL
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
SOURCE CMA_CTRL_MP 0 NUM_TAPS[4:0] 0x00 MULT_EQ_CTL[1:0]
1 0 0 0x00 0x00 0x1
Bit Name Function
15 SOURCE
(Available in Si475x/5xC-A55 and later only. Otherwise write to 0.)
When NUM_TAPS is in auto mode, this sets the metric source to use for
determining the number of taps to use.
0 = Determine number of taps from RSSI metric.
1 = Determine number of taps from SNR metric.
14 CMA_CTRL_MP
Sets the CMA_CTRL_MP value between a less aggressive setting and a more
aggressive setting.
0 = less aggressive setting.
1 = more aggressive setting.
AN543
162 Rev. 0.9
13 Reserved Always write to 0.
12:8 NUM_TAPS[4:0]
(Only applicable to Si475x/5xC-A55 and later, it is fixed at 6 taps for Si4754/55/
56/57-A30 and A40). Sets the number of taps for the CHEQ.
Default is Automatically control taps.
0 = Automatically changes the number of taps from 1 to 20 based on signal
quality metrics.
1=1 taps.
2=2 taps.
3=3 taps.
4=4 taps.
5=5 taps.
6=6 taps.
7=7 taps.
8=8 taps.
9=9 taps.
10 = 10 taps.
12 = 12 taps.
14 = 14 taps.
16 = 16 taps.
18 = 18 taps.
20 = 20 taps.
7:2 Reserved Always write to 0.
1:0 MULT_EQ_CTL[1:0]
Controls the multipath channel equalizer.
Default is 1.
0 = Channel equalizer OFF.
1 = Channel equalizer ON.
Bit Name Function
AN543
Rev. 0.9 163
Property 0x3401 FM_MULT_EQ_NOISE_DISABLE (Si4754/55/56/57 Only)
The FM_MULT_EQ_NOISE_DISABLE property sets the RSSI threshold below which the channel equalizer will
use noise measurements to enable/disable the channel equalizer. The CTS bit (and optional interrupt) is set when
it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available
Si475x-A30, Default: 0xFC81
Si475x-A40 and later, Default: 0xFCFA
Property 0x3402 FM_MULT_EQ_CTL_STEP (Si4754/55/56/57 Only)
The FM_MULT_EQ_CTL_STEP property controls the multipath channel equalizer tap updating step. The CTS bit
(and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A20 and earlier: This property is not available
Si475x-A30 and later, Default: 0x0000
FM_MULT_EQ_NOISE_DISABLE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
MULT_EQ_ON_LEVEL[7:0] MULT_EQ_OFF_LEVEL[7:0]
0xFC 0xFA
Bit Name Function
15:8 MULT_EQ_ON_LEVEL[7:0] RSSI level above which noise measurements will not be used to enable/
disable the equalizer. Range is –127 to 127.
7:0 MULT_EQ_OFF_LEVEL[7:0]
RSSI level below which noise measurements will be used to enable/dis-
able the equalizer. Set to –127 (0x81) to disable.
Range is –127 to 127.
FM_MULT_EQ_CTL_STEP
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
STEP[15:0]
0x0000
Bit Name Function
15:0 STEP[15:0]
Sets the multipath channel equalizer tap updating step. The number
should always be a positive number. Higher number indicates higher
updating step. Default is 0 (on chip control).
AN543
164 Rev. 0.9
Property 0x3409 FM_EQ_CTL_AUTOTAP
The FM_EQ_CTL_AUTOTAP property sets the SNR or RSSI trigger and end threshold for CHEQ auto tap control,
it only works when NUM_TAPS in property 0x3400 is set to be 0(automatic EQ taps). The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier: This property is not available.
Si475x/5xC-A55, Default: 0x03FB
FM_EQ_CTL_AUTOTAP
1514131211109876543210
TRIGTHR[7:0] ENDTHR[7:0]
0x03 0xFB
Bit Name Function
15:8 TRIGTHR[7:0]
Sets the SNR or RSSI threshold that CHEQ will automatically begin to reduce
its taps, there should be 0 < (TRIGTHR – ENDTHR) < 32, the range is –127 to
127.
Default is: 3
7:0 ENDTHR[7:0]
Sets the SNR or RSSI threshold that CHEQ will finally reduce to its minimum
tap, there should be 0 < (TRIGTHR – ENDTHR) < 32, the range is –127 to
127.
Default is: –5
AN543
Rev. 0.9 165
Property 0x3500 FM_BLEND_RSSI_THRESHOLDS
The FM_BLEND_RSSI_THRESHOLDS property sets the limits for the RSSI input metric on the stereo blend
mitigation engine. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: 0x3719
Units: dBµV
Property 0x3501 FM_BLEND_RSSI_STEREO_SEP
The FM_BLEND_RSSI_STEREO_SEP property sets the maximum and minimum stereo separation based on
RSSI (set by Property 0x3500) on the blend engine. You can force a constant stereo separation value by setting
ST_SEPMAX and ST_SEPMIN to the same value. To disable the stereo blend based on RSSI, set
ST_SEPMAX = ST_SEPMIN = 64. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Default: 0x2D00
Units: dB
FM_BLEND_RSSI_THRESHOLDS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RSSIMAX[7:0] RSSIMIN[7:0]
0x37 0x19
Bit Name Function
15:8 RSSIMAX[7:0]
Sets the RSSI Max threshold. If RSSI is above this threshold, maximum stereo
separation will be achieved as set by property 0x3501. Default is 55 dBµV. Range
is –20 to 120 dBµV.
7:0 RSSIMIN[7:0]
Sets the RSSI Min threshold. If RSSI is below this threshold, minimum stereo sepa-
ration will be achieved as set by property 0x3501. Default is 25 dBµV. Range is –20
to 120 dBµV.
FM_BLEND_RSSI_STEREO_SEP
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ST_SEPMAX[7:0] ST_SEPMIN[7:0]
0x2D 0x00
Bit Name Function
15:8 ST_SEPMAX[7:0] Sets the maximum stereo separation. Default is 45 dB. Range is 0–64 dB.
7:0 ST_SEPMIN[7:0] Sets the minimum stereo separation. Default is 0 dB. Range is 0–64 dB.
AN543
166 Rev. 0.9
Property 0x3502 FM_BL END_RSSI_ATTACK_TIME
The FM_BLEND_RSSI_ATTACK_TIME property sets the transition time for which the stereo blend mitigation
engine decreases the stereo separation based on RSSI. The CTS bit (and optional interrupt) is set when it is safe
to send the next command. This property may only be set or read in powerup mode.
Default: 16
Units: ms
Property 0x3503 FM_BLEND_RSSI_RELEASE_TIME
The FM_BLEND_RSSI_RELEASE_TIME property sets the transition time for which the stereo blend mitigation
engine increases the stereo separation based on RSSI. The CTS bit (and optional interrupt) is set when it is safe to
send the next command. This property may only be set or read in powerup mode.
Default: 4000
Units: ms
FM_BLEND_RSSI_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0010
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the stereo blend mitigation engine
decreases the stereo separation based on RSSI. Default is 16 ms. Range
is 1–32767 ms.
FM_BLEND_RSSI_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0FA0
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the stereo blend mitigation engine
increases the stereo separation based on RSSI. Default is 4000 ms. Range
is 1–32767 ms.
AN543
Rev. 0.9 167
Property 0x3508 FM_BLEND_MULTIPATH_THRESHOLDS
The FM_BLEND_MULTIPATH_THRESHOLDS property sets the Multipath thresholds for maximum and minimum
stereo separation (set by Property 0x3509) on the blend engine. The CTS bit (and optional interrupt) is set when it
is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 0x1E3C
Si475x/5xC-A55, Default: 0x0A14
FM_BLEND_MULTIPATH_THRESHOLDS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
MULTMIN[7:0] MULTMAX[7:0]
0x0A 0x14
Bit Name Function
15:8 MULTMIN[7:0]
Sets the Multipath Min threshold. If Multipath is below this threshold, maxi-
mum stereo separation will be achieved as set by property 0x3509.
Si475x/5xC-A55, Default is 10.
Si475x-A10 and earlier, and Si475x-A30 and later: Range is 0–127
Si475x-A20: Range: 0–100.
7:0 MULTMAX[7:0]
Sets the Multipath Max threshold. If Multipath is above this threshold, mini-
mum stereo separation will be achieved as set by property 0x3509.
Si475x/5xC-A55, Default is 20.
Si475x-A10 and earlier, and Si475x-A30 and later: Range is 0–127
Si475x-
A20: Range: 0–100
AN543
168 Rev. 0.9
Property 0x3509 FM_BLEND_MULTIPATH_STEREO_SEP
The FM_BLEND_MULTIPATH_STEREO_SEP property sets the maximum and minimum stereo separation based
on Multipath (set by Property 0x3508) on the blend engine. You can force a constant stereo separation value by
setting ST_SEPMAX and ST_SEPMIN to the same value. To disable the fast stereo blend based on Multipath, set
ST_SEPMAX = ST_SEPMIN = 64. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Default: 0x2D00
Units: dB
Property 0x350A FM_BLEND_MULTIPATH_ATTACK_TIME
The FM_BLEND_MULTIPATH_ATTACK_TIME property sets the transition time for which the stereo blend
mitigation engine decreases the stereo separation based on Multipath. The CTS bit (and optional interrupt) is set
when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 16
Units: ms
FM_BLEND_MULTIPATH_STEREO_SEP
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ST_SEPMAX[7:0] ST_SEPMIN[7:0]
0x2D 0x00
Bit Name Function
15:8 ST_SEPMAX[7:0] Sets the maximum stereo separation. Default is 45 dB. Range is 0–64 dB.
7:0 ST_SEPMIN[7:0] Sets the minimum stereo separation. Default is 0 dB. Range is 0–64 dB.
FM_BLEND_MULTIPATH_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0010
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the stereo blend mitigation engine
decreases the stereo separation based on Multipath.
Default is 16 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 169
Property 0x350B FM_BLEND_MULTIPATH_RELEASE_TIME
The FM_BLEND_MULTIPATH_RELEASE_TIME property sets the transition time for which the stereo blend
mitigation engine increases the stereo separation based on RSSI. The CTS bit (and optional interrupt) is set when
it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 4000
Units: ms
Property 0x3510 FM_BLEND_USN_THRESHOLDS
The FM_BLEND_USN_THRESHOLDS property sets the USN thresholds for maximum and minimum stereo
separation (set by Property 0x3511) on the blend engine. The CTS bit (and optional interrupt) is set when it is safe
to send the next command. This property may only be set or read in powerup mode.
Default: 0x341B
Units: –dBFS
FM_BLEND_MULTIPATH_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0FA0
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the stereo blend mitigation engine
increases the stereo separation based on Multipath.
Default is 4000 ms. Range is 1–32767 ms.
FM_BLEND_USN_THRESHOLDS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
USNMIN[7:0] USNMAX[7:0]
0x34 0x1B
Bit Name Function
15:8 USNMIN[7:0]
Sets the USN Min threshold. If USN is below this threshold, maximum ste-
reo separation will be achieved as set by property 0x3511.
Default is –52 dBFS. Range is 0–127 –dBFS.
7:0 USNMAX[7:0]
Sets the USN Max threshold. If USN is above this threshold, minimum ste-
reo separation will be achieved as set by property 0x3511.
Default is –27 dBFS. Range is 0–127 –dBFS.
AN543
170 Rev. 0.9
Property 0x3511 FM_BLEND_USN_STEREO_SEP
The FM_BLEND_USN_STEREO_SEP property sets the maximum and minimum stereo separation based on USN
(set by Property 0x3510) on the blend engine. You can force a constant stereo separation value by setting
ST_SEPMAX and ST_SEPMIN to the same value. To disable the stereo blend based on USN, set
ST_SEPMAX = ST_SEPMIN = 64. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Default: 0x2D00
Units: dB
Property 0x3512 FM_BL END_USN_ATTACK_TIME
The FM_BLEND_USN_ATTACK_TIME property sets the transition time for which the stereo blend mitigation
engine decreases the stereo separation based on USN. The CTS bit (and optional interrupt) is set when it is safe to
send the next command. This property may only be set or read in powerup mode.
Default: 16
Units: ms
FM_BLEND_USN_STEREO_SEP
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ST_SEPMAX[7:0] ST_SEPMIN[7:0]
0x2D 0x00
Bit Name Function
15:8 ST_SEPMAX[7:0] Sets the maximum stereo separation. Default is 45 dB. Range is 0–100 dB.
7:0 ST_SEPMIN[7:0] Sets the minimum stereo separation. Default is 0 dB. Range is 0–100 dB.
FM_BLEND_USN_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0010
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the stereo blend mitigation engine
decreases the stereo separation based on USN.
Default is 16 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 171
Property 0x3513 FM_BLEND_USN_RELEASE_TIME
The FM_BLEND_USN_RELEASE_TIME property sets the transition time for which the stereo blend mitigation
engine increases the stereo separation based on USN. The CTS bit (and optional interrupt) is set when it is safe to
send the next command. This property may only be set or read in powerup mode.
Default: 4000
Units: ms
Property 0x3518 FM_BLEND_CHBW_LIMITS (Si4754/55/56/57 Only)
The FM_BLEND_CHBW_LIMITS property sets the limits for the CHBW input metric on the stereo blend mitigation
engine. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Default: 0x0000
Units: 100 Hz
FM_BLEND_USN_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0FA0
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the stereo blend mitigation engine
increases the stereo separation based on USN.
Default is 4000 ms. Range is 1–32767 ms.
FM_BLEND_CHBW_LIMITS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
CHBWMAX[7:0] CHBWMIN[7:0]
0x00 0x00
Bit Name Function
15:8 CHBWMAX[7:0] Sets the value of the channel bandwidth that causes maximum stereo sep-
aration. Default is 0 kHz. Range is 0–15 kHz.
7:0 CHBWMIN[7:0] Sets the value of the channel bandwidth that causes minimum stereo sepa-
ration. Default is 0 kHz. Range is 0–15 kHz.
AN543
172 Rev. 0.9
Property 0x3519 FM_BLEND_CHBW_STER EO_SEP (Si4754/55/56/57 Only)
The FM_BLEND_CHBW_STEREO_SEP property sets the limits for the stereo separation when driven by CHBW
on the stereo blend mitigation engine. To force a given setting (either completely on or completely off) set
ST_SEPMIN = ST_SEPMAX. To disable the stereo blend based on CHBW, set ST_SEPMIN = ST_SEPMAX = 64
(0x40). The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Default: 0x2D2D
Units: dB
Property 0x351A FM_BLEND_CHBW_ATTACK_TIME
The FM_BLEND_CHBW_ATTACK_TIME property sets the transition time for which the stereo blend mitigation
engine decreases the stereo separation based on channel bandwidth. The CTS bit (and optional interrupt) is set
when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 1
Units: ms
FM_BLEND_CHBW_STEREO_SEP
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ST_SEPMAX[7:0] ST_SEPMIN[7:0]
0x2D 0x2D
Bit Name Function
15:8 ST_SEPMAX[7:0] Sets the maximum stereo separation for channel bandwidth based stereo
blend. Default is 45 dB. Range is 0–64 dB.
7:0 ST_SEPMIN[7:0] Sets the minimum stereo separation for channel bandwidth based stereo
blend. Default is 45 dB. Range is 0–64 dB.
FM_BLEND_CHBW_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0001
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the stereo blend mitigation engine
decreases the stereo separation based on channel bandwidth.
Default is 1 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 173
Property 0x351B FM_BLEND_CHBW_RELEASE_TIME
The FM_BLEND_CHBW_RELEASE_TIME property sets the transition time for which the stereo blend mitigation
engine increases the stereo separation based on channel bandwidth. The CTS bit (and optional interrupt) is set
when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 1
Units: ms
Property 0x3600 FM_HICUT_RSSI_ THRESHOLDS
The FM_HICUT_RSSI_THRESHOLDS property sets the RSSI thresholds for HICUT to begin band limiting and
reach maximum band limiting on L+R channel based on max and min cutoff frequency (set by Property 0x3601) on
the HICUT engine. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: 0x230F
Units: dBµV
FM_BLEND_CHBW_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0001
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the stereo blend mitigation engine
increases the stereo separation based on channel bandwidth.
Default is 1 ms. Range is 1–32767 ms.
FM_HICUT_RSSI_THRESHOLDS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RSSIMAX[7:0] RSSIMIN[7:0]
0x23 0x0F
Bit Name Function
15:8 RSSIMAX[7:0]
Sets the RSSI level at which HICUT begins to band limit on the L+R chan-
nel based on cutoff frequency set by property 0x3601.
Default is 35 dBµV. Range is –20–120 dBµV.
7:0 RSSIMIN[7:0]
Sets the RSSI level at which HICUT reaches maximum band limiting on the
L+R channel based on cutoff frequency set by property 0x3601.
Default is 15 dBµV. Range is –20–120 dBµV.
AN543
174 Rev. 0.9
Property 0x3601 FM_HICUT_RSSI_C UTOFF_FREQ
The FM_HICUT_RSSI_CUTOFF_FREQ property sets the maximum and minimum cutoff frequencies based on
RSSI (set by Property 0x3600) on the HICUT engine. You can force a constant cutoff frequency value by setting
FREQ_MAX and FREQ_MIN to the same value. To disable the HICUT based on RSSI, set
FREQ_MAX = FREQ_MIN = 180 (0xB4.) The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 0xB428
Si475x/5xC-A55, Default: 0xB419
Units: 100 Hz
Property 0x3602 FM_HICUT_RSSI_ATTACK_TIME
Th
e
FM
_HICUT_RSSI_A
TTACK_TIME
proper
ty
sets the
tr
ansition time for which the HICUT mitigation engine
lowers
the
cutoff
frequency
based
on
RSSI.
The
CTS
bit
(and
optional
interrupt)
is
set
when
it
is
safe
to
send
the
ne
xt
command
.
This proper
ty
may only be se
t
or read in powerup mode
.
Si475x-A40 and earlier, Default: 16
Si475x/5xC-A55, Default: 100
Units: ms
FM_HICUT_RSSI_CUTOFF_FREQ
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
FREQ_MAX[7:0] FREQ_MIN[7:0]
0xB4 0x19
Bit Name Function
15:8 FREQ_MAX[7:0] Sets the maximum cutoff frequency. Default is 18 kHz. Range is 0–18 kHz.
7:0 FREQ_MIN[7:0] Sets the minimum stereo separation. Range is 0–18 kHz.
Si475x/5xC-A55,
Default is 2.5 kHz.
FM_HICUT_RSSI_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0064
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the HICUT mitigation engine lowers the
cutoff frequency based on RSSI.
Si475x/5xC-A55, Default is 100 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 175
Property 0x3603 FM_HICUT_RSSI_RELEASE_TIME
The FM_HICUT_RSSI_RELEASE_TIME property sets the transition time for which the HICUT mitigation engine
increases the cutoff frequency based on RSSI. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read in powerup mode.
Default: 4000
Units: ms
Property 0x3608 FM_HICUT_MULTIPATH_THRESHOLDS
The FM_HICUT_MULTIPATH_THRESHOLDS property sets the Multipath thresholds for HICUT to begin
band limiting and reach maximum band limiting on L+R channel based on max and min cutoff frequencies
(set by Property 0x3609) on the HICUT engine. The CTS bit (and optional interrupt) is set when it is safe to send
the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 0x3250
Si475x/5xC-A55, Default: 0x0A14
Unit: %
FM_HICUT_RSSI_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0FA0
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the HICUT mitigation engine increases
the cutoff frequency based on RSSI.
Default is 4000 ms. Range is 1–32767 ms.
FM_HICUT_MULTIPATH_THRESHOLDS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
MULTMIN[7:0] MULTMAX[7:0]
0x0A 0x14
Bit Name Function
15:8 MULTMIN[7:0]
Sets the Multipath level at which HICUT reaches max band limiting on the
L+R channel based on cutoff frequency set by property 0x3609.
Si475x/5xC-A55, Default is 10. Range is 0–127%.
7:0 MULTMAX[7:0]
Sets the Multipath level at which HICUT begins to band limit on the L+R
channel based on cutoff frequency set by property 0x3609.
Si475x/5xC-A55, Default is 20. Range is 0–127%.
AN543
176 Rev. 0.9
Property 0x3609 FM_HICUT_MULTIPATH_CUTOFF_FREQ
The FM_HICUT_MULTIPATH_CUTOFF_FREQ property sets the maximum and minimum cutoff frequency based
on Multipath (set by Property 0x3608) on the HICUT engine. You can force a constant cutoff frequency value by
setting FREQ_MAX and FREQ_MIN to the same value. To disable the HICUT based on Multipath, set
FREQ_MAX
= FREQ_MIN = 180 (0xB4.) The CTS bit (and optional interrupt) is set when it is safe to send the next
command.
This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 0xB428
Si475x/5xC-A55, Default: 0x6419
Units: 100Hz
Property 0x360A FM_HICUT_MULTIPATH_ATTACK_TIME
Th
e
FM
_HICUT_MUL
TIPATH_ATT
ACK_
TIME
prop
erty sets
the
tr
ansition time for which the HICUT mitigation
engine
lowers
the
cutoff
frequency
based
on
Multipath.
The
CTS
bit
(and
optional
interrupt)
is
set
when
it
is
safe
to
send the ne
xt
command. This prop
erty may
only be set or read in powerup mode
.
Si475x-A40 and earlier, Default: 16
Si475x/5xC-A55, Default: 100
Units:ms
FM_HICUT_MULTIPATH_CUTOFF_FREQ
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
FREQ_MAX[7:0] FREQ_MIN[7:0]
0x64 0x19
Bit Name Function
15:8 FREQ_MAX[7:0] Sets the maximum cutoff frequency. Si475x/5xC-A55, Default is 10 kHz.
Range is 0–18 kHz.
7:0 FREQ_MIN[7:0] Sets the minimum stereo separation. Range is 0–18 kHz.
Si475x/5xC-A55,
Default is 2.5 kHz.
FM_HICUT_MULTIPATH_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0064
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the HICUT mitigation engine decreases
the cutoff frequency based on Multipath.
Si475x/5xC-A55, Default is 100 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 177
Property 0x360B FM_HICUT_MULTIPATH_RELEASE_TIME
The FM_HICUT_MULTIPATH_RELEASE_TIME property sets the transition time for which the HICUT mitigation
engine increases the cutoff frequency based on Multipath. The CTS bit (and optional interrupt) is set when it is safe
to send the next command. This property may only be set or read in powerup mode.
Default: 4000
Units: ms
Property 0x3610 FM_HICUT_USN_THRESHOLDS
The FM_HICUT_USN_THRESHOLDS property sets the USN thresholds for HICUT to begin band limiting and
reach maximum band limiting on L+R channel based on max and min cutoff frequencies (set by Property 0x3611)
on the HICUT engine. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: 0x250F
Units: –dBFS
FM_HICUT_MULTIPATH_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0FA0
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the HICUT mitigation engine increases the
cutoff frequency based on Multipath.
Default is 4000 ms. Range is 1–32767 ms.
FM_HICUT_USN_THRESHOLDS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
USNMIN[7:0] USNMAX[7:0]
0x25 0x0F
Bit Name Function
15:8 USNMIN[7:0]
Sets the USN level at which HICUT reaches max band limiting on the L+R
channel based on cutoff frequency set by property 0x3611.
Default is –37 dBFS. Range is 0–127 –dBFS.
7:0 USNMAX[7:0]
Sets the Multipath level at which HICUT begins to band limit on the L+R
channel based on cutoff frequency set by property 0x3611.
Default is –15 dBFS. Range is 0–127 –dBFS.
AN543
178 Rev. 0.9
Property 0x3611 FM_HICUT_USN_CUTOFF_FREQ
The FM_HICUT_USN_CUTOFF_FREQ property sets the maximum and minimum cutoff frequency based on USN
(set by Property 0x3610) on the HICUT engine. You can force a constant cutoff frequency value by setting
FREQ_MAX and FREQ_MIN to the same value. To disable the HICUT based on USN, set FREQ_MAX =
FREQ_MIN = 180 (0xB4.) The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 0xB428
Si475x/5xC-A55, Default: 0xB419
Units: 100 Hz
Property 0x3612 FM_HICUT_USN_ATTACK_TIME
Th
e
FM
_HICUT_USN_A
TTACK_TIME
prop
erty
se
t
s the
tr
ansition time for which the HICUT mitigation engine
lowers
the
cutoff
frequency
based
on
USN.
The
CTS
bit
(and
optional
interrupt)
is
set
when
it
is
safe
to
send
the
ne
xt
command
.
This proper
ty
may only be se
t
or read in powerup mode
.
Si475x-A40 and earlier, Default: 16
Si475x/5xC-A55, Default: 100
Units:ms
FM_HICUT_USN_CUTOFF_FREQ
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
FREQ_MAX[7:0] FREQ_MIN[7:0]
0xB4 0x19
Bit Name Function
15:8 FREQ_MAX[7:0] Sets the maximum cutoff frequency. Default is 18 kHz. Range is 0–18kHz.
7:0 FREQ_MIN[7:0] Sets the minimum stereo separation. Range is 0–18 kHz.
Si475x/5xC-A55,
Default is 2.5 kHz.
FM_HICUT_USN_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0064
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the HICUT mitigation engine lowers the
cutoff frequency based on USN.
Si475x/5xC-A55, Default is 100 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 179
Property 0x3613 FM_HICUT_USN_RELEASE_TIME
The FM_HICUT_USN_RELEASE_TIME property sets the transition time for which the HICUT mitigation engine
increases the cutoff frequency based on USN. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read in powerup mode.
Default: 4000
Units: ms
Property 0x3618 FM_HICUTN_CHBW_LIMITS (Si4754/55/56/57 Only)
The FM_BLEND_HICUTN_LIMITS property sets the limits for the CHBW input metric on the L+R high cut
mitigation engine. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: 0x0000
Units: 100 Hz
FM_HICUT_USN_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0FA0
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the HICUT mitigation engine increases
the cutoff frequency based on USN.
Default is 4000 ms. Range is 1–32767 ms.
FM_HICUTN_CHBW_LIMITS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
CHBWMAX[7:0] CHBWMIN[7:0]
0x00 0x00
Bit Name Function
15:8 CHBWMAX[7:0] Sets the value of the channel bandwidth that causes maximum cutoff fre-
quency. Default is 0 kHz. Range is 0–15 kHz.
7:0 CHBWMIN[7:0] Sets the value of the channel bandwidth that causes minimum cutoff fre-
quency. Default is 0 Hz. Range is 0–15 kHz.
AN543
180 Rev. 0.9
Property 0x3619 FM_HICUTN_CHBW_CUTOFF_FREQ (Si4754 /55/56/57 Only)
The FM_HICUTN_CHBW_CUTOFF_FREQ property sets the limits for the cutoff frequency when driven by CHBW
on the L+R high cut mitigation engine. To force a given setting (either completely on or completely off) set
FREQ_MIN = FREQ_MAX. To disable L+R high cut based on CHBW, set FREQ_MIN = FREQ_MAX = 180 (0xB4).
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Default: 0xB4B4
Units: 100 Hz
Property 0x361A FM_HICUTN_CHBW_ATTACK_TIME
The FM_HICUTN_CHBW_ATTACK_TIME property sets the transition time for which the L+R high cut mitigation
engine decreases the cutoff frequency based on channel bandwidth. The CTS bit (and optional interrupt) is set
when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 1
Units: ms
FM_HICUTN_CHBW_CUTOFF_FREQ
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
FREQ_MAX[7:0] FREQ_MIN[7:0]
0xB4 0xB4
Bit Name Function
15:8 FREQ_MAX[7:0] Sets the maximum cutoff frequency for channel bandwidth based L+R high
cut. Default is 18 kHz. Range is 0–18 kHz.
7:0 FREQ_MIN[7:0] Sets the minimum cutoff frequency for channel bandwidth based L+R high
cut. Default is 18 kHz. Range is 0–18 kHz.
FM_HICUTN_CHBW_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0001
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the L+R high cut mitigation engine
decreases the cutoff frequency based on channel bandwidth.
Default is 1 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 181
Property 0x361B FM_HICUTN_CHBW_RELEASE_TIME
The FM_HICUTN_CHBW_RELEASE_TIME property sets the transition time for which the L+R high cut mitigation
engine increases the cutoff frequency based on channel bandwidth. The CTS bit (and optional interrupt) is set
when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 1
Units: ms
Property 0x3700 FM_HIBLEND_RSSI_THRESHOLDS
The FM_HIBLEND_RSSI_THRESHOLDS property sets the RSSI thresholds for HIBLEND to begin band limiting
and reach maximum band limiting on L–R channel based on max and min cutoff frequency (set by Property
0x3701) on the HIBLEND engine. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Default: 0x371B
Units: dBµV
FM_HICUTN_CHBW_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0001
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the L+R high cut mitigation engine
increases the cutoff frequency based on channel bandwidth.
Default is 1 ms. Range is 1–32767 ms.
FM_HIBLEND_RSSI_THRESHOLDS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RSSIMAX[7:0] RSSIMIN[7:0]
0x37 0x1B
Bit Name Function
15:8 RSSIMAX[7:0]
Sets the RSSI level at which HIBLEND begins to band limit on the L–R
channel based on cutoff frequency set by property 0x3701.
Default is 55 dBµV. Range is –20 to 120 dBµV.
7:0 RSSIMIN[7:0]
Sets the RSSI level at which HIBLEND reaches maximum band limiting on
the L–R channel based on cutoff frequency set by property 0x3701.
Default is 27 dBµV. Range is –20 to 120 dBµV.
AN543
182 Rev. 0.9
Property 0x3701 FM_HIBLEND_R SSI_CUTOFF_FREQ
The FM_HIBLEND_RSSI_CUTOFF_FREQ property sets the maximum and minimum cutoff frequencies based on
RSSI (set by Property 0x3700) on the HIBLEND engine. You can force a constant cutoff frequency value by setting
FREQ_MAX and FREQ_MIN to the same value. To disable the HIBLEND based on RSSI, set FREQ_MAX =
FREQ_MIN = 180 (0xB4.) The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 0xB41E
Si475x/5xC-A55, Default: 0xB419
Units: 100 Hz
Property 0x3702 FM_HIBLEND_R SSI_ATTACK_TIME
The
FM_HIBLEND_RSSI_ATTACK_TIME
property
sets
the
transition
time
for
which
the
HIBLEND
mitigation
engine lowers the cutof
f
frequency based on RSSI. The CTS bi
t
(and optional in
terr
up
t)
is se
t
when it is sa
fe to
send
the
next
command.
This
property
may
only
be
set
or
read
in
powerup
mode.
Si475x-A40 and earlier, Default: 4
Si475x/5xC-A55, Default: 100
Units:ms
FM_HIBLEND_RSSI_CUTOFF_FREQ
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
FREQ_MAX[7:0] FREQ_MIN[7:0]
0xB4 0x19
Bit Name Function
15:8 FREQ_MAX[7:0] Sets the maximum cutoff frequency. Default is 18 kHz. Range is 0–18 kHz.
7:0 FREQ_MIN[7:0] Sets the minimum stereo separation. Si475x/5xC-A55, Default is 2.5 kHz.
Range is 0–18 kHz
FM_HIBLEND_RSSI_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0064
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the HIBLEND mitigation engine lowers the
cutoff frequency based on RSSI.
Si475x/5xC-A55, Default is 100 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 183
Property 0x3703 FM_HIBLEND_RSSI_RELEASE_TIME
The FM_HIBLEND_RSSI_RELEASE_TIME property sets the transition time for which the HIBLEND mitigation
engine increases the cutoff frequency based on RSSI. The CTS bit (and optional interrupt) is set when it is safe to
send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 8000
Si475x/5xC-A55, Default: 4000
Units: ms
Property 0x3708 FM_HIBLEND_MULTIPATH_THRESHOLDS
T
he FM_HIBLEND_MULTIPATH_THRESHOLDS property sets the Multipath thresholds for HIBLEND to
begin band limiting and reach maximum band limiting on L–R channel based on max and min cutoff frequencies
(set by Property 0x3709) on the HIBLEND engine. The CTS bit (and optional interrupt) is set when it is safe to send
the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 0x193C
Si475x/5xC-A55, Default: 0x080F
FM_HIBLEND_RSSI_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x1FA0
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the HIBLEND mitigation engine increases
the cutoff frequency based on RSSI.
Si475x/5xC-A55, Default is 4000 ms. Range is 1–32767 ms.
FM_HIBLEND_MULTIPATH_THRESHOLDS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
MULTMIN[7:0] MULTMAX[7:0]
0x08 0x0F
Bit Name Function
15:8 MULTMIN[7:0]
Sets the Multipath level at which HICUT reaches max band limiting on the
L–R channel based on cutoff frequency set by property 0x3709.
Si475x/5xC-A55, Default is 8.
Si475x-A10 and earlier, and Si475x-A30 and later: Range is 0–127 Si475x-
A20: Range: 0–100
7:0 MULTMAX[7:0]
Sets the Multipath level at which HICUT begins to band limit on the L–R
channel based on cutoff frequency set by property 0x3709.
Si475x/5xC-A55, Default is 15.
Si475x-A10 and earlier, and Si475x-A30 and later: Range is 0–127 Si475x-
A20: Range: 0–100
AN543
184 Rev. 0.9
Property 0x3709 FM_HIBLEND_MULTIPATH_CUTOFF_FREQ
The FM_HIBLEND_MULTIPATH_CUTOFF_FREQ property sets the maximum and minimum cutoff frequency
based on Multipath (set by Property 0x3708) on the HIBLEND engine. You can force a constant cutoff frequency
value by setting FREQ_MAX and FREQ_MIN to the same value. To disable the HIBLEND based on Multipath, set
FREQ_MAX = FREQ_MIN = 180 (0xB4). The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 0xB41E
Si475x/5xC-A55, Default: 0x6419
Units: 100 Hz
Property 0x370A FM_HIBLEND_MULTIPATH_ATTACK_TIME
The FM_HIBLEND_MULTIPATH_ATTACK_TIME property sets the transition time for which the HIBLEND
mitigation engine lowers the cutoff frequency based on Multipath. The CTS bit (and optional interrupt) is set when it
is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 4
Si475x/5xC-A55, Default: 100
Units: ms
FM_HIBLEND_MULTIPATH_CUTOFF_FREQ
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
FREQ_MAX[7:0] FREQ_MIN[7:0]
0x64 0x19
Bit Name Function
15:8 FREQ_MAX[7:0] Sets the maximum cutoff frequency. Si475x/5xC-A55, Default is 10 kHz.
Range is 0–18 kHz.
7:0 FREQ_MIN[7:0] Sets the minimum stereo separation. Si475x/5xC-A55, Default is 2.5 kHz.
Range is 0–18 kHz.
FM_HIBLEND_MULTIPATH_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0064
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the HIBLEND mitigation engine
decreases the cutoff frequency based on Multipath.
Si475x/5xC-A55, Default is 100 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 185
Property 0x370B FM_HIBLEND_MULTIPATH_RELEASE_TIME
The FM_HIBLEND_MULTIPATH_RELEASE_TIME property sets the transition time for which the HIBLEND
mitigation engine increases the cutoff frequency based on RSSI. The CTS bit (and optional interrupt) is set when it
is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 8000
Si475x/5xC-A55, Default: 4000
Units: ms
Property 0x3710 FM_HIBLEND_U SN_THRESHOLDS
The FM_HIBLEND_USN_THRESHOLDS property sets the USN thresholds for HIBLEND to begin band limiting
and reach maximum band limiting on L–R channel based on max and min cutoff frequencies (set by Property
0x3711) on the HIBLEND engine. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Default: 0x371E
Units: –dBFS
FM_HIBLEND_MULTIPATH_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0FA0
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the HIBLEND mitigation engine increases
the cutoff frequency based on Multipath.
Si475x/5xC-A55, Default is 4000 ms. Range is 1–32767 ms.
FM_HIBLEND_USN_THRESHOLDS
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
USNMIN[7:0] USNMAX[7:0]
0x37 0x1E
Bit Name Function
15:8 USNMIN[7:0]
Sets the USN level at which HIBLEND reaches max band limiting on the
L–R channel based on cutoff frequency set by property 0x3711.
Default is –55 dBFS. Range is 0–127 –dBFS.
7:0 USNMAX[7:0]
Sets the Multipath level at which HIBLEND begins to band limit on the L–R
channel based on cutoff frequency set by property 0x3711.
Default is –30 dBFS. Range is 0–127 –dBFS.
AN543
186 Rev. 0.9
Property 0x3711 FM_HIBLEND_USN_CUTOFF_FREQ
The FM_HIBLEND_USN_CUTOFF_FREQ property sets the maximum and minimum cutoff frequency based on
USN (set by Property 0x3710) on the HIBLEND engine. You can force a constant cutoff frequency value by setting
FREQ_MAX and FREQ_MIN to the same value. To disable the HIBLEND based on USN, set FREQ_MAX =
FREQ_MIN = 180 (0xB4.) The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 0xB41E
Si475x/5xC-A55, Default: 0x9619
Units: 100 Hz
Property 0x3712 FM_HIBLEND_USN_ATTACK_TIME
The FM_HIBLEND_USN_ATTACK_TIME property sets the transition time for which the HIBLEND mitigation
engine lowers the cutoff frequency based on USN. The CTS bit (and optional interrupt) is set when it is safe to send
the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 4
Si475x/5xC-A55, Default: 100
Units: ms
FM_HIBLEND_USN_CUTOFF_FREQ
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
FREQ_MAX[7:0] FREQ_MIN[7:0]
0x96 0x19
Bit Name Function
15:8 FREQ_MAX[7:0] Sets the maximum cutoff frequency. Si475x/5xC-A55, Default is 15 kHz.
Range is 0–18 kHz.
7:0 FREQ_MIN[7:0] Sets the minimum stereo separation. Si475x/5xC-A55, Default is 2.5 kHz.
Range is 0–18 kHz.
FM_HIBLEND_USN_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0064
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the HIBLEND mitigation engine lowers the
cutoff frequency based on USN.
Si475x/5xC-A55, Default is 100 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 187
Property 0x3713 FM_HIBLEND_U SN_RELEASE_TIME
The FM_HIBLEND_USN_RELEASE_TIME property sets the transition time for which the HIBLEND mitigation
engine increases the cutoff frequency based on USN. The CTS bit (and optional interrupt) is set when it is safe to
send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 8000
Si475x/5xC-A55, Default: 4000
Units: ms
Property 0x3718 FM_HIBLEND_C HBW_LIMITS (Si4754/55/56/57 Only)
The FM_HIBLEND_CHBW_LIMITS property sets the limits for the CHBW input metric on the high-blend (L-R high
cut) mitigation engine. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: 0x0000
Units: 100 Hz
FM_HIBLEND_USN_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0FA0
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the HIBLEND mitigation engine increases
the cutoff frequency based on USN.
Si475x/5xC-A55, Default is 4000 ms. Range is 1–32767 ms.
FM_HIBLEND_CHBW_LIMITS
1514131211109876543210
CHBWMAX[7:0] CHBWMIN[7:0]
0x00 0x00
Bit Name Function
15:8 CHBWMAX[7:0] Sets the value of the channel bandwidth that causes maximum cutoff
frequency. Default is 0 kHz. Range is 0–15 kHz.
7:0 CHBWMIN[7:0] Sets the value of the channel bandwidth that causes minimum cutoff fre-
quency. Default is 0 kHz. Range is 0–15 kHz.
AN543
188 Rev. 0.9
Property 0x3719 FM_HIBLEND_CHBW_CUTOFF_FREQ (Si4754/55/56/57 Only)
The FM_HIBLEND_CHBW_CUTOFF_FREQ property sets the limits for the cutoff frequency when driven by
CHBW on the hi-blend (L-R high cut) mitigation engine. To force a given setting (either completely on or completely
off) set FREQ_MIN = FREQ_MAX. To disable the hi-blend (L-R high cut) based on CHBW, set
FREQ_MIN = FREQ_MAX = 180 (0xB4). The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Default: 0xB4B4
Units: 100 Hz
Property 0x371A FM_HIBLEND_CHBW_ATTACK_TIME
The FM_HIBLEND_CHBW_ATTACK_TIME property sets the transition time for which the hi-blend (L-R high cut)
mitigation engine decreases the cutoff frequency based on channel bandwidth. The CTS bit (and optional interrupt)
is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 1
Units: ms
FM_HIBLEND_CHBW_CUTOFF_FREQ
1514131211109876543210
FREQ_MAX[7:0] FREQ_MIN[7:0]
0xB4 0xB4
Bit Name Function
15:8 FREQ_MAX[7:0] Sets the maximum cutoff frequency for channel bandwidth based hi-
blend (L-R high cut). Default is 18 kHz. Range is 0–18 kHz.
7:0 FREQ_MIN[7:0] Sets the minimum cutoff frequency for channel bandwidth based hi-
blend (L-R high cut). Default is 18 kHz. Range is 0–18 kHz.
FM_HIBLEND_CHBW_ATTACK_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ATTACK[15:0]
0x0001
Bit Name Function
15:0 ATTACK[15:0]
Sets the transition time for which the hi-blend (L-R high cut) mitigation
engine decreases the cutoff frequency based on channel bandwidth.
Default is 1 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 189
Property 0x371B FM_HIBLEND_CHBW_RELEASE_TIME
The FM_HIBLEND_CHBW_RELEASE_TIME property sets the transition time for which the hi-blend (L-R high cut)
mitigation engine increases the cutoff frequency based on channel bandwidth. The CTS bit (and optional interrupt)
is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 1
Units: ms
FM_HIBLEND_CHBW_RELEASE_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RELEASE[15:0]
0x0001
Bit Name Function
15:0 RELEASE[15:0]
Sets the transition time for which the hi-blend (L-R high cut) mitigation
engine increases the cutoff frequency based on channel bandwidth.
Default is 1 ms. Range is 1–32767 ms.
AN543
190 Rev. 0.9
Property 0x4000 FM_RDS_INTERRUPT_SOURCE (Si47 51/53/55/57 Only)
The FM_RDS_INTERRUPT_SOURCE property configures interrupt related to RDS. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 0x0000
FM_RDS_INTERRUPT_SOURCE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x000 RDSTPPTY RDSPI 0 RDSSYNC RDSRECV
0x000 0 0 0 0 0
Bit Name Function
15:5 Reserved Always write 0.
4 RDSTPPTY
If set, generates RDS Interrupt when first valid Block B data has been
received or if Block B data is different from last valid Block B data.
0 = Disabled.
1 = Enabled.
3 RDSPI
If set, generates RDS Interrupt when first valid Block A data has been
received or if Block A data is different from last valid Block A data.
0 = Disabled.
1 = Enabled.
2 Reserved Always write 0.
1 RDSSYNC
If set, generates RDS interrupt when RDS Synchronization status
changes. Default is 0.
0 = Disabled.
1 = Enabled.
0 RDSRECV
If set, generate an interrupt whenever the RDS FIFO has at least
FM_RDS_INTERRUPT_FIFO_COUNT entries. Default is 0
0 = Disabled.
1 = Enabled.
AN543
Rev. 0.9 191
Property 0x4001 FM_RDS_INTERRUPT_FIFO_COUNT (Si4751/53/55/57 Only)
The FM_RDS_INTERRUPT_FIFO_COUNT property sets the minimum number of RDS groups stored in the RDS
FIFO before RDSRECV is set. RDSRECV is disabled if set to 0. The CTS bit (and optional interrupt) is set when it
is safe to send the next command. This property may only be set or read in powerup mode.
Default: 0
FM_RDS_INTERRUPT_FIFO_COUNT
1514131211109876543210
0x00 DEPTH[7:0]
0x00 0x00
Bit Name Function
15:8 Reserved Always write 0.
7:0 DEPTH[7:0]
Sets the minimum number of RDS Groups stored in the RDS FIFO
required before RDSRECV is set. RDSRECV is disabled if set to 0.
Default is 0. Range is 0–25
AN543
192 Rev. 0.9
Property 0x4002 FM_RDS_CONF IG (Si4751/53/55/57 Only)
The FM_RDS_CONFIG property configures RDS settings to enable RDS processing (RDSEN) and set RDS block
error thresholds. When a RDS Group is received, all block errors must be less than or equal to the associated
block error threshold for the group to be stored in the RDS FIFO. If blocks with errors are permitted into the FIFO,
the block error information can be reviewed when the group is read using the FM_RDS_STATUS command. The
CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or
read in powerup mode.
Default: 0x0000
FM_RDS_CONFIG
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x00 BLETHB[1:0] BLETHCD[1:0] 0x0 RDSEN
0x00 0x0 0x0 0x0 0
Bit Name Function
15:8 Reserved Always write 0.
7:6 BLETHB[1:0]
Block Error Threshold BLOCKB. Block B is most critical because it tells what C
and D contain.
0 = No errors.
1 = 1–2 bit errors detected and corrected.
2 = 3–5 bit errors detected and corrected.
3 = Uncorrectable.
5:4 BLETHCD[1:0]
Block Error Threshold for BLOCKC and BLOCKD.
0 = No errors.
1 = 1–2 bit errors detected and corrected.
2 = 3–5 bit errors detected and corrected.
3 = Uncorrectable.
3:1 Reserved Always write 0.
0 RDSEN
Enables RDS processing. Default is 0.
0 = RDS Disabled.
1 = RDS Enabled.
AN543
Rev. 0.9 193
Property 0x4003 FM_RDS_CONFIDENCE (Si4751/53/55/57 Only)
The FM_RDS_CONFIDENCE property sets the required receiver confidence level for each RDS block prior to
demodulation. A higher confidence requirement will result in more block errors (higher percentage of blocks with
BLE = 3) but reduces the chance of decoder errors (lower percentage of blocks that contain incorrect information
despite having BLE<3). Higher confidence requirements may result in a decrease in the frequency with which RDS
data is stored in the FIFO. Higher block error rate will affect RDS sensitivity tests. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read when in the
powerup mode.
Default: 0x1111
FM_RDS_CONFIDENCE
1514131211109876543210
CONFIDENCEA[3:0] CONFIDENCEB[3:0] CONFIDENCEC[3:0] CONFIDENCED[3:0]
0x1 0x1 0x1 0x1
Bit Name Function
15:12 CONFIDENCEA[3:0]
Sets the decoder error rate threshold for BLOCK A.
0=Reserved.
1 = Lowest confidence required. A valid and usable confidence threshold.
2–14 = Medium confidence required. High value may result in all blocks
being marked as uncorrectable.
15 = Highest confidence required. This setting may result in all blocks being
marked as uncorrectable.
11:8 CONFIDENCEB[3:0]
Sets the decoder error rate threshold for BLOCK B.
0=Reserved.
1 = Lowest confidence required. A valid and usable confidence threshold.
2–14 = Medium confidence required. High value may result in all blocks
being marked as uncorrectable.
15 = Highest confidence required. This setting may result in all blocks being
marked as uncorrectable.
7:4 CONFIDENCEC[3:0]
Sets the decoder error rate threshold for BLOCK C.
0=Reserved.
1 = Lowest confidence required. A valid and usable confidence threshold.
2–14 = Medium confidence required. High value may result in all blocks
being marked as uncorrectable.
15 = Highest confidence required. This setting may result in all blocks being
marked as uncorrectable.
3:0 CONFIDENCED[3:0]
Sets the decoder error rate threshold for BLOCK D.
0=Reserved.
1 = Lowest confidence required. A valid and usable confidence threshold.
2–14 = Medium confidence required. High value may result in all blocks
being marked as uncorrectable.
15 = Highest confidence required. This setting may result in all blocks being
marked as uncorrectable.
AN543
194 Rev. 0.9
7.3. Commands and Properties for AM Receiver
Table 13. AM Receiver Command Summary
Number Name Summary
0x40 AM_TUNE_FREQ Tunes the AM receiver to a frequency in 1 kHz steps.
0x41 AM_SEEK_START Initiates a seek for a channel that meets the validation criteria for AM.
0x42 AM_RSQ_STATUS Returns status information about the received signal quality.
0x45 AM_ACF_STATUS Returns status information about automatically controlled features.
0x47 AM_AGC_STATUS Reports the status of AM AGC.
AN543
Rev. 0.9 195
Table 14. AM Receiver Properties Summary
Address Name Default Summary
A10 A20 A30 A40 A55
0x0303 AUDIO_PWR_LINE_FILTER
0x0200 0x0200 0x0200 0x0200 0x0200 Selects a 50 or 60 Hz notch filter for power
line noise mitigation.
512 512 512 512 512
0x0400 AM_SOFT_MUTE_MAX_ATTENUATION
0x000C 0x000C 0x000C 0x000C 0x000C Sets the maximum soft mute attenuation for
RSSI/SNR softmute engine.
12 12 12 12 12
0x0401 AM_SOFT_MUTE_TRIGGER_THRESHOLD
0x0008 0x0008 0x0008 0x0008 0x0008 Sets the trigger threshold for RSSI/SNR
softmute engine.
88888
0x0402 AM_SOFT_MUTE_END_THRESHOLD
0x0000 0x0000 0x0000 0x0000 0x0000 Sets the end threshold for RSSI/SNR soft-
mute engine.
00000
0x0403 AM_SOFT_MUTE_RELEASE_TIME
0x01F4 0x01F4 0x01F4 0x01F4 0x01F4 Sets the maximum soft mute release time in
ms for RSSI/SNR softmute engine.
500 500 500 500 500
0x0404 AM_SOFT_MUTE_ATTACK_TIME
0x0078 0x0078 0x0078 0x0078 0x0078 Sets the maximum soft mute attack time in
ms for RSSI/SNR softmute engine.
120 120 120 120 120
0x0405 AM_SOFT_MUTE_MAX_ATTENUATION_AGC N/A N/A
0x0080 0x0080 0x0080 Sets the maximum soft mute attenuation for
RSSI/SNR+AGC softmute engine.
128 128 128
0x0406 AM_SOFT_MUTE_TRIGGER_THRESHOLD_AGC N/A N/A
0x0008 0x0008 0x0008 Sets the trigger threshold for RSSI/
SNR+AGC softmute engine.
888
0x0407 AM_SOFT_MUTE_END_THRESHOLD_AGC N/A N/A
0x0000 0x0000 0x0000 Sets the end threshold for RSSI/SNR+AGC
softmute engine.
000
0x0408 AM_SOFT_MUTE_RELEASE_TIME_AGC N/A N/A
0x01F4 0x01F4 0x01F4 Sets the maximum soft mute release time in
ms for RSSI/SNR+AGC softmute engine.
500 500 500
196 Rev. 0.9
AN543
0x0409 AM_SOFT_MUTE_ATTACK_TIME_AGC N/A N/A
0x0078 0x0078 0x0078 Sets the maximum soft mute attack time in
ms for RSSI/SNR+AGC softmute engine.
120 120 120
0x0412 AM_SOFT_MUTE_MAX_ATTENUATION_MOD N/A N/A N/A N/A
0x008C Sets the maximum soft mute attenuation
when modulation index is used.
140
0x0413 AM_SOFT_MUTE_THRESHOLD_MOD N/A N/A N/A N/A
0x0E16 Sets the modulation index thresholds for
soft mute to start and stop.
3606
0x0414 AM_SOFT_MUTE_RELEASE_TIME_MOD N/A N/A N/A N/A
0x01F4 Sets the maximum soft mute release time in
ms when modulation index is used.
500
0x0415 AM_SOFT_MUTE_ATTACK_TIME_MOD N/A N/A N/A N/A
0x0078 Sets the maximum soft mute attack time in
ms when modulation index is used.
120
0x0416 AM_SOFT_MUTE_MOD_RSSI N/A N/A N/A N/A
0x0F0D Sets the RSSI level for AM modulation
based softmute to enable/disable.
3853
0x0500 AM_AVC_MIN_GAIN
0xF800 0xF800 0xF800 0xF800 0xF800 Sets the minimum gain for automatic vol-
ume control.
–2048 –2048 –2048 –2048 –2048
0x0501 AM_AVC_MAX_GAIN
0x27EC 0x27EC 0x27EC 0x27EC 0x4272 Sets the maximum gain for automatic vol-
ume control.
10220 10220 10220 10220 17010
0x0700 AM_AGC_FE_CONFIG
0x0094 0x0094 0xF094 0xF094 0xF094 Specifies the input path for the RF signal
and other front-end configuration options.
148 148 61588 61588 61588
0x0708 AM_IF_AGC_ATTACK_MS
0x0050 0x0050 0x0050 0x0050 0x0050 Sets the number of milliseconds the IF high-
peak detector must be exceeded before
attenuating the appropriate block.
80 80 80 80 80
Table 14. AM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 197
0x0709 AM_IF_AGC_RELEASE_MS
0x0050 0x0324 0x0324 0x0324 0x0324 Sets the number of milliseconds the IF low
peak detector must not be exceeded before
increasing the gain of the appropriate block.
80 804 804 804 804
0x070C AM_RF_AGC_ATTACK_MS
0x0008 0x0008 0x0008 0x0008 0x0008 Sets the number of milliseconds the wide-
band RF high-peak detector must be
exceeded before attenuating the appropri-
ate AGC block.
88888
0x070D AM_RF_AGC_RELEASE_MS
0x0320 0x0320 0x0320 0x0320 0x0320 Sets the number of milliseconds the wide-
band RF low-peak detector must not be
exceeded before increasing the gain of the
appropriate block.
800 800 800 800 800
0x070E AM_LNA_PD_THRESHOLD
0x5104 0x5104 0x5104 0x5104 0x5904 Sets the high threshold and hysteresis for
the LNA peak detector.
20740 20740 20740 20740 22788
0x0710 AM_AGC_OVERRIDE
0x0000 0x0000 0x0000 0x0000 0x0000 Overrides the AGC setting by disabling the
AGC and forcing the gain to be maximum.
00000
0x071B AM_AGC_RSSI_OFFSET N/A
0x0000 0x0000 0x0000 0x0000 Offsets the RSSI value so that it can take
into account front-end gain/loss.
0000
0x1006 AM_SEEK_TUNE_CHBW_HOLD_TIME N/A N/A
0x0050 0x0050 0x0050 Sets the length of time CHBW is held in
units of ms.
80 80 80
0x1007 AM_TUNE_CHBW N/A N/A
0x0000 0x0000 0x0000 Sets the maximum CHBW allowed during
the normal tune.
000
0x1100 AM_SEEK_BAND_BOTTOM
0x0208 0x0208 0x0208 0x0208 0x020A Sets the lower seek boundary of the AM
band in multiples of 1 kHz.
520 520 520 520 522
Table 14. AM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
198 Rev. 0.9
AN543
0x1101 AM_SEEK_BAND_TOP
0x06AE 0x06AE 0x06AE 0x06AE 0x06AE Sets the upper seek boundary for the AM
band in multiples of 1 kHz.
1710 1710 1710 1710 1710
0x1102 AM_SEEK_FREQUENCY_SPACING
0x000A 0x000A 0x000A 0x000A 0x0009 Sets the frequency spacing for the AM band
in multiples of 1 kHz when performing a
seek.
10 10 10 10 9
0x1104 AM_SEEK_CHBW N/A N/A
0x0014 0x0014 0x0014
Sets the CHBW during the seek.
20 20 20
0x1200 AM_RSQ_INTERRUPT_SOURCE
0x0000 0x0000 0x0000 0x0000 0x0000 Configures interrupt related to Received
Signal Quality metrics (AM_RSQ_STA-
TUS).
00000
0x1201 AM_RSQ_SNR_HIGH_THRESHOLD
0x007F 0x007F 0x007F 0x007F 0x007F Sets high threshold, which triggers the RSQ
interrupt if the SNR is above this threshold.
127 127 127 127 127
0x1202 AM_RSQ_SNR_LOW_THRESHOLD
0xFF80 0xFF80 0xFF80 0xFF80 0xFF80 Sets low threshold, which triggers the RSQ
interrupt if the SNR is below this threshold.
–128 –128 –128 –128 –128
0x1203 AM_RSQ_RSSI_HIGH_THRESHOLD
0x007F 0x007F 0x007F 0x007F 0x007F Sets high threshold, which triggers the RSQ
interrupt if the RSSI is above this threshold.
127 127 127 127 127
0x1204 AM_RSQ_RSSI_LOW_THRESHOLD
0xFF80 0xFF80 0xFF80 0xFF80 0xFF80 Sets low threshold, which triggers the RSQ
interrupt if the RSSI is below this threshold.
–128 –128 –128 –128 –128
0x1300 AM_ACF_INTERRUPT_SOURCE
0x0000 0x0000 0x0000 0x0000 0x0000
Enables the ACF interrupt sources.
00000
0x1301 AM_ACF_SM_THRESHOLD
0x001F 0x001F 0x001F 0x001F 0x001F
Sets the softmute interrupt threshold in dB.
31 31 31 31 31
Table 14. AM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 199
0x1302 AM_ACF_CHBW_THRESHOLD
0x0000 0x0000 0x0000 0x0000 0x0000 Sets the Channel Filter Bandwidth interrupt
threshold in units of 100 Hz.
00000
0x1303 AM_ACF_HICUT_THRESHOLD
0x0000 0x0000 0x0000 0x0000 0x0000 Sets the HICUT interrupt threshold in units
of 100 Hz.
00000
0x1306 AM_ACF_CONTROL_SOURCE
0x0000 0x0000 0x0000 0x0000 0x0000 Determines if SNR or RSSI will be used as
the controlling metric for ACF features.
00000
0x2000 AM_VALID_MAX_TUNE_ERROR
0x004B 0x004B 0x004B 0x004B 0x007E Sets the maximum frequency error allowed
before setting the AFCRL indicator.
75 75 75 75 126
0x2001 AM_VALID_RSSI_TIME
0x0005 0x0005 0x0005 0x0005 0x0005 Sets the amount of time in milliseconds to
allow the RSSI metric to settle before evalu-
ating.
55555
0x2002 AM_VALID_SNR_TIME
0x0024 0x0024 0x0024 0x0024 0x0024 Sets the amount of time in milliseconds to
allow the SNR metric to settle before evalu-
ating.
36 36 36 36 36
0x2003 AM_VALID_SNR_THRESHOLD
0x0005 0x0005 0x0005 0x0005 0x0005 Sets the SNR threshold for a valid AM Seek
Tune.
55555
0x2004 AM_VALID_RSSI_THRESHOLD
0x000A 0x000A 0x000A 0x000A 0x000A Sets the RSSI threshold for a valid AM
Seek Tune.
10 10 10 10 10
0x200C AM_VALID_FREQOFF_SCALE N/A N/A N/A
0x0000 0x0000 Changes FREQOFF from bppm units to
some multiple of Hz.
00
0x200D AM_VALID_FREQOFF_FILTER N/A N/A N/A
0x0064 0x0064 Changes the amount that FREQOFF is fil-
tered.
100 100
Table 14. AM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
200 Rev. 0.9
AN543
0x2100 AM_NB_DETECT_THRESHOLD
0x0012 0x0012 0x0012 0x0012 0x0012 Sets the threshold for detecting impulses in
dB above the noise floor.
18 18 18 18 18
0x2101 AM_NB_INTERVAL
0x0004 0x0004 0x0004 0x0004 0x0004 Sets the interval as the number of samples
to be replaced by interpolated clean sam-
ples.
44444
0x2102 AM_NB_DELAY
0x005D 0x175D 0x3AE8 0x3AE8 0x3AE8 Delay in units of number of samples from
where to select the good samples to
replace the samples corrupted by the
impulse.
93 5981 15080 15080 15080
0x2103 AM_SECONDARY_NB_DETECT_THRESHOLD
0x0015 0x0015 0x0015 0x0015 0x0015 Sets the threshold for detecting impulses in
dB above the noise floor. This blanker is
used in the presence of strong near-end
blockers.
21 21 21 21 21
0x2104 AM_SECONDARY_NB_INTERVAL
0x0004 0x0004 0x0004 0x0004 0x0004 Sets the interval that original samples are
replaced by interpolated clean samples.
This blanker is used in the presence of
strong near end blockers.
44444
0x2106 AM_NB_STRONG_SIGNAL_SHUTOFF NA NA NA NA
0x6070
Sets the RSSI threshold for determining
when to turn on/off the noise blanker.
24688
0x2107 AM_NB_DETECT_DELAY
0x0008 0x0008 0x0008 0x0008 0x0005 Delay in units of number of samples before
applying impulse blanking to the original
samples.
88885
0x2108 AM_NB_SCHEME N/A
0x0001 0x0000 0x0100 0x0101
Sets the noise blanking scheme.
1 0 256 257
Table 14. AM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 201
0x2109 AM_NB_MODE_CONTROL
0x0004 0x0004 0x0004 0x0004 0x0002
Sets the mode for the noise blanker.
44442
0x2110 AM_NB_BURST_NOISE_DETECT_THRESHOLD N/A N/A N/A
0x0609 0x0000 Sets the threshold for burst noises and
number of samples for the blanker.
1545 0
0x2200 AM_CHBW_SQ_MIN_MAX
0x1414 0x2314 0x2314 0x2314 0x2314 Sets the max(IQSNR,SNR) based maxi-
mum and minimum channel filter bandwidth
in units of 100 Hz.
5140 8980 8980 8980 8980
0x2201 AM_CHBW_SQ_HIGH_THRESHOLD
0x001E 0x001E 0x001E 0x001E 0x001E Sets the max (IQSNR,SNR) threshold for
maximum channel filter bandwidth.
30 30 30 30 30
0x2202 AM_CHBW_SQ_LOW_THRESHOLD
0x000F 0x000F 0x000F 0x000F 0x000F Sets the max (IQSNR/SNR) threshold for
minimum channel filter bandwidth.
15 15 15 15 15
0x2203 AM_CHBW_SQ_WIDENING_TIME
0x0800 0x0800 0x0800 0x0800 0x0800 Sets the channel filter bandwidth widening
time based on max(IQSNR/SNR) in units of
ms.
2048 2048 2048 2048 2048
0x2204 AM_CHBW_SQ_NARROWING_TIME
0x0010 0x0010 0x0010 0x0010 0x0010 Sets the channel filter bandwidth narrowing
time based on max(IQSNR/SNR) in units of
ms.
16 16 16 16 16
0x2205 AM_CHBW_ASSI_MIN_MAX N/A
0x3232 0x3232 0x3232 0x3232 Sets the maximum and minimum channel
filter bandwidth as determined by ASSI in
units of 100 Hz.
12850 12850 12850 12850
0x2206 AM_CHBW_ASSI_LOW_THRESHOLD N/A
0x000A 0x000A 0x000A 0x000A Sets the ASSI threshold for maximum chan-
nel filter bandwidth.
10 10 10 10
0x2207 AM_CHBW_ASSI_HIGH_THRESHOLD N/A
0x001E 0x001E 0x001E 0x001E Sets the ASSI threshold for minimum chan-
nel filter bandwidth.
30 30 30 30
Table 14. AM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
202 Rev. 0.9
AN543
0x2208 AM_CHBW_ASSI_WIDENING_TIME N/A
0x0010 0x0010 0x0010 0x0010 Sets the channel filter bandwidth widening
time based on ASSI in units of ms.
16 16 16 16
0x2209 AM_CHBW_ASSI_NARROWING_TIME N/A
0x0010 0x0010 0x0010 0x0010 Sets the channel filter bandwidth narrowing
time based on ASSI in units of ms.
16 16 16 16
0x220A AM_CHBW_RQ_MIN_MAX N/A N/A N/A N/A
0x2314 Sets the RSSI based maximum and mini-
mum channel bandwidth in 100 Hz.
8980
0x220B AM_CHBW_RQ_LOW_THRESHOLD N/A N/A N/A N/A
0x000F Sets RSSI threshold for minimum channel
filter bandwidth.
15
0x220C AM_CHBW_RQ_HIGH_THRESHOLD N/A N/A N/A N/A
0x001E Sets RSSI threshold for maximum channel
filter bandwidth.
30
0x220D AM_CHBW_RQ_WIDENING_TIME N/A N/A N/A N/A
0x0800 Sets the RSSI based channel filter band-
width widening time.
2048
0x220E AM_CHBW_RQ_NARROWING_TIME N/A N/A N/A N/A
0x0010 Sets the RSSI based channel filter band-
width narrowing time.
16
0x2300 AM_DEMOD_MODE
0x0001 0x0001 0x0001 0x0001 0x0100
Selects the demodulation scheme.
1111256
0x2301 AM_DEMOD_AFC_RANGE N/A N/A
0x0000 0x0000 0x0000
Selects the AFC range.
000
0x2302 AM_DEMOD_CARRIER_ENH N/A N/A N/A N/A
0x0014
Specify carrier enhance ratio.
20
Table 14. AM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
Rev. 0.9 203
0x3100 AM_HICUT_SQ_HIGH_THRESHOLD
0x0008 0x0008 0x0008 0x0008 0x0008 Sets the SNR/RSSI based HICUT high
SNR/RSSI threshold.
88888
0x3101 AM_HICUT_SQ_LOW_THRESHOLD
0x0000 0x0000 0x0000 0x0000 0x0000 Sets the SNR/RSSI based HICUT low SNR/
RSSI threshold.
00000
0x3102 AM_HICUT_ATTACK_TIME
0x0010 0x0010 0x0010 0x0010 0x0010 Sets the HICUT cutoff frequency attack time
in ms.
16 16 16 16 16
0x3103 AM_HICUT_RELEASE_TIME
0x07D0 0x07D0 0x07D0 0x07D0 0x07D0 Sets the HICUT cutoff frequency release
time in ms.
2000 2000 2000 2000 2000
0x3104 AM_HICUT_CUTOFF_FREQ
0x280A 0x280A 0x280A 0x280A 0x280A Sets the HICUT cutoff Max and Min audio
frequencies.
10250 10250 10250 10250 10250
0x3105 AM_LOWCUT_MIN_FREQ N/A N/A
0x0000 0x0000 0x0000 Sets the minimum LowCut cutoff audio fre-
quency.
000
0x3106 AM_LOWCUT_MAX_FREQ N/A N/A
0x0000 0x0000 0x0000 Sets the maximum LowCut cutoff audio fre-
quency.
000
Table 14. AM Receiver Properties Summary (Continued)
Address Name Default Summary
A10 A20 A30 A40 A55
AN543
204 Rev. 0.9
7.3.1. AM Receiver Commands
Command 0x40 AM_TUNE_FREQ
The AM_TUNE_FREQ command sets the AM Receiver to tune to a frequency in 1 kHz units. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. The ERR bit (and optional interrupt) is set if an
invalid argument is sent. Note that only a single interrupt occurs if both the CTS and ERR bits are set. The optional
STC interrupt is set when the command completes. This command may only be sent in powerup mode. The
command clears the STC bit if it is already set.
Command
Response
Bit76543210
CMD 0x40
ARG1 000000 INJSIDE[1:0]
ARG2 FREQH[7:0]
ARG3 FREQL[7:0]
ARG Bit Name Function
1 7:2 Reserved Always write 000000.
1 1:0 INJSIDE[1:0]
Selects injection side.
0 = Automatic injection side selection by the
tuner.
1 = Force low-side injection.
2 = Force high-side injection.
27:0FREQ
H[7:0]
Tune Frequency High Byte.
This byte in combination with FREQL selects
the tune frequency in units of 1 kHz. In MW
mode the valid range is from 520 to 1710
(520–1710 kHz). LW Range is 144 to 288
(144–288 kHz). SW Range is 2300 to 30000
(2300–30000 kHz).
37:0FREQ
L[7:0]
Tune Frequency Low Byte.
This byte in combination with FREQH selects
the tune frequency in units of 1 kHz. In MW
mode the valid range is from 520 to 1710
(520–1710 kHz). LW Range is 144 to 288
(144–288 kHz). SW Range is 2300 to 30000
(2300–30000 kHz)
Bit76543210
STATUS CTS ERR XX RSQINT X ACFINT STCINT
AN543
Rev. 0.9 205
Command 0x41 AM_SEEK_START
The AM_SEEK_START command begins searching for a valid frequency. In order for a station to be considered
valid, each of the following thresholds must be met: AM_VALID_SNR_THRESHOLD,
AM_VALID_RSSI_THRESHOLD, and AM_VALID_MAX_TUNE_ERROR. Clears any pending STCINT or RSQINT
interrupt status. Seek can be cancelled through setting the CANCEL bit in the AM_RSQ_STATUS command. The
CTS bit (and optional interrupt) is set when it is safe to send the next command. RSQINT status is only cleared by
the AM_RSQ_STATUS command when the RSQACK bit is set. The ERR bit (and optional interrupt) is set if an
invalid argument is sent. Note that only a single interrupt occurs if both the CTS and ERR bits are set. The optional
STC interrupt is set when the command completes. This command may only be sent in powerup mode. The
command clears the STCINT bit if it is already set.
Command
Response
Bit76543210
CMD 0x41
ARG1 0000 SEEKUP WRAP 00
ARG Bit Name Function
1 7:4 Reserved Always write 0000.
1 3 SEEKUP
Seek Up/Down.
Determines the direction of the search, either UP = 1 or
DOWN = 0.
12WRAP
Wrap/Halt.
Determines whether the seek should Wrap = 1, or Halt = 0 when
it hits the band limit.
1 1:0 Reserved Always write 00.
Bit76543210
STATUS CTS ERR XX RSQINT X ACFINT STCINT
AN543
206 Rev. 0.9
Command 0x42 AM_RSQ _ STATUS
The AM_RSQ_STATUS command returns status information about the received signal quality. This command
returns Received Signal Strength Indicator (RSSI), Signal to Noise Ratio (SNR), High Side Adjacent Channel
Strength (HASSI), Low Side Adjacent Channel Strength (LASSI), Frequency Offset (FREQOFF), and AM
Modulation Index (MOD) associated with the desired channel. It also indicates valid channel (VALID) and AFC rail
status (AFCRL). This command can be used to check if the received signal is above the RSSI high threshold as
reported by RSSIHINT, or below the RSSI low threshold as reported by RSSILINT. It can also be used to check if
the signal is above the SNR high threshold as reported by SNRHINT, or below the SNR low threshold as reported
by SNRLINT.
The command clears the RSQINT, SNRHINT, SNRLINT, RSSIHINT and RSSILINT interrupt bits when RSQACK bit
of ARG1 is set. If the condition is still true after the interrupt is cleared another interrupt will fire assuming that bit is
enabled in AM_RSQ_INTERRUPT_SOURCE. The CTS bit (and optional interrupt) is set when it is safe to send
the next command. This command may only be sent in powerup mode.
Command
Bit76543210
CMD 0x42
ARG1 0000 RSQACK ATTUNE CANCEL STCACK
ARG Bit Name Function
1 7:4 Reserved Always write 0000.
1 3 RSQACK Clears RSQINT, SNRHINT, SNRLINT, RSSIHINT, RSSILINT if
set.
1 2 ATTUNE
Returns the values of metrics as of tune time. When the
ATTUNE bit is set, values returned for RSQ_STATUS are the
values calculated at tune and do not change unless another
AM_TUNE_FREQ or AM_SEEK_START command is called.
This feature can be used to determine why seek stopped at the
current station.
1 1 CANCEL
Aborts a seek or tune currently in progress
0 = Don't abort.
1=Abort.
1 0 STCACK Clears the STC interrupt status indicator if set.
AN543
Rev. 0.9 207
Response
Bit765 4 3210
STATUS CTS ERR XX RSQINT X ACFINT STCINT
RESP1 XXXX SNRHINT SNRLINT RSSIHINT RSSILINT
RESP 2 BLTF X SNRREADY RSSIREADY X INJSIDE AFCRL VALID
RESP 3 READFREQ[15:8]
RESP 4 READFREQ[7:0]
RESP 5 FREQOFF[7:0]
RESP 6 RSSI[7:0]
RESP 7 SNR[7:0]
RESP 8 XXXXXXXX
RESP 9 LASSI[7:0]
RESP 10 HASSI[7:0]
RESP 11 IQSNR[7:0]
RESP 12 MOD[7:0]
AN543
208 Rev. 0.9
RESP Bit Name Function
1 7:4 Reserved Values may vary.
13
SNRHINT
SNR Detect High
0 = Received SNR has not exceeded above SNR
programmed using AM_RSQ_SNR_HIGH_THRESHOLD.
1 = Received SNR has exceeded above SNR threshold
programmed using AM_RSQ_SNR_HIGH_THRESHOLD.
12
SNRLINT
SNR Detect Low
0 = Received SNR has not fallen below SNR threshold
programmed using AM_RSQ_SNR_LOW_THRESHOLD.
1 = Received SNR has fallen below SNR threshold
programmed using AM_RSQ_SNR_LOW_THRESHOLD.
11
RSSIHINT
RSSI Detect High
0 = RSSI has not exceeded above RSSI threshold
programmed using AM_RSQ_RSSI_HIGH_THRESHOLD.
1 = RSSI has exceeded above RSSI threshold programmed
using AM_RSQ_RSSI_HIGH_THRESHOLD.
10
RSSILINT
RSSI Detect Low
0 = RSSI has not fallen below RSSI threshold. programmed
using AM_RSQ_RSSI_LOW_THRESHOLD.
1 = RSSI has fallen below RSSI threshold programmed
using AM_RSQ_RSSI_LOW_THRESHOLD.
27BLTF
Band Limit
Reports if a seek hit the band limit (WRAP = 0 in AM_-
SEEK_START) or wrapped to the original frequency
(WRAP = 1).
2 6 Reserved Values may vary.
2 5 SNRREADY
SNR Status
When set, indicates that the SNR metric was read as part of a
tune. If this flag is not set once tune completes, the SNR met-
ric was not measured. A metric not measured indicates that a
tune was terminated prematurely due to an invalidating condi-
tion (i.e., RSSI did not meet the minimum threshold).In this
case, tune time RSQ will report 0 for SNR. The normal run-
ning SNR is not affected by this flag.
0 = SNR measurement in progress (tune in progress).
1 = SNR measurement ready or not taken (tune completed).
2 4 RSSIREADY
RSSI Status
When set, indicates that the RSSI metric was read as part of
a tune. If this flag is not set once tune completes, the RSSI
metric was not measured. In this case, tune time RSQ will
report 0 for RSSI. The normal running RSSI is not affected by
this flag.
0 = RSSI measurement in progress (tune in progress).
1 = RSSI measurement ready or not taken (tune completed).
AN543
Rev. 0.9 209
2 3 Reserved Values may vary
2 2 INJSIDE
Function = Injection side used.
0 = Low-side injection is being used.
1 = High-side injection is being used.
21AFCRL
Set if the AFC rails (AFC gets railed if FREQOFF > MAX-
_TUNE_ERROR).
20VALID
Reports if the channel is valid based on the settings of
AM_VALID_RSSI_THRESHOLD, AM_VALID_SNR_-
THRESHOLD, AM_VALID_MAX_TUNE_ERROR.
3,4 15:0 READ-
FREQ[15:0] Returns the currently tuned frequency.
5 7:0 FREQOFF[7:0] Frequency offset in units of 2 ppm (–128 to 127).
6 7:0 RSSI[7:0] Received Signal Strength indicator in dBµV
(–128 to 127).
7 7:0 SNR[7:0] RF SNR indicator in dB (–128 to 127).
8 7:0 Reserved Values may vary
9 7:0 LASSI[7:0]
Low Side Adjacent Channel Strength Indicator reports the
Signal + Noise power relative to the carrier.
(–128 to 127).
10 7:0 HASSI[7:0]
High Side Adjacent Channel Strength Indicator reports the
Signal + Noise power relative to the carrier.
(–128 to 127).
11 7:0 IQSNR[7:0]
(Available in Si475x-A40 only)
I/Q based SNR for AM-SS in dB. This metric is only available
if IQSNR is set in AM_DEMOD_MODE
Range: –128 to 127
12 7:0 MOD[7:0] AM Modulation Index in percent range 0–100.
RESP Bit Name Function
AN543
210 Rev. 0.9
Command 0x45 AM_ AC F_ STATUS
The AM_ACF_STATUS command returns status information about automatically controlled features. This
command returns the Soft Mute Attenuation, Channel Filter Bandwidth, and HICUT cutoff frequency associated
with the desired channel. If SMUTE bit is high it indicates that is audio is soft muted. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This command may only be sent in powerup mode.
Command
Response
Bit76543210
CMD 0x45
ARG1 0x00 ACFACK
ARG Bit Name Function
1 7:1 Reserved Always write 0.
1 0 ACFACK If set to 1, clears ACFINT and any ACF interrupt bits.
Bit 7 6 5 4 3 2 1 0
STATUS CTS ERR XX RSQINT X ACFINT STCINT
RESP1 XX CHBWH_INT XX HICUT_INT CHBW_INT SOFTMUTE_INT
RESP2 XXXXXXX SMUTE
RESP3 X SMATTN[6:0]
RESP4 CHBW[7:0]
RESP5 HICUT [7:0]
RESP6 XXXXXXXX
RESP7 XXXXXXXX
RESP8 LOWCUT[7:0]
AN543
Rev. 0.9 211
RESP Bit Name Function
1 7:6 Reserved Values may vary.
1 5 CHBWH_INT
(Available in Si475x-A40 only)
CHBWH_INT - Indicates that the Channel Bandwidth is
greater than the threshold set by ACF_CBW_THRESHOLD.
1 4:3 Reserved Values may vary.
12 HICUT_INT
Indicates that HICUT cutoff frequency has crossed below the
HICUT threshold set by AM_ACF_HICUT_THRESHOLD.
1 1 CHBW_INT Indicates that Channel Filter Bandwidth is less than the
threshold set by AM_ACF_CHBW_THRESHOLD.
1 0 SOFTMUTE_INT Indicates that SM attenuation has increased above
AM_ACF_SM_THRESHOLD.
2 7:1 Reserved Values may vary.
20 SMUTE
0 = Audio is not soft muted.
1 = Audio is soft muted.
3 7 Reserved Values may vary.
3 6:0 SMATTN[6:0]
Soft mute attenuation level in dB.
Range: 0–31 in Si475x-A30 and earlier, 0–63 in Si475x-A40
and later.
4 7:0 CHBW[7:0] Channel Filter Bandwidth in 100 Hz.
Range: 0–150.
5 7:0 HICUT[7:0] HICUT cutoff frequency in units of 100 Hz.
Range: 10–50.
6 7:0 Reserved Values may vary.
7 7:0 Reserved Values may vary.
8 7:0 LOWCUT[7:0]
(Available in Si475x-A30 and later.)
Lowcut cutoff frequency in units of 10Hz. Only available if
lowcut is enabled by the AM_LOWCUT_MIN_FREQ property.
Range: 1–100
AN543
212 Rev. 0.9
Command 0x47 AM_ AG C_ STATUS
The AM_AGC_STATUS command reports the current status of the AM AGC. The command is complete when the
CTS bit (and optional interrupt) is set. This command may only be sent in powerup mode.
Command
Response
Bit76543210
CMD 0x47
Bit76543210
Status CTS ERR XX RSQINT X ACFINT STCINT
RESP1 XXXXXX AMHI AMLO
RESP 2 AMWHIPC
RESP 3 AMWHIPR
RESP 4 PGAGAIN[7:0]
RESP Bit Name Function
1 7:2 Reserved Values may vary.
11AMHI
0 = AM LNA PD high threshold is not tripped.
1 = AM LNA PD high threshold is tripped.
10AMLO
0 = AM LNA PD low threshold is not tripped.
1 = AM LNA PD low threshold is tripped.
2 7:0 AMWHIPC AM whip capacitive attenuation in dB.
Range: 0–37.
3 7:0 AMWHIPR AM whip resistive attenuation in dB.
Range: 0–31.
4 7:0 PGAGAIN[7:0] PGA gain in dB.
Range: 8-33.
AN543
Rev. 0.9 213
7.3.2. AM Receiver Properties
Property 0x0303 AUDIO_ PWR_LINE_FILTER (Si4754/55/56/57 Only)
The AUDIO_PWR_LINE_FILTER property selects a 50 Hz or 60 Hz notch filter for power line noise mitigation. The
CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or
read when in powerup mode.
Default: 0x0200
AUDIO_PWR_LINE_FILTER
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0AUTO[2:0] 0 PWRLINEHDWR PWRLINEFLTR 0x0 HARMONICS[4:0]
0000 0 100x00x00
Bit Name Function
15 Reserved Always write to 0.
14:12 AUTO[2:0]
The number of 60 ms cycles to wait before relieving 50/60 Hz suppression.
0 = disable automatic 50/60 Hz detection/suppression. (The PWRLINEH-
DWR setting is ignored.)
Default: 0
Recommended: 3
Range: 0 to 7
11:10 Reserved Always write to 00.
9 PWRLINEHDWR
Power Line Hardware Suppression
0 = Hardware is disabled.
1 = Hardware is enabled.
8 PWRLINEFLTR
(Available in Si475x-A30 and earlier only)
Power Line noise filter selection
0 = 50 Hz Filter is selected.
1 = 60 Hz Filter is selected.
7:5 Reserved Always write 0.
4:0 HARMONICS[4:0]
(Available in Si475x-A30 and earlier)
Sets the number of 50/60 Hz harmonics rejected by the Power Line Noise
filter.
Range 0–20.
0 indicates the filter is disabled.
AN543
214 Rev. 0.9
Property 0x0400 AM_SOFT_MUTE_MAX_ATTENUATION
The AM_SOFT_MUTE_MAX_ATTENUATION property sets the maximum attenuation in dB that will be applied by
the softmute feature. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: 12
Units: dB
AM_SOFT_MUTE_MAX_ATTENUATION
1514131211109876543210
0x000 SMATTN[6:0]
0x000 0x0C
Bit Name Function
15:7 Reserved Always write 0.
6:0 SMATTN[6:0]
Sets the maximum attenuation in dB that will be applied by the softmute
feature.
Default is 12 dB.
Si476x-A20 and earlier: Range is 0–31.
Si476x-A30 and later: Range is 0–63.
AN543
Rev. 0.9 215
Property 0x0401 AM_SOFT_MUTE_TRIGGER_THRESHOLD
The AM_SOFT_MUTE_TRIGGER_THRESHOLD property sets the SNR threshold in dB to engage softmute. The
CTS bit (and optional interrupt) is set when it is safe to send the next command. If USE_RSSI is set in
AM_ACF_CONTROL_SOURCE property, then property 0x0401 refers to RSSI threshold. This property may only
be set or read in powerup mode.
Default: 8
Units: dB
AM_SOFT_MUTE_TRIGGER_THRESHOLD
1514131211109876543210
0x00 SMTRGTH[7:0]
0x00 0x08
Bit Name Function
15:8 Reserved Always write 0.
7:0 SMTRGTH[7:0]
Sets the SNR threshold in dB to engage softmute.
Default is 8 dB.
(Si475x-A10 and earlier)
Range is 0-15 dB.
(Si475x-A20 and later)
Range is -127-127 dB.
AN543
216 Rev. 0.9
Property 0x0402 AM_SOFT_MUTE_END_THRESHOLD
The AM_SOFT_MUTE_END_THRESHOLD property sets the SNR threshold in dB at which softmute attenuation
will be set to its maximum value. When the SNR is at this level or lower, the audio attenuation will be set to
AM_SOFT_MUTE_MAX_ATTENUATION. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. If USE_RSSI is set in AM_ACF_CONTROL_SOURCE property, then property 0x0402 refers to
RSSI threshold. This property may only be set or read in powerup mode.
Default: 0
Units: dB
Property 0x0403 AM_SOFT_M UTE_RELEASE_TIME
The AM_SOFT_MUTE_RELEASE_TIME property sets the maximum time in ms it takes to unmute the audio. The
CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or
read in powerup mode.
Default: 500
Units: ms
AM_SOFT_MUTE_END_THRESHOLD
1514131211109876543210
0x00 SMENDTH[7:0]
0x00 0x00
Bit Name Function
15:8 Reserved Always write 0.
7:0 SMENDTH[7:0]
Sets the SNR threshold in dB at which softmute attenuation will be set to its
maximum value given by
AM_SOFT_MUTE_MAX_ATTENUATION property.
Default is 0 dB. Range is 0 to 15 dB for Si475x-A10 and –127 to 127 dB for
Si475x-A20 or later.
AM_SOFT_MUTE_RELEASE_TIME
1514131211109876543210
RELEASE[15:0]
0x01F4
Bit Name Function
15:0 RELEASE[15:0]
Sets the maximum time in ms it takes to unmute the audio.
Note that there will be 16 ms of filter delay for RSSI/SNR metric before soft-
mute can engage/disengage.
Default is 500 ms. Range is 1–32767 ms.
AN543
Rev. 0.9 217
Property 0x0404 AM_SOFT_MUTE_ATTACK_TIME
The AM_SOFT_MUTE_ATTACK_TIME property sets the maximum time in ms it takes to mute the audio. The CTS
bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 120
Units: ms
Property 0x0405 AM_SOFT_MUTE_MAX_ATTENUATION_AGC (Si4754/55/56/57 Only)
When AGC is engaged, the AM_SOFT_MUTE_MAX_ATTENUATION_AGC property sets the maximum
attenuation in dB that will be applied by the RSSI/SNR softmute feature. The CTS bit (and optional interrupt) is set
when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0x0080
AM_SOFT_MUTE_ATTACK_TIME
1514131211109876543210
ATTACK[15:0]
0x0078
Bit Name Function
15:0 ATTACK[15:0]
Sets the maximum time in ms it takes to mute the audio.
Note that there will be 16 ms of filter delay for RSSI/SNR metric before
softmute can engage/disengage.
Default is 120 ms. Range is 1–32767 ms.
AM_SOFT_MUTE_MAX_ATTENUATION_AGC
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x00 IGNORE_AGC SMATTN[6:0]
0x00 1 0x00
Bit Name Function
15:8 Reserved Always write to 0.
7 IGNORE_AGC
Selects which set of properties control softmute when AGC is engaged.
0 = Use properties 0x0405-0x0409 when the AGC is engaged, and proper-
ties 0x0400-0x0404 otherwise.
1 = Always use only properties 0x0400-0x0404.
6:0 SMATTN[6:0]
When AGC is engaged, sets the maximum attenuation in dB that will be
applied by the RSSI/SNR softmute feature.
Default is 0 dB. Range is 0–63 dB.
AN543
218 Rev. 0.9
Property 0x0406 AM_SOFT_MUTE_TRIGGER_THRESHOLD_AGC (Si4754/55/56/57 Only)
When AGC is engaged, the AM_SOFT_MUTE_TRIGGER_THRESHOLD_AGC property sets the RSSI/SNR
threshold in dB to engage softmute. If USE_RSSI bit is set in AM_ACF_CONTROL_SOURCE property (0x1306),
then this property refers to RSSI threshold. If USE_RSSI bit is not set, this property refers to SNR threshold. The
CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or
read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 8
Units: dB
AM_SOFT_MUTE_TRIGGER_THRESHOLD_AGC
1514131211109876543210
0x00 SMTRGTH_AGC[7:0]
0x00 0x08
Bit Name Function
15:8 Reserved Always write to 0.
7:0 SMTRGTH_AGC[7:0] When AGC is engaged, sets the RSSI/SNR threshold in dB to engage soft-
mute. Default is 8 dB. Range is –127 to 127 dB.
AN543
Rev. 0.9 219
Property 0x0407 AM_SOFT_MUTE_END_THRESHOLD_AGC (Si4754/55/56/57 Only)
When AGC is engaged, the AM_SOFT_MUTE_END_THRESHOLD_AGC property sets the RSSI/SNR threshold
in dB at which softmute attenuation will be set to its maximum value. When the RSSI/SNR is at this level or lower,
the audio attenuation will be set to AM_SOFT_MUTE_MAX_ATTENUATION_AGC. If USE_RSSI bit is set in
AM_ACF_CONTROL_SOURCE property (0x1306), then this property refers to RSSI threshold. If USE_RSSI bit is
not set, this property refers to SNR threshold. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 0
Units: dB
Property 0x0408 AM_SOFT_MUTE_RELEASE_TIME_AGC (Si4754/55/56/57 Only)
When AGC is engaged, the AM_SOFT_MUTE_RELEASE_TIME_AGC property sets maximum time in ms it takes
to unmute the audio. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 500
Units: ms
AM_SOFT_MUTE_END_THRESHOLD_AGC
1514131211109876543210
0x00 SMTRGTH_AGC[7:0]
0x00 0x00
Bit Name Function
15:8 Reserved Always write to 0.
7:0 SMTRGTH_AGC[7:0] When AGC is engaged, sets the RSSI/SNR threshold in dB to engage soft-
mute. Default is 8 dB. Range is –127 to 127 dB.
AM_SOFT_MUTE_RELEASE_TIME_AGC
1514131211109876543210
RELEASE_AGC[15:0]
0x01F4
Bit Name Function
15:0 RELEASE_AGC[15:0]
Sets the maximum time in ms it takes to unmute the audio. Note that there
will be 16 ms of filter delay for RSSI/SNR metric before softmute can
engage/disengage.
Default is 500 ms. Range is 1–32767 ms.
AN543
220 Rev. 0.9
Property 0x0409 AM_SOFT_MUTE_ATTACK_TIME_AGC (Si4754/55/56/57 Only)
When AGC is engaged, the AM_SOFT_MUTE_ATTACK_TIME_AGC property sets maximum time in ms it takes to
mute the audio. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property
may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 120
Units: ms
Property 0x0412 AM_SOFT_MUTE_MAX_ATTENUATION_MOD
Th
e AM_SOFT_MUTE_MAX_ATTENUATION_MOD
proper
ty
sets the maximum soft mute attenuation when
modulation index is used
. The feature is disabled by default by setting IGNORE[7]=1.
The
CTS bit
(and
optional
in
terr
up
t)
is set when it is safe to send the next command
.
This proper
ty
may only be se
t
or read in powerup mode
.
Si475x-A40 and earlier, this property is not available
Si475x/5xC-A55, Default:
0x008C
AM_SOFT_MUTE_ATTACK_TIME_AGC
1514131211109876543210
ATTACK_AGC[15:0]
0x0078
Bit Name Function
15:0 ATTACK_AGC[15:0]
Sets the maximum time in ms it takes to unmute the audio. Note that
there will be 16 ms of filter delay for RSSI/SNR metric before softmute
can engage/disengage.
Default is 120 ms. Range is 1–32767 ms.
AM_SOFT_MUTE_MAX_ATTENUATION_MOD
15141312111098 7 6543210
0x00 IGNORE SMATTN[6:0]
0x00 1 0x0C
Bit Name Function
15:8 0x00 Always write 0
7IGNORE
0 = enable the modulation based soft mute
1 = disable the modulation based soft mute
6:0 SMATTN[6:0]
Sets the maximum attenuation in dB that will be applied by the softmute fea-
ture.
Default is 12 dB. Range is 0 ~ 63.
AN543
Rev. 0.9 221
Property 0x0413 AM_SOFT_MUTE_THRESHOLD_MOD
The AM_SOFT_MUTE_THRESHOLD_MOD property sets the modulation index threshold for soft mute to start and
stop. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property
may only
be set or read in powerup mode.
Si475x-A40 and earlier: This property is not available.
Si475x/5xC-A55, Default: 0x0E16
Units: %
Property 0x0414 AM_SOFT_MUTE_RELEASE_TIME_MOD
Th
e AM_SOFT_MUTE_RELEASE_TIME_MOD
proper
ty
sets the maximum soft mute release time in ms when
modulation index is used
.
The
CTS
bit
(and
optional
in
terr
up
t)
is set when it is safe to send the next command
.
This proper
ty
may only be se
t
or read in powerup mode
.
Si475x-A40 and earlier, this property is not available.
Si475x/5xC-A55, Default: 500 ms
AM_SOFT_MUTE_THRESHOLD_MOD
1514131211109876543210
0 SMENDTH[6:0] 0 SMTRGTH[6:0]
0 0x0E 0 0x16
Bit Name Function
15 0 Always write to 0
14:8 SMENDTH[6:0]
Sets the soft mute end threshold in percentage, the conversion between
property value and threshold in percentage is SMENDTH[6:0] = threshold
x 1.27. Default is 14. Range is 0 ~ 127.
7 0 Always write to 0
6:0 SMTRGTH[6:0]
Sets the soft mute start threshold in percentage, the conversion between
property value and threshold in percentage is SMTRGTH[6:0] = threshold
x 1.27. Default is 22, Range is 0 ~127.
AM_SOFT_MUTE_RELEASE_TIME_MOD
1514131211109876543210
RELEASE[15:0]
0x01F4
Bit Name Function
15:0 RELEASE [15:0]
Sets the maximum time in ms to unmute the audio.
Default is 500 ms. Range is 1 ~ 32767 ms.
AN543
222 Rev. 0.9
Property 0x0415 AM_SOFT_MUTE_A TTACK_TIME_MOD
The AM_SOFT_MUTE_ATTACK_TIME_MOD property sets maximum time in ms it takes to
mute the audio. The
CTS bit (and optional interrupt) is set when it is safe to send the next command. This property
may only be set or
read in powerup mode.
Si475x-A40 and earlier: This property is not available.
Si475x/5xC-A55, Default: 120
Units: ms
Property 0x0416 AM_SOFT_MUTE_MOD_RSSI
Th
e AM_SOFT_MUTE_MOD_RSSI
proper
ty
sets the RSSI level for AM modulation based soft mute to enable or
disable
.
The
CTS
bit
(and
optional
in
terr
up
t)
is set when it is safe to send the next command
.
This proper
ty
may
only be se
t
or read in powerup mode
.
Si475x-A40 and earlier, this property is not available
Si475x/5xC-A55, Default: 0x0F0D
Units: dBµV
AM_SOFT_MUTE_ATTACK_TIME_MOD
1514131211109876543210
ATTACK[15:0]
0x0078
Bit Name Function
15:0 ATTACK [15:0]
Sets the maximum time in ms to unmute the audio.
Default is 120 ms. Range is 1–32767 ms.
AM_SOFT_MUTE_MOD_RSSI
1514131211109876543210
XMAX[7:0] XMIN[7:0]
0x0F 0x0D
Bit Name Function
15:8 XMAX [15:8]
Sets RSSI level above which the AM modulation based soft mute will be
automatically switched off. Default is 15 dBµV. Range is –127 ~ 127 dBµV.
7:0 XMIN[7:0]
Sets RSSI level below which the AM modulation based soft mute will be
automatically switched on. Default is 13 dBµV. Range is –127 ~ 127 dBµV
AN543
Rev. 0.9 223
Property 0x0500 AM_AVC_MIN_GAIN
The AM_AVC_MIN_GAIN property sets the minimum gain for automatic volume control. The minimum gain value
is given by MINGAIN = g x 170 where g is the desired minimum AVC gain in dB. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: –2048
AM_AVC_MIN_GAIN
1514131211109876543210
MINGAIN[15:0]
0xF800
Bit Name Function
15:0 MINGAIN[15:0]
The minimum gain value for the AVC. Gain in dB is MINGAIN x 6.02/1024.
Range for MINGAIN is –4096 to 0. This implies that the range of g is –24 dB
to 0 dB
AN543
224 Rev. 0.9
Property 0x0501 AM_AVC_MAX_GAIN
The AM_AVC_MAX_GAIN property sets the maximum gain for automatic volume control. The maximum gain
value is given by MAXGAIN = g x 170 where g is the desired maximum AVC gain in dB. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 10220
Si475x/5xC-A55, Default: 17010
Property 0x0700 AM_AGC_FE_CONFIG
Specifies the input path for the RF signal and other front-end configuration options. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. The property may only be set or read when in the
powerup mode. Changes to this property take effect after the next tune is completed.
Default: 0x0094
AM_AVC_MAX_GAIN
1514131211109876543210
0MAXGAIN[14:0]
00x27EC
Bit Name Function
15 Reserved Always set to 0.
14:0 MAXGAIN[14:0] The maximum gain value for the AVC. Gain in dB is MAXGAIN x 6.02/1024.
Range is 0–32767. This implies that the range of g is 0–193 dB
AM_AGC_FE_CONFIG
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0000000 FMLNAZ 10 ATTENFM HARMREJ INPUTSELECT[3:0]
0000000 010 01 0x4
AN543
Rev. 0.9 225
Bit Name Function
15:9 Reserved In Si475x-A20 and earlier, always write 0000000.
In Si475x-A30 and later, always write 1111000.
8FMLNAZ
0 = Normal LNA mode where the LNA input impedance is 50
1 = LNA loopthru mode where LNA input impedance is 100
7:6 Reserved Always write to 10.
5ATTENFM
0 = FM attenuators are turned on to improve FM intrusion.
1 = FM attenuators are off. This is the preferred setting to minimize desensi-
tization for a multiple receiver system sharing a single antenna.
4 HARMREJ 0 = Harmonic reject is disabled.
1 = Harmonic reject is enabled.
3:0 INPUTSELECT[3:0] 4 = Receive signal comes into the AMI
AN543
226 Rev. 0.9
Property 0x0708 AM_IF_AGC_ATTACK_MS
Sets the number of milliseconds the IF high peak detector must be exceeded before attenuating the appropriate
block. The peak detectors are only sampled once every 3–5 ms. If the peak detector trips, the internal counter is
incremented by 4 ms. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read when in the powerup mode.
Default: 80
Units: ms
Property 0x0709 AM_IF_AGC_RELEASE_MS
Sets the number of milliseconds the IF low peak detector must not be exceeded before increasing the gain of the
appropriate block. The peak detectors are only sampled once every 3–5 ms. If the peak detector trips, the internal
counter is incremented by 4 ms. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read when in the powerup mode.
Si475x-A10 and earlier, Default: 80
Si475x-A30 and later, Default: 804
Units: ms
AM_IF_AGC_ATTACK_MS
1514131211109876543210
IF_AGC_ATTACK_MS[15:0]
0x0050
Bit Name Function
15:0 IF_AGC_ATTACK_MS[15:0]
Number of milliseconds the IF high peak detector must be exceeded
before attenuating the appropriate block.
Si475x-A10 and earlier: Range: 4–248 ms.
Si475x-A20 and later: Range: 4–4096 ms.
AM_IF_AGC_RELEASE_MS
1514131211109876543210
IF_AGC_RELEASE_MS[15:0]
0x0324
Bit Name Function
15:0 IF_AGC_RELEASE_MS[15:0]
Number of milliseconds the IF low peak detector must not be
exceeded before increasing the gain of the appropriate block.
Si475x-A10 Range: 4–248 ms
Si475x-A20 and later, Range: 4–4096 ms
Note: For best performance AM_IF_AGC_RELEASE_MS > AM_RF_AGC_RELEASE_MS and set
AM_IF_AGC_RELEASE_MS to 804 ms for AM_RF_AGC_RELEASE_MS of 800 ms.
AN543
Rev. 0.9 227
Property 0x070C AM_RF_AGC_ATTACK_MS
The AM_RF_AGC_ATTACK_MS property sets the number of milliseconds the wideband RF high-peak detector
must be exceeded before attenuating the appropriate block. The peak detectors are only sampled once every 3–
5 ms. If the peak detector trips, the internal counter is incremented by 4 ms. The CTS bit (and optional interrupt) is
set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 8
Units: ms
AM_RF_AGC_ATTACK_MS
1514131211109876543210
RF_AGC_ATTACK_MS[15:0]
0x0008
Bit Name Function
15:0 RF_AGC_ATTACK_MS[15:0]
Number of milliseconds the wide-band RF high-peak detec-
tor must be exceeded before attenuating the appropriate
block. Default is 8 ms.
Si475x-A10 and earlier: Range: 4–248 ms.
Si475x-A20 and later: Range: 4–4096 ms.
AN543
228 Rev. 0.9
Property 0x070D AM_RF_AGC_RELEASE_MS
The AM_RF_AGC_RELEASE_MS property sets the number of milliseconds the wideband RF low-peak detector
must not be exceeded before increasing the gain of the appropriate block. The peak detectors are only sampled
once every 3–5 ms. If the peak detector trips, the internal counter is incremented by 4 ms. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 800
Units: ms
AM_RF_AGC_RELEASE_MS
1514131211109876543210
RF_AGC_RELEASE_MS[15:0]
0x0320
Bit Name Function
15:0 RF_AGC_RELEASE_MS[15:0]
Number of milliseconds the wideband RF low-peak detector
must not be exceeded before increasing the gain of the appropri-
ate block. Default is 800 ms.
(Si475x-A10 and earlier)
Range: 4–248 ms.
(Si475x-A20 and later)
Range is 4–4096 ms.
Note: For best performance, AM_IF_AGC_RELEASE_MS > AM_RF_AGC_RELEASE_MS
AN543
Rev. 0.9 229
Property 0x070E AM_LNA_P D_THRESHOLD
The AM_LNA_PD_THRESHOLD property sets the high threshold and hysteresis for the LNA peak detector. The
high threshold sets the level at which the AGC increases attenuation. The hysteresis is how many dB below the
high threshold the level must drop before the AGC decreases attenuation. The CTS bit (and optional interrupt) is
set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 0x5104
Si475x/5xC-A55, Default: 0x5904
AM_LNA_PD_THRESHOLD
1514131211109876543210
HIGH[7:0] HYST[7:0]
0x51 0x04
Bit Name Function
15:8 HIGH[7:0]
Sets the level in dBµV at which AGC increases attenuation.
HIGH[7:0] Range: 79–93.
79 = 79 dBµV.
81 = 81 dBµV.
83 = 83 dBµV.
85 = 85 dBµV.
87 = 87 dBµV.
89 = 89 dBµV.
91 = 91 dBµV.
93 = 93 dBµV.
7:0 HYST[7:0]
Sets how many dB below the high threshold the level must drop before the AGC
decreases attenuation.
HYST[7:0] Range: 3–6.
3=3 dB.
4=4 dB.
5=5 dB.
6=6 dB.
AN543
230 Rev. 0.9
Property 0x0710 AM_AGC_OVERRIDE
The AM_AGC_OVERRIDE property overrides the AGC setting by disabling the AGC and forcing the gain to be
maximum. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Default: 0x0000
Property 0x071B AM_AGC_RSSI_OFFSET
The AM_AGC_RSSI_OFFSET property sets the value of the offset applied to the RSSI value in order to account
for the front-end gain/loss due to the AGC. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read in powerup mode.
Si475x-A10 and earlier: This property is not available.
Si475x-A20 and later, Default: 0
Units: dB
AM_AGC_OVERRIDE
1514131211109876543210
0x000 AGC_OVERRIDE[5:0]
0x000 0
Bit Name Function
15:6 Reserved Always write 0.
5:0 AGC_OVERRIDE[5:0]
AGC_OVERRIDE selects whether the AGC is enabled or disabled.
0 = AGC is enabled.
0x3F = AGC is disabled and set to maximum gain.
AM_AGC_RSSI_OFFSET
1514131211109876543210
OFFSET[7:0] RSVD[7:0]
0x00 0x00
Bit Name Function
15:8 OFFSET[7:0]
Sets the RSSI offset value to take into account front-end gain/loss.
Default is 0.
Range is –128 to 127.
7:0 Reserved Always write 0.
AN543
Rev. 0.9 231
Property 0x1006 AM_SEEK_TUNE_CHBW_HOLD_TIME
The AM_SEEK_TUNE_CHBW_HOLD_TIME property sets the length of time channel filter bandwidth is held at
specified value after Seek or Tune. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode.
Si475x-A10: This property is not available.
Si475x-A20: This feature is not available. Do not write to this property.
Si475x-A30 and later, Default: 80
Units: ms
Property 0x1007 AM_TUNE_CHBW
The AM_TUNE_CHBW property sets the maximum channel filter bandwidth to allow during tune. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A20 and earlier: This property is not available
Si475x-A30 and later, Default: 0
Units: 100 Hz
AM_SEEK_TUNE_CHBW_HOLD_TIME
1514131211109876543210
CHBW_HOLD_TIME[15:0]
0x0050
Bit Name Function
15:0 CHBW_HOLD_TIME[15:0]
Sets the length of time channel filter bandwidth is held at specified value
after Seek or Tune.
Default is 80 ms.
Range is 4–1000.
AM_TUNE_CHBW
1514131211109876543210
0x00 TUNE_CHBW[7:0]
0x00 0x0000
Bit Name Function
15:8 Reserved Always write to 0.
7:0 TUNE_CHBW[7:0]
Sets the maximum channel filter bandwidth to allow during tune. Set to 0
to disable limiting of channel filter bandwidth during tune.
Default is 0.
Range is 0–150.
AN543
232 Rev. 0.9
Property 0x1100 AM_SEEK_BAND_BOTTOM
The AM_SEEK_BAND_BOTTOM property sets the bottom of the AM band for seek. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
The default is 520 kHz.
Si475x-A40 and earlier, Default: 520
Si475x/5xC-A55, Default: 522
Units: kHz
Property 0x1101 AM_SEEK_BAND_TOP
The AM_SEEK_BAND_TOP property sets the top of the AM band for seek. The CTS bit (and optional interrupt) is
set when it is safe to send the next command. This property may only be set or read in powerup mode. The default
is 1710 kHz
Default: 1710
Units: kHz
AM_SEEK_BAND_BOTTOM
1514131211109876543210
AMSKFREQL[15:0]
0x0208
Bit Name Function
15:0 AMSKFREQL[15:0]
Sets the bottom of the AM band for seek. Default is 520 kHz.
Range: 520–1710 (MW).
144–288 (LW).
2300–30000 (SW).
AM_SEEK_BAND_TOP
1514131211109876543210
AMSKFREQH[15:0]
0x06AE
Bit Name Function
15:0 AMSKFREQH[15:0]
Sets the top of the AM band for seek. Default is 1710 kHz.
Range: 520–1710 (MW).
144–288 (LW)
2300–30000 (SW)
AN543
Rev. 0.9 233
Property 0x1102 AM_SEEK_FREQUENCY_SPACING
The AM_SEEK_FREQUENCY_SPACING property selects frequency spacing for AM seek in multiples of 1 kHz.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode. The default is 10 kHz.
Si475x-A40 and earlier, Default: 10
Si475x/5xC-A55, Default: 9
Units: kHz
Property 0x1104 AM_SEEK_CHBW
The AM_SEEK_CHBW property sets the channel filter bandwidth during seek. The CTS bit (and optional interrupt)
is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available.
Si475x-A30 and later, Default: 20
Units: 100 Hz
AM_SEEK_FREQUENCY_SPACING
1514131211109876543210
0x000 AMSKSPACE[4:0]
0x000 0x0A
Bit Name Function
15:5 Reserved Always write 0.
4:0 AMSKSPACE[4:0]
Selects frequency spacing for AM seek. Default is 10 kHz. Range is 1–31.
5 = SW (5 kHz).
9 = AM in Asia (9 kHz).
9=LW (9kHz).
10 = AM in U.S. (10 kHz).
AM_SEEK_CHBW
1514131211109876543210
0x00 SEEK_CHBW[7:0]
0x00 0x14
Bit Name Function
15:8 Reserved Always write to 0.
7:0 SEEK_CHBW[7:0]
Sets the maximum channel filter bandwidth to allow during seek.
Default is 2 kHz.
Range is 0–150.
AN543
234 Rev. 0.9
Property 0x1200 AM_RSQ_INTERRUPT_SOURCE
The AM_RSQ_INTERRUPT_SOURCE property configures interrupt related to Received Signal Quality metrics.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode. The default is 0.
Default: 0
AM_RSQ_INTERRUPT_SOURCE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x000 SNRHINT SNRLINT RSSIHINT RSSILINT
0x000 0 0 0 0
Bit Name Function
15:4 Reserved Always write 0.
3 SNRHINT
0: Disable Interrupt.
1: Enable interrupt to occur if SNR goes above the threshold set by
AM_RSQ_SNR_HIGH_THRESHOLD.
2 SNRLINT
0: Disable Interrupt.
1: Enable interrupt to occur if SNR goes below the threshold set by
AM_RSQ_SNR_LOW_THRESHOLD.
1RSSIHINT
0: Disable Interrupt.
1: Enable interrupt to occur if RSSI goes above the threshold set by
AM_RSQ_RSSI_HIGH_THRESHOLD.
0RSSILINT
0: Disable Interrupt.
1: Enable interrupt to occur if RSSI goes below the threshold set by
AM_RSQ_RSSI_LOW_THRESHOLD.
AN543
Rev. 0.9 235
Property 0x1201 AM_RSQ_SNR_HIGH_THRESHOLD
The AM_RSQ_SNR_HIGH_THRESHOLD property sets the high threshold, which triggers the RSQ interrupt if the
SNR is above this threshold. The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Default: 127
Units: dB
Property 0x1202 AM_RSQ_SNR_LOW_THRESHOLD
The AM_RSQ_SNR_LOW_THRESHOLD property sets low threshold, which triggers the RSQ interrupt if the SNR
is below this threshold. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: –128
Units: dB
AM_RSQ_SNR_HIGH_THRESHOLD
1514131211109876543210
SIGN[7:0] SNRH[7:0]
0x00 0x7F
Bit Name Function
15:8 SIGN[7:0] Write 0 for (+) values, 0xFF for (–) values.
7:0 SNRH [7:0]
Sets the high threshold, which triggers the RSQ interrupt if the SNR is
above this threshold. Default is 127 dB. Range is –128 to 127 dB in steps of
1dB.
AM_RSQ_SNR_LOW_THRESHOLD
1514131211109876543210
SIGN[7:0] SNRL[7:0]
0xFF 0x80
Bit Name Function
15:8 SIGN[7:0] Write 0 for (+) values, 0xFF for (–) values.
7:0 SNRL [7:0] Sets low threshold, which triggers the RSQ interrupt if the SNR is below this
threshold. Default is –128 dB. Range is –128 to 127 dB in steps of 1 dB.
AN543
236 Rev. 0.9
Property 0x1203 AM_RSQ_RSSI_HIGH_THRESHOLD
The AM_RSQ_RSSI_HIGH_THRESHOLD property sets high threshold, which triggers the RSQ interrupt if the
RSSI is above this threshold. The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Default: 127
Units: dBµV
Property 0x1204 AM_RSQ_RSSI_LOW_THRESHOLD
The AM_RSQ_RSSI_LOW_THRESHOLD property sets low threshold, which triggers the RSQ interrupt if the RSSI
is below this threshold. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: –128
Units: dBµV
AM_RSQ_RSSI_HIGH_THRESHOLD
1514131211109876543210
SIGN[7:0] RSSIH[7:0]
0x00 0x7F
Bit Name Function
15:8 SIGN[7:0] Write 0 for (+) values, 0xFF for (–) values.
7:0 RSSIH [7:0]
Sets high threshold, which triggers the RSQ interrupt if the RSSI is above
this threshold. Default is 127 dBµV. Range is –128 to 127 dBµV in steps of
1dB.
AM_RSQ_RSSI_LOW_THRESHOLD
1514131211109876543210
SIGN[7:0] RSSIL[7:0]
0xFF 0x80
Bit Name Function
15:8 SIGN[7:0] Write 0 for (+) values, 0xFF for (–) values.
7:0 RSSIL [7:0]
Sets low threshold, which triggers the RSQ interrupt if the RSSI is below this
threshold. Default is –128 dBµV. Range is –128 to 127 dBµV in steps of
1dB.
AN543
Rev. 0.9 237
Property 0x1300 AM_ACF_INTERRUPT_SOURCE
The AM_ACF_INTERRUPT_SOURCE property enables the ACF interrupt sources. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 0
AM_ACF_INTERRUPT_SOURCE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x000 CHBWH_INT 00 HICUT_INT CHBW_INT SOFTMUTE_INT
0x000 000
00 0
Bit Name Function
15:6 Reserved Always write 0.
5 CHBWH_INT
(Available in Si475x-A40 only)
Enables the Channel Filter Bandwidth High Interrupt
0 = The Channel Bandwidth interrupt is disabled
1 = The Channel Bandwidth interrupt is enabled
4:3 Reserved Always write 0.
2 HICUT_INT
When set, enables the HICUT Interrupt. Default is 0.
0 = The HICUT interrupt is disabled.
1 = The HICUT interrupt is enabled.
1 CHBW_INT
When set, enables the Channel Filter Bandwidth Interrupt. Default is 0.
0 = The Channel Filter Bandwidth interrupt is disabled.
1 = The Channel Filter Bandwidth interrupt is enabled.
0SOFTMUTE_INT
When set, enables the softmute interrupt. Default is 0.
0 = The softmute interrupt is disabled.
1 = The softmute interrupt is enabled.
AN543
238 Rev. 0.9
Property 0x1301 AM_ACF_SM_THRESHOLD
The AM_ACF_SM_THRESHOLD property sets the softmute interrupt threshold in dB. When softmute attenuation
rises above the level set by this property and the SOFTMUTE_INT interrupt is enabled through the
AM_ACF_INTERRUPT_SOURCE property, the SOFTMUTE_INT interrupt will be asserted. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 31
Units: dB
AM_ACF_SM_THRESHOLD
1514131211109876543210
0x000 SMATTN_THRESH[4:0]
0x000 0x1F
Bit Name Function
15:5 Reserved Always write 0.
4:0 SMATTN_THRESH[4:0]
Softmute interrupt threshold in dB which triggers the softmute interrupt when
the softmute attenuation rises above this level. Default is 31 dB.
Range is 0–31 dB.
AN543
Rev. 0.9 239
Property 0x1302 AM_ACF_CHBW_THRESHOLD
The AM_ACF_CHBW_THRESHOLD property sets the Channel Filter Bandwidth interrupt threshold in units of
100 Hz. When the Channel Filter Bandwidth falls below this threshold and the CHBW_INT interrupt is enabled
through the AM_ACF_INTERRUPT_SOURCE property, the CHBW_INT interrupt will be asserted. The CTS bit
(and optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 0
Units: 100 Hz
AM_ACF_CHBW_THRESHOLD
1514131211109876543210
CHBW_THRESH_HIGH[7:0] CHBW_THRESH[7:0]
0x00 0x00
Bit Name Function
15:8 CHBW_THRESH_HIGH[7:0]
(Available in Si475x-A40 and later only)
Channel Filter Bandwidth High interrupt threshold in units of 100 Hz,
which triggers the Channel Filter Bandwidth Interrupt when the
channel filter bandwidth rises above this threshold.
Default is 0 kHz. Range is 0–255.
7:0 CHBW _THRESH[7:0]
Channel Filter Bandwidth Low interrupt threshold in units of 100 Hz,
which triggers the Channel Filter Bandwidth Interrupt when the
Channel Filter Bandwidth falls below this threshold.
Default is 0 kHz. Range is 0–255.
AN543
240 Rev. 0.9
Property 0x1303 AM_ACF_HICUT_THRESHOLD
The AM_ACF_HICUT_THRESHOLD property sets the HICUT interrupt threshold in units of 100 Hz. When the
HICUT cutoff frequency falls below this threshold and the HICUT_INT interrupt is enabled through the
AM_ACF_INTERRUPT_SOURCE property, the HICUT_ INT interrupt will be asserted. The CTS bit (and optional
interrupt) is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Default: 0
Units: 100 Hz
AM_ACF_HICUT_THRESHOLD
1514131211109876543210
0x00 HICUT_THRESH[7:0]
0x00 0x00
Bit Name Function
15:8 Reserved Always write 0.
7:0 HICUT_THRESH[7:0]
HICUT interrupt threshold in units of 100 Hz, which triggers the HICUT Inter-
rupt when the HICUT cutoff frequency falls below this threshold. Default is
0 kHz. Range is 0–200.
AN543
Rev. 0.9 241
Property 0x1306 AM_ACF_CONTROL_SOURCE
The AM_ACF_CONTROL_SOURCE property determines if SNR or RSSI will be used as the controlling metric for
ACF features. This will affect all automatically controlled features that are controlled by SNR. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 0
Property 0x2000 AM_VALID_MAX_TUNE_ERROR
The AM_VALID_MAX_TUNE_ERROR property sets the maximum frequency error allowed in units of 2 ppm
before setting the AFC rail indicator (AFCRL). The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 75 (150 ppm)
Si475x/5xC-A55, Default: 126 (252 ppm)
Units: 2 ppm
AM_ACF_CONTROL_SOURCE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x0000 AFC_DIS AFC_SM 0 USE_RSSI
0x0000 000 0
Bit Name Function
15:4 Reserved Always write 0.
3AFC_DIS
When set, disables the use of AFC in tune validation
0 = Use AFC in tune validation.
1 = Do not use AFC in tune validation.
2AFC_SM
When set, softmute will be triggered by an AFC rail.
(Si475x-A20 and later only).
0 = Do not use AFC rail to force softmute.
1 = Use AFC rail to force softmute.
1 Reserved Always write 0.
0 USE_RSSI
When set, RSSI will be used instead of SNR as the ACF controlling metric.
0 = Use SNR as the controlling metric.
1 = Use RSSI as the controlling metric.
AM_VALID_MAX_TUNE_ERROR
1514131211109876543210
0x00 AMMAXTUNEERR[7:0]
0x00 0x4B
AN543
242 Rev. 0.9
Property 0x2001 AM_VALID_RSSI_TIME
The AM_VALID_RSSI_TIME property sets the amount of time in milliseconds to allow the RSSI metric to settle
before evaluating. For 4 MHz crystal operation, the minimum recommended settling time for RSSI is 8
milliseconds. The reliability of the valid bit for identifying valid stations relies on this parameter being set properly.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set
or read in powerup mode.
Default: 5
Units: ms
Property 0x2002 AM_VALID_SNR_TIME
The AM_VALID_SNR_TIME property sets the amount of time in milliseconds to allow the RSSI metric to settle
before evaluating. The minimum SNR settling delay is 27 milliseconds. The reliability of the valid bit for identifying
valid stations relies on this parameter being set properly. The CTS bit (and optional interrupt) is set when it is safe
to send the next command. This property may only be set or read in powerup mode.
Default: 36
Units: ms
Bit Name Function
15:8 Reserved Always write 0.
7:0 AMMAXTUNEERR [7:0] Sets the maximum freq error allowed in units of 2 ppm before setting the AFC
rail indicator (AFCRL). Default is 75. Range is 0–126.
AM_VALID_RSSI_TIME
1514131211109876543210
0x00 RSSIVALTIME[5:0]
0x00 0x05
Bit Name Function
15:6 Reserved Always write to 0.
5:0 RSSIVALTIME[5:0]
Validation time in milliseconds. Default is 5 ms.
Range is 5–63 ms in Si475x-A30 and earlier.
Range is 5–127 ms in si475x-A40 and later.
Note: The recommended minimum RSSI settling time is 8 ms.
AM_VALID_SNR_TIME
1514131211109876543210
0x00 SNRVALTIME [5:0]
0x00 0x24
AN543
Rev. 0.9 243
Property 0x2003 AM_VALID_SNR_THRESHOLD
The AM_VALID_SNR_THRESHOLD property sets the SNR threshold for a valid AM Seek/Tune. If the desired
channel SNR is above this threshold, then it is considered valid. The CTS bit (and optional interrupt) is set when it
is safe to send the next command. This property may only be set or read in powerup mode.
Default: 5
Units: dB
Bit Name Function
15:6 Reserved Always write to 0.
5:0 SNRVALTIME[5:0]
Validation time in milliseconds. Default is 36 ms. Range is 0–63 ms.
Range is 27–63 ms in Si475x-A30 and earlier.
Range is 27–127 ms in si475x-A40 and later.
AM_VALID_SNR_THRESHOLD
1514131211109876543210
AMVALUSN[7:0] AMVALSNR[7:0]
0x00 0x05
Bit Name Function
15:8 AMVALUSN[7:0]
(Available in Si475x-A40 only)
AM Seek/Tune USN Threshold.
Default: 0
Range: 0 to 127 - Specified in units of negative -dBFS. (0 is full scale, 127 is
127dB down from full scale.)
0 = USN is not used as a criterion in determining the validity of a station.
(In Si475x-A30 and earlier, this field should be the continued SIGN of
AMVALSNR. That is, it should be 0x00 for positive (+) values and 0xFF for neg-
ative (–) values.)
7:0 AMVALSNR [7:0]
Sets the SNR threshold for a valid AM Seek/Tune. Default is 5 dB. Range is
–128 to 127 in steps of 1 dB.
–128 = SNR is not used as a criterion in determining the validity of a station.
AN543
244 Rev. 0.9
Property 0x2004 AM_VALID_RSSI_THRESHOLD
The AM_VALID_RSSI_THRESHOLD property sets the RSSI threshold for a valid AM Seek/Tune. If the desired
channel RSSI is above this threshold, then it is considered valid. The CTS bit (and optional interrupt) is set when it
is safe to send the next command. This property may only be set or read in powerup mode.
Default: 10
Units: dBµV
Property 0x200C AM_VALID_FREQOFF_SCALE
The AM_VALID_FREQOFF_SCALE sets the units in Hz for the AM_RSQ_STATUS response FREQOFF metric, as
well as AM_VALID_MAX_TUNE_ERROR. (For example, if AM_VALID_FREQOFF_SCALE is set to 100, then
AM_VALID_MAX_TUNE_ERROR will have units of 100 Hz per property value step.) The default is to use units of
binary ppm instead of any number of Hz. The CTS bit (and optional interrupt) is set when it is safe to send the next
command. This property may only be set or read in powerup mode. In Si475x-A30 and earlier, FREQOFF is always
in units of bppm (binary ppm, or 2 ppm).
Si475x-A30 and earlier: This property is not available.
Si475x-A40 and later, Default: 0
Units: Hz
AM_VALID_RSSI_THRESHOLD
1514131211109876543210
0x00 AMVALRSSI[7:0]
0x00 0x0A
Bit Name Function
15:8 Reserved Write 0 for (+) values, 0xFF for (–) values.
7:0 AMVALRSSI[7:0]
Sets the RSSI threshold for a valid AM Seek/Tune. Default is 10 dBµV.
Range is –128 to 127 in steps of 1 dB.
–128 = RSSI is not used as a criterion in determining the validity of a station.
AM_VALID_FREQOFF_SCALE
1514131211109876543210
SCALE[15:0]
0x0000
Bit Name Function
15:0 SCALE[15:0]
Sets the units in Hz for the frequency offset metric and the AM_VALID_MAX-
_TUNE_ERROR. The recommended value for AM is 50 Hz.
Default is 0.
0 = Use units of bppm.
AN543
Rev. 0.9 245
Property 0x200D AM_VALID_FREQOFF_FILTER
The AM_VALID_FREQOFF_FILTER sets the number of FREQOFF samples averaged by the metric filter before
reporting FREQOFF as part of AM_RSQ_STATUS. The CTS bit (and optional interrupt) is set when it is safe to
send the next command. This property may only be set or read in powerup mode.
Si475x-A30 and earlier: This property is not available.
Si475x-A40 and later, Default: 100
Property 0x2100 AM_NB_DETECT_THRESHOLD
The AM_NB_DETECT_THRESHOLD property sets the threshold for detecting impulses in dB above the noise
floor. The noise blanker can be disabled by setting the noise blanker detect threshold to 0.The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 18
Units: dB
AM_VALID_RSSI_THRESHOLD
1514131211109876543210
0x00 FILTER[7:0]
0x00 0x64
Bit Name Function
15:8 Reserved Always write 0.
7:0 FILTER[7:0]
The number of FREQOFF values that are averaged when reporting the value
in AM_RSQ_STATUS. (Values below 10 will begin to track audio and are not
recommended. If low-cut is being used then the minimum value will need to
be increased accordingly to avoid tracking low frequency audio.)
Default is 100 samples. Range is 0–127.
AM_NB_DETECT_THRESHOLD
1514131211109876543210
DETECT_THRESHOLD[15:0]
0x0012
Bit Name Function
15:0 DETECT_THRESHOLD[15:0]
Sets the threshold for detecting impulses in dB above the
noise floor. Default is 18 dB. Range is 0–90 dB.
To disable the noise blanker, set the DETECT_THRESH-
OLD to 0.
AN543
246 Rev. 0.9
Property 0x2101 AM_NB_INT ERVAL
The AM_NB_INTERVAL property sets the interval in microseconds that original samples are replaced by
interpolated clean samples. The noise blanker can be disabled by setting the noise blanker detect threshold to
0.The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be
set or read in powerup mode.
Default: 4
AM_NB_INTERVAL
1514131211109876543210
NB_INTERVAL[15:0]
0x0004
Bit Name Function
15:0 NB_INTERVAL[15:0]
Sets the interval in number of audio samples that original sam-
ples are replaced by interpolated clean samples.
Default is 4. Range is 1–40.
AN543
Rev. 0.9 247
Property 0x2102 AM_ NB_DEL AY
The AM_NB_DELAY property sets the noise blanker delay in number of samples from where to select the good
samples to replace the samples corrupted by the impulse. The CTS bit (and optional interrupt) is set when it is safe
to send the next command. This property may only be sent when in powerup mode.
Si475x-A10, Default: 0x005D
Si475x-A20, Default: 0x175D
Si475x-A30, Default: 0x3AE8
AM_NB_DELAY
1514131211109876543210
0x0 SECONDARY_BLANKER_DELAY[5:0] PRIMARY_BLANKER_DELAY[7:0]
0x0 0x3A 0xE8
Bit Name Function
15:14 Reserved Always write to 00.
13:8 SECONDARY_BLANKER_DELAY[5:0]
Delay in units of number of samples from where to select the
good samples to replace the samples corrupted by the
impulse for the secondary blanker at 23k sample/second.
(Available in Si475x-A20 and later only).
Si475x-A20 Default is 23 (1 ms).
Si475x-A30 and later, Default is 58 (2.5 ms).
Range is 1–256. Sum of SECONDARY_BLANKER_DELAY,
NB_INTERVAL, and DETECT_DELAY may not exceed 256.
7:0 PRIMARY_BLANKER_DELAY[7:0]
Delay in units of number of samples from where to select the
good samples to replace the samples corrupted by the
impulse for the primary blanker at 93k sample/second.
Si475x-A20 and earlier: Default is 93 (1 ms), Range: 1–63.
Si475x-A30 and later: Default is 232 (2.5 ms), Range: 1–255.
AN543
248 Rev. 0.9
Property 0x2103 AM_SECONDARY_NB_DETECT_THRESHOLD
The AM_SECONDARY_NB_DETECT_THRESHOLD property sets the threshold for detecting impulses in dB
above the noise floor. The noise blanker can be disabled by setting the noise blanker detect threshold to 0.This
blanker is used in the presence of strong near end blockers. The CTS bit (and optional interrupt) is set when it is
safe to send the next command. This command may only be sent in powerup mode.
Default: 21
Units: dB
Property 0x2104 AM_SECONDARY_NB_INTERVAL
The AM_SECONDARY_NB_INTERVAL property sets the interval in microseconds that original samples are
replaced by interpolated clean samples. The noise blanker can be disabled by setting the noise blanker detect
threshold to 0. The secondary blanker is used in the presence of strong near end blockers. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This command may only be sent in powerup
mode.
Default: 4
AM_SECONDARY_NB_DETECT_THRESHOLD
1514131211109876543210
SECONDARY_DETECT_THRESHOLD[15:0]
0x0015
Bit Name Function
15:0 SECONDARY_DETECT_
THRESHOLD[15:0]
Sets the threshold for detecting impulses in dB above the
noise floor. Default is 21 dB. Range is 0–90 dB.
To disable the noise blanker, set the SECONDARY_DE-
TECT_THRESHOLD to 0.
AM_SECONDARY_NB_INTERVAL
1514131211109876543210
SECONDARY_NB_INTERVAL[15:0]
0x0004
Bit Name Function
15:0 SECONDARY_NB_INTERVAL[15:0]
Sets the interval in microseconds that original samples are
replaced by interpolated clean samples
Default if 4. Range is 0–25.
AN543
Rev. 0.9 249
Property 0x2106 AM_NB_STRONG_SIGNAL_SHUTOFF
The AM_NB_STRONG_SIGNAL_SHUTOFF property sets the RSSI thresholds for determining turn on/off the
noise blanker.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be
sent when in powerup mode. Note that this feature is off by default, but the recommended value when turned on is
0x322D.
Si475x-A40 and earlier, not available.
Si475x/5xC-A55, Default: 0x6070
Property 0x2107 AM_NB_DETECT_DELAY
The AM_NB_DETECT_DELAY property sets the number of samples to delay after detection of a noise pulse
condition before applying impulse blanking.
The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be
sent when in powerup mode.
Si475x-A40 and earlier, Default: 8
Si475x/5xC-A55, Default: 5
AM_NB_STRONG_SIGNAL_SHUTOFF
1514131211109876543210
XMAX [7:0] XMMIN [7:0]
0x60 0x70
Bit Name Function
15:8 XMAX [15:8] RSSI level above which the noise blanker is effectively off.
Range is –127 to 127.
7:0 XMMIN [7:0] RSSI level below which the noise blanker is effectively on.
Range is –127 to 127.
AM_NB_DETECT_DELAY
1514131211109876543210
DETECT_DELAY [15:0]
0x0008
Bit Name Function
15:0 DETECT_DELAY [15:0] Delay in units of number of samples before applying impulse blanking
to the original samples.Range is 0–25.
AN543
250 Rev. 0.9
Property 0x2108 AM_NB_SCHEME
The AM_NB_SCHEME property selects the noise blanking scheme. The CTS bit (and optional interrupt) is set
when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A10 is not available.
Si475x-A20, Default: 0x0001
Si475x-A30, Default: 0x0000
Si475x-A40, Default: 0x0100
Si475x/5xC-A55, Default: 0x0101
AM_NB_SCHEME
1514131211109876543210
0 LEARNINGSTEP[6:0] 0x00 MODE[1:0]
00x01 0x00 0x0
Bit Name Function
15 Reserved Always write to 0.
14:8 LEARNINGSTEP[6:0]
(Available in Si475x-A40 only)
I/Q Blanker learning step size. This controls the update speed of the
adaptive I/Q predictor. The higher the value the faster the convergence,
but too fast could cause overshoot.
Range: 1 to 127
7:2 Reserved Always write to 0.
1:0 MODE[1:0]
Selects the noise blanking scheme. Default is 0.
0 = Sample/hold at IF. Delay determined by 0x2102 AM_NB_DELAY.
1 = Linear extrapolation at IF.
AN543
Rev. 0.9 251
Property 0x2109 AM_NB_MODE_CONTROL
The AM_NB_MODE_CONTROL property sets high-level control for the FM noise blanker. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Si475x-A40 and earlier, Default: 0x0004
Si475x/5xC-A55, Default: 0x0002
Property 0x2110 AM_NB_BURST_NOISE_DETECT_THRESHOLD
The AM_NB_BURST_NOISE_DETECT_THRESHOLD sets the threshold for an additional AM noise blanker to
detect and blank a longer “burst-style” noise profile to target the noise from a vehicle accessory electronic actuator
motor. This additional noise blanking is in 93 kS/s I/Q signal and added to control the I/Q blanker. Enabling this
feature may cause the noise blanker to engage too often, which may introduce audio artifacts. Unless the specific
application environment includes longer, burst-style noise which is not mitigated by the other blankers, it is
recommended to disable this property by setting it to 0x0000. The CTS bit (and optional interrupt) is set when it is
safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A30 and earlier, not available
Si475x-A40, Default: 0x0609
Si475x/5xC-A55, Default: 0x0000
AM_NB_MODE_CONTROL
1514131211109876543210
0x0000 MODE[2:0]
0x0000 0x4
Bit Name Function
15:3 Reserved Always write 0.
2:0 MODE[2:0]
Sets the mode for the I/Q noise blanker.
0 = wideband (93 kS/s) blanker.
1 = narrowband (23 kS/s) blanker with pre-channel filter.
2 = narrowband (23 kS/s) blanker without pre-channel filter.
4 = Automatic selection based on blocker levels.
AM_NB_MODE_CONTROL
1514131211109876543210
SAMPLE[7:0] THRESH[7:0]
0x00 0x00
AN543
252 Rev. 0.9
Property 0x2200 AM_CHBW_SQ_MIN_MAX
The AM_CHBW_SQ_MIN_MAX property sets the maximum and minimum Channel Filter Bandwidth in units of 100
Hz based on max(IQSNR,SNR). To force a given Channel Filter Bandwidth, set the min and max to the same
value. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only
be set or read in powerup mode.
Note: Since the Si4750/51/52/53 do not support dynamic bandwidth control MIN[7:0] = MAX[7:0], MAX[7:0] determines the
channel filter setting.
Si475x-A20 and earlier, Default: 0x1414
Si475x-A30 and later, Default: 0x2314
Units: 100 Hz
Bit Name Function
15:8 SAMPLE[7:0] Number of samples blanker at 93 kS/s due to longer bursts from automo-
tive environment. Range 2~64.
7:0 THRESH[7:0] Sets the threshold for detecting longer bursts from automotive environ-
ment. Do not set lower than 7 dB.
AM_CHBW_SQ_MIN_MAX
1514131211109876543210
MAX[7:0] MIN[7:0]
0x23 0x14
Bit Name Function
15:8 MAX [7:0]
Sets the maximum Channel Filter Bandwidth in units of 100 Hz.
Default is 3.5 kHz.
Range is 15–100.
7:0 MIN [7:0]
Sets the minimum Channel Filter Bandwidth in units of 100 Hz.
Default is 2 kHz.
Range is 15–100.
AN543
Rev. 0.9 253
Property 0x2201 AM_CHBW_SQ_HIGH_THRESHOLD (Si4754/55/56/57 Only)
The AM_CHBW_SQ_HIGH_THRESHOLD property sets the max(IQSNR,SNR) threshold for maximum Channel
Filter Bandwidth. If the max(IQSNR,SNR) reported by the device is greater than the SQ High threshold
programmed, then the Channel Filter Bandwidth will be set to the maximum value programmed through Property
0x2200. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Default: 30
Units: dB (for SNR), dBµV (for RSSI)
Property 0x2202 AM_CHBW_SQ_LOW_THRESHOLD (Si4754/55/56/57 Only)
The
AM_CHBW_SQ_LOW_THRESHOLD
property
sets
the
max(IQSNR,SNR)
threshold
for
minimum
Channel
Filter
Bandwid
t
h
.
If
the max(IQSNR,SNR) reported by the device is less than the
SQ
Low threshold programmed,
then the
Channel
Filter
Bandwidth
will
be
set
to
the
minimum
value
programmed
through
Property
0
x2200.
The
CTS
bit (and
optional
interrupt)
is
set
when
it
is
safe
to
send
the
next
command.
This
property
may
only
be
set
or
read
in
powerup mode.
Default: 15
Units: dB
AM_CHBW_SQ_HIGH_THRESHOLD
1514131211109876543210
SQMAX[15:0]
0x001E
Bit Name Function
15:0 SQMAX[15:0]
Sets the max(IQSNR,SNR)threshold for maximum Channel Fil-
ter Bandwidth.
Default is 30 dB.
Range is –128 to 127 dB (or dBµV for RSSI).
AM_CHBW_SQ_LOW_THRESHOLD
1514131211109876543210
SQMIN[15:0]
0x000F
Bit Name Function
15:0 SQMIN[15:0]
Sets the max(IQSNR,SNR) threshold for minimum Channel Filter
Bandwidth.
Default is 15 dB.
Range is –128 to 127 dB
AN543
254 Rev. 0.9
Property 0x2203 AM_CHBW_SQ_WIDENING_TIME (Si4754/55/56/57 Only)
The AM_CHBW_SQ_WIDENING_TIME property sets the Channel Filter Bandwidth widening time based on
max(IQSNR,SNR). The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Default: 2048
Units: ms
Property 0x2204 AM_CHBW_SQ_NARROWING_TIME (Si4754/55/56/57 Only)
Th
e AM_CHBW_SQ_N
ARROWING_TIME
proper
ty
sets the Channel Filter Bandwid
t
h narrowing time based on
max(IQSNR,SNR).
T
he CTS bit (and optional in
terr
upt) is se
t
when it is sa
fe to
send the ne
xt
command. This
prop
erty may
only
be
set
or
read
in
powerup
mode
.
Default: 16
Units: ms
AM_CHBW_SQ_WIDENING_TIME
1514131211109876543210
WIDENING_TIME[15:0]
0x0800
Bit Name Function
15:0 WIDENING_TIME[15:0]
Sets the max(IQSNR,SNR) based Channel Filter Bandwidth
widening time. Default is 2048 ms.
Range is 1–32767 ms.
AM_CHBW_SQ_NARROWING_TIME
1514131211109876543210
NARROWING_TIME[15:0]
0x0010
Bit Name Function
15:0 NARROWING_TIME [15:0]
Sets the max(IQSNR,SNR) based Channel Filter Bandwidth
narrowing time. Default is 16 ms.
Range is 1–32767 ms.
AN543
Rev. 0.9 255
Property 0x2205 AM_CHBW_ASSI_MIN_MAX (Si4754/55/56/57 Only)
The AM_CHBW_ASSI_MIN_MAX property sets the maximum and minimum Channel Filter Bandwidth in units of
100 Hz. Based on adjacent signal strength indicator (ASSI.) To force a given Channel Filter Bandwidth, set the min
and max to the same value. The CTS bit (and optional interrupt) is set when it is safe to send the next command.
This property may only be set or read in powerup mode.
Note: Si4750/51/52/53 do not support dynamic bandwidth control, but MIN[7:0] = MAX[7:0] can determine the channel filter
setting.
Si475x-A10 is not available.
Si475x-A20 and later, Default: 0x3232.
Units: 100 Hz
AM_CHBW_ASSI_MIN_MAX
1514131211109876543210
MAX[7:0] MIN[7:0]
0x32 0x32
Bit Name Function
15:8 MAX[7:0] Sets the maximum Channel Filter Bandwidth in units of 100 Hz. Default is
5 kHz. Range is 15–100.
7:0 MIN[7:0] Sets the minimum Channel Filter Bandwidth in units of 100 Hz. Default is
5 kHz. Range is 15–100.
AN543
256 Rev. 0.9
Property 0x2206 AM_CHBW_ASSI_LOW_THRESHOLD (Si4754/55/56/57 Only)
The AM_CHBW_ASSI_LOW_THRESHOLD property sets the ASSI threshold in dB for maximum Channel Filter
Bandwidth. ASSI is calculated as the worse (higher) value between HASSI and LASSI. If the ASSI reported by the
device is less than the ASSI Low threshold programmed, then the Channel Filter Bandwidth will be set to the
maximum value programmed through Property 0x2205. The CTS bit (and optional interrupt) is set when it is safe to
send the next command. This property may only be set or read in powerup mode.
Si475x-A10 is not available.
Si475x-A20 and later, Default: 10
Units: dB
Property 0x2207 AM_CHBW_ASSI_HIGH_THRESHOLD (Si4754/55/56/57 Only)
The AM_CHBW_ASSI_HIGH_THRESHOLD property sets the ASSI threshold in dB for minimum Channel Filter
Bandwidth. ASSI is calculated as the worse (higher) value between HASSI and LASSI. If the ASSI reported by the
device is greater than the ASSI High threshold programmed, then the Channel Filter Bandwidth will be set to the
minimum value programmed through Property 0x2205. The CTS bit (and optional interrupt) is set when it is safe to
send the next command. This property may only be set or read in powerup mode.
Si475x-A10 is not available.
Si475x-A20 and later, Default: 30
Units: dB
AM_CHBW_ASSI_LOW_THRESHOLD
1514131211109876543210
ASSIMIN[15:0]
0x000A
Bit Name Function
15:0 ASSIMIN[15:0] Sets the ASSI threshold for maximum Channel Filter Bandwidth.
Default is 10 dB. Range is –128 to 127 dB.
AM_CHBW_ASSI_HIGH_THRESHOLD
1514131211109876543210
ASSIMAX[15:0]
0x001E
Bit Name Function
15:0 ASSIMAX[15:0] Sets the ASSI threshold for minimum Channel Filter Bandwidth.
Default is 30 dB. Range is –128 to 127 dB.
AN543
Rev. 0.9 257
Property 0x2208 AM_CHBW_ASSI_WIDENING_TIME (Si4754/55/56/57 Only)
The AM_CHBW_ASSI_WIDENING_TIME property sets the Channel Filter Bandwidth widening time based on
ASSI. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only
be set or read in powerup mode.
Si475x-A10 is not available.
Si475x-A20 and later, Default: 16
Units: ms
Property 0x2209 AM_CHBW_ASSI_NARROWING_TIME (Si4754/55/56/57 Only)
The AM_CHBW_ASSI_NARROWING_TIME property sets the Channel Filter Bandwidth narrowing time based on
ASSI. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only
be set or read in powerup mode.
Si475x-A10 is not available.
Si475x-A20 and later, Default: 16
Units: ms
AM_CHBW_ASSI_WIDENING_TIME
1514131211109876543210
WIDENING_TIME[15:0]
0x0010
Bit Name Function
15:0 WIDENING_TIME[15:0] Sets the channel filter widening time in ms.
Default is 16 ms. Range is 1–32767 ms.
AM_CHBW_ASSI_NARROWING_TIME
1514131211109876543210
NARROWING_TIME[15:0]
0x0010
Bit Name Function
15:0 NARROWING_TIME[15:0] Sets the channel filter narrowing time in ms.
Default is 16 ms. Range is 1–32767 ms.
AN543
258 Rev. 0.9
Property 0x220A AM_CHBW_RQ_MIN_MAX
The AM_CHBW_RQ_MIN_MAX property sets the RSSI maximum and minimum channel bandwidth in the unit of
100 Hz. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Si475x-A40 and earlier is not available.
Si475x/5xC-A55, Default: 0x2314
Units: 100 Hz
Property
0
x22
0
B
AM_CHBW_RQ_LOW_THRESHOLD
T
he AM_CHBW_
RQ_LOW_THRESHOLD property sets the RSSI threshold for minimum channel bandwidth
.
The
CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only
be
set
or
read
in
powerup
mode.
Si475x-A40 and earlier is not available.
Si475x/5xC-A55, Default: 15
Units: 100 Hz
AM_CHBW_RQ_MIN_MAX
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
MAX [7:0] MIN [7:0]
0x23 0x14
Bit Name Function
15:8 MAX [7:0] Sets the maximum channel bandwidth in 100 kHz.
Default is 35. Range is 15 ~ 100.
7:0 MIN[7:0] Sets the minimum channel bandwidth in 100 kHz.
Default is 20. Range is 15 ~ 100.
AM_CHBW_RQ_LOW_THRESHOLD
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RQMIN [15:0]
0x000F
Bit Name Function
15:0 RQMIN[15:0] Sets the RSSI threshold for minimum channel bandwidth.
Default is 15 dBµV
.
AN543
Rev. 0.9 259
Property 0x220C AM_CHBW_RQ_HIGH_THRESHOLD
The AM_CHBW_RQ_HIGH_THRESHOLD property sets the RSSI threshold for maximum channel filter
bandwidth. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Si475x-A40 and earlier is not available.
Si475x/5xC-A55, Default: 30
Units: dBµV
Property
0x220D
AM_CHBW_RQ_WIDENING_TIME
T
he AM_CHBW_
RQ_WIDENING
_TIME property sets the RSSI based channel filter bandwidth widening time. The
CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only be set or
read in powerup mode.
Si475x-A40 and earlier is not available.
Si475x/5xC-A55, Default: 2048
Units: ms
AM_CHBW_RQ_HIGH_THRESHOLD
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RQMAX[15:0]
0x001E
Bit Name Function
15:0 RQMAX[15:0] Sets the RSSI threshold for maximum channel bandwidth.
Default is 30 dBµV
.
AM_CHBW_RQ_WIDENING_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
WIDENING_TIME[15:0]
0x0800
Bit Name Function
15:0 WIDENING_TIME[15:0] Sets the RSSI based channel filter bandwidth widening time.
Default is 2048 ms.
AN543
260 Rev. 0.9
Property 0x220E AM_CHBW_RQ_NARROWING_TIME
The AM_CHBW_RQ_NARROWING_TIME property sets the RSSI based channel filter bandwidth narrowing
time. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only
be set or read in powerup mode.
Si475x-A40 and earlier is not available.
Si475x/5xC-A55, Default: 16
Property 0x2300 AM_DEMOD_MODE
The AM_DEMOD_MODE property selects the demodulation technique. To force to envelope demodulation, set this
property to 0x0100. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This
property may only be set or read in powerup mode.
Si475x-A40 and earlier, Default: 0x0001
Si475x/5xC-A55, Default: 0x0100
AM_CHBW_RQ_NARROWING_TIME
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
NARROWING_TIME[15:0]
0x0010
Bit Name Function
15:0 NARROWING_TIME[15:0] Sets the RSSI based channel filter bandwidth narrowing time.
Default is 16 ms.
AM_DEMOD_MODE
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x00 IQSNR FIXED_MODE 0x00 MODE[2:0]
0x00 0 1 0x00 0x0
Bit Name Function
15:10 Reserved Always write to 0.
9IQSNR
(Available in Si475x-A40 and A55 only)
When set, enables the I/Q SNR metric, which is more robust when AM car-
rier varied greatly (as with AM-SS).
0 = Normal SNR metric
1 = Enable AM-SS resistant SNR metric. This should only be used with
envelope demodulation.
8FIXED_MODE
0 = The demodulation technique is not fixed.
1 = The demodulation technique is fixed and will not automatically switch.
AN543
Rev. 0.9 261
Property 0x2301 AM_DEMOD_AFC_RANGE
The AM_DEMOD_AFC_RANGE property specifies the range of AFC in Hz to allow for wideband AM. Envelope
demod (property 0x2300) should be forced when this property is non-zero. The part must be retuned after
modifying this property before it takes effect. The CTS bit (and optional interrupt) is set when it is safe to send the
next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This property is not available
Si475x-A30 and later, Default: 0
Units: Hz
Property 0x2302 AM_DEMOD_CARRIER_ENH
The AM_DEMOD_CARRIER_ENH property configures the envelope demodulation with carrier enhancement
demodulator mode. Carrier enhancement has been found to reduce audio distortion while maintaining the robust
reception benefits of envelope demodulation. This mode is selected by setting API property AM_DEMOD_MODE
field MODE[2:0] to 2. This property only has an effect when API property AM_DEMOD_MODE field MODE[2:0] is
set to 2. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Si475x-A40 and earlier; this property is not available.
Si475x/5xC-A55; Default: 20
Units: %
7:3 Reserved Always write to 0.
2:0 MODE[2:0]
0 = Envelope demodulation
1 = Coherent demodulation
2 = Envelope demodulation with carrier enhancement.
AM_DEMOD_AFC_RANGE
1514131211109876543210
RANGE[15:0]
0X0000
Bit Name Function
15:0 RANGE[15:0] Specify the range of AFC. If set to 0, range is determined by AM_VALID_-
MAX_TUNE_ERROR. Default is 0. Range is 0–6000 Hz.
AM_DEMOD_CARRIER_ENH
1514131211109876543210
0x000 RATIO[6:0]
0x000 0x14
AN543
262 Rev. 0.9
Property 0x3100 AM_HICUT_SQ_HIGH_THRESHOLD
The AM_HICUT_SQ_HIGH_THRESHOLD property sets the SNR or RSSI level at which HICUT begins to band
limit. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may only
be set or read in powerup mode.
Default: 8
Units: dB (for SNR), dBµV (for RSSI)
Bit Name Function
15:7 Reserved Always write 0.
6:0 RATIO[6:0] Sets amount of carrier enhancement. Default is 20%, recommended range is
0 ~ 50%. Range is 0 to 100%.
AM_HICUT_SQ_HIGH_THRESHOLD
1514131211109876543210
0x000 SQ_HIGH[6:0]
0x000 0x08
Bit Name Function
15:7 Reserved Always write 0.
6:0 SQ_HIGH[6:0] Sets the SNR or RSSI level at which HICUT begins to band limit. Default is 8.
Range is from –127 to 127 dB (for SNR), dBµV (for RSSI).
AN543
Rev. 0.9 263
Property 0x3101 AM_HICUT_SQ_LOW_THRESHOLD
The AM_HICUT_SQ_LOW_THRESHOLD property sets the SNR or RSSI level at which HICUT reaches maximum
band limiting. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property
may only be set or read in powerup mode.
Default: 0
Units: dB
Property 0x3102 AM_HICUT_ATTACK_TIME
The AM_HICUT_ATTACK_TIME property sets the transition time in ms for which high cut lowers the cutoff
frequency. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Default: 16
Units: ms
AM_HICUT_SQ_LOW_THRESHOLD
1514131211109876543210
0x000 SQ_LOW[6:0]
0x000 0x08
Bit Name Function
15:7 Reserved Always write 0.
6:0 SQ_LOW[6:0] Sets the SNR or RSSI level at which HICUT reaches maximum band limiting.
Default is 0. Range is from –127 to 127 dB (for SNR), dBµV (for RSSI).
AM_HICUT_ATTACK_TIME
1514131211109876543210
ATTACK[15:0]
0x0010
Bit Name Function
15:0 ATTACK[15:0] Sets the transition time in ms for which high cut lowers the cutoff frequency.
Default is 16 ms. Range is 1–32767 ms.
AN543
264 Rev. 0.9
Property 0x3103 AM_HICUT_RELEASE_TIME
The AM_HICUT_RELEASE_TIME property sets the transition time in ms for which high cut increases the cutoff
frequency. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Default: 2000
Units: ms
Property 0x3104 AM_HICUT_CUTOFF_FREQ
The AM_HICUT_CUTOFF_FREQ property sets the maximum and minimum HICUT transition frequencies in units
of 100 Hz. To force a given HICUT filter bandwidth, set the min and max to the same value. The CTS bit (and
optional interrupt) is set when it is safe to send the next command. This property may only be set or read in
powerup mode.
Default: 0x280A
Units: 100 Hz
AM_HICUT_RELEASE_TIME
1514131211109876543210
RELEASE[15:0]
0x07D0
Bit Name Function
15:0 RELEASE[15:0] Sets the transition time in ms for which high cut increases the cutoff
frequency. Default is 2000 ms. Range is 1–32767 ms.
AM_HICUT_CUTOFF_FREQ
1514131211109876543210
MAX[7:0] MIN[7:0]
0x28 0x0A
Bit Name Function
15:8 MAX [7:0] Maximum HICUT transition frequency in units of 100 Hz.
Default is 4 kHz. Range is 10–50.
7:0 MIN [7:0] Minimum HICUT transition frequency in units of 100 Hz.
Default is 1 kHz. Range is 10–50.
AN543
Rev. 0.9 265
Property 0x3105 AM_LOWCUT_MIN_FREQ
The AM_LOWCUT_MIN_FREQ property sets the minimum cutoff frequency. The LowCut tracks the HICUT
engine; therefore, thresholds are programmed in property 0x3100 and 0x3101. Setting the property to 0 disables
LowCut. The CTS bit (and optional interrupt) is set when it is safe to send the next command. This property may
only be set or read in powerup mode.
Note: Once set, this property may not be observed until after the next AM_TUNE_FREQ command is issued.
Si475x-A20 and earlier: This feature is not available. Do not write to this property.
Si475x-A30 and later, Default: 0
Units: Hz
Property 0x3106 AM_LOWCUT_MAX_FREQ
The AM_LOWCUT_MAX_FREQ property sets the maximum cutoff frequency. The LowCut tracks the HICUT
engine, therefore thresholds are programmed in property 0x3100 and 0x3101. The CTS bit (and optional interrupt)
is set when it is safe to send the next command. This property may only be set or read in powerup mode.
Si475x-A20 and earlier: This feature is not available. Do not write to this property.
Si475x-A30 and later, Default: 0
Units: Hz
AM_LOWCUT_MIN_FREQ
1514131211109876543210
FREQ_MIN[15:0]
0x0000
Bit Name Function
15:0 FREQ_MIN[15:0]
Sets the minimum LOW-CUT cutoff frequency in Hz. Default is disabled.
Range is 0 (disable) or 8–1000 Hz.
0 = Disabled.
AM_LOWCUT_MAX_FREQ
1514131211109876543210
FREQ_MAX[15:0]
0x0000
Bit Name Function
15:0 FREQ_MAX[15:0]
Sets the maximum LOW-CUT cutoff frequency in Hz. Note that if property
0x3105 (AM_LOWCUT_MIN_FREQ) is greater than 7, this property must be
set to a value no less than property 0x3105. Default is 0 Hz. Range is 0–
1000 Hz.
AN543
266 Rev. 0.9
8. Programming Examples
8.1. Configuration
The following tables summarize the available
configuration options for FM and AM functions. Refer to
section “7. Commands and Properties”for detailed
descriptions of commands and properties.
Table 15. FM Configuration Commands and Properties
Pin Configuration Commands Properties
Interrupts 0x1C 0x0000
Analog/MPX audio 0x1B
RF/Audio Configuration Commands Properties
Softmute 0x0400
RF Signal routing, AGC thresholds and timing 0x0700
Channel spacing 0x1100
RSQ (RSSI, SNR) Interrupts 0x1200
ACF (Softmute, Channel Filter Bandwidth, HIBLEND, HICUT) Interrupts 0x1300
Tune/seek metric thresholds and timing (RSSI, SNR, ISSI, ASSI, frequency
error) 0x2000
Noise blankers 0x2100
Channel Filter Bandwidth (RSSI, STRONGDEV, ASSI, ASSI200, ASSI200DEV,
ASSI100 B) range and timing 0x2200
Pop filter 0x3200
Blend (RSSI/SNR, Multi-path, USN) range and timing 0x3500
HICUT (RSSI/SNR, Multi-path, USN) range and timing 0x3600
HIBLEND (RSSI/SNR, Multi-path, USN) range and timing 0x3700
RDS Configuration Commands Properties
RDS Interrupts, FIFO size and management, decoder configuration
(Si4751/53/55/57 only). 0x4000
AN543
Rev. 0.9 267
8.1.1. Analog/MPX Audio (MPX Si4755/57 Only)
Analog and MPX audio setup includes pin configuration.
1. Complete steps up to and including 5 in section "5.1. Powerup Receiver from Internal Memory" on page 4 or 10
in "5.2. Powerup Receiver from a Patch" on page 7.
2. Send the ANA_AUDIO_PIN_CFG command to route analog left and right channel to LOUT/ROUT pins, or to
route the MPX to the LOUT pin. This step may be omitted if analog audio is not required.
Example:
Table 16. AM Configuration Commands and Properties
Pin Configuration Commands Properties
Interrupts 0x1C 0x0000
Analog audio 0x1B
RF/Audio Configuration Commands Properties
Power line filtering 0x0300
Softmute 0x0400
AVC (automatic volume control) 0x0500
RF Signal routing, AGC thresholds and timing 0x0700
Channel spacing 0x1100
RSQ (RSSI, SNR) Interrupts 0x1200
ACF (Softmute, Channel Filter Bandwidth, HICUT) Interrupts 0x1300
Tune/seek metric thresholds and timing (RSSI, SNR, ISSI, ASSI frequency error) 0x2000
Noise blankers 0x2100
Channel Filter Bandwidth (RSSI, SNR, ASSI) range and timing 0x2200
HICUT (RSSI/SNR) range and timing 0x3100
ANA_AUDIO_PIN_CFG Command
Action Data Description
CMD 0x1B ANA_AUDIO_PIN_CFG
ARG1 0x02 2 = LOUT/ROUT pins configured to output audio.
STATUS →0x80
AN543
268 Rev. 0.9
8.1.2. AGC
For FM and AM modes, the AGC default configuration is generally optimal. The following section describes the
settings and options. AGC settings may be over-ridden by setting property 0x0710 FM_AGC_OVERRIDE (or
similar property 0x0710 AM_AGC_OVERRIDE) and the state of the AGC peak detectors may be monitored by
sending command 0x17 AGC_STATUS (or similar property 0x17 AM_AGC_STATUS).
8.1.2.1. FM
FM AGC configuration involves setting signal routing, AGC and peak detector.
The default property settings are configured for routing through the LNA input (instead of directly to the mixer) with
50 Ω LNA impedance as shown in Figure 8.
Figure 8. FM Single Receiver System Diagram
Note: For primary/companion configuration in which two receivers are connected to the same antenna, the LNA input imped-
ance should be set to 100 as shown in Figure 9.
to AM
Reg
LNA
RF Pkd
Si475x
FMXI
RFREG
FMO
FMI RF Pkd
RL
50
FMAGC1
FMAGC2
AN543
Rev. 0.9 269
Figure 9. Primary and Companion Receiver System Diagram
For optimal weak signal, blocker and intermodulation performance, the default property settings are configured to
disable the LNA peak detector and associated attack/release time constants, and enable the mixer peak detector
thresholds to 85 dBµV and 3 dB hysteresis, with an attack time of 4 ms and release time of 80 ms.
To improve weak signal performance at the expense of intermodulation performance, the mixer peak detector
thresholds may be increased to as high as 93 dBµV. To improve blocker and intermodulation performance at the
expense of weak signal performance, the mixer peak detector thresholds may be decreased to as low as 79 dBµV.
To improve impulsive noise desensitization (caused by engaging the AGC) at the expense of AGC response time,
the mixer peak detector attack time may be increased from 4 ms to an attack time greater than the period of the
impulses.
8.1.2.2. AM
AM AGC configuration involves configuring signal routing, AGC and peak detector characteristics.
The default property settings are configured for optimal performance with the harmonic rejection enabled, IF AGC
attack time of 80 ms and release time of 804 ms, RF attack time of 8 ms and RF release time of 800 ms.
Reg
LNA
to AM
Reg
LNA
Si475x
Si4769
RF Pkd
RF Pkd
100
FMXIP
50
RFREG
FMO
FMI
FMXI
RFREG
FMO
FMI
RF Pkd
RF Pkd
RL
RL
100
FMAGC1
FMAGC2
FMXIN
AN543
270 Rev. 0.9
8.1.3. Interrupts
The interrupt status can be monitored by sending command 0x15 GET_INT_STATUS. Note that the command
response varies based on FM or AM mode. Interrupt pins can be configured by sending command 0x1C
INTB_PIN_CFG.
Property 0x0000 INT_CTL_ENABLE enables top-level interrupt sources and interrupt repetition characteristics.
Property group 0x1200 configures RSQ (RSSI, SNR) interrupts. Property group 0x1300 configures ACF (Softmute,
Channel Filter Bandwidth, HIBLEND, HICUT) interrupts. Note that HIBLEND only applies to FM mode operation.
Property group 0x4000 configures RDS interrupts.
8.1.4. Noise Blankers
8.1.4.1. FM
Property group 0x2100 configures the noise blankers for FM mode.
The FM noise blanking system consists of a detector and audio sample blanker after the FM demodulator.
The detector compares average USN with USN scaled by the FM_NB_DETECT_THRESHOLD property setting. If
the scaled USN is greater than the filtered USN audio samples will be blanked. Lower values of
FM_NB_DETECT_THRESHOLD result in more aggressive noise blanking.
For weak signal levels, the USN of only the L+R portion of the MPX spectrum is used as the detector input. For
higher signal levels, the USN of the entire MPX spectrum is used as the detector input. The signal levels at which
the switch between weak/strong blanking occurs is set by the FM_NB_STRONG_WEAK_SWITCH property (by
default, SNR < 9 dB for weak signal blanking and SNR >11 dB for strong signal blanking). For strong signal levels
(RSSI > 50 dBμV) the noise blanker is disabled as configured by FM_NB_STRONG_SIGNAL_SHUTOFF.
The number of samples to blank is set by the FM_NB_INTERVAL property setting. Higher values result in more
aggressive noise blanking, as more samples are replaced with repaired ones.
8.1.4.2. AM
Property group 0x2100 configures the noise blankers for AM modes.
The AM noise blanking system consists of a wide band detector and I/Q sample blanker before the first channel
filter and a narrow band detector and I/Q sample blanker after the first channel filter.
The detectors compare average USN with USN scaled by the AM_NB_DETECT_THRESHOLD (wide band) and
AM_SECONDARY_NB_DETECT_THRESHOLD (narrow band) property setting. If the scaled USN is greater than
the filtered USN audio samples will be blanked. Lower values of AM_NB_DETECT_THRESHOLD or
AM_SECONDARY_NB_DETECT_THRESHOLD result in more aggressive noise blanking.
The narrow band noise blanker with pre-channel filter is enabled if ±1 channel adjacent blocker is detected. In this
mode, the wide band detector AM_NB_DETECT_THRESHOLD is used.
The narrow band noise blanker without pre-channel filter is enabled if ±2 or ±3 channel adjacent blocker is
detected. In this mode, the narrow band detector AM_SECONDARY_NB_DETECT_THRESHOLD is used.
The wide band noise blanker is enabled if no adjacent blocker is detected. In this mode, the wide band detector
AM_NB_DETECT_THRESHOLD is used.
8.1.5. Pop Filter
Property group 0x3200 configures the pop filter for FM mode operation.
Two independent pop filter engines can be configured for minimum and maximum limiting of the MPX using RSSI
and USN as the metric. Limiting ranging from minimum to maximum occurs at the specified attack rate as the RSSI
or USN metric increases above the minimum threshold and reaches the maximum threshold. Limiting ranging from
maximum to minimum occurs at the specified release rate as the RSSI or USN metric decreases below the
maximum threshold and reaches the minimum threshold. The resulting limiting level is the maximum of the result of
the two pop filter engines. Refer to Figure 10.
AN543
Rev. 0.9 271
Figure 10. Pop Filter Thresholds
8.1.6. Channel Filter Bandwidth
8.1.6.1. FM
Property group 0x2200 configures Channel Filter Bandwidth characteristics for FM mode.
Six independent Channel Filter Bandwidth engines can be configured using RSSI/deviation (weak signal engine),
ASSI100 (absolute value of difference between ±100 kHz channel RSSI), ASSI200 (sum of ±200 kHz channel
RSSI minus desired channel RSSI), strong signal deviation, 200 kHz blocker deviation and strong 100 kHz blocker
as the metric. For RSSI, ASSI100, ASSI200 and strong signal deviation, Channel Filter Bandwidth ranging from
minimum to maximum occurs at the specified widening rate as the metric increases above the minimum threshold
and reaches maximum threshold. Channel Filter Bandwidth ranging from maximum to minimum occurs at the
specified narrowing rate as the metric decreases below the maximum threshold and reaches the minimum
threshold. For 200 kHz blocker deviation, Channel Filter Bandwidth ranging from 80 to 32 kHz occurs at 1 ms rate
as the metric increases above 75 kHz and reaches 100 kHz. Channel Filter Bandwidth ranging from 32 to 80 kHz
occurs at the 300 ms rate as the metric decreases below 100 kHz and reaches 75 kHz. The resulting Channel
Filter Bandwidth is the minimum of the result of the six blend engine calculations.
Property 0x1306 FM_ACF_CONTROL_SOURCE is used to select RSSI or deviation as a metric for the weak
signal engine. The default condition is RSSI.
Property 0x220F FM_CHBW_WEAKSIG_THR is used to set the hysteresis window for enabling the weak signal
RSSI/deviation engine. The default is to enable above 16 dBuV RSSI and disable below 14 dBµV RSSI. Note that
this hysteresis range is always determined by RSSI and is not configurable with the
FM_ACF_CONTROL_SOURCE property.
Property 0x2210 FM_CHBW_BLOCKER_THR is used to set the hysteresis window for engaging the 200 kHz
blocker engine. The default is to enable above 20 dB ASSI200 and disable below 10 dB ASSI200. Note that 2 dB
ASSI200 indicates that the sum of the energy at +200 kHz and –200 kHz is 20 dB greater than the desired
channel. The 200 kHz blocker deviation engine is only enabled when sufficient pilot energy is present on the
desired channel.
RSSI or USN
Limiting
Max
Min
MaxMin
AN543
272 Rev. 0.9
8.1.6.2. AM
Property group 0x2200 configures Channel Filter Bandwidth characteristics for AM.
Two independent Channel Filter Bandwidth engines can be configured using RSSI or SNR and ASSI (independent
±9/10 kHz channel RSSI relative to on-channel RSSI). Channel Filter Bandwidth ranging from minimum to
maximum occurs at the specified widening rate as the metric increases above the minimum threshold and reaches
maximum threshold. Channel Filter Bandwidth ranging from maximum to minimum occurs at the specified
narrowing rate as the metric decreases below the maximum threshold and reaches the minimum threshold. The
resulting Channel Filter Bandwidth is the minimum of the result of the two blend engine calculations.
Property 0x1306 AM_ACF_CONTROL_SOURCE is used to select RSSI or SNR as a metric for the Channel Filter
Bandwidth.
8.1.7. Softmute
Property group 0x0400 configures softmute characteristics for FM and AM.
Property 0x1306 FM_ACF_CONTROL_SOURCE (and AM_ACF_CONTROL_SOURCE) is used to select SNR
(default) or RSSI as a metric for the softmute engine. For FM and AM modes, the property is also used to select
whether an AFC rail condition will engage softmute. The most common cause for an AFC rail condition is tuning to
an idle channel.
Softmute engages as SNR (or RSSI) drops below a trigger threshold and audio level reaches a maximum
attenuation at the end threshold. Softmute releases as SNR (or RSSI) rises above the end threshold and audio
level reaches full level at the trigger threshold. The attack and release rates are configurable along with maximum
attenuation and trigger and end thresholds.
8.1.8. Automatic Volume Control (AVC)
Property group 0x0500 configures automatic volume control (AVC) for AM.
The AVC minimum and maximum gain can be configured. The AVC maintains a constant carrier level.
8.1.9. Mono/stereo Blend
Property group 0x3500 configures the mono/stereo blend characteristics for FM mode.
Six independent blend engines can be configured using RSSI, multipath, and USN as the metric. Blend from
minimum stereo to maximum stereo separation occurs at the specified attack rate as the metric increases above
the minimum threshold and reaches maximum threshold. Blend from maximum stereo to minimum stereo
separation occurs at the specified release rate as the metric decreases below the maximum threshold and reaches
the minimum threshold. The resulting stereo separation is the minimum of the result of the six blend engine
calculations.
8.1.10. HICU T
HICUT applies a lowpass filter to the L+R MPX audio.
8.1.10.1. FM
Property group 0x3600 configures the HICUT characteristics for FM mode.
Six independent blend engines can be configured using RSSI, multipath, and USN as the metric. HICUT from
minimum to maximum occurs at the specified attack rate as the metric increases above the minimum threshold and
reaches maximum threshold. HICUT from maximum to minimum occurs at the specified release rate as the metric
decreases below the maximum threshold and reaches the minimum threshold. The resulting HICUT is the
minimum of the result of the six blend engine calculations.
AN543
Rev. 0.9 273
8.1.10.2. AM
Property group 0x3100 configures the HICUT characteristics for AM mode.
The blend engine can be configured with RSSI or SNR as the metric. HICUT from minimum to maximum occurs at
the specified attack rate as the metric increases above the minimum threshold and reaches maximum threshold.
HICUT from maximum to minimum occurs at the specified release rate as the metric decreases below the
maximum threshold and reaches the minimum threshold.
8.1.11. HIBLEND
HIBLEND applies a lowpass filter to the L–R MPX audio. Property group 0x3700 configures the HIBLEND
characteristics for FM mode.
Six independent blend engines can be configured using RSSI, multipath, and USN as the metric. HIBLEND from
minimum to maximum occurs at the specified attack rate as the metric increases above the minimum threshold and
reaches maximum threshold. HIBLEND from maximum to minimum occurs at the specified release rate as the
metric decreases below the maximum threshold and reaches the minimum threshold. The resulting HIBLEND is
the minimum of the result of the six blend engine calculations.
8.1.12. Calibrating Crystal Loading Capacitance (XCLOAD)
Tuning accuracy depends on accurate clocking from an external clock or the internal crystal oscillator. When the
internal crystal oscillator is used, it is important to determine the optimum load capacitance of the crystal in order to
minimize tuning error. This value is provided to the chip at power-up through the POWER_UP command's
XCLOAD parameter. This procedure describes to how to determine the optimum value of XCLOAD. This
procedure needs to be done once on a typical PCB for your application in order to determine a single value of
XCLOAD which can work across as many devices as possible.
1. We will begin with and XCLOAD value of 0x1F, the middle value for the parameter.
2. Power up the device in FM mode with a POWER_UP command (as described in Section 5 Powerup and
Powerdown) with the chosen value for the XCLOAD parameter.
3. Using a calibrated bench source, input an unmodulated, 98 MHz, 60 dBµV signal to the part.
4. Tune the part to 98 MHz
5. Issue an FM_RSQ_STATUS command, and note the value of the frequency offset (FreqOff) returned by that
command.
6. If FreqOff is greater than 0, decrease the value of XCLOAD downward. If FreqOff is less than 0, increase the
value of CXLOAD.
7. Repeat steps 2 through 5 until FreqOff is 0 bppm.
8. Repeat the measurement described in steps 2 through 5 at 85 °C, and again at –40 °C.
9. If the value of FreqOff at 85 °C or –40 °C exceeds the crystal frequency accuracy specification for the tuner, you
can attempt to adjust XCLOAD to bring the system back into specification. If FreqOff is positive and exceeds
crystal frequency accuracy specifications, decrease the value of XCLOAD. If FreqOff is negative and exceeds
crystal frequency accuracy specifications, increase the value of XCLOAD.
10.Repeat steps 2 through 9 across as many PCBs and crystals for your application as are necessary to account
for part-to-part variation.
11.In production, we recommend you average XCLOAD across all such samples to determine an optimal value of
XCLOAD for your application.
AN543
274 Rev. 0.9
8.2. Operation
Operations including sending a command, checking CTS and ERR state, checking STC state, tune, seek, and
RDS are possible.
8.2.1. Tune
The tune operation provides options for configuring tuning mode (validated normal tune, unvalidated fast tune,
validated AF Tune, or validated AF Check) and audio filter state management (re-initialize based on new channel,
or smoothly transition from current to new channel). In the case of tuning mode, 0x2000 property group sets the
tune/seek metric thresholds and timing (RSSI, SNR, frequency error). Note that references to “AFC Rail” in this
manual refers to a condition in which the frequency offset of the desired channel is outside the frequency error as
configured with property group 0x2000.
2. FM_TUNE_FREQ or
AM_TUNE_FREQ
Start
End
3. Check CTS & ERR
4. Check STC
1. Configure Tune
parameters
AN543
Rev. 0.9 275
1. Complete the appropriate steps in section“8.1. Configuration”.
2. Send the FM_TUNE_FREQ command to tune to a specific frequency. If the receiver has been muted, set
property 0x0301 to disable mute. If using AF check, set the SMOOTHMETRICS bit to transition audio state from
previous channel. Note that AM tuning is very similar. Refer to the AM_TUNE_FREQ command.
Example:
3. Check the CTS and ERR state to determine whether it is safe to send the next command. Refer to section
“8.2.4. Check CTS and ERR Status”.
4. Check the STC state to determine tune status. Refer to section xxx Check STC state.
5. Repeat steps 2, 3, and 4 as necessary.
FM_TUNE_FREQ Command
Action Data Description
CMD 0x30 FM_TUNE_FREQ
ARG1 0x00
Unconditionally stay on chan-
nel, initialize audio state based
on new channel.
ARG2 0x27 0x27A6 = tune to 101.50 MHz.
ARG3 0xA6
STATUS →0x80 CTS = 1
AN543
276 Rev. 0.9
8.2.2. Seek
1. Complete the appropriate steps in section “8.1. Configuration”.
2. Set the 0x1100 property group to configure the seek start, stop and channel spacing.
3. Set the 0x2000 property group to set the tune/seek metric thresholds and timing (RSSI, SNR, frequency error).
Note that because every system will have unique signal gain and noise characteristics, RSSI and SNR
thresholds should be carefully evaluated.
4. Send the FM_SEEK_START command to begin the seek operation.
Example:
5. Check the CTS and ERR state to determine whether it is safe to send the next command. Refer to section
“8.2.4. Check CTS and ERR Status”.
6. Check the STC state to determine seek status and abort if desired. Refer to Check STC state.
7. Repeat steps 4, 5, and 6 as necessary.
FM_SEEK_START Command
Action Data Description
CMD 0x30 FM_SEEK_START
ARG1 0x08 Seek up, don’t wrap at the top
of the band.
STATUS →0x80 CTS = 1
4. FM_SEEK_START
or
AM_SEEK_START
Start
End
5. Check CTS and ERR
6. Check STC
1/2/3. Configure Seek
parameters
AN543
Rev. 0.9 277
8.2.3. RDS (Si4751/53/55/57 Only)
1. Complete the appropriate steps in section “8.1. Configuration”and section “8.2.1. Tune”.
2. Set the 0x4000 property group to configure RDS Interrupts, FIFO size and management, and decoder
configuration.
3. (Optional) Send the FM_RDS_BLOCKCOUNT command to verify RDS block error rate. The block error rate is
defined as BLER = (UNCORRECTABLE + (EXPECTED-RECEIVED)) / EXPECTED.
Example:
In this example, the BLER = (27 + (10015-9355)) / 10015 = 6.8%.
4. Send the FM_RDS_STATUS in response to a configured RDS interrupt or at a set time interval. For example,
an interrupt can be configured when the 25 group FIFO has any number of entries between 1 and 25.
Alternatively, the command can be sent every 88 ms (time for one group to be received) to 2.2 seconds (time for
25 groups to be received). The FM_RDS_STATUS command must be called once for each entry. The
FIFOUSED field can be used to monitor FIFO status. Refer to the RDS and RBDS specifications for further
decoding information.
Example:
FM_RDS_BLOCKCOUNT Command
Action Data Description
CMD 0x37 FM_RDS_BLOCKCOUNT
ARG1 0x01 Clear the block count.
STATUS →0x80 CTS = 1
RESP1 →0x00
RESP2 →0x27 Expected 0x271F = 10015
RESP3 →0x1F
RESP4 →0x24 Received 0x248B = 9355
RESP5 →0x8B
RESP6 →0x00 Uncorrectable 0x001B = 27
RESP7 →0x1B
FM_RDS_STATUS Command
Action Data Description
CMD 0x36 FM_RDS_STATUS
ARG1 0x01 Acknowledge the STC interrupt.
STATUS →0x80 CTS = 1
RESP1 →0x00
RESP2 →0x1A
TP/PTY has changed, PI has
changed, synchronization has
changed.
RESP3 →0x05 PTY = 5
RESP4 →0x3E PI = 0x3E67
AN543
278 Rev. 0.9
5. Repeat steps 3 and 4 as necessary.
RESP5 →0x67
RESP6 →0x01 FIFO used = 1 (out of a maxi-
mum of 25)
RESP7 →0x00 BLEA = 0, BLEB = 0,
BLEC = 0, BLED = 0
RESP8 →0x3E BLOCKA = 0x3E67 (PI code)
RESP9 →0x67
RESP10 →0x20
BLOCKB = 0x20A7, group 2A
(RadioText), PTY = 5, A/B
flag = 0,
text segment address code = 7
RESP11 →0xA7
RESP12 →0x6C BLOCKC = 0x6C74
(ASCII) = “lt”
RESP13 →0x74
RESP14 →0x65 BLOCKD = 0x6572
(ASCII) = “er”
RESP15 →0x72
FM_RDS_STATUS Command
Action Data Description
AN543
Rev. 0.9 279
8.2.4. Check CTS and ERR Status
After every command the CTS bit state should be checked to determine whether it is safe to send the next
command and the ERR bit state should be checked to determine whether an error has occurred.
1. Start Timer
Start
3. CTS = 1?
5. ERR = 0? 6. ERR = 0x18?No
6. Set CANCEL =1
and call
FM_RSQ_STATUS
or
AM_RSQ_STATUS
Yes
7. ERR = 0x20,
0x30 or 0x31?
No
7. STOP
Yes
End
Yes
Yes
No
6. Wait 5ms
4. Wait tCTS
2. Read STATUS and
RESP1
4 .Timer >
125 ms?
No No
4. STOP
Yes
6. Set STCACK =1
and call
FM_RSQ_STATUS
or
AM_RSQ_STATUS
6. Wait tCTS
AN543
280 Rev. 0.9
1. Start a timer capable of measuring 100 µs to 125 ms.
2. Read the STATUS byte and RESP1.
3. If CTS is set, it is safe to send the next command. Go to step 5.
4. If CTS is not set, check if the timer measures greater than 125 ms (time to execute the POWER_UP command
plus 20% margin). If it does, it is likely that the receiver is not in the power up state. Refer to "5. Powerup and
Powerdown" on page 3. If it doesn’t, wait time tCTS (100 µs). Refer to "6. Timing" on page 14.
5. If ERR (error) is set, check the specific error code reported in RESP1.
6. If the error code is 0x18, the tune or seek command is in progress and should be aborted by setting
CANCEL = 1 and sending the FM_RSQ_STATUS command (or AM_RSQ_STATUS), waiting 5 ms for the seek
operation to abort and set the STC bit, acknowledge and clear the STC bit by setting STCACK = 1 and sending
the FM_RSQ_STATUS command (or AM_RSQ_STATUS) again, and then waiting time tCTS (100 µs). Refer to
"6. Timing" on page 14.
7. If the error code is 0x30 or 0x31 the boot operation failed and the powerup operation should be attempted.
Refer to "5. Powerup and Powerdown" on page 3. If the error code is 0x20 contact Silicon Labs. All other errors
are recoverable. and the error code reported in RESP1 will clear when the next valid command is sent. See
Table 17.
Table 17. Error Codes and Remedies
RESP1 Error Code Explanation and Remedy
0x10 Bad command
Unsupported command, possibly due to programming error or
incorrect device population. For example an Si4751 is mistak-
enly placed on a design instead of the Si4755 and FM tune is
attempted.
0x11 Bad ARG1
Argument out of range or invalid mode, possibly due to pro-
gramming error or incorrect device population.
0x12 Bad ARG2
0x13 Bad ARG3
0x14 Bad ARG4
0x18 Command Busy Wait for command completion, or abort tune/seek.
0x20 Bad internal memory Internal memory corruption. Contact Silicon Labs.
0x30 Bad patch Patch CRC is incorrect. Recover by repeating the powerup
sequence with correct patch.
0x31 Bad boot mode
Mode is not supported (for example RDS on an Si4752).
Recover by repeating the powerup sequence with supported
mode (AM, FM).
0x40 Bad property Unsupported property, possibly due to programming error or
incorrect device population.
AN543
Rev. 0.9 281
8.2.5. Check STC Status
After every command the STC (seek/tune complete) bit state should be checked to determine the state of the tune
or seek command and abort the operation if desired.
1. Read the STATUS byte.
2. If STC (seek/tune complete) is set, set STCACK = 1 to acknowledge and clear the STC bit and set ATTUNE = 1
to return RSQ metrics from tune time and call FM_RSQ_STATUS (or AM_RSQ_STATUS).
1. Read STATUS
Start
2. STC = 1?
End
3. User Abort?No No
3. Set CANCEL = 1
and call
FM_RSQ_STATUS
or
AM_RSQ_STATUS
Yes
3. Wait 5ms
2. Set STCACK = 1,
set ATTUNE = 1
and call
FM_RSQ_STATUS
or
AM_RSQ_STATUS
Yes 4. Wait tSTC
2. Wait tCTS
AN543
282 Rev. 0.9
Example:
3. If STC is not set and the user wishes to abort the tune, set CANCEL = 1 to abort and call FM_RSQ_STATUS (or
AM_RSQ_STATUS). Wait 5 ms for the tune or seek to abort and set the STC bit.
4. Wait tSTC (21–40 ms depending AM or FM modes). Refer to "6. Timing" on page 14.
FM_RSQ_STATUS Command
Action Data Description
CMD 0x32 FM_RSQ_STATUS
ARG1 0x05 Return metrics from tune time,
acknowledge the STC interrupt.
STATUS →0x81 CTS = 1, STC = 1
RESP1 →0x00
RESP2 →0x31 SNR ready, RSSI ready, valid chan-
nel.
RESP3 →0x27 Tuning frequency
0x027A6 = 101.50 MHz
RESP4 →0xA6
RESP5 →0x10 Frequency offset = 16 ppm
RESP6 →0x25 RSSI = 37 dBµV
RESP7 →0x14 SNR = 20 dB
RESP8 →0x00
RESP9 →0xFB –100 kHz channel signal strength
(LASSI) 0xFB = –5 dB
RESP10 →0xF4
+100 kHz channel signal strength
(HASSI) 0xFB =
–12 dB
RESP11 →0x00
RESP12 →0x0F Reserved, values will vary.
RESP13 →0x00 0x000 = Antenna capacitance, only
for tracking filter applications
RESP14 →0x00
RESP15 →0xE5 ±200 kHz channel signal strength
(ASSI) 0xE5 = –27 dB
RESP16 →0x2A Ultrasonic noise (USN) 0x2A = 42
AN543
Rev. 0.9 283
DOCUMENT CHANGE LIST
Revision 0.1 to Revision 0.2
Revised "1. Introduction" on page 1.
Added "4. Control Interface" on page 2.
Added "5. Powerup and Powerdown" on page 3.
Added "6. Timing" on page 14.
Revised "7. Commands and Properties" on page 19.
Added "8. Programming Examples" on page 266.
Removed appendixes.
Revision 0.2 to Revision 0.3
Added new softmute engines.
Added new metrics to RSQ response.
Added new metrics to Seek/Tune validation.
Added new Channel Filter Bandwidth control engine.
Added FM keyed AGC.
Recommend new power-up sequence for 4 MHz crystal operation.
Revision 0.3 to Revision 0.4
Added 6-Tap channel equalizer properties.
Added “Property 0x40A–0x411” to FM section.
Revision 0.4 to Revision 0.5
Added Si475x-40 information.
Updated properties.
Added Crystal XCLOAD calibration procedure.
Revision 0.5 to Revision 0.6
Updated properties.
Updated commands.
Added Property 0x3210 FM_POP_NOISE_SCALE.
Added blend CHBW properties 0x3518–0x351B.
Added HICUTN CHBW properties 0x3618–0x361B.
Added HIBLEND CHBW properties 0x3718–0x371B.
Revision 0.6 to Revision 0.7
Updated " Property 0x3518 FM_BLEND_CHBW_LIMITS (Si4754/55/56/57 Only)" on page 171.
" Property 0x3519 FM_BLEND_CHBW_STEREO_SEP (Si4754/55/56/57 Only)" on page 172.
Updated " Property 0x3618 FM_HICUTN_CHBW_LIMITS (Si4754/55/56/57 Only)" on page 179.
Updated " Property 0x3619 FM_HICUTN_CHBW_CUTOFF_FREQ (Si4754/55/56/57 Only)" on page 180.
Updated " Property 0x3718 FM_HIBLEND_CHBW_LIMITS (Si4754/55/56/57 Only)" on page 187.
Updated " Property 0x3719 FM_HIBLEND_CHBW_CUTOFF_FREQ (Si4754/55/56/57 Only)" on page 188.
AN543
284 Rev. 0.9
Revision 0.7 to Revision 0.8
Updated the powerup sequence to a powerup sequence with an external circuit for the 4 MHz crystal detailed in
“AN750: Si475x 4 MHz Crystal Circuit and Power-Up Procedure”.
Revision 0.8 to Revision 0.9
Added support for Si475xC parts.
Added FM properties 0x2111 ~ 0x2118.
Corrected description for property 0x360B.
Changed “…based on RSSI” to “…based on Multipath”.
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Disclaimer
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intending to use the Silicon Labs products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific device, and "Typical"
parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Labs reserves the right to make changes
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