SigmaDSP Multichannel
28-Bit Audio Processor
AD1940/AD1941
Rev. B
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FEATURES
16-channel digital audio processor
Accepts sample rates up to 192 kHz
28-bit × 28-bit multiplier with full 56-bit accumulator
Fully programmable program RAM for custom
program download
Parameter RAM allows complete control of 1,024 parameters
Control port features safeload for transparent parameter
updates and complete mode and memory transfer control
Target/slew RAM for click-free volume control and dynamic
parameter updates
Double precision mode for full 56-bit processing
PLL for generating MCLK from 64 × fS, 256 × fS, 384 × fS, or
512 × fS clocks
Hardware-accelerated DSP core
21 kB (6,144 words) data memory for up to 128 ms of audio
delay at fs = 48 kHz
Flexible serial data port with I2S-compatible, left-justified,
and right-justified serial port modes
8- and 16-channel TDM input/output modes
On-chip voltage regulator for compatibility with 3.3 V and
5 V systems
Programmable low power mode
Fast start-up and boot time from power-on or reset
48-lead LQFP plastic package
APPLICATIONS
Automotive sound systems
Digital televisions
Home theater systems (Dolby digital/DTS postprocessor)
Multichannel audio systems
Mini-component stereos
Multimedia audio
Digital speaker crossover
Musical instruments
In-seat sound systems (aircrafts/motor coaches)
FUNCTIONAL BLOCK DIAGRAM
VOLTAGE
REGULATOR
AD1940/AD1941
28 × 28
DSP CORE
DATA FORMAT:
PLL
SERIAL
CONTROL
INTERFACE
SERIAL DATA/
TDM INPUTS
MASTER
CLOCK
INPUT
SPI/I
2
C I/O RAM ROM
SERIAL
DATA/
TDM
OUTPUTS
04607-0-001
2
4
4
2
2
5.23 (SINGLE
PRECISION)
10.46 (DOUBLE
PRECISION)
Figure 1.
GENERAL DESCRIPTION
The AD1940/AD1941 are a complete 28-bit, single-chip, multi-
channel audio SigmaDSP™ for equalization, multiband dynamic
processing, delay compensation, speaker compensation, and
image enhancement. These algorithms can be used to compen-
sate for the real world limitations of speakers, amplifiers, and
listening environments, resulting in a dramatic improvement of
perceived audio quality.
The signal processing used in the AD1940/AD1941 is
comparable to that found in high end studio equipment. Most
of the processing is done in full, 56-bit double-precision mode,
resulting in very good, low level signal performance and the
absence of limit cycles or idle tones. The dynamics processor
uses a sophisticated, multiple-breakpoint algorithm often found
in high end broadcast compressors.
The AD1940/AD1941 are a fully programmable DSP. Easy to
use software allows the user to graphically configure a custom
signal processing flow using blocks such as biquad filters, dyna-
mics processors, and surround sound processors. An extensive
control port allows click-free parameter updates, along with
readback capability from any point in the algorithm flow.
The AD1940/AD1941’s digital input and output ports allow a
glueless connection to ADCs and DACs by multiple, 2-channel
serial data streams or TDM data streams. When in TDM mode,
the AD1940/AD1941 can input 8 or 16 channels of serial data,
and can output 8 or 16 channels of serial data. The input and
output port configurations can be individually set. The AD1940
is controlled by a 4-wire SPI® port; the AD1941 is controlled by
a 2-wire I2C® bus. Other than the control interface, the
functions of the two parts are identical.
AD1940/AD1941
Rev. B | Page 2 of 36
TABLE OF CONTENTS
Specifications ..................................................................................... 3
Digital I/O ..................................................................................... 3
Power .............................................................................................. 3
Digital Timing ............................................................................... 4
PLL ................................................................................................. 5
Regulator ........................................................................................ 5
Temperature Range ...................................................................... 5
Absolute Maximum Ratings ............................................................ 6
ESD Caution .................................................................................. 6
Digital Timing Diagrams ................................................................. 7
Pin Configuration and Function Descriptions ............................. 9
Features ............................................................................................ 11
Pin Functions .............................................................................. 12
Signal Processing ............................................................................ 14
Overview ...................................................................................... 14
Numeric Formats ........................................................................ 14
Programming .............................................................................. 14
Control Port ..................................................................................... 15
Overview ...................................................................................... 15
AD1940 SPI Port ........................................................................ 15
AD1941 I2C Port ......................................................................... 15
RAMs and Registers ....................................................................... 19
Control Port Addressing ........................................................... 19
Parameter RAM Contents ......................................................... 19
Recommended Program/Parameter Loading Procedures .... 20
Target/ Sle w R AM ....................................................................... 20
Safeload Registers ....................................................................... 23
Data Capture Registers .............................................................. 23
DSP Core Control Register ....................................................... 24
RAM Configuration Register ................................................... 25
Control Port Read/Write Data Formats .................................. 25
Serial Data Input/Output Ports .................................................... 28
Serial Output Control Registers ............................................... 30
Serial Input Control Register .................................................... 30
Initialization .................................................................................... 33
Power-Up Sequence ................................................................... 33
Setting Master Clock/PLL Mode .............................................. 33
Volt age Regulator ....................................................................... 33
Outline Dimensions ....................................................................... 35
Ordering Guide .......................................................................... 35
REVISION HISTORY
4/10—Rev. A to Rev. B
Changes to Voltage Regulator Section ..................................... 34
Updated Outline Dimensions ................................................... 35
Changes to Ordering Guide ...................................................... 35
4/05—Rev. 0 to Rev. A
Added AD1941 .............................................................. Universal
Changes to Specifications ............................................................ 3
Changes to Pin Function Descriptions ...................................... 9
Changes to Features Section...................................................... 11
Changes to Pin Functions Section ............................................ 13
Addition of AD1940 SPI Port Section ..................................... 15
Added Table 13 to Table 16 ....................................................... 18
7/04—Revision 0: Initial Version
AD1940/AD1941
Rev. B | Page 3 of 36
SPECIFICATIONS
Test conditions, unless otherwise noted.
Table 1.
Parameter Conditions
Supply Voltage (VDD) 2.5 V
PLL Voltage (PLL_VDD) 2.5 V
Output Voltage (ODVDD) 5.0 V
INVDD Voltage 5.0 V
Ambient Temperature 25°C
Master Clock Input 3.072 MHz, 64 × fs mode
Load Capacitance 50 pF
Load Current ±1 mA
Input Voltage, HI 2.4 V
Input Voltage, LO 0.8 V
DIGITAL I/O
VDD = 2.25 V to 2.75 V. Specifications measured across −40°C to 125°C (case).
Table 2.
Parameter Comments Min Max Unit
Input Voltage, HI (VIH) 2.1 V
Input Voltage, LO (VIL) 0.8 V
Input Leakage (IIH) 10 μA
Input Leakage (IIL) 10 μA
High Level Output Voltage (VOH) ODVDD = 4.5 V, IOH = 1 mA 3.9 V
High Level Output Voltage (VOH) ODVDD = 3.0 V, IOH = 1 mA 2.6 V
Low Level Output Voltage (VOL) ODVDD = 4.5 V, IOL = 1 mA1 0.4 V
Low Level Output Voltage (VOL) ODVDD = 3.0 V, IOL = 1 mA1 0.3 V
Input Capacitance 5 pF
1 SDA is measured with a 3 mA sink current.
POWER
Table 3.
Parameter Min Typ Max1 Unit
SUPPLIES
Voltage 2.25 2.5 2.75 V
Digital Current 92 1552 mA
PLL Current 3.5 8 mA
Digital Current, Reset 4.53 133 mA
PLL Current, Reset 3 8.5 mA
DISSIPATION
Operation, All Supplies 238.8 mW
Reset, All Supplies 10.8 mW
1 Maximum specifications are measured across −40°C to 125°C (case) and across VDD = 2.25 V to 2.75 V.
2 Measurement running a typical large program that writes to all 16 outputs with 0 dB digital sine waves applied to all eight inputs. The end user’s program may differ.
3 The digital reset current is specified for the given test conditions. This current scales with the input MCLK rate, so higher input clocks draw more current while in reset.
AD1940/AD1941
Rev. B | Page 4 of 36
DIGITAL TIMING
VDD = 2.25 to 2.75 V. Specifications measured across –40°C to 125°C.
Table 4. Digital Timing1
Parameter Mnemonic Comments Min Max Unit
MASTER CLOCK, SERIAL DATA PORTS, RESET
MCLK Period tMP 512 fS mode 36 244 ns
MCLK Period tMP 384 fS mode 48 366 ns
MCLK Period tMP 256 fS mode 73 488 ns
MCLK Period tMP 64 fS mode 291 1953 ns
MCLK Period tMP Bypass mode 12 ns
MCLK Duty Cycle tMDC Bypass mode 40 60 %
BCLK_IN LO Pulse Width tBIL 4 ns
BCLK_IN HI Pulse Width tBIH 2 ns
LRCLK_IN Setup tLIS To BCLK_IN rising 12 ns
LRCLK_IN Hold tLIH From BCLK_IN rising 0 ns
SDATA_INx Setup tSIS To BCLK_IN rising 3 ns
SDATA_INx Hold tSIH From BCLK_IN rising 2 ns
LRCLK_OUTx Setup tLOS Slave mode 2 ns
LRCLK_OUTx Hold tLOH Slave mode 2 ns
BCLK_OUTx Falling to LRCLK_OUTx
Timing Skew
tTS 2 ns
SDATA_OUTx Delay tSODS Slave mode, from
BCLK_OUTx falling 17 ns
SDATA_OUTx Delay tSODM Master mode, from
BCLK_OUTx falling 17 ns
RESETB LO Pulse Width tRLPW 10 ns
SPI PORT (AD1940)
CCLK Pulse Width LO tCCPL 1 × INTMCLK (14)2 ns
CCLK Pulse Width HI tCCPH 1 × INTMCLK (14)2 ns
CLATCH Setup tCLS To CCLK rising 0 ns
CLATCH Hold tCLH From CCLK rising 2 × INTMCLK + 4 (32)2 ns
CLATCH Pulse Width HI tCLPH 2 × INTMCLK (28)2 ns
CDATA Setup tCDS To CCLK rising 0 ns
CDATA Hold tCDH From CCLK rising 2 × INTMCLK + 2 (30)2 ns
COUT Delay tCOD From CCLK rising 4 × INTMCLK +18 (74)2 ns
I2C PORT (AD1941)
SCL Clock Frequency fSCL 400 kHz
SCL Low tSCLL 1.3 μs
SCL High tSCLH 0.6 μs
Setup Time (Start Condition) tSCS Relevent for repeated start
condition
0.6 μs
Hold Time (Start Condition) tSCH First clock generated after
this period
0.6 μs
Setup Time (Stop Condition) tSSH 0.6 μs
Data Setup Time tDS 100 ns
SDA and SCL Rise Time tSR 300 ns
SDA and SCL Fall Time tSF 300 ns
Bus-Free Time tBFT Between stop and start 1.3 μs
1 All timing specifications are given for the default (I2S) states of the serial input control port and the serial output control ports. See Table 37.
2 These specifications are based on the internal master clock period in a specific application. In normal operation, the master clock runs at 1,536 × fs, so the internal
master clock at fs = 48 kHz has a 14 ns period. The values in parentheses are the timing values for fs = 48 kHz.
AD1940/AD1941
Rev. B | Page 5 of 36
PLL
VDD = 2.25 to 2.75 V. Specifications measured across –40°C to 125°C.
Table 5.
Parameter Min Typ Max Unit
Lock Time 3 20 ms
REGULATOR
VDD = 2.25 to 2.75 V. Specifications measured across –40°C to 125°C.
Table 6.
Parameter Min Typ Max Unit
VSENSE Output Voltage 2.25 2.5 2.68 V
TEMPERATURE RANGE
Table 7.
Parameter Min Typ Max Unit
Functionality Guaranteed –40 +105 °C Ambient
–40 +125 °C Case
AD1940/AD1941
Rev. B | Page 6 of 36
ABSOLUTE MAXIMUM RATINGS
Table 8.
Parameter Min Max Unit
VDD to DGND –0.3 +3.0 V
PLL_ VDD to PGND –0.3 +3.0 V
OD VDD to DGND –0.3 +6.0 V
INVDD to DGND ODVDD +6.0 V
Digital Inputs DGND – 0.3 INVDD + 0.3 V
Maximum Junction
Temperature
135 °C
Storage Temperature
Range
–65 +150 °C
Soldering (10 sec) 300 °C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only and functional operation of the device at these or
any other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
Table 9. Package Characteristics
Parameter Min Typ Max Unit
θJA Thermal Resistance (Junction-
to-Ambient)
72 °C/W
θJC Thermal Resistance (Junction-
to-Case)
19.5 °C/W
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the
human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
AD1940/AD1941
Rev. B | Page 7 of 36
DIGITAL TIMING DIAGRAMS
BCLK_IN
LRCLK_IN
SDATA_INX
LEFT-JUSTIFIED
MODE
LSB
SDATA_INX
I
2
S-JUSTIFIED
MODE
SDATA_INX
RIGHT-JUSTIFIED
MODE
t
BIH
MSB MSB-1
MSB
MSB
8-BIT CLOCKS
(24-BIT DATA)
12-BIT CLOCKS
(20-BIT DATA)
14-BIT CLOCKS
(18-BIT DATA)
16-BIT CLOCKS
(16-BIT DATA)
t
LIS
t
SIS
t
SIH
t
SIH
t
SIS
t
SIS
t
SIH
t
SIS
t
SIH
t
LIH
t
BIL
04607-0-013
Figure 2. Serial Input Port Timing
BCLK_OUTX
LRCLK_OUTX
SDATA_OUTX
LEFT-JUSTIFIED
MODE
LSB
SDATA_OUTX
I2S-JUSTIFIED
MODE
SDATA_OUTX
RIGHT-JUSTIFIED
MODE
tBIH
MSB MSB-1
MSB
MSB
8-BIT CLOCKS
(24-BIT DATA)
12-BIT CLOCKS
(20-BIT DATA)
14-BIT CLOCKS
(18-BIT DATA)
16-BIT CLOCKS
(16-BIT DATA)
tLOS
tSDDS
tSDDM
tSDDS
tSDDM
tSDDS
tSDDM
tLCH tTS
tBIL
04607-0-014
Figure 3. Serial Output Port Timing
AD1940/AD1941
Rev. B | Page 8 of 36
CLATCH
CCLK
CDATA
COUT
tCLS
tCDS
tCDH
tCOD
tCCPH
tCCPL
tCLH tCLPH
04607-0-015
Figure 4. AD1940 SPI Port Timing
t
TSCH
t
SCLH
t
SR
t
SCLL
t
ST
t
DS
SDA
SCLK
t
TSCH
t
SSH
04607-026
t
SCS
Figure 5. AD1941 I2C Port Timing
MCLK
RESETB
t
MP
t
RLPW
04607-0-016
Figure 6. Master Clock and Reset Timing
AD1940/AD1941
Rev. B | Page 9 of 36
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
36
35
34
33
32
31
30
29
28
27
26
25
13 14 15 16 17 18 19 20 21 22 23 24
1
2
3
4
5
6
7
8
9
10
11
12
48 47 46 45 44 39 38 3743 42 41 40
GND
BCLK_OUT1
LRCLK_OUT1
ODVDD
SDATA_OUT3
SDATA_OUT2
SDATA_OUT1
VDD
MCLK
RESERVED
PLL_VDD
NC SDATA_OUT0
ODVDD
BCLK_OUT0
LRCLK_OUT0
GND VDD
PIN 1
INDICATOR
PLL_CTRL0
PLL_CTRL1
PLL_CTRL2
PLL_GND
AD1940
TOP VIEW
(Not to Scale)
VDD
SDATA_IN1
SDATA_IN2
SDATA_IN3
COUT
CCLK
CLATCH
CDATA
RESETB
GND
SDATA_IN0
ADR_SEL
GND
VREF
VDRIVE
VSENSE
VSUPPLY
INVDD
SDATA_OUT7
SDATA_OUT6
ODVDD
SDATA_OUT5
SDATA_OUT4
VDD
04607-0-002
LRCLK_IN
BCLK_IN
NC = NO CONNECT
36
35
34
33
32
31
30
29
28
27
26
25
13 14 15 16 17 18 19 20 21 22 23 24
1
2
3
4
5
6
7
8
9
10
11
12
48 47 46 45 44 39 38 3743 42 41 40
GND
BCLK_OUT1
LRCLK_OUT1
ODVDD
SDATA_OUT3
SDATA_OUT2
SDATA_OUT1
VDD
MCLK
RESERVED
PLL_VDD
I2C_FILT_EN SDATA_OUT0
ODVDD
BCLK_OUT0
LRCLK_OUT0
GND VDD
PIN 1
INDICATOR
PLL_CTRL0
PLL_CTRL1
PLL_CTRL2
PLL_GND
AD1941
TOP VIEW
(Not to Scale)
VDD
SDATA_IN1
SDATA_IN2
SDATA_IN3
SDA
SCL
NC
NC
RESETB
GND
SDATA_IN0
ADR_SEL
GND
VREF
VDRIVE
VSENSE
VSUPPLY
INVDD
SDATA_OUT7
SDATA_OUT6
ODVDD
SDATA_OUT5
SDATA_OUT4
VDD
04607-0-011
LRCLK_IN
BCLK_IN
NC = NO CONNECT
Figure 7. 48-Lead LQFP Pin Configuration, AD1940 Figure 8. 48-Lead LQFP Pin Configuration, AD1941
Table 10. Pin Function Descriptions
Pin No.
AD1940 AD1941 I/O Mnemonic Description
1, 25, 37 1, 25, 37 VDD Core Power.
2 2 IN MCLK Master Clock Input.
3 3 RESERVED This pin should be connected to ground.
4 4 IN PLL_CTRL0 PLL Control 0.
5 5 IN PLL_CTRL1 PLL Control 1.
6 6 IN PLL_CTRL2 PLL Control 2.
7 7 PLL_GND PLL Ground.
8 8 PLL_VDD PLL Power.
9 21, 22 NC No Connect.
9 IN I2C_FILT_ENB I2C Filter Enable, Active Low.
10 10 IN LRCLK_IN Left/Right Clock for Serial or TDM Data Inputs.
11 11 IN BCLK_IN Bit Clock for Serial or TDM Data Inputs.
12, 24, 36,
48
12, 24, 36,
48
GND Digital Ground.
13 13 VDD Core Power.
14 14 IN SDATA_IN0 Serial Data Input 0.
15 12 IN SDATA_IN1 Serial Data Input 1.
16 16 IN SDATA_IN2/TDM_IN1 Serial Data Input 2/TDM Input 1.
17 17 IN SDATA_IN3/TDM_IN0 Serial Data Input 3/TDM Input 0.
18 18 IN ADR_SEL Control Port Address Select.
19 OUT COUT SPI Data Output.
20 IN CCLK Clock for SPI.
21 IN CLATCH SPI Data Latch.
AD1940/AD1941
Rev. B | Page 10 of 36
Pin No.
AD1940 AD1941 I/O Mnemonic Description
22 IN CDATA Data Input for SPI.
19 IN/OUT SDA I2C Serial Data I/O.
20 IN SCL I2C Clock.
23 23 IN RESETB Reset the AD1940/AD1941.
26 26 IN/OUT LRCLK_OUT0 Left/Right Clock Output 0.
27 27 IN/OUT BCLK_OUT0 Bit Clock Output 0.
28, 33, 40 28, 33, 40 ODVDD Power Connection for Output Pins.
29 29 OUT SDATA_OUT0/TDM_O0 Serial Data Output 0/TDM (16- or 8-Channel) Output 0.
30 30 OUT SDATA_OUT1 Serial Data Output 1.
31 31 OUT SDATA_OUT2 Serial Data Output 2.
32 32 OUT SDATA_OUT3 Serial Data Output 3.
34 34 IN/OUT LRCLK_OUT1 Left/Right Clock Output 1.
35 35 IN/OUT BCLK_OUT1 Bit Clock Output 1.
38 38 OUT SDATA_OUT4/TDM_O1 Serial Data Output 4./TDM (8-Channel) Output 1.
39 39 OUT SDATA_OUT5 Serial Data Output 5.
41 41 OUT SDATA_OUT6 Serial Data Output 6.
42 42 OUT SDATA_OUT7/DCSOUT Serial Data Output 7/Data Capture Output.
43 43 INVDD Input Voltage Reference.
44 44 IN VSUPPLY Voltage Level Input to Regulator. Usually 3.3 V or 5 V.
45 45 IN VSENSE Digital Power Level. Should be tied to VDD.
46 46 OUT VDRIVE Drive for External PNP Transistor.
47 47 OUT VREF Reference Level for Voltage Regulator.
AD1940/AD1941
Rev. B | Page 11 of 36
FEATURES
The core of the AD1940/AD1941 is a 28-bit DSP (56-bit, double
precision) optimized for audio processing. The parts’ program
RAM can be loaded with a custom program after power-up.
Signal processing parameters are stored in a 1024 location
parameter RAM, which is initialized on power-up by an
internal boot ROM. New values are written to the parameter
RAM using the control port. The values stored in the parameter
RAM control individual signal processing blocks, such as IIR
equali-zation filters, dynamics processors, audio delays, and
mixer levels. A safeload feature allows parameters to be
transparently updated without causing clicks on the output
signals.
The target/slew RAM contains 64 locations and can be used as
channel volume controls or for other parameter updates. These
RAM locations take a target value for a given parameter and
ramp the current parameter value to the new value using a
specified time constant and one of a selection of linear or
logarithmic curves.
The AD1940/AD1941 contain eight independent data capture
circuits that can be programmed to tap the signal flow of the
processor at any point in the DSP algorithm flow. Six of these
captured signals can be accessed by reading from the data
capture registers through the control port. The remaining two
data capture registers can be used to send any internal captured
signal to a stereo digital output signal on Pin SDATA_OUT7 for
driving external DACs or digital analyzers.
The AD1940/AD1941 have a sophisticated control port that
supports complete read/write capability of all memory
locations. Five control registers (Core, RAM configuration,
Serial Output 0 to 7, Serial Output 8 to 15, and serial input) are
provided to offer complete control of the chip’s configuration
and serial modes. Handshaking is included for ease of memory
uploads/downloads. The AD1940 is SPI-controlled and the
AD1941 is controlled by an I2C bus.
The AD1940/AD1941 have very flexible serial data
input/output ports that allow glueless interconnection to a
variety of ADCs, DACs, general-purpose DSPs, S/PDIF
receivers and trans-mitters, and sample rate converters. The
AD1940/AD1941 can be configured in I2S, left-justified, right-
justified, or TDM serial port-compatible modes. It can support
16, 20, and 24 bits in all modes. The AD1940/AD1941 accepts
serial audio data in MSB first and twos complement format.
A master clock phase-locked loop (PLL) allows the AD1940/
AD1941 to be clocked from a variety of different clock speeds.
The PLL can accept inputs of 64 × fS, 256 × fS, 384 × fS, or 512 ×
fS to generate the core’s internal master clock.
The AD1940/AD1941 operate from a single 2.5 V power supply.
An on-board voltage regulator can be used to operate the chip
with 3.3 V or 5 V supplies. They are fabricated on a single
monolithic integrated circuit and are housed in 48-lead
LQFP packages for operation over the –40°C to +105°C
temperature range.
04607-0-003
28 × 28
DSP CORE
DATA FORMAT:
5.23 (SINGLE PRECISION)
10.46 (DOUBLE PRECISION)
VOLTAGE REGULATORMEMORY CONTROLLERS
CONTROL
REGISITER
TRAP REG.
SAFELOAD
REGISTER
SERIAL
CONTROL
PORT
MCLK
PLL
DATA MEMORY
6k × 28
TARGET/SLEW
RAM
64 × 28
SERIAL
DATA/TDM
INPUT
GROUP
PLL MODE
SELECT
MASTER
CLOCK
INPUT
CONTROL PORT
I/O GROUP
RESETB
PROGRAM
RAM
1536 × 40
BOOT ROM
BOOT ROM
PARAMETER
RAM
1024 × 28
COEFFICIENT
ROM
512 × 28
2
2
4
4
2
2
SERIAL DATA/
TDM OUTPUT
GROUP
REGULATOR
GROUP
ADDRESS SELECT
Figure 9. Block Diagram
AD1940/AD1941
Rev. B | Page 12 of 36
PIN FUNCTIONS
Table 1 0 shows the AD1940/AD1941’s pin numbers, names, and
functions. Input pins have a logic threshold compatible with
TTL input levels and may be used in systems with 3.3 V or
5 V logic.
SDATA_IN0
SDATA_IN1
SDATA_IN2/TDM_IN1
SDATA_IN3/TDM_IN0
Serial Data/TDM Inputs. The serial format is selected by
writing to Bits 2:0 of the serial input port control register.
SDATA_IN2 and SDATA_IN3 are dual-function pins that can
be set to a variety of standard 2-channel formats or to TDM
mode. Two of these four pins (SDATA_IN2 and SDATA_IN3)
can be used as TDM inputs in either dual-wire 8-channel mode
or single-wire 16-channel mode (TDM_O0 only). In dual-wire
8-channel mode, Channels 0 to 7 are input on SDATA_IN3 and
Channels 8 to 15 on SDATA_IN2. In single-wire 16-channel
mode, Channels 0 to 15 are input on SDATA_IN2. See the
Serial Data Input/Output Ports section for further explanation.
LRCLK_IN
BCLK_IN
Left/Right and Bit Clocks for Timing the Input Data. These
input clocks are associated with the SDATA_IN0 through
SDATA_IN3 signals. The input port is always in a slave
configuration. These pins also function as frame sync and bit
clock for the input TDM stream.
SDATA_OUT0/TDM_O0
SDATA_OUT1
SDATA_OUT2
SDATA_OUT3
SDATA_OUT4/TDM_O1
SDATA_OUT5
SDATA_OUT6
SDATA_OUT7/DCSOUT
Serial Data/TDM/Data Capture Outputs. These pins are used
for serial digital outputs. For non-TDM systems, these eight
pins can output 16 channels of digital audio, using a variety of
standard 2-channel formats. They are grouped into two groups
of four pins (Pins 0 to 3 and Pins 4 to 7); each group can be
independently set to any of the available serial modes, allowing
the AD1940/AD1941 to simultaneously communicate with two
external devices with different serial formats. Two of these eight
pins (SDATA_OUT0 and SDATA_OUT4) can be used as TDM
outputs in either dual-wire 8-channel mode or single-wire 16-
channel mode (TDM_OUT0 only). In dual-wire 8-channel
mode, Channels 0 to 7 are output on SDATA_OUT0 and
Channels 8 to 15 on SDATA_OUT4. See the Serial Data
Input/Output Ports section for further explanation.
SDATA_OUT7 can also be used as a data capture output, as
described in the Data Capture Registers section.
LRCLK_OUT0
BCLK_OUT0
Output Clocks. This clock pair is used for outputs
SDATA_OUT0 through SDATA_OUT3. In slave mode, these
clocks are inputs to the AD1940/AD1941. On power-up, these
pins are set to slave mode to avoid conflicts with external
master mode devices.
LRCLK_OUT1
BCLK_OUT1
Output Clocks. This clock pair is used for outputs
SDATA_OUT4 through SDATA_OUT7. In slave mode, these
clocks are inputs to the AD1940/AD1941. On power-up, these
pins are set to slave mode to avoid conflicts with external
master mode devices.
MCLK
Master Clock Input. The AD1940/AD1941 uses a PLL to
generate the appropriate internal clock for the DSP core. An
in-depth description of using the PLL is found in the Setting
Master Clock/PLL Mode section.
PLL_CTRL0
PLL_CTRL1
PLL_CTRL2
PLL Mode Control Pins. The functionality of these pins is
described in the Setting Master Clock/PLL Mode section.
CDATA (AD1940)
Serial Data Input for the SPI Control Port.
COUT (AD1940)
Serial Data Output for the SPI Port. This is used for reading
back registers and memory locations. It is three-stated when an
SPI read is not active.
CCLK (AD1940)
SPI Bit Clock. This clock may either run continuously or be
gated off between SPI transactions.
CLATCH (AD1940)
SPI Latch Signal. This must go low at the beginning of an SPI
transaction and high at the end of a transaction. Each SPI
transaction may take a different number of CCLKs to complete,
depending on the address and read/write bit that are sent at the
beginning of the SPI transaction.
SCL (AD1941)
I2C Clock. This pin is always an input because the AD1941
cannot act as a master on the I2C bus. The line connected to this
pin should have a 2 kΩ pull-up resistor on it.
SDA (AD1941)
I2C Serial Data. The data line is bidirectional. The line
connected to this pin should have a 2 kΩ pull-up resistor on it.
AD1940/AD1941
Rev. B | Page 13 of 36
I2C_FILT_ENB (AD1941)
I2C Spike Filter Enable/Disable. This enables (active low) the I2C
spike filter, which is used to prevent noise or glitches on the I2C
bus from improperly affecting the AD1941.
ADR_SEL
Address Select. This pin selects the address for the AD1940/
AD1941’s communication with the control port. This allows
two AD1940s to be used with a single CLATCH signal or two
AD1941s to be used on the same I2C bus.
RESETB
Active-Low Reset Signal. After RESETB goes high, the
AD1940/AD1941 goes through an initialization sequence where
the program and parameter RAMs are initialized with the
contents of the on-board boot ROMs. All registers are set to 0,
and the data RAMs are also set to 0. The initialization is com-
plete after 8,192 internal MCLK cycles (referenced to the rising
edge of RESETB), which corresponds to 1,366 external MCLK
cycles if the part is in 256 × fS mode. New values should not be
written to the control port until the initialization is complete.
VREF
Voltage Reference for Regulator. This pin is driven by an
internal 1.15 V reference voltage.
VDRIVE
Drive for External Transistor. The base of the voltage regulator’s
external PNP transistor is driven from this pin.
VSENSE
Digital Power Level. The voltage level on the VDD pins is
sensed on VSENSE. VSENSE should be tied to VDD.
VSUPPLY
Main Supply Voltage Level. This pin is tied to the board’s main
voltage supply. This is usually 3.3 V or 5 V.
VDD (4)
Digital VDD for Core. 2.5 V nominal.
GND (4)
Digital Ground.
PLL_VDD
Supply for AD1940/AD1941 PLL. 2.5 V nominal.
PLL_GND
PLL Ground.
ODVDD (3)
VDD for All Digital Outputs. The high levels of the digital
output signals are set on this pin. The voltage can range from
2.5 V to 5.0 V.
INVDD
Peak Input Voltage Level. The highest voltage level that the
input pin sees should be connected to INVDD. This is to
protect the chip inputs from voltage overstress. The voltage on
this pin must always be at or above the level of ODVDD.
AD1940/AD1941
Rev. B | Page 14 of 36
SIGNAL PROCESSING
OVERVIEW
The AD1940/AD1941 are designed to provide all signal
processing functions commonly used in stereo or multichannel
playback systems. The signal processing flow is set by using the
ADI-supplied software, which allows graphical entry and real-
time control of all signal processing functions.
Many of the signal processing functions are coded using full,
56-bit double-precision arithmetic. The input and output word
lengths are 24 bits. Four extra headroom bits are used in the
processor to allow internal gains up to 24 dB without clipping.
Additional gains can be achieved by initially scaling down the
input signal in the signal flow.
The signal processing blocks can be arranged in a custom pro-
gram that can be loaded to the AD1940/AD1941’s RAM. The
available signal processing blocks are explained in the following
sections.
NUMERIC FORMATS
It is common in DSP systems to use a standardized method of
specifying numeric formats. Fractional number systems are
specified by an A.B format, where A is the number of bits to the
left of the decimal point and B is the number of bits to the right
of the decimal point.
The AD1940/AD1941 use the same numeric format for both
the coefficient values (stored in the parameter RAM) and the
signal data values. The format is as follows:
Numerical Format: 5.23
Range: –16.0 to (+16.0 − 1 LSB)
Examples:
1000 0000 0000 0000 0000 0000 0000 = –16.0
1110 0000 0000 0000 0000 0000 0000 = –4.0
1111 1000 0000 0000 0000 0000 0000 = –1.0
1111 1110 0000 0000 0000 0000 0000 = –0.25
1111 1111 1111 1111 1111 1111 1111 = (1 LSB below 0.0)
0000 0000 0000 0000 0000 0000 0000 = 0.0
0000 0010 0000 0000 0000 0000 0000 = 0.25
0000 1000 0000 0000 0000 0000 0000 = 1.0
0010 0000 0000 0000 0000 0000 0000 = 4.0
0111 1111 1111 1111 1111 1111 1111 = (16.0 – 1 LSB).
The serial port accepts up to 24 bits on the input and is sign-
extended to the full 28 bits of the core. This allows internal
gains of up to 24 dB without encountering internal clipping.
A digital clipper circuit is used between the output of the DSP
core and the serial output ports (see Figure 10). This clips the
top four bits of the signal to produce a 24-bit output with a
range of 1.0 (minus 1 LSB) to –1.0.
4-BIT SIGN EXTENSION
DATA IN SERIAL PORT
1.23 5.23
SIGNAL PROCESSING
(5.23 FORMAT) DIGITAL
CLIPPER
5.23 1.23
04607-0-005
Figure 10. Numeric Precision and Clipping Structure
PROGRAMMING
On power-up, the AD1940/AD1941’s default program passes
the unprocessed input signals to the outputs (Figure 28) but the
outputs are muted by default (see Power-Up Sequence section).
There are 1,536 instruction cycles per audio sample, resulting in
an internal clock rate of 73.728 MHz (for fS = 48 kHz). This DSP
runs in a stream-oriented manner, meaning all 1,536 instruc-
tions are executed each sample period. The AD1940/AD1941
may also be set up to accept double- or quad-speed inputs by
reducing the number of instructions/sample, which can be set
in the core control register.
The part can be programmed easily using graphical tools pro-
vided by Analog Devices. No knowledge of writing DSP code is
needed to program this part. The user simply can connect
graphical blocks such as biquad filters, dynamics processors,
mixers, and delays in a signal flow schematic, compile the
design, and load the program and parameter files into the
AD1940/AD1941’s program RAM through the control port.
Signal processing blocks available in the provided libraries
include
• Single- and double-precision biquad filters
• Mono and multichannel dynamics processors
• Mixers and splitters
• Tone and noise generators
• First-order filters
• Fixed and variable gain
• RMS look-up tables
• Loudness
• Delay
• Stereo enhancement (Phat Stereo™)
• Dynamic bass boost
• Interpolators and dececimators
More blocks are always in development. Analog Devices also
provides proprietary and third-party algorithms for applications
such as matrix decoding, bass enhancement, and surround
virtualizers. Contact an ADI sales representative for infor-
mation about licensing these algorithms.
AD1940/AD1941
Rev. B | Page 15 of 36
CONTROL PORT
OVERVIEW
The AD1940/AD1941 have many different control options that
can be set through an SPI or I2C interface. The AD1940 uses a
4-wire SPI control port and the AD1941 uses a 2-wire I2C bus
control port. Most signal processing parameters are controlled
by writing new values to the parameter RAM using the control
port. Other functions, such as mute and input/output mode
control, are programmed by writing to the control registers.
The control port is capable of full read/write operation for all of
the memories and registers. All addresses may be accessed in
both a single-address mode or a burst mode. A control word
consists of the chip address, the register/RAM subaddress, and
the data to be written. The number of bytes per word depends
on the type of data that is written.
The first byte of a control word (Byte 0) contains the 7-bit chip
address plus the R/W bit. The next two bytes (Bytes 1 and 2)
form the subaddress of the memory or register location within
the AD1940/AD1941. This subaddress needs to be two bytes
because the memories within the AD1940/AD1941 are directly
addressable, and their sizes exceed the range of single-byte
addressing. All subsequent bytes (Bytes 3, 4, etc.) contain the
data, such as control port, program, or parameter data.
The exact formats for specific types of writes are shown in Table
26 to Table 35.
The AD1940/AD1941 have several mechanisms for updating
signal processing parameters in real time without causing pops
or clicks. In cases where large blocks of data need to be down-
loaded, the output of the DSP core can be halted (using Bit 9 of
the core control register), new data loaded, and then restarted.
This is typically done during the booting sequence at start-up or
when loading a new program into RAM. In cases where only a
few parameters need to be changed, they can be loaded without
halting the program. To avoid unwanted side effects while
loading parameters on the fly, the SigmaDSP provides the
safeload registers. The safeload registers can be used to buffer a
full set of parameters (for example, the five coefficients of a
biquad) and then transfer these parameters into the active
program within one audio frame. The safeload mode uses
internal logic to prevent contention between the DSP core and
the control port.
AD1940 SPI PORT
The SPI port uses a 4-wire interface, consisting of CLATCH,
CCLK, CDATA, and COUT signals. The CLATCH signal goes
low at the beginning of a transaction and high at the end of a
transaction. The CCLK signal latches CDATA on a low-to-high
transition. COUT data is shifted out of the AD1940/AD1941 on
the falling edge of CCLK and should be clocked into the
receiving device, such as a microcontroller, on CCLK’s rising
edge. The CDATA signal carries the serial input data and the
COUT signal is the serial output data. The COUT signal
remains three-stated until a read operation is requested. This
allows other SPI-compatible peripherals to share the same
readback line. All SPI transactions follow the same basic format,
shown in Tabl e 11. A timing diagram is shown in Figure 4. All
data written should be MSB first.
Table 11. Generic SPI Word Format
Byte 0 Byte 1 Byte 2 Byte 3
Byte 4,
etc.
chip_adr [6:0],
R/W
0000,
subadr
[11:8]
subadr [7:0] Data Data
Chip Address R/W
The first byte of an SPI transaction includes the 7-bit chip
address and a R/W bit. The chip address is set by the ADR_SEL
pin. This allows two AD1940s to share a CLATCH signal, yet
operate independently. When ADR_SEL is low, the chip address
is 0000000; when it is high, the address is 0000001. The LSB of
this first byte determines whether the SPI transaction is a read
(Logic Level 1) or a write (Logic Level 0).
Subaddress
The 12-bit subaddress word is decoded into a location in one of
the memories or registers. This subaddress is the location of the
appropriate RAM location or register.
Data Bytes
The number of data bytes varies according to the register or
memory being accessed. In burst write mode, an initial
subaddress is given followed by a continuous sequence of data
for consecutive memory/register locations. The detailed data
format diagram for continuous mode operation is given in the
Control Port Read/Write Data Formats section.
A sample timing diagram for a single SPI write operation to the
parameter RAM is shown in Figure 11. A sample timing
diagram of a single SPI read operation is shown in Figure 12.
The COUT pin goes from three-state to driven at the beginning
of Byte 3. In this example, Bytes 0 to 2 contain the addresses and
R/W bit, and subsequent bytes carry the data.
AD1941 I2C PORT
The AD1941 supports a 2-wire serial (I2C-compatible) micro-
processor bus driving multiple peripherals. Two pins, serial data
(SDA) and serial clock (SCL), carry information between the
AD1941 and the system I2C master controller. The AD1941 is
always a slave on the I2C bus, which means that it never initiates
a data transfer. Each slave device is recognized by a unique
address. The AD1941 has four possible slave addresses, two for
writing operations and two for reading. These are unique
addresses for the device and are illustrated in Table 12. The LSB
AD1940/AD1941
Rev. B | Page 16 of 36
of the byte sets either a read or write operation; Logic Level 1
corresponds to a read operation and Logic Level 0 corresponds
to a write operation. The seventh bit of the address is set by
tying the ADR_SEL pin of the AD1941 to Logic Level 0 or Logic
Level 1.
The AD1941 I2C port uses a spike filter that can be enabled or
disabled by the I2C_FILT_ENB pin. Enabling this filter guar-
antees that all isolated spikes, both positive and negative, less
than 50 ns wide are removed from the I2C signal. The filter is
active when the I2C_FILT_ENB pin is low and is disabled when
the pin is high. Typically, the largest spike that is filtered is
67 ns wide.
Table 12. AD1941 I2C Addresses
ADR_SEL R/W Slave Address
0 0 0x28
0 1 0x29
1 0 0x2A
1 1 0x2B
Addressing
Initially, all devices on the I2C bus are in an idle state, which is
where the devices monitor the SDA and SCL lines for a start
condition and the proper address. The I2C master initiates a
data transfer by establishing a start condition, defined by a
high-to-low transition on SDA while SCL remains high. This
indicates that an address/data stream will follow. All devices on
the bus respond to the start condition and read the next byte
(7-bit address + R/W bit) MSB first. The device that recognizes
the transmitted address responds by pulling the data line low
during the ninth clock pulse. This ninth bit is known as an
acknowledge bit. All other devices withdraw from the bus at
this point and return to the idle condition. The R/W bit
determines the direction of the data. A Logic 0 on the LSB of
the first byte means the master writes information to the
peripheral. A Logic 1 on the LSB of the first byte means the
master reads information from the peripheral. A data transfer
takes place until a stop condition is encountered. A stop
condition occurs when SDA transitions from low to high while
SCL is held high. Figure 13 shows the timing of an I2C write.
Burst mode addressing, where the subaddresses are automati-
cally incremented at word boundaries, can be used for writing
large amounts of data to contiguous memory locations. This
increment happens automatically if a stop condition is not
encountered after a single-word write. The registers and
memories in the AD1941 range in width from one to five bytes,
so the autoincrement feature knows the mapping between sub-
addresses and the word length of the destination register (or
memory location). A data transfer is always terminated by a
stop condition.
Stop and start conditions can be detected at any stage during
the data transfer. If these conditions are asserted out of
sequence with normal read and write operations, these cause an
immediate jump to the idle condition. During a given SCL high
period, the user should only issue one start condition, one stop
condition, or a single stop condition followed by a single start
condition. If an invalid subaddress is issued by the user, the
AD1941 does not issue an acknowledge and returns to the idle
condition. If the user exceeds the highest subaddress while in
autoincrement mode, one of two actions are taken. In read
mode, the AD1941 outputs the highest subaddress register
contents until the master device issues a no-acknowledge,
indicating the end of a read. A no-acknowledge condition is
where the SDA line is not pulled low on the ninth clock pulse
on SCL. If the highest subaddress location is reached while in
write mode, the data for the invalid byte is not loaded into any
subaddress register, a no-acknowledge is issued by the AD1941
and the part returns to the idle condition.
I2C Read and Write Operations
Table 1 3 shows the timing of a single-word write operation.
Every ninth clock, the AD1941 issues an acknowledge by
pulling SDA low.
Table 1 4 shows the timing of a burst mode write sequence.
This figure shows an example where the target destination
registers are two bytes. The AD1941 knows to increment its
subaddress register every two bytes because the requested
subaddress corresponds to a register or memory area with a
2-byte word length.
The timing of a single word read operation is shown in Table
15. Note that the first R/W bit is still a 0, indicating a write
opera-tion. This is because the subaddress still needs to be
written in order to set up the internal address. After the
AD1941 acknow-ledges the receipt of the subaddress, the
master must issue a repeated start command followed by the
chip address byte with the R/W set to 1 (read). This causes the
AD1941’s SDA to turn around and begin driving data back to
the master. The master then responds every ninth pulse with an
acknowledge pulse to the AD1941.
Table 1 6 shows the timing of a burst mode read sequence. This
figure shows an example where the target read registers are two
bytes. The AD1941 knows to increment its subaddress register
every two bytes because the requested subaddress corresponds
to a register or memory area with word lengths of two bytes.
Other address ranges may have a variety of word lengths
ranging from one to five bytes; the AD1941 always decodes the
subaddress and sets the autoincrement circuit so that the
address increments after the appropriate number of bytes.
AD1940/AD1941
Rev. B | Page 17 of 36
CLATCH
CCLK
CDATA BYTE 0MSB LSB BYTE 1 BYTE 2 BYTE 3
04607-0-006
Figure 11. SPI Write Format (Single Write Mode)
04607-0-007
CLATCH
CCLK
CDATA
COUT
BYTE 0 BYTE 1
HI-Z DATA DATA
BYTE 2
DATA HI-Z
Figure 12. SPI Read Format (Single Read Mode)
R/W
0000 ADR
SEL
00
04607-027
ACK. BY
AD1941
SCK
SDA
SCK
(CONTINUED)
SDA
(CONTINUED)
FRAME 2
SUBADDRESS BYTE 1
ACK. BY
AD1941
FRAME 1
CHIP ADDRESS BYTE 1
START BY
MASTER
ACK. BY
AD1941
ACK. BY
AD1941 STOP BY
MASTER
FRAME 4
DATA BYTE 1
FRAME 3
SUBADDRESS BYTE 2
Figure 13. AD1941 I2C Write Format
AD1940/AD1941
Rev. B | Page 18 of 36
R/W
SCK
ADR
SEL
R/W
ADR
SEL
04607-028
SDA
START BY
MASTER ACK. BY
AD1941
ACK. BY
AD1941
FRAME 2
SUBADDRESS BYTE 1
FRAME 1
CHIP ADDRESS BYTE 1
FRAME 3
SUBADDRESS BYTE 2 FRAME 4
CHIP ADDRESS BYTE
ACK. BY
AD1941 REPEATED
START BY
MASTER
SCK
(CONTINUED)
SDA
(CONTINUED)
SCK
STOP BY
MASTER
ACK. BY
MASTER
FRAME 6
READ DATA BYTE 2
ACK. BY
MASTER
(CONTINUED)
SDA
(CONTINUED)
ACK. BY
AD1941
FRAME 5
READ DATA BYTE 1
Figure 14. AD1941 I2C Read Format
Table 13. Single Word I2C Write
S Chip Address,
R/W = 0
AS Subaddress High AS Subaddress Low AS Data Byte 1 AS Data Byte 2 … AS Data Byte N P
Table 14. Burst Mode I2C Write
S Chip
Address,
R/W = 0
AS Subaddress
High
AS Subaddress
Low
AS Data
Word 1,
Byte 1
AS Data
Word 1,
Byte 2
AS Data
Word 2,
Byte 1
AS Data
Word 2,
Byte 2
AS … P
Table 15. Single Word I2C Read
S Chip
Address,
R/W = 0
AS Subaddress
High
AS Subaddress
Low
AS S Chip
Address,
R/W = 1
AS Data
Byte 1
AM Data
Byte 2
… AM Data
Byte N
P
Table 16. Burst Mode I2C Read
S Chip
Address,
R/W = 0
AS Subaddress
High
AS Subaddress
Low
AS S Chip
Address,
R/W = 1
AS Data
Word 1,
Byte 1
AM Data
Word 1,
Byte 2
AM … P
S - Start Bit
P - Stop Bit
AM - Acknowledge by Master
AS - Acknowledge by Slave
AD1940/AD1941
Rev. B | Page 19 of 36
RAMS AND REGISTERS
Table 17. Control Port Addresses
SPI/ I2C Subaddress Register Name Read/Write Word Length
0–1023 (0x0000–0x03FF) Parameter RAM Write: 4 bytes, read: 4 bytes
1024–2559 (0x0400–0x09FF) Program RAM Write: 5 bytes, read: 5 bytes
2560–2623 (0x0A00–0x0A3F) Target/Slew RAM Write: 5 bytes, read: n/a
2624–2628 (0x0A40–0x0A44) Parameter RAM Data Safeload Registers 0–4 Write: 5 bytes, read: n/a
2629–2633 (0x0A45–0x0A49) Parameter RAM Indirect Address Safeload Registers 0–4 Write: 2 bytes, read: n/a
2634–2639 (0x0A4A–0x0A4F) Data Capture Registers 0–5 (Control Port Readback) Write: 2 bytes, read: 3 bytes
2640–2641 (0x0A50–0x0A51) Data Capture Registers (Digital Output) Write: 2 bytes, read: n/a
2642 (0x0A52) DSP Core Control Register Write: 2 bytes, read: 2 bytes
2643 (0x0A53) RAM Configuration Register Write: 1 byte, read: 1 byte
2644 (0x0A54) Serial Output Control Register 1 (Channels 0–7) Write: 2 bytes, read: 2 bytes
2645 (0x0A55) Serial Output Control Register 2 (Channels 8–15) Write: 2 bytes, read: 2 bytes
2646 (0x0A56) Serial Input Control Register Write: 1 byte, read: 1 byte
Table 18. RAM Read/Write Modes
Memory Size
Subaddress
Range Read Write
Burst Mode
Available Write Modes
Parameter RAM 1024 × 28 0–1023
(0x0000–0x03FF)
Yes Yes Yes Direct write1 or safeload write
Program RAM 1536 × 40 1024–2559
(0x0400–0x09FF)
Yes Yes Yes Direct write1
Target/Slew RAM 64 × 34 2560–2623
(0x0A00–0x0A3F)
No Yes (via
safeload)
Yes2 Safeload write
1 DSP core should be shut down first to avoid clicks/pops.
2 The target/slew RAMs need to be written through the safeload registers. Safeload writes may be done in either single write mode or burst mode.
CONTROL PORT ADDRESSING
Table 1 7 shows the addressing of the AD1940/AD1941’s RAM
and register spaces. The address space encompasses a set of
registers and three RAMs: one each for holding signal
processing parameters, holding the program instructions, and
ramping parameter values. The program and parameter RAMs
are initialized on power-up from on-board boot ROMs.
Table 1 8 shows the sizes and available writing modes of the
parameter, program, and target/slew RAMs.
PARAMETER RAM CONTENTS
The parameter RAM is 28 bits wide and occupies Addresses 0 to
1023. The parameter RAM is initialized to all 0s on power-up.
The data format of the parameter RAM is twos complement
5.23. This means that the coefficients may range from +16.0
(minus 1 LSB) to –16.0, with 1.0 represented by the binary word
0000 1000 0000 0000 0000 0000 0000.
Options for Parameter Updates
The parameter RAM can be written and read using one of the
two following methods.
1. Direct Read/Write. This method allows direct access to
the program and parameter RAMs. This mode of operation
is normally used during a complete new load of the RAMs,
using burst mode addressing. The clear register bit in the
core control register should be set to 0 using this mode to
avoid any clicks or pops in the outputs. Note that it is also
possible to use this mode during live program execution,
but since there is no handshaking between the core and the
control port, the parameter RAM is unavailable to the DSP
core during control writes, resulting in clicks and pops in
the audio stream.
2. Safeload Write. Up to five safeload registers can be loaded
with parameter RAM address/data. The data is then
transferred to the requested address when the RAM is not
busy. This method can be used for dynamic updates while
live program material is playing through the AD1940/
AD1941. For example, a complete update of one biquad
section can occur in one audio frame, while the RAM is
not busy. This method is not available for writing to the
program RAM or control registers.
The following sections discuss these two options in more detail.
AD1940/AD1941
Rev. B | Page 20 of 36
RECOMMENDED PROGRAM/PARAMETER
LOADING PROCEDURES
When writing large amounts of data to the program or para-
meter RAM in direct write mode, the processor core should be
disabled to prevent unpleasant noises from appearing at the
audio output. The AD1940/AD1941 contain several
mechanisms for disabling the core.
If the loaded program does not use the target/slew RAM as the
main system volume control (for example, the default power-up
program),
1. Assert Bit 9 (low to assert—default setting) and Bit 6 (high
to assert) of the core control register. This zeroes the
accumulators, the serial output registers, and the serial
input registers.
2. Fill the program RAM using burst mode writes.
3. Fill the parameter RAM using burst mode writes.
4. Assert Bit 7 of the core control register to initiate a data-
memory clear sequence. Wait at least 100 μs for this
sequence to complete. This bit is automatically cleared after
the operation is complete.
5. Deassert Bit 9 and Bit 6 of the core control register to allow
the core to begin normal operation
If the loaded program does use the target/slew RAM as the
main system volume control,
1. Assert Bit 12 of the core control register. This begins a
volume ramp down, with a time constant determined by
the upper bits of the target RAM. Wait for this ramp down
to complete (the user may poll Bit 13 of the core control
register, or simply wait for a given amount of time).
2. Assert Bit 9 (low to assert) and Bit 6 (high to assert) of the
core control register. This zeroes the accumulators, the
serial output registers, and the serial input registers.
3. Fill the program RAM using burst mode writes.
4. Fill the parameter RAM using burst mode writes.
5. Assert Bit 7 of the core control register to initiate a data-
memory clear sequence. Wait at least 100 μs for this
sequence to complete. This bit is automatically cleared after
the operation is complete.
6. Deassert Bit 9 and Bit 6 of the core control register.
7. If the newly loaded program also uses the target/slew
RAM, deassert Bit 12 of the core control register to begin a
volume ramp up procedure.
TARGET/SLEW RAM
The target/slew RAM is a bank of 64 RAM locations, each of
which can be set to autoramp from one value to a desired final
value in one of four modes.
Summary
The target/slew RAM is used by the DSP when a program is
loaded into the program RAM that uses one or more locations
in the slew RAM to access internal coefficient data. Typically,
these coefficients are used for volume controls or smooth cross-
fading effects, but may be used to update any value in the para-
meter RAM. Each of the 64 locations in the slew RAM are
linked to corresponding locations in the target RAM. When a
new value is written to the target RAM using the control
port, the corresponding slew RAM location begins to ramp
toward the target. The value is updated once per audio frame
(LRCLK period).
The target RAM is 34 bits wide. The lower 28 bits contain the
target data in 5.23 format for the linear and exponential
(constant dB and RC type) ramp types. For constant time
ramping, the lower 28 bits contain 16 bits in 2.14 format and
12 bits to set the current step. The upper six bits are used to
determine the type and speed of the ramp envelope in all
modes. The format of the data write for linear and exponential
formats is shown in Table 19. Table 20 shows the data write
format for the constant time ramping.
Data can only be written to the target/slew RAM using the
safeload registers as described in the Safeload Registers section.
A mute slew RAM bit is included in the core control register to
simultaneously set all the slew RAM target values to 0. This is
useful for implementing a global multichannel mute. When this
bit is deasserted, all slew RAM values return to their original
premuted states.
Table 19. Linear, Constant dB, and RC Type
Ramp Data Write
Byte 0 Byte 1 Bytes 2–4
000000, curve_type [1:0] time_const [3:0],
data [27:24]
Data [23:0]
Table 20. Constant Time Ramp Data Write
Byte 0 Byte 1 Bytes 2–4
000000,
curve_type [1:0]
update_step [0],
#_of_steps [2:0], data
[15:12]
Data [11:0],
reserved [11:0]
AD1940/AD1941
Rev. B | Page 21 of 36
The four ramping curve types are
• Linear—Value slews to target using a fixed step size.
• Constant dB—Value slews to target using the current value
to calculate the step size. The resulting curve has a
constant rise and decay when measured in dB.
• RC type—Value slews to target using the difference
between target and current values to calculate the step size,
producing a simple RC type curve for rising and falling.
• Constant Time—Value slews to the target in a fixed
number of steps in a linear fashion. The control port mute
has no affect on this type.
Table 21. Target/Slew RAM Ramp Type Settings
Setting Ramp Type
00 Linear
01 Constant dB
10 RC type
11 Constant time
The following sections detail how the control port writes to
the target/slew RAM to control the time constant and ramp
type parameters.
Ramp Types 1 to 3: Linear, Constant dB, RC Type (34-Bit
Write)
The target word for the first three ramp types is broken up into
three parts. The 34-bit command is written with six leading 0s
to extend the data write to five bytes. The parts of the target
RAM write are the following:
• Ramp Type (2 bits)
• Time Constant (4 bits)
0000 = Fastest
1111 = Slowest
• Data (28 Bits): 5.23 Format
Ramp Type 4—Constant Time (34-Bit Write)
The target word for the constant time ramp type is written in
five parts, with the 34-bit command again written with six
leading zeros to extend the data write to five bytes. The parts of
the constant time target RAM write are the following:
• Ramp Type (2 bits).
• Update Step (1 bit). Set to 1 when new target is loaded to
trigger step value update. Value is automatically reset after
the step value is updated.
• Number of Steps (3 bits). The number of steps that it takes
to slew to the target value is set by these three bits, with the
number of steps equal to 23-bit setting + 6.
000 = 64
001 = 128
010 = 256
011 = 512
100 = 1024
101 = 2048
110 = 4096
111 = 8196
• Data (16 bits). 2.14 format.
• Reserved (12 bits). When writing to the RAM, these bits
should all be set to 0.
Target and Slew RAM Initialization
On reset, the target/slew RAM initializes to preset values. The
target RAM initializes to a linear ramp type with a time
constant of 5 and the data set to 1.0. The slew RAM initializes to
a value of 1.0. These defaults give a full-scale (1.0 to 0.0) ramp
time of 21.3 ms.
Linear Update Math
Linear math is the addition or subtraction of a constant value
(step). The equation to describe this step size is
()
20
10
13
52
2
−×
=tconst
step
The result of the equation is normalized to a 5.23 data format.
This gives a time constant range from 6.75 ms to 213.4 ms
(–60 dB relative to 0 dB full scale). An example of this kind of
update is shown in Figure 15 and Figure 16. All slew RAM
figure examples, except the half-scale constant time ramp plot,
show an increasing or decreasing ramp between –80 dB and
0 dB (full scale). All figures except the constant time plots
(Figure 19 and Figure 21) use a time constant of 0x7 (0x0 being
the fastest and 0xF being the slowest).
TIME (ms)
OUTPUT LEVEL (V)
1
0.4
0.6
0.8
0.2
0
–0.4
–0.2
–1
–0.8
–0.6
0102030
04607-0-017
Figure 15. Slew RAM—Linear Update Increasing Ramp
AD1940/AD1941
Rev. B | Page 22 of 36
–1.0
–0.8
–0.6
–0.4
–0.2
0
0.2
0.4
0.6
0.8
1.0
3525155 TIME (ms)
OUTPUT LEVEL (V)
04607-029
2010030
Figure 16. Slew RAM—Linear Update Decreasing Ramp
Constant dB and RC Type (Exponential) Update Math
Exponential math is accomplished by shifts and adds with a
range from 6.1 ms to 1.27 s (–60 dB relative to 0 dB full scale).
When the ramp type is set to 01 (constant dB), each step size is
set to the current value in the slew data. When the ramp type
bits are set to 10 (RC type), the step sizes are equal to the
difference between the values in the target RAM and slew RAM.
Figure 17 and Figure 18 show examples of this type of
target/slew RAM ramping. A decreasing ramp of both the
constant dB and RC type ramps is a mirror image of the
constant dB increasing ramp, and is show in Figure 19.
04607-0-018
TIME (ms)
OUTPUT LEVEL (V)
1
0.8
0.6
0.4
0.2
0
–0.6
–0.4
–0.2
–0.8
–1 01052015 3025 35
Figure 17. Slew RAM—Constant dB Update Increasing Ramp
04607-0-019
TIME (ms)
OUTPUT LEVEL (V)
1
0.8
0.6
0.4
0.2
0
–0.6
–0.4
–0.2
–0.8
–1 3525155 201003
0
Figure 18. Slew RAM—RC Type Update Increasing Ramp
–1.0
–0.8
–0.6
–0.4
–0.2
0
0.2
0.4
0.6
0.8
1.0
TIME (ms)
OUTPUT LEVEL (V)
04607-030
3525155 2010030
Figure 19. Slew RAM—Constant dB and RC Type
Update Decreasing Ramp, Full Scale
04607-0-020
TIME (ms)
OUTPUT LEVEL (V)
1
0.8
0.6
0.4
0.2
0
–0.6
–0.4
–0.2
–0.8
–1 3525155 201003
0
Figure 20. Slew RAM—Constant Time Update Increasing Ramp, Full Scale
AD1940/AD1941
Rev. B | Page 23 of 36
04607-0-021
TIME (ms)
OUTPUT LEVEL (V)
1
0.8
0.6
0.4
0.2
0
–0.6
–0.4
–0.2
–0.8
–1 3525155 2010030
Figure 21. Slew RAM—Constant Time Update Increasing Ramp, Half Scale
–1.0
–0.8
–0.6
–0.4
–0.2
0
0.2
0.4
0.6
0.8
1.0
TIME (ms)
OUTPUT LEVEL (V)
04607-031
3525155 2010030
Figure 22. Slew RAM—Constant Time Update Decreasing Ramp, Full Scale
Constant Time Update Math
Constant time math is accomplished by adding a step value that
is calculated after each new target is loaded. The equation for
this step size is
Step = (Target D ata − Slew Data)/(Number of Steps)
Figure 20 shows a plot of the target/slew RAM operating in
constant time mode. For this example, 128 steps are used to
reach the target value. This type of ramping takes a fixed
amount of time for a given number of steps, regardless of the
difference in the initial state and the target value. Figure 21
shows a plot of a constant time ramp from –80 dB to –6 dB (half
scale) using 128 steps. You can see that the ramp takes the same
amount of time as the previous ramp from –80 dB to 0 dB. A
constant time decreasing ramp plot is shown in Figure 21.
SAFELOAD REGISTERS
Many applications require real time control of signal processing
parameters, such as filter coefficients, mixer gains, multichannel
virtualizing parameters, or dynamics processing curves. To
prevent instability from occurring, all of the parameters of a
biquad filter must be updated at the same time. Otherwise, the
filter could execute for one or two audio frames with a mix of
old and new coefficients. This mix could cause temporary
instability, leading to transients that could take a long time to
decay. To eliminate this problem, the AD1940/AD1941 load a
set of 10 registers in the control port (five for 28-bit parameters,
and another five for indirectly addressing the target/slew
RAMs) with the desired parameter or target/slew RAM address
and data. Five registers are used because a biquad filter uses five
coefficients and it is desirable to be able to do a complete
biquad update in one transaction. The safeload registers can be
used to update either the parameter RAM or target/slew RAM
values. Once these registers are loaded, the appropriate initiate
safe transfer bit (there are separate bits for parameter and
target/slew loads) in the core control register should be set to
initiate the loading into RAM. Program lengths should be
limited to 1,531 cycles (1,536 − 5) to ensure that the SigmaDSP
is able to perform the safeloads. It can be guaranteed that the
safeload will have occurred within one LRCLK period (21 μs at
fs = 48 kHz) of the initiate safe transfer bit being set.
The safeload logic automatically sends only those safeload regis-
ters that have been written to since the last safeload operation.
For example, if only two parameters are to be sent, only two of
the five safeload registers must be written to. When the initial
safe transfer bit (in the core control register) is asserted, only
those two registers are sent; the other three registers are not sent
to the RAM and can still hold old or invalid data.
Table 22. Data Capture Control Registers (2634–2641)
Register Bits Function
12:2 11-Bit program counter address
1:0 Register select
00 = Mult_X_input
01 = Mult_Y_input
10 = MAC_output
11 = Accum_fback
DATA CAPTURE REGISTERS
The AD1940/AD1941’s data capture feature allows the data at
any node in the signal processing flow to be sent to one of six
control port-readable registers or to a serial output pin. This can
be used to monitor and display information about internal
signal levels or compressor/limiter activity.
The AD1940/AD1941 contain six independent control port-
readable data capture registers, and two digital output
capture registers. The digital output registers are output on
SDATA_OUT7 when the data capture serial out enable bit
(Bit 14) is set in serial output Control Register 2. These reg-
isters are useful when debugging the signal processing flow.
For each of the data capture registers, a capture count and a
register select must be set. The capture count is a number
between 0 and 1,535 that corresponds to the program step
number where the capture occurs. The register select field
programs one of four registers in the DSP core that is
transferred to the data capture register when the program
AD1940/AD1941
Rev. B | Page 24 of 36
counter equals the capture count. The register select field
selections are shown in Table 23.
Table 23. Data Capture Output Register Select
Setting Register
00 Multiplier X input (Mult_X_input)
01 Multiplier Y input (Mult_Y_input)
10 Multiplier-Accumulator Output (MAC_out)
11 Accumulator Feedback (Accum_fback)
The capture count and register select bits are set by writing to
one of the eight data capture registers at the following
register addresses:
2634: Control Port Data Capture Setup Register 0
2635: Control Port Data Capture Setup Register 1
2636: Control Port Data Capture Setup Register 2
2637: Control Port Data Capture Setup Register 3
2638: Control Port Data Capture Setup Register 4
2639: Control Port Data Capture Setup Register 5
2640: Digital Out Data Capture Setup Register 0
2641: Digital Out Data Capture Setup Register 1
The captured data is in 5.19 twos complement data format for
all eight register select fields. The four LSBs are truncated from
the internal 5.23 data-word.
The data that must be written to set up the data capture is a
concatenation of the 11-bit program count index with the 2-bit
register select field. The capture count and register select values
that correspond to the desired point to be monitored in the
signal processing flow can be found in a file output from the
program compiler. The capture registers can be accessed by
reading from locations 2634 to 2639 (for control port capture
registers). The format for reading and writing to the data
capture registers can be seen in Table 32 and Table 33.
DSP CORE CONTROL REGISTER
The controls in this register set the operation of the AD1940/
AD1941’s DSP core. Bits 6 to 9 can be set to initiate a shutdown
of the core. The output is muted when this is performed, so it is
best to first assert the mute slew RAM bit (if slew RAM loca-
tions are used as volume controls in the program) to avoid a
click or pop when shutdown is asserted.
Slew RAM Muted (Bit 13)
This bit is set to 1 when the slew RAM mute operation has been
completed. This bit is read-only and is automatically cleared
by reading.
Mute Slew RAM, All Locations (Bit 12)
Setting this bit to 1 initiates a mute of all 64 slew RAM
locations. When reset to 0, all RAM locations return to their
previous state. This bit is only functional if slew RAM locations
are used in the custom program design. Keep in mind that the
AD1940/AD1941’s default program does not use any slew RAM
volume controls, so this bit has no effect in that case. The mute
operation is identical to writing all 0s to the data portion of the
target RAM, and therefore the time constant and linear/
exponential curve selection is determined by the bits that have
been previously written to the high bits of the target RAM.
Table 24. DSP Core Control Register (2642)
Register Bits Function
15:14 Reserved
13 Slew RAM muted (read-only)
12 Mute slew RAM, all locations
11 Reserved, set to 0
10 Use serial out LRCLK for output latch
9 Clear internal registers to all 0s, active low
8 Force multiplier to 0
7 Inititalize data memory with 0s
6 Mute serial input port
5 Initiate safe transfer to target RAM
4 Initiate safe transfer to parameter RAM
3:2 Input serial port to sequencer sync
00 = LRCLK
01 = LRCLK/2
10 = LRCLK/4
11 = LRCLK/8
1:0 Program length
00 = 1536
01 = 768
10 = 384
11 = 192
Use Serial Out LRCLK for Output Latch (Bit 10)
Normally, data is transferred from the DSP core to the serial
output registers at the end of each program cycle. In some cases
(for example, when the output sample rate is set to some
multiple of the input sampling rate), it is desirable to transfer
the internal core data multiple times during a single input audio
sample period. Setting this bit to 1 allows the output LRCLK
signal to control this data transfer rather than the internal end-
of-sequence signal. Operation in this mode may require custom
assembly language coding in the ADI graphical tools.
Clear Registers to All Zeros (Bit 9)
Setting this bit to 0 sets the contents of the accumulators and
serial output registers to 0. Like the other register bits, this one
powers up to 0. This means the AD1940/AD1941 power up in
clear mode and do not pass a signal until a 1 is written to this
bit. This is intended to prevent noise from inadvertently
occurring during the power-up sequence.
Force Multiplier to Zero (Bit 8)
When this bit is set to 1, the input to the DSP multiplier is set to
0, which results in the multiplier output being 0. This control
bit is included for maximum flexibility and is normally not
used.
AD1940/AD1941
Rev. B | Page 25 of 36
Initialize Data Memory with Zeros (Bit 7)
Setting this bit to 1 initializes all data memory locations to 0.
This bit is cleared to 0 after the operation is complete. This bit
should be asserted after a complete program/parameter
download has occurred to ensure click-free operation.
Zero Serial Input Port (Bit 6)
When this bit is set to 1, the 16 serial input channels are forced
to all 0s.
Initiate Safe Transfer to Target RAM (Bit 5)
Setting this bit to 1 initiates a safeload transfer to the target/slew
RAM. This bit clears when the operation is completed. Of five
safeload register pairs (address/data), only those registers that
have been written since the last safeload event are transferred.
Address 0 corresponds to the first target RAM location.
Initiate Safe Transfer to Parameter RAM (Bit 4)
Setting this bit to 1 initiates a safeload transfer to the parameter
RAM. This bit clears when the operation is completed. Of five
safeload registers pairs (address/data), only those registers that
have been written since the last safeload event are transferred.
Address 0 corresponds to the first parameter RAM location.
Input Serial Port to Sequencer Sync (Bits 3:2)
Normally, the internal sequencer is synchronized to the
incoming audio frame rate by comparing the internal program
counter with the edge of the LRCLK input signal. In some cases
the AD1940/AD1941 may be used to decimate an incoming
signal by some integer factor. In this case, it is desirable to
synchronize the sequencer to a submultiple of the incoming
LRCLK rate so more than one audio input sample is available to
the program during a single audio output frame. For example, if
these bits are set to 01 (LRCLK/2), a 96 kHz input can be used
with a 48 kHz output, allowing two consecutive input samples
to be processed during a single audio output frame. Operation
in this mode may require custom assembly language coding in
the ADI graphical tools.
Program Length (Bits 1:0)
96 kHz and 192 kHz Modes
These bits set the length of the internal program. The default
program length is 1,536 instructions for fS = 48 kHz, but the
program length can be shortened by factors of 2 to accom-
modate sample rates higher than 48 kHz. For fS = 96 kHz, the
program length should be set to 768 (01). For fS = 192 kHz, the
program length should be set to 384 steps (10). A program
length of 192 steps is available, but is not commonly used.
Low Power Mode
This setting can also be used to reduce the power consumption
of the AD1940/AD1941. If the program length is set to
768 steps and fS = 48 kHz instead of 96 kHz, then the power
consumption of the part is cut approximately in half.
Correspondingly, when the program length is set to 384 steps
with fS = 48 kHz, the power consumption is about ¼ of
what it is in normal operation with 1,536 program steps and
fS = 48 kHz.
Table 25. RAM Configuration Register (2643)
Register Bits Function
7:4 Reserved
3:0 RAM modulo, 1 LSB corresponds to
512 locations, max = 0b1100 (6 k words)
RAM CONFIGURATION REGISTER
The AD1940/AD1941 use a modulo RAM addressing scheme
to allow filters and other blocks to be coded easily without
requiring filter data to be explicitly moved during the filtering
operation. This is accomplished by adding the contents of an
address offset counter to the actual base address supplied in the
AD1940/AD1941’s cores. This address offset counter is incre-
mented automatically at the audio frame rate.
This method works well for most audio applications that
involve filtering. In some cases, however, it is desirable to have
direct access to the RAM, bypassing the autoincrementing
address offset counter. For this reason, the data memories in the
AD1940/AD1941 can be divided into modulo and nonmodulo
portions by programming the RAM configuration register
(Table 25). The address range from 0 to 512 × (RAM config-
uration register contents) is treated as modulo memory with
autoincrementing address offset registers. The maximum
setting of this register is the full size of the RAM, or 6,144 (6 k
words) data words. Note that addresses in this range
automatically wrap around the modulo boundary as set by the
register. This feature is not normally used with ADI supplied
blocks. For normal operation, this register may be left in its
default state, which sets up the entire RAM to use the
autoincrement feature. This feature is included for maximum
programming flexibility and may be used in the case of special
software development.
CONTROL PORT READ/WRITE DATA FORMATS
The read/write formats of the control port are designed to be
byte oriented. This allows easy programming of common
microcontroller chips. In order to fit into a byte-oriented
format, 0s are appended to the data fields before the MSB in
order to extend the data word to the next multiple of eight bits.
For example, 28-bit words written to the parameter RAM are
appended with four leading 0s to reach 32 bits (four bytes);
40-bit words written to the program RAM are not appended
with any 0s because it is already a full 5 bytes. These zero
extended data fields are appended to a 3-byte field consisting of
a 7-bit chip address, a read/write bit, and an 11-bit RAM/
register address. The control port knows how many data bytes
to expect based on the address that is received in the first three
bytes.
AD1940/AD1941
Rev. B | Page 26 of 36
The total number of bytes for a single location write command
can vary from four bytes (for a control register write), to eight
bytes (for a program RAM write). Burst mode may be used to
fill contiguous register or RAM locations. A burst mode write is
done by writing the address and data of the first RAM/register
location to be written. Rather than ending the control port
transaction (by bringing the CLATCH signal high in the
AD1940/AD1941, after the data word, as would be done in a
single address write, the next data word can be written
immediately without first writing its specific address). The
AD1940/AD1941 control ports autoincrement the address of
each write, even across the boundaries of the different RAMs
and registers.
Table 26. Parameter RAM Read/Write Format (Single Address)
Byte 0 Byte 1 Byte 2 Byte 3 Bytes 4–6
chip_adr [6:0], W/R 0000, param_adr [11:8] param_adr [7:0] 0000, param [27:24] param [23:0]
Table 27. Parameter RAM Block Read/Write Format (Burst Mode)
Byte 0 Byte 1 Byte 2 Byte 3 Bytes 4–6 Bytes 7-10 Bytes 11-141
chip_adr [6:0], W/R 0000, param_adr [11:8] param_adr [7:0] 0000, param [27:24] param [23:0] 0000, param [27:0] 0000, param
[27:0]
<—param_adr—> param_adr + 1 param_adr + 2
1 Burst mode data transfers can continue beyond the three words that are illustrated here in the same sequential word format. The register/RAM address auto-
increments until the data transfer reaches the IC's last address.
Table 28. Program RAM Read/Write Format (Single Address)
Byte 0 Byte 1 Byte 2 Bytes 3–7
chip_adr [6:0], W/R 0000, prog_adr [11:8] prog_adr [7:0] prog [39:0]
Table 29. Program RAM Block Read/Write Format (Burst Mode)
Byte 0 Byte 1 Byte 2 Bytes 3-7 Bytes 8-12 Bytes 13-171
chip_adr [6:0], W/R 0000, prog_adr [11:8] prog_adr [7:0] prog [39:0] prog [39:0] prog [39:0]
<—prog_adr—> prog_adr +1 prog_adr +2
1 Burst mode data transfers can continue beyond the three words that are illustrated here in the same sequential word format. The register/RAM address auto-
increments until the data transfer reaches the IC's last address.
Table 30. Control Register Read/Write Format (Core, Serial Out 0, Serial Out 1)
Byte 0 Byte1 Byte 2 Byte 3 Byte 4
chip_adr [6:0], W/R 0000, reg_adr [11:8] reg_adr [7:0] data [15:8] data [7:0]
Table 31. Control Register Read/Write Format (RAM Configuration, Serial Input)
Byte 0 Byte1 Byte 2 Byte 3
chip_adr [6:0], W/R 0000, reg_adr [11:8] reg_adr [7:0] data [7:0]
AD1940/AD1941
Rev. B | Page 27 of 36
Table 32. Data Capture Register Write Format
Byte 0 Byte 1 Byte 2 Byte 3 Byte 4
chip_adr [6:0], W/R 0000, data_capture_adr [11:8] data_capture_adr [7:0] 000, progcount [10:6]1 progcount [5:0]1, regsel [1:0]2
1 Progcount [10:0] = value of program counter where trap occurs (the table of values is generated by the program compiler).
2 Regsel [1:0] selects one of four registers (see Data Capture Registers section).
Table 33. Data Capture (Control Port Readback) Register Read Format
Byte 0 Byte 1 Byte 2 Bytes 3–5
chip_adr [6:0], W/R 0000, data_capture_adr [11:8] data_capture_adr [7:0] data [23:0]
Table 34. Safeload Register Data Write Format
Byte 0 Byte 1 Byte 2 Byte 3 Bytes 4–7
chip_adr [6:0], W/R 0000, safeload_adr [11:8] safeload_adr [7:0] 000000, data [33:32] data [31:0]
Table 35. Safeload Register Address Write Format
Byte 0 Byte 1 Byte 2 Byte 3 Byte 4
chip_adr [6:0], W/R 0000, safeload_adr [11:8] safeload_adr [7:0] 000000, param_adr [9:8] param_adr [7:0]
AD1940/AD1941
Rev. B | Page 28 of 36
SERIAL DATA INPUT/OUTPUT PORTS
The AD1940/AD1941’s flexible serial data input and output
ports can be set to accept or transmit data in 2-channel formats
or in an 8- or 16-channel TDM stream. Data is processed in
twos complement, MSB first format. The left channel data field
always precedes the right channel data field in the 2-channel
streams. In the TDM modes, Slots 0 to 3 (8-channel TDM) or
Slots 0 to 7 (16-channel TDM) fall in the first half of the audio
frame, and Slots 4 to 7 (or Slots 8 to 15 in 16-channel TDM) are
in the second half of the frame. The serial modes are set in the
serial output and serial input control registers.
The input control register allows control of clock polarity and
data input modes. The valid data formats are I2S , left-justified,
right-justified (24-, 20-, 18-, or 16-bit), 8-channel, and
16-channel TDM. In all modes except for the right-justified
modes, the serial port accepts an arbitrary number of bits up to
a limit of 24. Extra bits do not cause an error, but they are trun-
cated internally. Proper operation of the right-justified modes
requires that there be exactly 64 BCLKs per audio frame. The
TDM data is input on SDATA_IN2 and SDATA_IN3 when in
2 × 8-channel TDM mode, and on SDATA_IN2 in 16-channel
TDM mode. The LRCLK in TDM mode can be input to the
AD1940/AD1941 as either a 50/50 duty cycle clock or as a bit-
wide pulse.
The two clock domains on the serial output ports can generate
two separate 8-channel TDM streams or one 16-channel TDM
stream. When in 16-channel TDM mode, the data is clocked by
LRCLK_OUT0 and BCLK_OUT0. The AD1940/AD1941 must
be in slave mode for 16-channel TDM mode, unless the data is
sampled at 48 kHz; the parts cannot generate a TDM bit clock
that is fast enough to support 96 kHz or 192 kHz. In 8-channel
TDM mode, the AD1940/AD1941 can be masters for 48 kHz
and 96 kHz data, but not for 192 kHz data. Table 36 displays the
modes in which the serial output port will function.
The output control registers give the user control of clock
polarities, clock frequencies, clock types, and data format. In all
modes except for the right-justified modes (MSB delayed by 8,
12, or 16), the serial port accepts an arbitrary number of bits up
to a limit of 24. Extra bits do not cause an error, but are
truncated internally. Proper operation of the right-justified
modes requires the LSB to align with the edge of the LRCLK.
The default settings of all serial port control registers
correspond to 2-channel I2S mode. LRCLK_OUT0 and
BCLK_OUT0 are clocks for Serial Output Ports 0 to 7, and
LRCLK_OUT1 and BCLK_OUT1 Clock Ports 8 to 15.
All registers default to being set as all 0s. All register settings
apply to both master and slave modes unless otherwise noted.
Table 37 shows the proper configurations for standard audio
data formats.
Table 36. Serial Output Port Master/Slave Mode Capabilities
fS 2-Channel Modes (I2S, Left-Justified, Right-Justified) 8-Channel TDM 16-Channel TDM
48 kHz Master and slave Master and slave Master and slave
96 kHz Master and slave Master and slave Slave only
192 kHz Master and slave Slave only Slave only
Table 37. Data Format Configurations
Format LRCLK Polarity LRCLK Type BCLK Polarity MSB Position
I2S (Figure 23) Frame begins on
falling edge
Clock Data changes on falling edge Delayed from LRCLK edge by one BCLK
Left-Justified
(Figure 24)
Frame begins on
rising edge
Clock Data changes on falling edge Aligned with LRCLK edge
Right-Justified
(Figure 25)
Frame begins on
rising edge
Clock Data changes on falling edge Delayed from LRCLK edge by 8, 12, or 16 BCLKs
TDM with Clock
(Figure 26)
Frame begins on
falling edge
Clock Data changes on falling edge Delayed from start of word clock by one BCLK
TDM with Pulse
(Figure 27)
Frame begins on
rising edge
Pulse Data changes on falling edge Delayed from start of word clock by one BCLK
AD1940/AD1941
Rev. B | Page 29 of 36
Table 38. Serial Output Control Register 1
(Channels 0–7) (2644)
Bits Function
15 Dither enable
0 = Diabled
1 = Enabled
14 Internally link TDM streams into single,
16-channel stream
0 = Indepenent
1 = Linked
13 LRCLK polarity
0 = Frame begins on falling edge
1 = Frame begins on rising edge
12 BCLK polarity
0 = Data changes on falling edge
1 = Data changes on rising edge
11 Master/Slave
0 = Slave
1 = Master
10:9 BCLK frequency (master mode only)
00 = core_clock/24
01 = core_clock/12
10 = core_clock/6
11 = core_clock/3
8:7 Frame sync frequency (master mode only)
00 = core_clock/1536
01 = core_clock/768
10 = core_clock/384
6 Frame sync type
0 = LRCLK
1 = Pulse
5 Serial output/TDM mode control
0 = 8 Serial data outputs
1 = Enable TDM (8- or 16-channel) on
SDATA_OUT0
4:2 MSB position
000 = Delay by 1
001 = Delay by 0
010 = Delay by 8
011 = Delay by 12
100 = Delay by 16
101 Reserved
111 Reserved
1:0 Output word length, Channels 0–7
00 = 24 bits
01 = 20 bits
10 = 16 bits
11 = Reserved
Table 39. Serial Output Control Register 2
(Channels 8–15) (2645)
Bits Function
15 Dither enable
0 = Disabled
1 = Enabled
14 Data capture serial out enable
(Uses SDATA_OUT7)
0 = Disable
1 = Enable
13 LRCLK polarity
0 = Frame begins on falling edge
1 = Frame begins on rising edge
12 BCLK polarity
0 = Data changes on falling edge
1 = Data changes on rising edge
11 Master/Slave
0 = Slave
1 = Master
10:9 BCLK frequency (master mode only)
00 = core_clock/24
01 = core_clock/12
10 = core_clock/6
11 = core_clock/3
8:7 Frame sync frequency (master mode only)
00 = core_clock/1536
01 = core_clock/768
10 = core_clock/384
6 Frame sync type
0 = LRCLK
1 = Pulse
5 Serial output/TDM mode control
0 = 8 serial data outputs
1 = Enable TDM on SDATA_OUT4 (8-channel)
or SDATA_OUT0 (16-channel)
4:2 MSB position
000 = Delay by 1
001 = Delay by 0
010 = Delay by 8
011 = Delay by 12
100 = Delay by 16
101 Reserved
111 Reserved
1:0 Output word length, Channels 8–15
00 = 24 bits
01 = 20 bits
10 = 16 bits
11 = Reserved
AD1940/AD1941
Rev. B | Page 30 of 36
SERIAL OUTPUT CONTROL REGISTERS
Dither Enable (Bit 15)
Setting this bit to 1 enables dither on the appropriate channels.
Internally Link TDM Streams into Single 16-Channel Stream
(Bit 14, Serial Output Control Register 1)
When this bit is set to 1, the TDM output stream is output in a
single 16-channel stream on SDATA_OUT0. When set to 0,
TDM data is output on two independent 8-channel streams on
Pins SDATA_OUT0 and SDATA_OUT4.
Data Capture Serial Out Enable (Bit 14, Serial Output
Control Register 2)
When set to 1, SDATA_OUT7 is set as the output of the data
capture digital output registers (2640–2641). See the Data
Capture Registers section for a full explanation of this mode.
LRCLK Polarity (Bit 13)
When set to 0, the left channel data is clocked when LRCLK is
low, and the right data clocked when LRCLK is high. When set
to 1, this is reversed.
BCLK Polarity (Bit 12)
This bit controls on which edge of the bit clock the output data
is clocked. Data changes on the falling edge of BCLK_OUTx
when this bit is set to 0, and on the rising edge when this bit is
set at 1.
Master/Slave (Bit 11)
This bit sets whether the output port is a clock master or slave.
The default setting is slave; on power-up, Pins BCLK_OUTx
and LRCLK_OUTx are set as inputs until this bit is set to 1, at
which time they become clock outputs.
BCLK Frequency (Bits 10:9)
When the output port is being used as a clock master, these bits
set the frequency of the output bit clock, which is divided down
from the internal 73.728 MHz core clock.
Frame Sync Frequency (Bits 8:7)
When the output port is used as a clock master, these bits set
the frequency of the output word clock on the LRCLK_OUTx
pins, which is divided down from the internal 73.728 MHz
core clock.
Frame Sync Type (Bit 6)
This bit sets the type of signal on the LRCLK_OUTx pins.
When set to 0, the signal is a word clock with a 50% duty cycle;
when set to 1, the signal is a pulse with a duration of one bit
clock at the beginning of the data frame.
Serial Output/TDM Mode Control (Bit 5)
Setting this bit to 1 changes the output port from multiple serial
outputs to a single TDM output stream on the appropriate
SDATA_OUTx pin. This bit must be set in both serial output
control registers to enable 16-channel TDM on SDATA_OUT0.
MSB Position (Bits 4:2)
These three bits set the position of the MSB of data with respect
to the LRCLK edge. The data outputs of the AD1940/AD1941
are always MSB first.
Output Word Length (Bits 1:0)
These bits set the word length of the output data-word. All bits
following the LSB are set to 0.
Table 40. Serial Input Control Register (2646)
Register Bits Function
5 8-/16-channel TDM input
0 = Dual 8-channel TDM
1 = 16-channel TDM input
4 LRCLK polarity
0 = Frame begins on falling edge
1 = Frame begins on rising edge
3 BCLK polarity
0 = Data changes on falling edge
1 = Data changes on rising edge
2:0 Serial input mode
000 = I2S
001 = Left-justified
010 = TDM
011 = Right-justified, 24-bit
100 = Right-justified, 20-bit
101 = Right-justified, 18-bit
110 = Right-justified, 16-bit
SERIAL INPUT CONTROL REGISTER
8-/16-Channel TDM Input (Bit 5)
Setting this bit to 0 puts the AD1940/AD1941 into dual
8-channel TDM input mode, with the two streams coming
in on SDATA_IN2/TDM_IN1 and SDATA_IN3/TDM_IN0.
Channels 0 to 7 are input on TDM_IN0 and Channels 8 to 15
come in on TDM_IN1. Setting this bit to 1 puts the part in
16-channel TDM input mode, input on TDM_IN1.
LRCLK Polarity (Bit 4)
When set to 0, the left channel data on the SDATA_INx pins is
clocked when LRCLK_IN is low; the right input data clocked
when LRCLK_IN is high. When set to 1, this is reversed. In
TDM mode, when this bit is set to 0, data is clocked in starting
with the next appropriate BCLK edge (set in Bit 3 of this
register) that follows a falling edge on the LRCLK_IN pin.
When set to 1 and running in TDM mode, the input data is
valid on the BCLK edge following a rising edge on the word
clock (LRCLK_IN). The serial input port can also operate with
a pulse input signal, rather than a clock. In this case, the first
edge of the pulse is used by the AD1940/AD1941 to start the
data frame. When this polarity bit is set to 0, a low pulse should
be used, and a high pulse should be used when the bit it set to 1.
AD1940/AD1941
Rev. B | Page 31 of 36
BCLK Polarity (Bit 3)
This bit controls on which edge of the bit clock the input data
changes, and on which edge it is clocked. Data changes on the
falling edge of BCLK_IN when this bit is set to 0, and on the
rising edge when this bit is set at 1.
Serial Input Mode (Bits 2:0)
These two bits control the data format that the input port
expects to receive. Bits 3 and 4 of this control register override
the settings in Bits 2:0, so all four bits must be changed together
for proper operation in some modes. The clock diagrams for
these modes are shown in Figure 23, Figure 24, and Figure 25.
Note that for left-justified and right-justified modes the LRCLK
polarity is high, then low, which is opposite from the default
setting of Bit 4.
When these bits are set to accept a TDM input, the AD1940/
AD1941’s data starts after the edge defined by Bit 4. Figure 26
shows an 8-channel TDM stream with a high-to-low triggered
LRCLK and data changing on the falling edge of the BCLK. The
AD1940/AD1941 expects the MSB of each data slot delayed by
one BCLK from the beginning of the slot, just like in the stereo
I2S format. In 8-channel TDM mode, Channels 0 to 3 are in the
first half of the frame, and Channels 4 to 7 are in the second
half. When in 16-channel TDM mode, the first half-frame holds
Channels 0 to 7, and the second half-frame holds Channels 8 to
15. Figure 26 shows just one of the formats in which the
AD1940/AD1941 can operate in TDM mode. Please refer to the
Serial Data Input/Output Ports section for a more complete
description of the modes of operation. Figure 27 shows an
example of a TDM stream running with a pulse word clock,
which would be used to interface to ADI codecs in their
auxiliary mode. To work in this mode on either the input or
output serial ports, the AD1940/AD1941 should be set to frame
beginning on the rising edge of LRCLK, data changing on the
falling edge of BCLK, and MSB position delayed from the start
of the word clock by one BCLK.
Table 37 explains the clock settings for each of these formats.
LRCLK
BCLK
SDATA MSB
LEFT CHANNEL
LSB MSB
RIGHT CHANNEL
LSB
1 /FS
04607-0-023
Figure 23. I2S Mode—16 to 24 Bits per Channel
LRCLK
BCLK
SDATA
LEFT CHANNEL
MSB LSB MSB
RIGHT CHANNEL
LSB
1 /F
S
04607-0-024
Figure 24. Left-Justified Mode—16 to 24 Bits per Channel
LRCLK
BCLK
SDATA
LEFT CHANNEL
MSB LSB MSB
RIGHT CHANNEL
LSB
1 /F
S
04607-0-025
Figure 25. Right-Justified Mode—16 to 24 Bits per Channel
AD1940/AD1941
Rev. B | Page 32 of 36
LRCLK
BCLK
DATA SLOT 0 SLOT 1 SLOT 4 SLOT 5
32 BCLKs
MSB MSB–1 MSB–2
256 BCLKs
SLOT 2 SLOT 3 SLOT 6 SLOT 7
LRCLK
BCLK
DATA
04607-0-012
Figure 26. 8-Channel TDM Mode
LRCLK
SLOT 0 SLOT 1 SLOT 2 SLOT 3 SLOT 4 SLOT 5 SLOT 6 SLOT 7
CH
0
BCLK
SDATA MSB TDM
8TH
CH
32
BCLKs
MSB TDM
04607-0-022
Figure 27. TDM Mode with Pulse Word Clock
AD1940/AD1941
Rev. B | Page 33 of 36
INITIALIZATION
POWER-UP SEQUENCE
The AD1940/AD1941 have a built-in power-up sequence that
initializes the contents of all internal RAMs. During this time,
the contents of the internal program boot ROM are copied to
the internal program RAM memory and the parameter RAM
(all 0s) is filled with values from its associated boot ROM. The
default boot ROM program simply copies the serial inputs to
the serial outputs with no processing. The data memories are
also cleared during this time.
The boot sequence, which starts on the rising edge of the
RESETB pin, lasts for 8,192 cycles of the signal on the MCLK
pin at start-up. Assuming even the slowest possible signal on
this pin, a 64 × fS clock, the boot sequence still completes before
the PLL locks to the input clock. Since the boot sequence
requires a stable master clock, the user should avoid writing to
or reading from the registers until the MCLK input signal has
settled and the PLL has locked. The PLL takes approximately
3 ms to lock. Coming out of reset, the clock mode is imme-
diately set by the PLL_CTRL0, PLL_CTRL1, and PLL_CTRL2
pins. Reset is synched to the falling edge of the internal MCLK.
The power-up default signal processing flow in the AD1940/
AD1941 simply takes the eight inputs and copies these signals
to the 16 digital outputs, as shown in Figure 28.
04607-0-004
SDATA_IN0
SDATA_IN1
SDATA_IN2
SDATA_IN3
SDATA_OUT0
SDATA_OUT1
SDATA_OUT2
SDATA_OUT3
SDATA_OUT4
SDATA_OUT5
SDATA_OUT6
SDATA_OUT7
Figure 28. Default Program Signal Flow
SETTING MASTER CLOCK/PLL MODE
The AD1940/AD1941’s MCLK input feeds a PLL, which gen-
erates the 1536 × fS clock to run the DSP core. In normal
operation, the input to MCLK must be one of the following;
64 × fS, 256 × fS, 384 × fS, or 512 × fS, where fS is the input
sampling rate. The mode is set on PLL_CTRL0, PLL_CTRL1,
and PLL_CTRL2, according to Table 4 1. If the
AD1940/AD1941 are set to receive double-rate signals (by
reducing the number of program steps/sample by a factor of 2
using the core control register), then the master clock
frequencies must be either 32 × fS, 128 × fS, 192 × fS, or 256 × fS.
If the AD1940/AD1941 are set to receive quad rate signals (by
reducing the number of program steps/sample by a factor of 4
using the core control register), then the master clock
frequencies must be 16 × fS, 64 × fS, 96 × fS, or 128 × fS. On
power-up, a clock signal must be present on MCLK so that the
AD1940/AD1941 can complete their initialization routine. The
PLL can also run in bypass mode, where the clock present on
MCLK is fed directly to the
DSP core, although this setting is not recommended for
normal operation.
Table 41. PLL Modes
MCLK Input PLL_CTRL2 PLL_CTRL1 PLL_CTRL0
64 × fS 0 0 0
256 × fS 0 1 0
384 × fS X
1 X1 1
512 × fS 1 0 0
Bypass 1 1 0
1 X = don’t care
The clock mode should not be changed without also resetting
the AD1940/AD1941. If the mode is changed on the fly, a click
or pop may result on the outputs. The state of the PLL_CTRLx
pins should be changed while RESETB is held low.
VOLTAGE REGULATOR
The AD1940/AD1941 include an on-board voltage regulator
that allows the chip to be used in systems where a 2.5 V supply
is not available, but 3.3 V or 5 V is. The only external
components needed for this are a PNP transistor such as a
ZX5T953G, a single capacitor, and a single resistor. The
recommended design for the voltage regulator is shown in
Figure 29. The 10 μF and 100 nF capacitors shown in this
schematic are recommended for bypassing, but are not
necessary for operation. Here, VDD is the main system voltage
(3.3 V or 5 V) and should be connected to VSUPPLY. 2.5 V is
generated at the transistor’s collector, which is connected to the
VDD pins, PLL_VDD and VSENSE. The reference voltage on
VREF is 1.15 V and is generated by the regulator. A 1 nF
capacitor should be connected between this pin and ground.
VDRIVE is connected to the base of the PNP transistor. A 1 kΩ
resistor should be connected between VDRIVE and VSUPPLY.
10μF10μF
100nF 100nF
1nF
1kΩ
AD1940/AD1941
DVDD
ZX5T953G
04607-0-009
VSUPPLY
VREF
VDRIVE
VSENSE
VDD
++
PLL_VDD
Figure 29. Voltage Regulator Design
AD1940/AD1941
Rev. B | Page 34 of 36
There are two specifications that should be taken into
consideration when choosing a regulator transistor. First, the
transistor’s current amplification factor (hFE or beta) should be
at least 100. Second, the transistor’s collector needs to be able to
dissipate the heat generated when regulating from 3.3 V or 5 V
to 2.5 V. The maximum current draw of the AD1940/AD1941 is
163 mA (maximum digital current + maximum PLL current).
The equations for the minimum power dissipation specs for
both 3.3 V and 5 V follow:
(5 V – 2.5 V) × 163 mA = 480 mW
(3.3 V – 2.5 V) × 163 mA = 130 mW
If the regulator is not used in the design, VREF, VDRIVE, and
VSENSE can be tied to ground. VSUPPLY should be connected
to the same or higher potential as the VDD pin.
AD1940/AD1941
Rev. B | Page 35 of 36
OUTLINE DIMENSIONS
COMP LI ANT TO JE DE C S TANDARDS MS-026-BBC
TOP VIEW
(PINS DOWN)
1
12 13 25
24
36
37
48
0.27
0.22
0.17
0.50
BSC
LEAD P ITCH
1.60
MAX
0.75
0.60
0.45
VIEW A
PIN 1
0.20
0.09
1.45
1.40
1.35
0.08
COPLANARITY
VIEW A
RO TAT E D 90° CCW
SEATING
PLANE
7°
3.5°
0°
0.15
0.05
9.20
9.00 S Q
8.80
7.20
7.00 SQ
6.80
051706-A
Figure 30. 48-Lead Low-Profile Quad Flat Package [LQFP]
(ST-48)
Dimensions shown in millimeters
ORDERING GUIDE
Model1 Temperature Range Package Description Package Option
AD1940YSTZ –40°C to +105°C 48-Lead LQFP ST-48
AD1940YSTZRL –40°C to +105°C 48-Lead LQFP, 13” Tape and Reel ST-48
AD1941YSTZ –40°C to +105°C 48-Lead LQFP ST-48
AD1941YSTZRL –40°C to +105°C 48-Lead LQFP, 13” Tape and Reel ST-48
Eval-AD1940AZ Evaluation Board
Eval-AD1940MINIBZ Evaluation Board
1 Z = RoHS Compliant Part.
AD1940/AD1941
Rev. B | Page 36 of 36
NOTES
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Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips.
©2004–2010 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D04607-0-4/10(B)
