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ACS8525 LC/P
ADVANCED COMMUNICATIONS FINAL
Line Card Protection Switch for
SONET/SDH Systems
ADVANCED COMMUNICATIONS FINAL DATASHEET
The ACS8525 is a highly integrated, single-chip solution
for “Hit-less” protection switching of SEC (SDH/SONET
Equipment Clock) + Sync clock “Groups”, from Master
and Slave SETS clock cards and a third (Stand-by) source,
for Line Cards in a SONET or SDH Network Element. The
ACS8525 has fast activity monito rs on the SEC clock
inputs and will implement automatic system protec tion
switching against the Master clock failure. The selection
of the Master/Slave input can be forced by a Force Fast
Switch pin. If both the Master and Slave input clocks fail,
the Stand-by “Group” is selected or, if no Stand-by is
available, the device enters Digital Holdover mode.
The ACS8525 can perform frequency translation,
converting, for example, an 8 kHz SEC input clock from a
backplane into a 155.52 MHz clock for local line cards.
Master and Slave SEC inputs to the device support
TTL/CMOS and PECL/LVDS. The Stand-by SEC and three
Sync inputs are TTL/CMOS only.
The ACS8525 generates two SEC clock outputs, via one
PECL/LVDS and one TTL/CMOS port, with spot
frequencies from 2 kHz up to 311.04 MHz (up to 155.52
MHz on the TTL/CMOS port). It also provides an 8 kHz
Frame Sync and a 2 kHz Multi-Frame Sync signal output
with programmable pulse width and polarity.
The ACS8525 includes a Serial Port, whic h can be SPI
compatible, providing access to the configuration and
status registers for device setup.
IEEE 1149.1 JTAG B o undary Scan is supported.
SONET/SDH applications up to OC-3/STM-1 bit rates
Switches between grouped inputs (SEC/Sync pairs)
Inputs: three SECs at any of 2, 4, 8 kHz (and N x 8 kHz
multiples up to 155.52 MHz), plus Frame Sync/Multi-
Frame Sync
Outputs: two SEC clocks at any of several spot
frequencies from 2 kHz up to 77.76 MHz via the
TTL/CMOS port and up to 311.04 MHz via the
PECL/LVDS port
Selectable clock I/O port technologies
Modes for E3/DS3 and multiple E1/DS1 rate output
clocks
Frequency translation of SEC input clock to a different
local line card clock
Robust input clock source activity monitoring on all
inputs
Supports Free-run, Locked and Digital Holdover
modes of operation
Automatic “Hit-less” source switchover on loss of
input
External force fast swit ch be t ween SEC1/S E C2 i np uts
Phase Build-out for output clock phase continuity
during input switchover
PLL “Locked” and “Acquisition” bandwid ths
individually selectable from 18, 35 or 70 Hz
Serial interface for device set-up
Single 3.3 V operation, 5 V I/O compatible
Operating temperature (ambient) of -40 to +85°C
Available in LQFP 64 package
Lead (Pb)-free version available (ACS8525T), RoHS
and WEEE compliant
Figure 1 Block Diagram of the ACS8525 LC/P
Block Diagram
Description Features
IEEE
1149.1
JTAG
Chip
Clock
Generator
TCK
TDI
TMS
TRST
TDO
F8525D_001BLOCKDIA_05
Selector
DPLL1 DPLL2
E1/DS1
Synthesis
APLL2
APLL3 APLL 1
01 and 02:
E1/DS1 (2.048/1.544 MHz)
and frequency multiples:
1.5x, 2x, 3x, 4x, 6x, 12x,
16x, and 24x E1/DS1
E3/DS3, 2 kHz, 8 kHz.
and OC-N* rates: OC-1 51.84 MHz
OC-3 155.52 MHz and derivatives:
6.48 MHz (O2 port only)
19.44 MHz, 25.92 MHz,
38.88 MHz, 51.84 MHz, 77.76 MHz,
155.52 MHz (01 port only)
311.04 MHz (01 port only)
3 x SEC/Sync Input Groups
SEC1 & SEC2:
T
TL/PECL/LVDS,
SEC3 and all Syncs
T
TL only
SEC Inputs:
Programmable
Frequencies
2 kHz, 4 kHz,
N x 8 kHz
1.544/2.048 MHz
6.48 MHz
19.44 MHz
25.92 MHz
38.88 MHz
51.84 MHz
77.76 MHz
155.52 MHz
FrSync 8 kHz (TTL)
Output
Port
Frequency
Selection
Priority
Table Register Set
Digital Feedback
Serial Interface
Port
TCXO or
XO
Input
SEC Port
Monitors
and
Input
Selection
Control
Master
Slave
Stand-by
01 (PECL/LVDS)
02 (TTL)
MFrSync 2 kHz (TTL)
SEC Outputs:
Sync Outputs:
SEC1
SYNC1
SEC2
SYNC2
SEC3
SYNC3
MUX
2
MUX
1
Table of Contents
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ACS8525 LC/P
Section Page
ADVANCED COMMUNICATIONS FINAL DATASHEET
Description................................................................................................................................................................................................. 1
Block Diagram............................................................................................................................................................................................ 1
Features..................................................................................................................................................................................................... 1
Table of Contents ...................................................................................................................................................................................... 2
Pin Diagram ............................................................................................................................................................................................... 4
Pin Description ........................................................................................................................................................................................... 5
Introduction................................................................................................................................................................................................ 7
General Description.......... ................. ............................... ............................... ................. ......................................................................... 7
Inputs..................................................................................................................................................................................................7
Preconfiguring Inputs................................... ............................... ............................... .............................................................. 8
PECL/LVDS Input Port Selection.................................... ................................ ......................................................................... 9
Input Locking Frequency Modes............................................................................................................................................. 9
Input SEC Activity Monitors...............................................................................................................................................................9
Leaky Bucket Accumulator........................................................................................................................................... ........ 10
Fast Activity Monitor.................................................................................................................................. ............................ 11
Selector............................................................................................................................................................................................11
Selection of Input SECs.............................................. ............................... ............................... ............................... .............. 11
External Protection Switching Mode-SRCSW pin............................................................................................... ................. 13
Output Clock Phase Continuity on Source Switchover ....................................................................................................... 13
Forcing of the Operating Mode of the Device........................................................................................................... ........... 13
Phase Locked Loops (PLLs)...........................................................................................................................................................13
PLL Overview ................................................................................................................................................................. ........ 13
PLL Architecture........................................................................................................................................... ......................... 14
PLL Operational Controls............................................................................................................................... ....................... 17
Phase Compensation Functions .................................................................................................................................... ...... 19
DPLL Feature Summary................................................................................................................................. ....................... 20
Outputs............................................................................................................................................................................................22
PECL/LVDS Output Port Selection........................................................................................................... ............................ 22
Output Freq uency Selection and PLL Configuration........................................................................................................... 22
Operating Modes (States) of the Device.......................................................................................................................................30
Free-run Mode.................................................................................................................... ............................... .................... 30
Pre-locked Mode ...................................................................................................................... ............................... .............. 30
Locked Mode................. ............................... ............................... ............................... ............................ ............................... 30
Lost-phase Mode........................................................................................................................................................ ........... 30
Digital Holdover Mode......................................................................................................................... ................. ................. 30
Pre-locked2 Mode.................... ............................... ............................... .......................................... ............................... ...... 32
Local Oscillator Clock......................................................................................................................................................................32
Status Reporting and Phase Measurement..................................................................................................................................32
Input Status Interrupts.............................................................................................................................. ............................ 32
Input Status Information............................................................................................................. .................................. ........ 32
DPLL Frequency Reporting............................................................................................................................... ................. ... 32
Measuring Phase Between Master and Slave/Stand-by SEC Sources...................................... ....................................... 33
Sync Reference Sources .................. ............................... ............................... ................................................................................33
Aligning Phase of MFrSync and FrSync Outputs to Phase of Sync Inputs......................................................................... 34
Power-On Reset...............................................................................................................................................................................35
Serial Interface................................................................................................................................................................................35
Register Map........................................................................................................................................................................................... 38
Register Organization.....................................................................................................................................................................38
Multi-word Registers................................................................................................................ ............................... .............. 38
Register Access....................................................................................................................................................... .............. 38
Interrupt Enable and Clear............................................................................................................................... .................... 38
Defaults..................................................................................................................................... ............................... .............. 38
Register Descriptions............................................................................................................................................................................. 42
Table of Contents
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ACS8525 LC/P
Section Page
ADVANCED COMMUNICATIONS FINAL DATASHEET
Electrical Specifications......................................................................................................................................................................... 98
JTAG.................................................................................................................................................................................................98
Over-voltage Protection..................................................................................................................................................................98
ESD Protection........................................ ............................... ............................... ..........................................................................98
Latchup Protection...................... ............................... ............................... ......................................................................................98
Maximum Ratings...........................................................................................................................................................................99
Operating Conditions......................................................................................................................................................................99
DC Characteristics ..........................................................................................................................................................................99
Jitter Performance .......................................... ............................... ............................... ................................................................103
Input/Output Timing.....................................................................................................................................................................105
Package Information....................................... ............................... ............................... ............................ ............................... ............ 106
Thermal Conditions.......................................................................................................................................................................107
Application Information................................................................................................................................................. ....................... 108
References........................................................................................................................ ............................... ............................... ...... 109
Abbreviations.................................................................................................................................. ................. ............................... ...... 109
Notes................................................................................................................................................................ ............................... ...... 110
Trademark Acknowledgements............................................................................................................................................... ............ 110
Revision Status/History ......................................................................................................................... ............................... ............... 11 1
Ordering Information............................................ ............................... ................. ............... ................ ............................... .................. 112
Disclaimers....................................................................................................................................................................................112
Contact Information for Semtech International AG................................................................................................................... ......... 112
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ACS8525 LC/P
Figure 2 ACS8525 Pin Diagram Line Card Protection Switch for SONET/SDH Systems
Pin Diagram
F8525D_002PINDIAG_02
1 AGND1
2 IC1
3 AGND2
4 VA1+
5 INTREQ
6 REFCLK
7 DGND1
8 VD1+
9 VD2+
10 DGND2
11 DGND31
12 VD3+
13 SRCSW
14 VA2+
15 AGND3
16 IC2
48 PORB
47 SCLK
46 VDD6
45 VDD5
44 CSB
43 SDI
42 CLKE
41 TMS
40 DGND5
39 VDD4
38 VDD3
37 TRST
36 VDD2
35 SYNC3
34 SEC3
33 SYNC2
17 FrSync
18 MFrSync
19 O1POS
20 O1NEG
21 GND_DIFF
22 VDD_DIFF
23 SEC1POS
24 SEC1NEG
25 SEC2POS
26 SEC2NEG
27 VDD5V
28 SYNC1
29 SEC1
30 SEC2
31 DGND4
32 VDD1
64 SONSDHB
63 IC6
62 IC5
61 IC4
60 IC3
59 NC2
58 AGND4
57 VA3+
56 O2
55 NC1
54 VDD7
53 DGND6
52 SDO
51 TDI
50 TDO
49 TCK
ACS8525
LC/P
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ACS8525 LC/P
Note...I = Input, O = Output, P = Power, TTLU = TTL input with pull-up resistor, TTLD = TTL input with pull-down resistor.
Pin Description
Table 1 Power Pins
Pin Number Symbol I/O Type Description
8, 9,
12 VD1+, VD2+,
VD3+ P - Supply Voltage: Digital supply to gates in analog section, +3.3 Volts
±10%.
22 VDD_DIFF P - Supply Voltage: Digital suppl y for differential output pins 19 and 20,
+3.3 Volts ±10%.
27 VDD5V P - Digital Supply for +5 Volts Tolerance to Input Pins. Connect to +5 Volts
(±10%) for clamping to +5 Volts. Connect to VDD for clamping to
+3.3 Volts. Leave floating for no clamping. Input pins tolerant up to
+5.5 Volts.
32, 36,
38, 39,
45, 46,
54
VDD1, VDD2,
VDD3, VDD4,
VDD5, VDD6,
VDD7
P - Supply Voltage: Digital supply to logic, +3.3 Volts ±10%.
4 VA1+ P - Supply Voltage: Analog supply to clock multiplying PLL,
+3.3 Volts ±10%.
14, 57 VA2+, VA3+ P - Supply Voltage: Analog supply to output PLLs APLL2 and APPL1,
+3.3 Volts ±10%.
15, 58 AGND3, AGND4 - Supply Ground: Analog ground for output PLLs APLL2 and APPL1.
7, 10,
11 DGND1, DGND2,
DGND3 P - Supply Ground: Digital ground for components in PLLs.
31, 40,
53 DGND4, DGND5,
DGND6 P - Supply Ground: Digital ground for logic.
21 GND_DIFF P - Supply Ground: Digital ground for differential ports.
1, 3 AGND1, AGND2 P - Supply Ground: Ana log grounds.
Table 2 Internally Connected
Pin Number Symbol I/O Type Description
2, 16, 60, 61,
62, 63 IC1, IC2, IC3, IC4,
IC5, IC6, - - Internally Connected: Leave to float.
55, 59 NC1, NC2 - - Not Connected: Leave to float.
Table 3 Other Pins
Pin Number Symbol I/O Type Description
5 INTREQ O TTL/CMOS Interrupt Request: Active High/Low software Interrupt output.
6 REFCLK I TTL Reference Clock: 12.800 MHz (refer to section headed Local Oscillator
Clock).
13 SRCSW I TTLDSource Switching: Force Fast Source Switching on SEC1 and SEC2.
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ACS8525 LC/P
17 FrSync O TTL/CMOS Output Reference: 8 kHz Frame Sync output.
18 MFrSync O TTL/CMOS Output Reference: 2 kHz Multi-Frame Sync output.
19,
20 O1POS,
O1NEG O LVDS/PECL Output Reference: Programmable, default 38.88 MHz, LVDS.
23,
24 SEC1_POS,
SEC1_NEG I PECL/LVDS Input Reference: Programmable, default 19.44 MHz, PECL.
25,
26 SEC2_POS,
SEC2_NEG I PECL/LVDS Input Reference: Programmable, default 19.44 MHz PECL.
28 SYNC1 I TTLD(Master) Multi-Frame Sync 2kHz Input: Connect to 2 or 8 kHz
Multi-Frame Sync output of Master SETS.
29 SEC1 I TTLD(Master) Input Reference: Prog ra mma bl e, defa u lt 8 kHz .
30 SEC2 I TTLD(Slave) Input Reference: Programmable, default 8 kHz.
33 SYNC2 I TTLD(Slave) Multi-Frame Sync 2 kHz: Connect to 2 or 8 kHz Multi-Frame Sync
output of Slave SETS.
34 SEC3 I TTLD(Stand-by) Input Reference: External stand-by reference clock source,
programmable, default 19.44MHz.
35 SYNC3 I TTLD(Stand-by) Input Reference: External stand-by 2 or 8 kHz Multi-Frame
Sync clock source.
37 TRST I TTLDJTAG Control Reset Input: TRST = 1 to enable JTAG Boundary Scan
mode. TRST = 0 is Boundary Scan stand-by mode, still allowing normal
device operation (JTAG logic transparent). NC if not used.
41 TMS I TTLDJTAG Test Mode Select: Boundary Scan enable. Sampled on rising edge
of TCK. NC if not used.
42 CLKE I TTLDSCLK Edge Select: SCLK active edge select, CLKE = 1, selects falling
edge of SCLK to be active.
43 SDI I TTLDSerial Interface Address: Serial Data Input.
44 CSB I TTLUChip Select (Active Low): This pin is asserted Low by the microproc essor
to enable the microprocessor interface.
47 SCLK I TTLDSerial Data Clock. When this pin goes High data is latched from SDI pin.
48 PORB I TTLUPower-On Reset: Master reset. If PORB is forced Low, all internal states
are reset back to default values.
49 TCK I TTLDJTAG Clock: Boundary Scan clock input.
50 TDO O TTL/CMOS JTAG Output: Serial test data output. Updated on falling edge of TCK.
51 TDI I TTLDJTAG Input: Serial test data Input. Sampled on rising edge of TCK.
52 SDO O TTLDInterface Address: SPI compatible Ser ial Data Output.
56 O2 O TTL/CMOS Output Reference: Programmable, default 19.44 MHz.
64 SONSDHB I TTLDSONET or SDH Frequency Select: Sets the initial power-up state (or
state after a PORB) of the SONET/SDH frequency selection registers,
Reg. 34, Bit 2 and Reg. 38, Bit 5, Bit 6 and Reg. 64 Bit 4. When set Low,
SDH rates are selected (2.048 MHz etc.) and when set High, SONET
rates are selected (1.544 MHz etc.) The register states can be changed
after power-up by software.
Table 3 Other Pins (cont...)
Pin Number Symbol I/O Type Description
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ACS8525 LC/P
The ACS8525 is a highly integrated, single-chip solution
for “Hit-less” protection switching of SEC + Sync clock
“Groups”, from M aster and Slav e SETS cloc k cards and a
third (Stand-by) source, for Line Cards in a SONET or SDH
Network Element. The ACS8525 has fast activity monitors
on the SEC clock inputs and will implement automatic
system protection switching against failure of the
selected clock. The selection of the Master/Slave input
can be forced by a Force Fast Switch pin. The Stand-by
“Group” is selected if both the Master and Slave input
clocks fail, or, if not available, the device enters a Digital
Holdover mode.
Digital Phase Locked Loop (DPLL) and Direct Digital
Synthesis (DDS) methods are used in the device so that
the overall PLL characteristics are very stable and
consistent compared to traditional analog PLLs.
The ACS8525 has three SEC/SYNC input groups from
which it can select any group as input. It generates
independent clocks on outputs 01 and 02, with a total of
53 possible output frequencies, and generates two Sync
outputs on outputs FrSync and MFrSync: 8 kHz Frame
Synchronization (FrSync) signal and 2 kHz Multi-Frame
Synchronization (MFrSync) signal.
The device has three main operating modes (states);
Free-run, Locked, or Digital Holdover. In Free-Run mode,
the ACS8525 generates a stable, low-noise clock signal at
a frequency to the same accuracy as the external
oscillator, or it can be made more accurate via software
calibration to within ±0.02 ppm. In Locked mode, the
ACS8525 selects the most appropriate of the three input
SECs and generates a stable, low-noise clock signal
locked to the selected reference. In Digital Holdover
mode, the ACS8525 generate s a stable, low-noise clock
signal, adjusted to match the frequency of the last
selected SEC.
One key architectural advant age that the ACS8525 has
over traditional solutions is in the use of DPLL technology
for precise and repeatable performance over temperature
or voltage variations and between parts. The overall PLL
bandwidth, loop damping, pull-in range and frequency
accuracy are all determined by digital parameters that
provide a consistent level of performance. An Analog PLL
(APLL) takes the signal from the DPLL output and provides
a lower jitter output. The APLL bandwidth is set four orders
of magnitude higher than the DPLL bandwidth. This
ensures that the overall system performance still
maintains the advantage of consistent behavior provided
by the digital approach.
The DPLLs are clocked by the external Oscillator module
(TCXO or XO) so that the Free-run or Digital Holdover
frequency stability is only determined by the stability of
the external oscillator module. This second key advantage
confines all temperature critical components to one well
defined and pre-calibrated module, whose performance
can be chosen to match the application.
All performance parameters of the DPLLs are
programmable without the need to understand detailed
PLL equations. Bandwidth, damping factor and lock range
can all be set directly.
The ACS8525 includes an SPI compatible serial interface
port, providing access to the configuration and status
registers for device setup, external control and
monitoring. The device is primarily controlled according to
values in this Register block.
Each register (8-bit wide data field) is identified and
referred to by its two-digit hexadecimal address and
name, e.g. Reg. 7D cnfg_interrupt. The “Register Map” on
page 38 summarizes the content of all of the registers,
and each register is individually described in the
subsequent Register Tables, organized in order of
ascending Address (hexadecimal), in the “Register
Descriptions” from page 42 onwards.
An Evaluation Board and intuitive GUI-based software
package is available for this device to help designers
learn how to use the ACS8525 and rapidly configure the
device for particular applications. This has its own
documentation: “ACS8525 -EVB”.
The following description refers to the Block Diagram
(Figure 1 on page 1).
Inputs
The ACS8525 SETS device has input ports for input clock
groups from three sources, typically Maste r, Slave and
Stand-by, where each clock group comprises one SEC and
optionally one Sync signal. This is so that when any SEC
input changeover is made, the corresponding Sync signal
changeover is also made.
TTL/CMOS and PECL/LVDS ports are prov ided for the
Master and Slave SEC inputs to the device. The Stand-by
SEC input and three Frame Sync/Multi-frame Sync inputs
to the device are via TTL Ports. All the TTL/CMOS parts are
3 V and 5 V compatible (with clamping if required by
connecting the VDD5V pin). Refer to the “Electrical
Introduction
General Description
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ACS8525 LC/P
Specifications” on page 98 for more information on
electrical compatibility.
Input frequencies supported range from 2 kHz to
155.52 MHz. Common E1, DS1, OC-3 and sub-divisions
are supported as spot frequencies that the DPLLs will
directly lock to. Any input frequency, up to 100 MHz, that
is a multiple of 8 kHz can also be locked to via an inbuilt
programmable divider.
Preconfiguring Inputs
Each input device has to be preconfigured with:
zExpected input frequency cnfg_ref_source_frequency
register (Reg. 22 to 25 and Reg. 28)
zTechnology (TTL or PECL/LVDS) where applicable, via
cnfg_differential_inputs (Reg. 36)
zSelection Priority (Reg. 19, 1A and 1C).
Table 4 gives details of the input reference ports, showing
the input technologies and the range of frequencies
supported on each port; the default spot frequencies and
default priorities assigned to each port on power-up or by
reset are also shown.
SDH and SONET networks use different default
frequencies; the network type is selectable using the
cnfg_input_mode Reg. 34 Bit 2, ip_sonsdhb.
zFor SONET, ip_sonsdhb = 1
zFor SDH, ip_sonsdhb = 0
On power-up or by reset, the default will be set by the state
of the SONSDHB pin (pin 64). Specific frequencies and
priorities are set by configuration.
The frequency selection is programmed via the
cnfg_ref_source_frequency register (Reg. 22 - Reg. 28).
Notes: (i) TTL ports (compatible also with CMOS signals) support clock speeds up to 100 MHz, with the highest spot frequency being
77.76 MHz. The actual spot frequencies are: 2 kHz, 4 kHz, 8 kHz (and N x 8 kHz), 1.544 MHz (SONET)/2.048 MHz (SDH), 6.48 MHz,
19.44 MHz, 25.92 MHz, 38.88 MHz, 51.84 MHz, 77.76 MHz. SONET or SDH input rate is selected via Reg. 34 Bit 2, ip_sonsdhb).
(ii) PECL and LVDS ports support the spot clock frequencies listed above plus 155.52 MHz (and 311.04 MHz for Output O1 only).
(iii) SEC1 TTL and SEC2 TTL ports are on pins SEC1 and SEC2. SEC1 DIFF (Differential) port uses pins SEC1POS and SEC1NEG, similarly
SEC2DIFF uses pins SEC2POS and SEC2NEG.
Table 4 Input Reference Source Selection and Priority Table
Port Name Channel
Number (Bin) Input Port
Technology Frequencies Supported Default
Priority
SEC1 TTL 0011 TTL/CMOS Up to 100 MHz (see Note (i))
Default (SONET): 8 kHz Default (SDH): 8 kHz 2
SEC2 TTL 0100 TTL/CMOS Up to 100 MHz (see Note (i))
Default (SONET): 8 kHz Default (SDH): 8 kHz 3
SEC1 DIFF 0101 PECL/LVDS
PECL default Up to 155.52 MHz (see Note (ii))
Default (SONET): 19.44 MHz Default (SDH): 19.44 MHz 0
SEC2 DIFF 0110 PECL/LVDS
PECL default Up to 155.52 MHz (see Note (ii))
Default (SONET): 19.44 MHz Default (SDH): 19.44 MHz 0
SYNC1 0111 TTL/CMOS 2/4/8 kHz auto-sensing n/a
SYNC2 1000 TTL/CMOS 2/4/8 kHz auto-sensing n/a
SEC3 1001 TTL/CMOS Up to 100 MHz (see Note (i))
Default (SONET): 19.44 MHz Default (SDH): 19.44 MHz 4
SYNC3 1010 TTL/CMOS 2/4/8 kHz auto-sensing n/a
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ACS8525 LC/P
PECL/LVDS Input Port Selection
The choice of PECL or LVDS compatibility is programmed
via the cnfg_differential_inputs register. Unused PECL
differential inputs should be fixed with one input High
(VDD) and the other input Low (GND), or set in LVDS mode
and left floating, in which case one input is internally
pulled High and the other Low.
Input Locking Frequency Modes
Each input port has to be configured to receive the
expected input frequency. To achieve this, three Input
Locking Frequency modes are provided: Direct Lock,
Lock8K and DivN.
Direct Lock Mode
In Direct Lock mode, DPLL1 can lock to the selected input
at the spot frequency of the input, for example 19.44 MHz
performs the DPLL phase comparisons at 19.44 MHz.
In Lock8K and DivN modes (and for the special case of
155 MHz), an intern al divider is used prior to DPLL1 to
divide the input frequency before it is used for phase
comparisons.
Direct Lock Mode 155 MHz.
The max frequency allowed for phase comparison is
77.76 MHz, so for the special case of a 155 MHz input set
to Direct Lock mode, there is a divide-by-two function
automatically selected to bring the frequency down to
within the limits of operation.
Lock8K Mode
Lock8K mode automatically sets the divider parameters
to divide the input frequency down to 8 kHz. Lock8K can
only be used on the supported spot frequencies (see
Table 4 Note(i)). Lock8k mode is enabled by setting the
Lock8k bit (Bit 6) in the appropriate
cnfg_ref_source_frequency register location. Using lower
frequencies for phase comparisons in the DPLL results in
a greater tolerance to input jitter. It is possible to choose
which edge of the input reference clock to lock to, by
setting 8K Edge Polarity (Bit 2 of Reg. 03, test_register1).
DivN Mode
In DivN mode, the divider parameters are set manually by
configuration (Bit 7 of the cnfg_ref_source_frequency
register), but must be set so that the frequency after
division is 8 kHz.
The DivN function is defined as:
DivN = “Divide by N + 1”, i.e. it is the dividing factor used
for the division of the input frequency, and has a value of
(N + 1) where N is an integer from 1 to 15624 inclusive.
Therefore, in DivN mode the input frequency can be
divided by any integer value between 2 to 15625.
Consequently, any input frequency which is a multiple of
8 kHz, between 8 kHz and 125 MHz, can be supported by
using DivN mode.
Note...Any reference input can be set to use DivN
independently of the frequencies and configurations of the
other inputs. However only one value of N is allowed, so all
inputs with DivN selected must be running at the same
frequency.
DivN Examples
(a)To lock to 2.000 MHz:
(i) Set the cnfg_ref_source_frequency register to
10XX0000 (binary) to enable DivN, and set the
frequency to 8 kHz - the frequency re quired after
division. (XX = “Leaky Bucket” ID for this input).
(ii) To achieve 8 kHz, the 2 MHz input must be
divided by 250. So, if DivN = 250 = (N + 1)
then N must be set to 249. This is done by writing
F9 hex (249 decimal) to the DivN register pair
Reg. 46/47.
(b)To lock to 10.000 MHz:
(i) The cnfg_ref_source_frequency register is set to
10XX0000 (binary) to set the DivN and the
frequency to 8 kHz, the post-division frequency.
(XX = “Leaky Bucket” ID for this input).
(ii) To achieve 8 kHz, the 10 MHz input must be
divided by 1,250. So, if DivN, = 250 = (N+1)
then N must be set to 1,249. This is done by
writing 4E1 hex (1,249 decimal) to the DivN
register pair Reg. 46/47.
Input SEC Activity Monitors
An input reference activity monitor is assigned to each of
the three SEC inputs. The monitors operate con tinuously
such that at all times the activity status of each SEC input
is known.
SEC activity monitoring is used to declare whether or not
an input is valid. Any SEC that suffers a loss-of-activity will
be declared as invalid and unavailable for selection.
SEC activity monitoring is a continuous process which is
used to identify clock problems. There is a difference in
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dynamics between the selected clock and the other
reference clocks. Anomalies occurring on non-selected
SECs affect only that source's suitability for selection,
whereas anomalies occurring on the selected clock could
have a detrimental impact on the accuracy of the output
clock.
Leaky Bucket Accumulator
Anomalies detected by the Activity Monitor are integrated
in a Leaky Bucket Accumulator. There is one Leaky Bucket
Accumulator per SEC input. Each Leaky Bucket can be
programmed with a Bucket ID (0 to 3) which assigns to the
Leaky Bucket the corresponding Leaky Bucket
Configuration (from four available Configurations). Each
Leaky Bucket Configuration comprises the following
programmable parameters (See Reg. 50 to Reg. 5F):
zBucket size
zAlarm trigger (set threshold)
zAlarm clear (reset threshold)
zLeak rate (decay rate)
There are occasional anomalies that do not cause the
Accumulator to cross the alarm setting threshold, so the
selected SEC is retained. Persistent anomalies cause the
alarm setting threshold to be crossed and result in the
selected SEC being rejected.
Each Leaky Bucket Accumulator is a digital circuit which
mimics the operation of an analog integrator. If several
events occur close together, each event adds to the
amplitude and the alarm will be triggered quickly; if events
occur over a greater time period but still sufficiently close
together to overcome the decay, the alarm will be
triggered eventually. If events occur at a rate which is not
sufficient to overcome the decay, the alarm will not be
triggered. Similarly, if no defect events occur for a
sufficient time, the amplitude will decay gradually and the
alarm will be cleared when the amplitude falls below the
alarm clearing threshold. The ability to decay the
amplitude over time allows the importance of defect
events to be reduced as time passes by. This means tha t,
in the case of isolated events, the alarm will not be set,
whereas, once the alarm becomes set, it will be held on
until normal operation has persisted for a suitable time
(but if the operation is still erratic, the alarm will remain
set).
Figure 3 illustrates the behavior of the Leaky Bucket
Accumulator.
Each SEC input is monitored over a 128 ms period. If,
within a 128 ms period, an irregularity occurs that is not
deemed to be due to allowable jitter/wander, then the
accumulator is increm ented.
The Accumulator will continue to increment up to the
point that it reaches the programmed Bucket size. The “fill
rate” of the Leaky Bucket is, therefore, 8 units/second.
The “leak rate” of the Leaky Bucket is programmable to
be in multiples of the fill rate (x 1, x 0.5, x 0.25 and
x 0.125) to give a programmable leak rate from
8 units/sec down to 1 unit/sec. A conflict between trying
to “leak” at the same time as a “fill” is avoided by
preventing a leak when a fill event occurs.
Figure 3 Inactivity and Irregularity Monitoring
Inactivities/Irregularities
Programmable Fall Slopes
Reference
Source
Leaky
Bucket
Response
Alarm
bucket_size
upper_threshold
lower_threshold
(all programmable)
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Disqualification of a non-selected SEC is based on
inactivity noted by the Activity Monitors. The currently
selected SEC can be disqualified for being out-of phase,
inactive, or if the source is outside the DPLL lock range.
If the currently selected SEC is disqualified, the next
highest priority qualified SEC is selected.
Interrupts for Activity Monitors
The loss of the currently selected SEC will eventually
cause the input to be considered invalid, triggering an
interrupt. The time taken to raise this interrupt is
dependant on the Leaky Bucket Configuration of the
activity monitors. The fastest Leaky Bucket setting will still
take up to 128 ms to trigger the interrupt. The interrupt
caused by the brief loss of the currently selected SEC is
provided to facilitate very fast sour ce failure dete ction if
desired. It is triggered after missing just a couple of cycles
of the SEC. Some applications require the facility to switch
downstream devices based on the status of the SECs. In
order to provide extra flexibility, it is possible to flag the
main_ref_failed interrupt (Reg. 06 Bit 6) on the pin TDO.
This is simply a copy of the status bit in the interrupt
register and is independent of the mask register settings.
The bit is reset by writing to the interrupt status register in
the normal way. This feature can be enabled and disabled
by writing to Reg. 48 Bit 6.
Leaky Bucket Timing
The time taken (in seconds) to raise an inactivity alarm on
an SEC that has previously been fully active (Leaky Bucket
empty) will be:
(cnfg_upper_threshold_n) / 8
where n is th e number of the Leaky Bucket Con figuration.
If an input is intermittently inactive then this time can be
longer. The default setting of cnfg_upper_threshold_n is
6, therefore the default time is 0.75 s.
The time taken (in seconds) to cancel the activity alarm on
a previously completely inactive SEC is calculated, for a
particular Leaky Bucket, as:
[2 (a) x (b - c)]/ 8
where:
a = cnfg_decay_rate_n
b = cnfg_Bucket_size_n
c = cnfg_lower_threshold_n
(where n = the number of the relevant Leaky
Bucket Configuration in each case).
The default setting is shown in the following:
[21 x (8 - 4)] /8 = 1.0 secs
Fast Activity Monitor
Anomalies on the selected clock have to be detected as
they occur and the PLL must be temporarily isolated until
the clock is once again pure. The SEC activity monitoring
process cannot be used for this because the high degree
of accuracy required dictates that the proce ss be slow. To
achieve the immediacy required, the PLL requires an
alternative mechanism. The phase locked loop itself
contains a fast activity detector such that within
approximately two missing input clock cycles, a no-activity
flag is raised and the DPLL is frozen in Digital Holdover
mode. This flag can also be read as the DPLL1
main_ref_failed bit (from Reg. 06 sts_interrupts, Bit 6)
and can be set to indicate a phase lost state by enabling
Reg. 73, Bit 6. With the DPLL in Digital Holdover mode it
is isolated from further disturbances. If the input becomes
available again before the activity monitor rejection alarm
has been raised, then the DPLL will continue to lock to the
input, with little disturbance. In this scenario, with the
DPLL in the “locked” state, the DPLL uses “nearest edge
locking” mode (±180° capture) avoiding cycle slips or
glitches caused by trying to lock to an edge 360° away, as
would happen with traditional PLLs.
Selector
This block has two main functions:
zSelection of the Input reference clock source via
Reg. 33 force_select_reference_source
zForcing of the Operating mode of the device, via
Reg. 32 cnfg_operating_mode
Selection of Input SECs
Under normal operation, the input SECs are selected
automatically by an order of priority given in the Priority
Table. For special circumstances however, such as chip or
board testing, the selection may be forced by
configuration.
Automatic operation selects an SEC based on its
predefined priority and its current validity. A table is
maintained which lists all valid SECs in the order of
priority. This is initially downloaded into the ACS8525 via
the Serial interface by the Network Manager, and is
subsequently modified by the results of the ongoing
quality monitoring. In this way, when all the defined
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ACS8525 LC/P
sources are active and valid, the source with the highest
programmed priority is selected, but if this source fails,
the next-highest source is selected, and so on.
Restoration of repaired SECs is handled carefully to avoid
inadvertent disturbance of the output clock. For this, the
ACS8525 has two modes of operation; Revertive and
Non-revertive.
In Revertive mode, if a re-valid ated (or newly validated)
source has a higher priority than the SEC which is
currently selected, a switchover will take place. Many
applications prefer to minimize the clock switching events
and choose Non-revertive mode.
In Non-revertive mode, when a re-validated (or newly
validated) source has a higher priority, then the selected
source will be maintained. The re-validation of the SEC will
be flagged in the sts_sources_valid register (Reg. 0E and
0F) and, if not masked, will generate an interrupt.
Selection of the re-validated source can take place under
software control or if the currently selected source fails.
To enable software control, the software should briefly
enable Revertive mode to effect a switch-over to the
higher priority source. When there is a reference available
with higher priority than the selected reference, there will
be NO change of SEC as long as the Non-revertive mode
remains on, and the currently selected source is valid. A
failure of the selected reference will always trigger a
switch-over regardless of whether Revertive or
Non-revertive mode has been chosen .
Forced Control Selection
A configuration register, force_select_reference_source
Reg. 33, controls both the choice of automatic or forced
selection and the selection itself (when forced selection is
required). For Automatic ch oice of source selection, t he 4
LSB bit value force_select_SEC_input is set to all zeros or
all ones (default). To force a particular input, the bit value
is set according to the description for Reg. 33. Forced
selection is not the normal mode of operation, and
force_select_SEC_input defaults to the all-ones value on
reset, thereby adopting the automatic selection of the
SEC.
Automatic Control Selection - Priority Table
When an automatic selection is required, the
force_select_reference_source register LSB 4 bits
(force_select_SEC_input) must be set to all zeros or all
ones.
The Priority Table register cnfg_ref_selection_priority,
occupying three 8-bit register addresses (Reg. 19, 1A and
1C), is organized as one 4-bit word per input SEC port.
Each 4 bit word represent s the desired priority of that
particular port. Unused ports should be given the value
0000 in the relevant register to indicate they are not to be
included in the priority table. On power-up, or following a
reset, the input priority configuration is set to the default
values defined by Table 4. The selection priority values
are all relative to each other, with lower-valued numbers
taking higher priorities. Each SEC should be given a
unique number; the valid values are 1 to 15 (dec). A value
of 0 disables the SEC. However if two or more inputs are
given the same priority number those input s will be
selected on a first in, first out basis. If the first of two same
priority number sources goes invalid the second will be
switched in. If the first then becomes valid again, it
becomes the second source on the first in, first out basis,
and there will not be a switch. If a third source with the
same priority number as the other two becomes valid, it
joins the priority list on the same first in, first out basis.
There is no implied priority based on the channel
numbers. Revertive/Non-revertive mode has no effect on
sources with the same priority value.
The priority of Sync inputs is determined by the priority of
their associated SEC inputs. The Sync inputs do not have
their own separate priority table.
Ultra Fast Switching
An SEC is normally disqualified after the Leaky Bucket
monitor thresholds have been crossed. An option for a
faster disqualification has been implemented, whereby if
Reg. 48 Bit 5 (ultra_fast_switch) is set, then a loss of
activity of just two or three reference clock cycles causes
a reference switch, and sets the DPLL1_main_ref_failed
bit (see Reg. 06 Bit 6) which raises an interrupt (if not
masked).
The sts_interrupts register Reg. 06 Bit 6
(DPLL1_main_ref_failed) is used to flag inactivity on the
reference that the device is locked to much faster than
the activity monitors can support. If Reg. 48 Bit 6 of the
cnfg_monitors register (los_flag_on_TDO) is set, then th e
state of this bit is driven onto the TDO pin of the device.
Note...The flagging of the loss of the main reference failure on
TDO is simply allowing the status of the sts_interrupts bit
DPLL1_main_ref_failed to be reflected in the state of the TDO
output pin. The pin will, therefore, remain High until the
interrupt is cleared. This functionality is not enabled by default
so the usual JTAG functions can be used. When the TDO output
from the ACS8525 is connected to the TDI pin of the next
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ACS8525 LC/P
device in the JTAG scan chain, the implementation should be
such that a logic change caused by the action of the interrupt
on the TDI input should not effect the operation when JTAG is
not active.
External Protection Switching Mode-SRCSW pin
External Protection Switching mode, for fast switching
between inputs SEC1 or SEC2, can be triggered directly
from the dedicated pin SRCSW, once the mode has been
initialized.
The mode is initialized by either holding SRCSW pin High
during reset (SRCSW must remain High for at least a
further 251 ms after PORB has gone High - see following
Note), or by writing to Reg. 48 Bit 4. After External
Protection Switching mode has been initialized, the value
on this pin directly selects either SEC1 (SRCSW High) or
SEC2 (SRCSW Low). If this mode is activated at reset by
pulling the SRCSW pin High, then it configures the default
frequency tolerance of SEC1 and SE C2 to ±80 ppm
(Reg. 41 and Reg. 42), as opposed to the normal
frequency tolerance of ±9.2 ppm. These registers can be
subsequently set by external software, if required.
Note...The 251 ms comprises 250 ms allowance for the
internal reset to be removed plus 1 ms allowance for APLLs to
start-up and become stable.
The control of TTL or DIFF selection for inputs SEC1 and
SEC2 is independently determined by the priority values
of the TTL inputs; if the programmed priority of SEC1 TTL
is 0, then SEC1 DIFF is available for selection by SRCSW
pin; similarly, if SEC2 TTL is 0 priority, SEC2 DIFF is
available for selection by SRCSW pin (See Reg. 19 and 1A
cnfg_ref_selection_priority and Figure 4).
Figure 4 SEC1 and SEC2 Switching
When external protection switching is enabled, the device
will operate as a simple switch. All clock monitoring is
disabled and the DPLL will simply be forced to try to lock
on to the indicated reference source . Consequently the
device will always indicate “Locked” state in the operating
mode register (Reg. 09, Bits 2:0).
Output Clock Phase Continuity on Source
Switchover
If either PBO is selected on (default), or, if DPLL frequency
limit set to less than ±30 ppm (±9.2 ppm default), the
device will always comply with GR-1244-CORE[13]
specifications for Stratum 3 (max rate of phase change of
81 ns/1.326 ms), for all input frequencies.
A well designed system would have Master and Slave
clock from the clock sync cards aligned to within a few
nanoseconds. In which case a complete system using the
Semtech SETS clock card parts (ACS8530, ACS8520 or
ACS8510) and this Line Card part would be fully
compliant to GR-1244-CORE[13] specifications under all
conditions due to the low frequency range and bandwidth
set at the clock card end. These parts and the ACS8 525
LC/P also allow easy frame sync (8 kHz) alignment both at
the clock card and at the Line Card end through the use
of dedicated frame sync (8 kHz) inputs, in addition to the
main clock inputs.
Forcing of the Operating Mode of the Device
The Selector can force the following Operating modes,
(cnfg_operating_mode, Reg. 32):
zAuto
zFree-run
zHoldover
zLocked
zLost-phase
zPre-locked
zPre-locked2
See “Operating Modes (States) of the Device” on page 30.
Phase Locked Loops (PLLs)
PLL Overview
Figure 1 shows the PLL circuitry to comprise two Digital
PLLs (DPLL1 and DPLL2), two output multiplying and
filtering Analog PLLs (APLL1 and APLL2), output
frequency dividers in an Output Port Frequency Selection
block, a synthesis block, multiplexers MUX1 and MUX2,
and a feedback Analog PLL (APLL3). These functional
blocks, and their interconnections are highly configurable,
SEC1 TTL Priority >0
SEC2 TTL Priority >0
SEC1 TTL
SEC1 DIFF
1
0
1
0
DPLL1
SRCSW
SEC2 TTL
SEC2 DIFF
1
0
F8525D_006secSwitch_01
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ACS8525 LC/P
via register control, which provides a range of output
frequencies and levels of jitter performance.
The DPLLs give a stable and consistent level of
performance that can be easily pr ogrammed for different
dynamic behavior or operating range. They are not
affected by operating conditions or silicon process
variations. Digital Synthesis is used to generate all
required SONET/SDH output frequencies. The digital logic
operates at 204.8 MHz that is multiplied up from the
external 12.800 MHz oscillator module. Hence the best
resolution of the output signals from the DPLLs is one
204.8 MHz cycle or 4.9 ns.
Additional resolution and lower final output jitter is
provided by a de-jittering APLL that reduces the 4.9 ns p-p
jitter from the digital down to 500 ps p-p and 60 ps RMS
as typical final outputs measured broadband (from 10 Hz
to 1 GHz).
This arrangement combines the advantages of the
flexibility and repeatability of a DPLL with the low jitter of
an APLL. The DPLLs in the ACS8525 are programmable
for PLL parameters of bandwidth (18, 35 and 70 Hz),
damping factor (from 1.2 to 20), frequency acceptance
and output range (from 0 to 80 ppm, typically 9.2 ppm),
input frequency (12 common SONET/SDH spot
frequencies) and input-to-output phase offset (in 6 ps
steps up to 200 ns). There is no requirement to
understand the loop filter equations or detailed gain
parameters since all high level factors such as overall
bandwidth can be set directly via registers in the
microprocessor interface. No external critical
components are required for either the in ternal DPLLs or
APLLs, providing another key advantage over traditional
discrete designs.
Either the software or an internal state machine controls
the operation of DPLL1. The state machine for DPLL2 is
very simple and cannot be manually/externally controlled.
One additional feature of DPLL2 is the ability to measure
a phase difference between two inputs.
DPLL1 always produces an output at 77.76 MHz to feed
the APLL, regardless of the frequency selected at the
output pins or the locking frequency (frequency at the
input of the Phase and Frequency Detector- PFD).
DPLL2 can be operated at a number of frequencies. T his
is to enable the generation of extra output frequencies,
which cannot be easily related to 77.76 MHz. If DPLL2 is
enabled, it locks to the 8 kHz from DPLL1. This is because
all of the frequencies of operation of DPLL2 can be
divided to 8 kHz and this will ensure synchronization of
frequencies, from 8kHz upwards, within the two DPLLs.
Both of the DPLLs’ outputs can be connected to
multiplying and filtering APLLs. The outputs of these
APLLs are divided making a number of frequencies
simultaneously available for selection at the output clock
ports. The various combinations of DPLL, APLL and divider
configurations allow for generation of a comprehensive
set of frequencies, as listed in Table 7, “Output Frequency
Selection,” on page 22.
A function is provided to synchronize the lower output
frequencies when DPLL1 is locked to a high frequency
reference input. The dividers that generate the 2 kHz and
8 kHz outputs are reset such that the output 2/8 kHz
clocks are lined up with the input 2 kHz.
The ACS8525 also supports Sync pulse references of
4 kHz or 8 kHz although in these cases frequencies lower
than the Sync pulse reference may not necessarily be in
phase.
The PLL configurations for particular output frequencies is
described in “Output Frequency Selection and PLL
Configuration” on page 22.
PLL Architecture
Figure 5 shows the PLL arrangement in more detail. Each
DPLL comprises a generic Phase and Frequency Detector
(PFD), a Digital Loop filter, and a Digital Timed Oscillator
(DTO- not shown); together with Forward, Feedback, and
Low Frequency (LF) (DPLL1 only) Digital Frequency
Synthesis (DFS) blocks. The DPLL architecture for DPLL1.
is actually more complex than that of DPLL2, and provides
greater functionality.
The selected SEC input is always supplied to DPLL1.
DPLL1 may use either digital feedback or analog
feedback (via APLL3).
DPLL2 always takes its feed from DPLL1 and cannot be
used to select a different input to that of DPLL1, except in
the case where the device is being used to measure
phase differenc e between input sources. In this case, the
PFD of DPLL2 is used for phase measurement and the
DPLL2 normal output is rendered unusable.
DPLL1 and APLLs
DPLL1 always produces 77.76 MHz regardless of eit he r
the reference frequency (frequency at the input pin of the
device) or the locking frequency (frequency at the input of
the DPLL PFD).
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Figure 5 PLL Block Diagram
The input referen ce is either passed directly to t he PFD or
via a pre-divider (not shown) to produce the reference
input. The feedback 77.76 MHz is either divided or
synthesized to generate the locking frequency.
Any Digital Frequency Synthesis (DFS) generated clock
will inherently have jitter on it equivalent to one period of
the generating clock (p-p). The DPLL1 77M Forward DFS
block uses DFS clocked by the 204.8 MHz system clock to
synthesize the 77.76 MHz and, therefore, has an inherent
4.9 ns of p-p jitter. There is an option to use a feedback
APLL (APLL3) to filter out this jitter before the 77.76 MHz
is used to generate the feed back locking frequency in the
DPLL1 feedback DFS block. This analog feedback option
allows a lower jitter (<1 ns) feedback signal to give
maximum performance.
The DPLL1 77M Forward DFS block is also the block that
handles Phase Build-out and any phase offset
programmed into the device. Hence, the DPLL1 77M
Forward DFS and the DPLL1 77M Output DFS blocks are
locked in frequency but may be offset in phase.
The DPLL1 77M Output DFS block also uses the
204.8 MHz system clock and always generates
77.76 MHz for the output clocks (with inherent 4.9 ns of
jitter). This is fed to DPLL1 LF Output DFS block and to
APLL1. The low frequency DPLL1 LF Output DFS block is
used to produce three fre q ue ncie s; tw o of them, Digital1
and Digital2, are available for selection to be produc ed at
outputs O1 and O2, and the third frequency can produce
multiple E1/DS1 rates via t he filtering APLLs. The input
clock to the DPLL1 LF Output DFS block is either
77.76 MHz from APLL1 (post jitter filtering) or 77.76 MHz
direct from the DPLL1 77M Output DFS.
Utilizing the clock from APLL1 will result in lower jitter
outputs from the DPLL1 LF Output DFS block. However,
when the input to the APLL1 is taken from t he DPLL1 LF
Output DFS block, the input to that block c omes directly
from the DPLL1 7 7M Output DFS block so that a “loop” is
not created.
APLL1 is for multiplying and filtering. The input to APLL1
can be either 77.76 MHz from the DPLL1 77M Output
DFS block or an alternative frequency from the DPLL1 LF
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ACS8525 LC/P
Output DFS block (offering 77.76 MHz, 12E1, 16E1,
24DS1 or 16DS1). The frequency from APLL1 is four
times its input frequency i.e. 311.04 MHz when used with
a 77.76 MHz input. APLL1 is subsequently divided by 1, 2,
4, 6, 8, 12, 16 and 48 and these are available at the O1
and O2 Outputs.
DPLL2 & APLLs
DPLL2 is simpler than DPLL1. DPLL2 offers no PBO or
phase offset. The DPLL2 input can only be used to lock to
DPLL1. Unlike DPLL1, the DPLL2 Forward DFS block does
not always generate 77.76 MHz. The possible frequencies
are listed in Table 10, “APLL2 Frequencies,” on page 27.
Similar to DPLL1, the output of the DPLL2 Forward DFS
block is generated using DFS clocked by the 204.8 MHz
system clock and will have an inherent jitter of 4.9 ns.
The DPLL2 feedback DFS also has the facility to be able
to use the post APLL2 (jitter-filtered) clock to generate the
feedback locking frequency. Again, this will give the
maximum performance by using a low jitter feedback.
APLL2 block is also for multiplying and filtering. The input
to APLL2 can come either from the DPLL2 Forward DFS
block or from DPLL1. The input to APLL2 can be
programmed to be one of the following:
(a)Output from the DPLL2 Forward DFS block (12E1,
24DS1, 16E1, 16DS1, E3, DS3, OC-N),
(b)12E1 from DPLL1,
(c) 16E1 from DPLL1,
(d)24DS1 from DPLL1,
(e)16DS1 from DPLL1.
The frequency gener ated from the APLL2 is four times its
input frequency i.e. 311.04 MHz when used with a
77.76 MHz input. APLL2 is subsequently divided by 2, 4,
8, 12, 16, 48 and 64 and these are available at the O1
and 02 Outputs.
“Digital” Frequencies
The DPLL1 LF Output DFS block shown in the diagram,
clocked either by the DPLL1 77M Output DFS bloc k or via
the APLL1, generates the single frequencies Digital1 and
Digital2 (see Table 11 and Table 12). The input clock
frequency of the DFS is always 77.76 MHz and as such
has a period of approximately 12 ns. The jitter generated
on the Digital outputs is relatively high, because they do
not pass through an APLL for jitter filtering. The minimum
level of jitter is when DPLL1 is in analog feedback mode,
when the p-p jitter will be approximately 13 ns (equivalent
to a period of the DFS clock). The maximum jitter is
generated when in digital feedback mode, when the tota l
is approximately 18 ns.
The E1/DS1 Synthesis block generates the E1/DS1 rates
for the APLLs, using the output from DPLL1. It can
generate 12E1, 16E1, 16DS1 or 24DS1, for selection by
the multiplexers.
FrSync, MFrSync, 2 kHz and 8 kHz Clock Outputs
Whilst the FrSync and MFrSync Outputs are always
supplied from DPLL1, the 2 kHz and 8 kHz options
available from the O1 and O2 Outputs can be supplied
from either DPLL1 or DPLL2 (Reg. 7A Bit 7).
Multiplexers
Multiplexers MUX1 and MUX2 are used to select the
appropriate inputs to the Analog PLLs. The function they
represent is controlled by Reg. 65
cnfg_DPLL1_frequency.
APLL2 Input Selection using MUX 2
zDPLL2 selected for input to APLL2 (Reg. 65 Bit 6 = 0)
The input frequency is selected from the operating
frequency of DPLL2 (Reg. 64 Bits [2:0])
zDPLL1 + LF Output DFS selected for Input to APLL2
• 12E1 (Reg. 65 Bit 6 = 1 and Bits [5:4] set to 00)
• 16E1 (Reg. 65 Bit 6 = 1 and Bits [5:4] set to 01)
• 24DS1 (Reg. 65 Bit 6 = 1 and Bits [5:4] set to 10)
• 16DS1 (Reg. 65 Bit 6 = 1 and Bits [5:4] set to 11)
APLL1 Input Selection using MUX 1
zDPLL1 (77.76 MHz) output fed to input of APLL1.
Analog feedback used in DPLL1 (Reg. 65 Bits [2:0] set
to 000)
zDPLL1 (77.76 MHz) output fed to input of APLL1.
Digital feedback used in DPLL1 (Reg. 65 Bits [2:0] set
to 001)
zDPLL1 + LF Output DFS selected for input to APLL1
• 12E1 (Reg. 65 Bits [2:0] set to 010)
• 16E1 (Reg. 65 Bits [2:0] set to 011)
• 24DS1 (Reg. 65 Bits [2:0] set to 100)
• 16DS1 (Reg. 65 Bits [2:0] set to 101)
Notes: (i) DPLL2 output cannot be selected for input to APLL1
(ii) If both multiplexers select LF Output DFS, the same
frequency value must be selected in Reg. 65 Bits
[2:0] and Reg. 65 Bits [5:4].
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APLLs
There are three main APLLs. APLL1 and APLL2 provide a
lower final output jitter reducing the 4.9 ns p-p jitter from
the digital down to 500 ps p-p and 60 ps rms as typical
final outputs measured broadband (from 10 Hz to 1 GHz).
The feedback APLL (APLL3) is selected by default; it
provides improved performance over the digital feedback.
APLL Output Dividers
Each APLL has its own divider. Each divider
simultaneously outputs a series of fixed ratios of its APLL
input. Any of these divided outputs may be selected as the
output on Output Ports O1 or O2 by configuring Reg. 61
and Reg. 62, with the following exceptions: (APLL1)/2 and
(APLL1)/1 only available for Output 01 (differential port),
and (APLL1)/48 only available for Output 02.
PFD and Loop Filters
The PFD compares the input reference with that of the
locking frequency (feedback) giving a phase error which is
then filtered by a 100 Hz low pass filter, to give the
average phase error for input into a loop filter. The PFD is
quite complex and has several programmable options to
determine what phase error value is fed to the loop (see
“Phase and Frequency Detectors” on page 18) depending
on the type of jitter/wander expected.
The loop filter bandwidth and damping is programmable
to optimize the lock ing time/ability to track the input. See
“Damping Factor Programmability” on page 18 and
Figure 6 on page 18.
PLL Operational Controls
The main factors controlling the operation of the PLL are:
1. The operating mode of the device. See “Operating
Modes (States) of the Device” on page 30.
2. Input reference and feedback frequency selection.
See “PLL Architecture” on page 14 and “Input Locking
Frequency Modes” on page 9.
3. Loop Bandwidth (Input Acquisition/Locked
Bandwidth) and Damping factor of the DPLLs - these
determine how fast the device can to lock to the
selected input, or how tightly it can track the input.
See from “Input Acquisition Bandwidth” to “Damping
Factor Programmability” next.
4. PFD settings - these affect the input phase error to the
Loop filter and relate to jitter and wander tolerance.
See “Phase/Frequen cy/Lock Detection” on page 18 .
5. Phase compensation functions - See “Phase
Compensation Functions” on page 19.
Input Acquisition Bandwidth
DPLL1 has programmable acquisition bandwidth of 18,
35 or 70 Hz. The default is set to 70 Hz.
Input Locked Bandwidth
The ACS8525 has programmable Locked Bandwidth of
18, 35 or 70 Hz. These bandwidth settings correspond to
the -3 dB jitter attenuatio n point on the ACS8525’s jitter
transfer characteristic shown in Figure 6. If the ACS8525
is used with only DPLL1, the highest bandwidth setting is
recommended to ensure the closest tracking of the input
SEC. If DPLL2 is also to be used, DPLL1 should be set to
a lower bandwidth setting than DPLL2. The lowest
bandwidth setting will provide the highest jitter
attenuation although this is not the main function of the
ACS8525 device.
Table 5 Available Damping Factors for different DPLL
Bandwidths, and Associated Gain Peak Values
Bandwidth/Hz Reg. 6B [2:0] Damping
Factor selected Gain Peak/dB
18 1 1.2 0.4
22.50.2
3, 4, 5 5 0.1
35 1 1.2 0.4
22.50.2
350.1
4, 5 10 0.06
70 1 1.2 0.4
22.50.2
350.1
4100.06
5200.03
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Figure 6 DPLL1 Jitter Transfer Characteristic, (Freq = 1.544 MHz, Jitter = 0.2 UI p-p, Damping Factor = 5)
Damping Factor Programmability
The DPLL damping factor is set by default to provide a
maximum wander gain peak of around 0.1 dB. Many of
the specifications (e.g. GR-1244-CORE [13], G.812[7] and
G.813[8]) specify a wander transfer gain of less than
0.2 dB. GR-253[11] specifies jitter (not wander) transfer of
less than 0.1 dB. To accommodate the required levels of
transfer gain, the ACS8525 provides a choice of damping
factors, with more choice given as the bandwidth setting
increases into the frequency regions classified as jitter.
Table 5 shows which damping factors are available for
selection at the different bandwidth settings, and what
the corresponding jitter transfer approximate gain peak
will be.
Phase/Frequency/Lock Detection
Two main types of detector are used in the ACS8525:
zPhase and frequency detectors, and
zPhase Loss/Lock detectors.
Phase and Frequency Detectors
There are two multi-phase and frequency detectors, one
for each DPLL. The multi-phase and frequenc y detector s
are used to compare input and feedback clocks. They
operate at input frequencies up to 77.76 MHz. DPLL1 can
lock to input spot frequencies from 2 kHz up to
77.76 MHz (155.52 MHz is internally divided down to
77.76 MHz). A common arrangement however is to use
Lock8k mode (See Bit 6 of Reg. 22 to R eg. 28), where all
input frequencies are divided down to 8 kHz internally.
Marginally better MTIE figures may be possible in direct
lock mode due to more regular phase updates. This direct
locking capability is one of the unique features of the
ACS8525.
A patented multi-phase detector is used in order to give
an infinitesimally small input phase resolution combined
with large jitter tolerance. A multi-phase detector
comprises the following phase detectors:
zPhase and frequency detector (±360°or ±180°
range)
F8525D_005WANJITTXFR_02bitmap.bmp
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zAn Early/Late phase detector for fine resolutio n
zA multi-cycle phase detector for large input jitter
tolerance (up to 8191 UI), whic h captures and
remembers phase differences of many cycles
between input and feedback clocks.
The phase detectors can be configured to be immune to
occasional missing input clock pulses by using nearest
edge detection (±180°captu re) or the normal
± 360° phase capture range which gives freque ncy
locking. The device will automatically switch to nearest
edge locking when the multi-UI phase detector is not
enabled, and the other phase detectors have detected
that phase lock has been achieved. It is possible to
disable the selection of nearest edge locking via Reg. 03
Bit 6 (set to 1). In this setting, frequency locking will
always be enabled.
The balance between the first two types of phase detector
employed can be adjust ed vi a Reg. 6A to 6D. The default
settings should be sufficient for all modes. Adjustment of
these settings affects only small signal overshoot and
bandwidth.
The multi-cycle phase detector (wide-range) is enabled via
Reg. 74, Bit 6 set to 1 and the range is set in exponentially
increasing steps from ±1 UI up to 8191 UI via Reg. 74,
Bits [3:0].
When this detector is enabled it keeps a track of the
correct phase position over many cycles of phase
difference to give excellen t jitter tolerance. This provides
an alternative to switching to Lock8k mode as a method
of achieving high jitter tolerance.
An additional control (Reg. 7 4 Bit 5) enables the
multi-phase detector value to be used in the final phase
value as part of the DPLL loop. When enabled by setting
High, the multi cycle phase value will be used in the loop
and gives faster pull-in (but more overshoot). The
characteristics of the loop will be similar to Lock8k mode
where again large input phase differences contribute to
the loop dynamics. Setting the bit Low only uses a max
figure of 360° in the loop and will give slower pull-in but
gives less overshoot. The final phase position that the
loop has to pull in to is still tracked and remembered by
the multi-cycle phase dete ct or in eit her case.
Phase Lock/Loss Detectors
Phase lock detection is handled in several ways. Phase
loss can be triggered from:
zThe fine phase lock detector, which measures the
phase between input and feedback clock
zThe coarse phase lock detector, which monitors whole
cycle slips
zDetection that the DPLL is at min. or max. frequency
zDetection of no activity on the input
Each of these sources of phase loss indication is
individually enabled via register bits (see Reg. 73 and 74).
Phase lock or lost is used to determine whether to switch
to nearest edge locking and whether to use acquisition or
normal bandwidth settings for the DPLL. Acquisition
bandwidth is used for faster pull-in from an unlocked
state.
The coarse phase lock detector detects phase differences
of n cycles between input and feedback clocks, where n is
set by Reg. 74 Bits [3:0]; the same register that is used for
the coarse phase detector range, since these functions go
hand in hand. This detector may be used in the case
where it is required that a phase loss indication is not
given for reasonable amounts of input jitter and so the
fine phase loss detector is disabled and the coarse
detector is used instead.
Phase Compensation Functions
The ACS8525 has the following phase compensation
functions and controls:
zPhase Build-out (PBO)
zPBO Phase Offset
zInput-to-Output Phase Adjustment
Phase Build-out
Phase Build-out (PBO) is the function to minimize phase
transients on the output SEC clock during input reference
switching. If the currently sele cted input reference clock
source is lost (due to a short interruption or complete loss
of reference), the next highest priority SEC will be
selected, and a PBO event triggered. When a PBO event is
triggered, the device enters a temporary Holdove r state.
When in this temporary state, the phase of the input
reference is measured, relative to the output. The device
then automatically accounts for any measured phase
difference and adds the appropriate phase offset into the
DPLL to compensate.
Following a PBO event, whatever the phase difference on
change of input, the output ph ase transient is minimized
to be typically less than ±2.5 ns (in digital feedback
mode).
On the ACS8525, PBO can be enabled, disabled or frozen
using the Serial interface. By default, it is enabled. When
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ACS8525 LC/P
PBO is enabled, PBO can also be frozen (at the current
offset setting). The device will then ignore any further PBO
events occurring on any subsequent reference switch,
and maintain the current phase offset. If PBO is disabled
while the device is in the Locked mode, there may be a
phase shift on the output SEC clocks as the DPLL locks
back to 0° phase error. The rate of phase shift will depend
on the programmed bandwidth. Enabling PBO whilst in
the Locked stated will also trigger a PBO event.
PBO Phase Offset
In order to minimize the systematic (average) phase error
for PBO, a PBO Phase Offset can be programmed in
0.101 ns steps in the cnfg_PBO_phase_offset register,
Reg. 72. The range of the programmable PBO phase
offset is restricted to ±1.4 ns. This can be used to
eliminate an accumulation of phase shifts in one
direction.
Input to Output Phase Adjustment
When PBO is off such that the system always tries to align
the outputs to the inputs at the 0° position, there is a
mechanism provided in the ACS8525 for prec ise fine
tuning of the output phase position with respect to the
input. This can be used to compensate for circuit and
board wiring delays. The output phase can be adjusted in
6 ps steps up to 200 ns in a positive or negative direction.
The phase adjustment actually changes the phase
position of the feedback clock so that the DPLL adjusts
the output clock phases to compensate. The rate of
change of phase is therefore related to the DPLL
bandwidth. For the DPLL to track large instant changes in
phase, either Lock8k mod e should be on, or the coarse
phase detector should be enabled. Register
cnfg_phase_offset at Reg. 70 and 71 controls the output
phase, which is only used when Phase Build-out is off
(Reg. 48, Bit 2 = 0, and Reg. 76, Bit 4 = 0).
DPLL Feature Summary
DPLL1 is the more feature rich of the two DPLLs. The
features of the two DPLLs are summarized here. Refer to
the Register Descriptions for more information.
DPLL1 Main Features
zMultiple E1 and DS1 outputs supported
zLow jitter MFrSync (2 kHz) and FrSync (8 kHz) outputs
zMultiple phase loss and multiple phase detectors (see
“DPLL1 Advanced Features” on page 20”)
zDirect PLL locking to common SONET/SDH input
frequencies or any multiple of 8 kHz
zAutomatic mode switching between Free-r un, Locked
and Digital Holdover states (see “Operating Modes
(States) of the Device” on page 30)
zFast detection on input failure and entry into Digital
Holdover mode (holds at the last good frequency
value)
zFrequency translation between input and output rates
via direct digital synthesis
zHigh accuracy digital architecture for stable PLL
dynamics combined with an APLL for low jitter final
output clocks
zNon-revertive mode
zFrame Sync pulse alignment
zSelectable Automatic DPLL bandwidth control (auto
selects either Locked bandwidth, or Acquisition
bandwidth), or Locked DPLL bandwidth (Reg. 3B
Bit 7)
zTwo programmable bandwidth controls:
• Locked bandwidth: 18, 35 or 70 Hz (Reg. 67)
• Acquisition bandwidth: 18, 35 or 70 Hz (Reg. 69)
zProgrammable damping factor (for optional faster
locking and peaking control). Factors = 1.2, 2.5, 5, 10
or 20. (Reg. 6B, Bits [2:0])
zProgrammable DPLL pull-in frequency range (Reg. 41,
Reg. 42)
zPhase Build-out on source switching (hit-less source
switching), on/off (Reg. 48 Bit 3)
zFreeze Phase Build-out, on/off (Reg. 48 Bit 2)
DPLL1 Advanced Features
Phase Loss Indicators
zPhase loss fine limit. on/off (Reg. 73 Bit 7) and
programmable range 0 to 7 dec (Reg. 73 Bits [2:0])
zMulti-cycle phase loss course limit, on/off (Reg. 74 Bit
7) and selectable range from ±1 to 8191 UI in 13
steps (Reg. 74 Bits [3:0])
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ACS8525 LC/P
Output Phase Adjustment
zProgrammable Input to Output phase offset
adjustment, ±200 ns, 6 ps resolution step size
(Reg. 70 and 71)
zProgrammable mean offset on Phase Build-out event
(PBO phase offset on source switching) - disturbance
down to ±5 ns. (Reg. 72 Bits [5:0]). Requires PBO to
be on (Reg. 48 Bit 3)
Phase Detector Controls
zMulti-cycle phase detection - Course phase lock &
capture range on/off (Reg. 74 Bit 6) and selectable
range from ±1 to 8191 UI in 13 steps (Reg. 74 Bits
[3:0]). If selected, this feature increases jitter and
wander tolerance to a maxi mum of 8192 UI (normally
limited to ±0.5 UI)
zUse of coarse phase detector result in DPLL algorithm,
on/off (Reg. 74 Bit 6) - speeds up phase locking
zLimit DPLL1 Integral when at DPLL frequency limit,
on/off (Reg. 3B Bit 3) - reduces overshoot
zAnti-noise filter for low frequency inputs, on/off
(Reg. 76 Bit 7)
Advanced Phase Detector Controls
The phase detector actually comprises two different
phase detector types, PD1 and PD2. Their interworking
and selection algorithms are beyond the scope of this
datasheet, however it should be noted the gain of only
PD2 is adjustable by configuration, in the following
feature:
zDPLL1 PD2 gain control enable, on/off (Reg. 6D
Bit 7)
If on, this allows automatic gain selection according to
the type of feedback to the DPLL (For the digital
feedback setting, the gain used for PD2 is given by
Reg. 6D Bits [2:0]). If off, PD2 is not used.
zAdjustable gain settings for PD2 (with auto switching
enabled), for the following feedback cases:
• Digital feedback (Reg. 6D Bits [2:0])
• Analog feedback (all frequencies above 8 kHz)
(Reg. 6D Bits [6:4])
• Analog 8k (or less) feedback (Reg. 6B Bits [2:0])
Phase Monitors
zInput phase measured at DPLL1 or DPLL2. DPLL
select (Reg. 4B Bit 4), 16-bit p hase status
(Reg. 77/Reg. 78)
zPhase measured between two inputs (uses DPLL2’s
PFD (Reg. 65 Bit 7))
DPLL2 Main Features
The main features of DPLL2 are:
zAlways locked to DPLL1
zA single programmable bandwidth control: 18, 35 or
70 Hz
zDamping factor, (For optional faster locking and
peaking control) Factors = 1.2, 2.5, 5, 10 or 20.
zDigital feedback, on/off (Reg. 35 Bit 6)
zOutput frequency selection (Reg. 64)
• DS3/E3 support (44.736 MHz / 34.368 MHz)
independent of rates from DPLL1
• Low jitter E1/DS1 options independent of rates
from DPLL1
• Frequencies of n x E1/DS1 including 16 and 12 x
E1, and 16 an d 24 x DS1 supported
• Squelched (clock off)
zCan provide the source for the 2 kHz and 8 kHz
outputs available at Outputs 01 and 02 (Reg. 7A Bit 7)
zCan use the phase detector in DPLL2 to measure the
input phase difference between two inputs
zSelectable DPLL2 digital feedback, on/off (Reg. 64
Bit 6)
DPLL2 Advanced Features
The advanced features are the same as those for DPLL1,
with DPLL2 using the configuration values for DPLL1, with
the following exceptions :
Advanced Phase Detector Controls
zPD2 gain control enable, on/off (Reg. 6C, Bit 7)
If on, this allows automatic gain selection according to
the type of feedback to the DPLL (For the digital
feedback setting, the gain used for PD2 is given by
(Reg. 6C Bits [2:0]). If off, PD2 is not used.
zAdjustable gain settings for PD2 (with auto switching
enabled), for the following feedback cases:
• Digital feedback (Reg. 6C Bits [2:0])
• Analog feedback (all frequencies above 8K)
(Reg. 6C Bits [6:4])
• Analog 8k (or less) feedback (Reg. 6A Bits [2:0])
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ACS8525 LC/P
Outputs
The ACS8525 delivers four output signals on the following
ports: Two clocks, one each on ports Output O1 and
Output O2; and two Sync signals, on ports FrSync and
MFrSync. Output O1 and Output O2 are independent of
each other and are individually selectable. Output 01 is a
differential port (pins O1POS and O1NEG), and can be
selected PECL or LVDS. Output O2 (pin O2) and the Sync
outputs are TTL/CMOS.
The two Sync outputs, FrSync (8 kHz) and MFrSync
(2 kHz), are derived from DPLL1.
PECL/LVDS Output Port Selection
The choice of PECL or LVDS compatibility for Output 01 is
programmed via the cnfg_differential_output register,
Reg. 3A.
Output Frequency Selection and PLL Configuration
The output frequency at many of the outputs is controlled
by a number of inter-dependent parameters (refer to “PLL
Architecture” on page 14). The frequencies of the output
clocks are selectable fro m a rang e of pre-defined spot
frequencies/port technologies, as defined in Tables 6 and
7.
Outputs O1 & O2 Frequency Configuration Steps
The output frequency selection is performed in the
following steps:
6. Refer to Table 8, Frequency Divider Look-up, to
choose a set of output frequencies.
7. Refer to the Table 8 to determine the required APLL
frequency to support the frequency set.
8. Refer to Table 9, APLL1 Frequencies, and Table 10,
APLL2 Frequencies, to determine in what mode
DPLL1 and DPLL2 need to be configured, considering
the output jitter level.
9. Refer to Table 11, O1 and O2 Output Frequency
Selection, and the column headings in Table 8,
Frequency Divider Look-up, to select the appropriate
frequency from either of the APLLs on eac h output as
required.
Note...1.544 MHz/2.048 MHz are shown for SONET/SDH respectively. Pin SONSDHB controls default, when High SONET is default
Table 6 Output Reference Source Selection Table
Port
Name Output Port
Technology Frequencies Supported
Output
O1 LVDS/PECL
(LVDS default) Frequency selection as per Table 7 and Table 11
Output
O2 TTL/CMOS
FrSync TTL/CMOS FrSync, 8 kHz programmable pulse width and polarity, see Reg. 7A.
MFrSync T TL/CMOS MFrSy nc, 2 kHz programmable pulse width and polarity, see Reg. 7A.
Table 7 Output Frequency Selection
Frequency (MHz, unless stated otherwise) DPLL1 Mode DPLL2 Mode APLL2 Input Mux Jitter Level (Typ)
rms
(ps) p-p
(ns)
2 kHz 77.76 MHz Analog - - 60 0.6
2 kHz Any digital feedback mode - - 1400 5
8 kHz 77.76 MHz Analog - - 60 0.6
8 kHz Any digital feedback mode - - 1400 5
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1.536 - 12E1 mode Select DPLL2 500 2.3
1.536 - - Select DPLL1 12E1 250 1.5
1.544 - 16DS1 mode Select DPLL2 200 1.2
1.544 - - Select DPLL1 16DS1 150 1.0
1.544 via Digital1 or Digital2 (not Output O1) 77.76 MHz Analog - - 3800 13
1.544 via Digital1 or Digital2 (not Output O1) Any digital feedback mode - - 3800 18
2.048 - 12E1 mode Select DPLL2 500 2.3
2.048 - - Select DPLL1 12E1 250 1.5
2.048 - 16E1 mode Select DPLL2 400 2.0
2.048 - - Select DPLL1 16E1 220 1.2
2.048 (not Output O1) 12E1 mode - - 900 4.5
2.048 via Digital1 or Digital2 (not Output O1) 77.76 MHz Analog - - 3800 13
2.048 via Digital1 or Digital2 (not Output O1) Any digital feedback mode - - 3800 18
2.059 - 16DS1 mode Select DPLL2 200 1.2
2.059 - - Select DPLL1 16DS1 150 1.0
2.059 (not Output O1) 16DS1 mode - - 760 2.6
2.316 - 24DS1 mode Select DPLL2 110 0.75
2.316 - - Select DPLL1 24DS1 110 0.75
2.731 - 16E1 mode Select DPLL2 400 1.5
2.731 - - Select DPLL1 16E1 220 1.2
2.731 (not Output O1) 16E1 mode - - 250 1.6
2.796 - DS3 mode Select DPLL2 110 1.0
3.088 - 24DS1 mode Select DPLL2 110 0.75
3.088 - - Select DPLL1 24DS1 110 0.75
3.088 (not Output O1) 24DS1 mode - - 110 0.75
3.088 via Digital1 or Digital2 (not Output O1) 77.76 MHz Analog - - 3800 13
3.088 via Digital1 or Digital2 (not Output O1) Any digital feedback mode - - 3800 18
3.728 -DS3 mode Select DPLL2 110 1.0
4.096 via Digital1 or Digital2 (not Output O1) 77.76 MHz Analog - - 3800 13
4.096 via Digital1 or Digital2 (not Output O1) Any digital feedback mode - - 3800 18
4.296 - E3 mode Select DPLL2 120 1.0
Table 7 Output Frequency Selection (cont...)
Frequency (MHz, unless stated otherwise) DPLL1 Mode DPLL2 Mode APLL2 Input Mux Jitter Level (Typ)
rms
(ps) p-p
(ns)
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4.86 - 77.76 MHz mode Select DPLL2 60 0.6
5.728 - E3 mode Select DPLL2 120 1.0
6.144 12E1 mode - - 900 4.5
6.144 - 12E1 mode Select DPLL2 500 2.3
6.144 - - Select DPLL1 12E1 250 1.5
6.176 16DS1 mode - - 760 2.6
6.176 - 16DS1 mode Select DPLL2 200 1.2
6.176 - - Select DPLL1 16DS1 150 1.0
6.176 via Digital1 or Digital2 (not Output O1) 77.76 MHz Analog - - 3800 13
6.176 via Digital1 or Digital2 (not Output O1) Any digital feedback mode - - 3800 18
6.48 - 77.76 MHz mode Select DPLL2 60 0.6
6.48 (not Output O1) 77.76 MHz analog - - 60 0.6
6.48 (not Output O1) 77.76 MHz digital - - 60 0.6
8.192 12E1 mode - - 900 4.5
8.192 16E1 mode - - 250 1.6
8.192 - 16E1 mode Select DPLL2 400 2.0
8.192 - - Select DPLL1 16E1 220 1.2
8.192 via Digital1 or Digital2 (not Output O1) 77.76 MHz Analog - - 3800 13
8.192 via Digital1 or Digital2 (not Output O1) Any digital feedback mode - - 3800 18
8.235 16DS1 mode - - 760 2.6
9.264 24DS1 mode - - 110 0.75
9.264 - 24DS1 mode Select DPLL2 110 0.75
9.264 - - Select DPLL1 24DS1 110 0.75
10.923 16E1 mode - - 250 1.6
11.184 - DS3 mode Select DPLL2 110 1.0
12.288 12E1 mode - - 900 4.5
12.288 - 12E1 mode Select DPLL2 500 2.3
12.288 - - Select DPLL1 12E1 250 1.5
12.352 24DS1 mode - - 110 0.75
12.352 16DS1 mode - - 760 2.6
12.352 - 16DS1 mode Select DPLL2 200 1.2
Table 7 Output Frequency Selection (cont...)
Frequency (MHz, unless stated otherwise) DPLL1 Mode DPLL2 Mode APLL2 Input Mux Jitter Level (Typ)
rms
(ps) p-p
(ns)
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12.352 - - Select DPLL1 16DS1 150 1.0
12.352 via Digital1 or Digital2 (not Output O1) 77.76 MHz Analog - - 3800 13
12.352 via Digital1 or Digital2 (not Output O1) Any digital feedback mode - - 3800 18
16.384 12E1 mode - - 900 4.5
16.384 16E1 mode - - 250 1.6
16.384 - 16E1 mode Select DPLL2 400 2.0
16.384 - - Select DPLL1 16E1 220 1.2
16.384 via Digital1 or Digital2 (not Output O1) 77.76 MHz Analog - - 3800 13
16.384 via Digital1 or Digital2 (not Output O1) Any digital feedback mode - - 3800 18
16.469 16DS1 mode - - 760 2.6
17.184 - E3 mode Select DPLL2 120 1.0
18.528 24DS1 mode - - 110 0.75
18.528 - 24DS1 mode Select DPLL2 110 0.75
18.528 - - Select DPLL1 24DS1 110 0.75
19.44 77.76 MHz analog - - 60 0.6
19.44 77.76 MHz digital - - 60 0.6
19.44 - 77.76MHz mode Select DPLL2 60 0.6
21.845 16E1 mode - - 250 1.6
22.368 - DS3 mode Select DPLL2 110 1.0
24.576 12E1 mode - - 900 4.5
24.576 - 12E1 mode Select DPLL2 500 2.3
24.576 - - Select DPLL1 12E1 250 1.5
24.704 24DS1 mode - - 110 0.75
24.704 16DS1 mode - - 760 2.6
24.704 - 16DS1 mode Select DPLL2 200 1.2
24.704 - - Select DPLL1 16DS1 150 1.0
25.92 77.76 MHz analog - - 60 0.6
25.92 77.76 MHz digital - - 60 0.6
32.768 16E1 mode - - 250 1.6
32.768 - 16E1 mode Select DPLL2 400 2.0
32.768 - - Select DPLL1 16E1 220 1.2
Table 7 Output Frequency Selection (cont...)
Frequency (MHz, unless stated otherwise) DPLL1 Mode DPLL2 Mode APLL2 Input Mux Jitter Level (Typ)
rms
(ps) p-p
(ns)
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34.368 - E3 mode Select DPLL2 120 1.0
37.056 24DS1 mode - - 110 0.75
37.056 - 24DS1 mode Select DPLL2 110 0.75
37.056 - - Select DPLL1 24DS1 110 0.75
38.88 77.76 MHz analog - - 60 0.6
38.88 77.76 MHz digital - - 60 0.6
38.88 - 77.76 MHz mode Select DPLL2 60 0.6
44.736 - DS3 mode Select DPLL2 110 1.0
49.152 (Output O1 only) 12E1 mode - - 900 4.5
49.408 (Output O1 only) 16DS1 mode - - 760 2.6
51.84 77.76 MHz analog - - 60 0.6
51.84 77.76 MHz digital - - 60 0.6
65.536 (Output O1 only) 16E1 mode - - 250 1.6
68.736 - E3 mode Select DPLL2 120 1.0
74.112 (Output O1 only) 24DS1 mode - - 110 0.75
77.76 77.76 MHz analog - - 60 0.6
77.76 77.76 MHz digital - - 60 0.6
77.76 - 77.76 MHz mode Select DPLL2 60 0.6
98.304 (Output O1 only) 12E1 mode - - 900 4.5
98.816 (Output O1 only) 16DS1 mode - - 760 2.6
131.07 (Output O1 only) 16E1 mode - - 250 1.6
148.22 (Output O1 only) 24DS1 mode - - 110 0.75
155.52 (Output O1 only) 77.76 MHz analog - - 60 0.6
155.52 (Output O1 only) 77.76 MHz digital - - 60 0.6
311.04 (Output O1 only) 77.76 MHz analog - - 60 0.6
311.04 (Output O1 only) 77.76 MHz digital - - 60 0.6
Table 7 Output Frequency Selection (cont...)
Frequency (MHz, unless stated otherwise) DPLL1 Mode DPLL2 Mode APLL2 Input Mux Jitter Level (Typ)
rms
(ps) p-p
(ns)
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ACS8525 LC/P
Note...All frequencies in MHz
Note...If using Synthesis for inputs to both APLL1 and APLL2, then they must both use the same synthesis settings.
Table 8 Frequency Divider Look-up
Transmission Rate APLL Frequency APLL/2 APLL/4 APLL/6 APLL/8 APLL/12 APLL/16 APLL/48 APLL/64
OC-N Rates 31 1.0 4 155.52 77.76 51.84 38.88 25.92 19.44 6.48 4.86
E3 274.944 137.472 68.376 - 34.368 - 17.184 5.728 4.296
DS3 178.944 89.472 44.736 - 22.368 - 11.184 3.728 2.796
24DS1 148.224 74.112 37.056 24,704 18.528 12.352 9.264 3.088 2.316
16E1 131.072 65.536 32.768 21.84533 16.384 10.92267 8.192 2.730667 2.048
16DS1 98.816 49.408 24.704 16.46933 12.352 8.234667 6.176 2.058667 1.544
12E1 98.304 49.152 24.576 16.384 12.288 8.192 6.144 2.048 1.536
Table 9 APLL1 Frequencies
APLL1 Frequency Synthesis/MUX setting for
APLL1 input DPLL1 Frequency Control Register Bits
Reg. 65 Bits[2:0] Output Jitter Level
ns (p-p)
311.04 Normal (digital feedback) 000 <0.5
311.04 MHz Normal (analog feedback) 001 < 0.5
98.304 MHz 12E1 (digital feedback) 010 <2
131.072 MHz 16E1 (digital feedback) 011 <2
148.224 MHz 24DS1 (digital feedback) 100 <2
98.816 MHz 16DS1 (digital feedback) 101 <2
- Do not use 110 -
- Do not use 111 -
Table 10 APLL2 Frequencies
APLL2
Frequency DPLL Mode DPLL2 Forward
DFS Frequency
(MHz)
DPLL2 Freq Control
Register Bits
Reg. 64 Bits [2:0]
APLL2 Input from
DPLL1 or 2.
Reg. 65 Bit 6
DPLL1 + Synt hesis
Freq to APLL2
Register Bits
Reg. 65 Bits [5:4]
Output Jitter
Level ns (p-p)
311.04 MHz DPLL2-Squel ched 77.76 000 0 (DPLL2 enable d) XX <0.5
311.04 MHz DPLL2-Normal 77.76 001 0 (DPLL2 enabled) XX <0.5
98.304 MHz DPLL2-12E1 24.576 010 0 (DPLL2 enabled) XX <0.5
131.072 MHz DP LL2-16E1 3 2.768 011 0 (DPLL2 enabled) XX <0.5
148.224 MHz DP LL2-24DS1 37.056
(2*18.528) 100 0 (DPLL2 enabled) XX <0.5
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ACS8525 LC/P
98.816 MHz DPLL2-16DS1 24.704 101 0 (DPLL2 enabled) XX <0.5
274.944 MHz DP LL2-E3 68.736
(2*34.368) 110 0 (DPLL2 enabled) XX <0.5
178.944 MHz DPLL2-DS3 44.736 111 0 (DPLL2 enabled) XX <0.5
98.304 MHz DPLL1-12E1 - XXX 1 (DPLL1 enabled) 00 <2
131.072 MHz DP LL1-16E1 - XXX 1 (DPLL1 enabled) 01 <2
148.224 MHz DP LL1-24DS1 - XXX 1 (DPLL1 enabled) 10 <2
98.816 MHz DPLL1-16DS1 - XXX 1 (DPLL1 enabled) 11 <2
Table 10 APLL2 Frequenc ies (cont...)
APLL2
Frequency DPLL Mode DPLL2 Forward
DFS Frequency
(MHz)
DPLL2 Freq Control
Register Bits
Reg. 64 Bits [2:0]
APLL2 Input from
DPLL1 or 2.
Reg. 65 Bit 6
DPLL1 + Synt hesis
Freq to APLL2
Register Bits
Reg. 65 Bits [5:4]
Output Jitter
Level ns (p-p)
Table 11 O1 and O2 Output Frequency Selection
Output Frequency for given “Value in Register” for each Output Port’s Cnf_output_frequency Register
Value in Register Output O2
Reg. 61 Bits [3:0] Output O1
Reg. 62 Bits [7:4]
0000 Off Off
0001 2 kHz 2 kHz
0010 8 kHz 8 kHz
0011 Digital2 APLL1/2
0100 Digital1 Digital1
0101 APLL1/48 APLL1/1
0110 APLL1/16 APLL1/16
0111 APLL1/12 APLL1/12
1000 APLL1/8 APLL1/8
1001 APLL1/6 APLL1/6
1010 APLL1/4 APLL1/4
1011 APLL2/64 APLL2/64
1100 APLL2/48 APLL2/48
1101 APLL2/16 APLL2/16
1110 APLL2/8 APLL2/8
1111 APLL2/4 APLL2/4
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“Digital” Frequencies
Table 11, “O1 and O2 Output Frequency Selection,” lists
Digital1 and Digital2 as available for selection. Digital1 is
a single frequency selected from the range shown in
Table 12. Digital2 is another single frequency selected
from the same range.
Using Output O2 to Control Pulse Width of 2/8 kHz on FrSync,
MFrSync and 01 Outputs
It can be seen from Table 11 (01 and 02 Output
Frequency Selection) that frequencies listed as 2 kHz and
8 kHz can be selected. Whilst the FrSync and MFrSync
outputs are always supplied from DPLL1, the 2 kHz and
8 kHz options available from the O1 and O2 outputs are
all supplied via DPLL1 or DPLL2 (Reg. 7A Bit 7).
The outputs can be either clocks (50:50 mark-space) or
pulses, and can be inverted. When pulse configuration is
used, the pulse width will be one cycle of the rate selected
on Output O2 (Output O2 must be configured to generate
at least 1,544 kHz to ensure that pulses are gene rated
correctly). Figure 7 shows the various options with the
8 kHz controls in Reg. 7A. There is an identical
arrangement with Reg. 7A Bits [1:0] for the 2 kHz 01 and
MFrSync outputs. Outputs FrSync and MFrSync can be
disabled via Reg. 63 Bits [7:6].
Figure 7 Control of 8k Options.
Table 12 Digital Frequency Selections
Digital1 Control
Reg.39 Bits [5:4] Digital1 SONET/
SDH Reg. 38 Bit5 Digital1 Freq. (MHz) Digital2 Control
Reg. 39 Bits[7:6] Digital2 SONET/SDH
Reg.38 Bit6 Digital2 Freq. (MHz)
00 0 2.048 00 0 2.048
01 0 4.096 01 0 4.096
10 0 8.192 10 0 8.192
11 0 16.384 11 0 16.384
00 1 1.544 00 1 1.544
01 1 3.088 01 1 3.088
10 1 6.176 10 1 6.176
11 1 12.352 11 1 12.352
F8525_016outputoptions8k_01
02 Output
FrSync at 8 kHz, or
Output 01 at 8kHz
FrSync at 8 kHz, or
Output 01 at 8kHz
FrSync at 8 kHz, or
Output 01 at 8kHz
FrSync at 8 kHz, or
Output 01 at 8kHz
a) Clock non-inverted, Reg.7A[3:2] = 00
b) Pulse non-inverted, Reg.7A[3:2] = 01
c) Clock inverted, Reg.7A[3:2] = 10
d) Pulse inverted, Reg.7A[3:2] = 11
02 Output
02 Output
02 Output
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ACS8525 LC/P
Operating Modes (States) of the Device
The ACS8525 has three primary modes of operation, or
operating states: Free-Run, Locked and Digital Holdover.
These are supported by three secondary, temporary
modes (Pre-Locked, Lost-Phase and Pre-Locked2). Refer
to the State Transition Diagram for DPLL1, Figure 8.
The ACS8525 can operate in Forced or Automatic control.
On reset, the ACS8525 reverts to Automatic Control,
where transitions between states are controlled
completely automatically. Forced Control can be invoked
by configuration, allowing transitions to be perfor med
under external control. This is not the normal mode of
operation, but is provided for special occasions such as
testing, or where a high degree of hands-on control is
required.
Free-run Mode
The Free-run mode is typically used following a
power-on-reset or a device reset before network
synchronization has been achieved. In the Free-run mode,
the timing and synchronization signals generated from
the ACS8525 are based on the 12.800 MHz clock
frequency provided from the external oscillator and are
not synchronized to an input SEC. By default, the
frequency of the output clock is a fixed multiple of the
frequency of the external oscillator, and the accuracy of
the output clock is equal to the accuracy of the oscillator.
However the extern al os cillator frequency can be
calibrated to improve its accuracy by a software
calibration routine using register
cnfg_nominal_frequency (Reg. 3C and 3D). For example a
500 ppm offset crystal could be made to look like one
accurate to 0.02 ppm.
The transition from Free-run to Pre-locked occurs when
the ACS8525 selects an SEC.
Pre-locked Mode
The ACS8525 will enter the Locked state in a maximum of
100 seconds, as defined by GR-1244-CORE[13]
specification, if the selected SEC is of good quality. If the
device cannot achieve lock within 100 seconds, it reverts
to Free-Run mode and another SEC is selected.
Locked Mode
The Locked mode is entered from Pre-locked, Pre-locked2
or Phase-lost mode when an input reference source has
been selected and t he DPLL has locked. The DPLL is
considered to be locked when the phase loss/lock
detectors (See“Phase Lock/Loss Detectors” on page 19)
indicate that the DPLL has remained in phase lock
continuously for at least one second. When the ACS8525
is in Locked mode, the output frequency and phase tracks
that of the selected input reference source.
Lost-phase Mode
Lost-phase mode is used whenever the phase loss/lock
detectors (See“Phase Lock/Loss Detectors” on page 19)
indicate that the DPLL has lost phase lock. The DPLL will
still be trying to lock to the input clock reference, if it
exists. If the Leaky Bucket Accumulator calculates that
the anomaly is serious, the device disqualifies the
reference source. If the device spends more than 100
seconds in Lost-phase mode, the reference is disqualified
and a phase alarm is raised on it. If the reference is
disqualified, one of the following transitions takes place:
1. Go to Pre-locked2;
- If a known good stand-by source is available.
2. Go to Holdover;
- If no stand-by sources are available.
Digital Holdover Mode
Digital Holdover mode is the operating condition the
device enters when its curr ently selected input source
becomes invalid, and no other valid replacement source
is available.
In Digital Holdover mode, the ACS8525 provides the
timing signals to maintain the Line Card but is not phase
locked to an input SEC.
Digital Holdover op er at es Instantaneously, which means
the DPLL freezes at t he frequency it was operatin g at the
time of entering Digital Holdover mode. This determines
the output frequency accuracy.
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ACS8525 LC/P
Figure 8 Automatic Mode Control State Diagram (DPLL1)
Note...The state diagram above is for DPLL1 only, and the 3-bit state value refers to the re gister sts_operating Reg. 09 Bits
[2:0] DPLL1_operating _mode. By contrast, the DPLL2 has only automatic operation and can be in one of only two possible
states: “Instantaneous Automatic Holdover” with zero frequency offset (its start-up state), or “Locked”. The states of DPLL2
are not configurable by the User and there is no “Free-run” state.
Free-run
select ref
(state 001)
(1) Reset
(3) no valid standby ref
&
(main ref invalid
or out of lock > 100s
(2) all refs evaluated
&
at least one ref valid
Pre-locked
wait for up to 100s
(state 110)
(4) valid standby ref
&
[main ref invalid or
(higher-priority ref valid
& in revertive mode) or
out of lock > 100s]
(5) selected ref
phase locked
Locked
keep ref
(state 100)
Lost-phase
wait for up to 100s
(state 111)
(10) selected source
phase locked
(6) no valid standby ref
&
main ref invalid
(7) phase lost
on main ref
(8) phase
regained
within 100s
(9) valid standby ref
&
[main ref invalid or
(higher priority ref valid
& in revertive mode)]
Pre-locked2
wait for up to 100s
(state 101)
Digital Holdover
select ref
(state 010)
(12) valid standby ref
&
(main ref invalid
or out of lock >100s)
(11) no valid standby ref
&
(main ref invalid
or out of lock >100s)
(15) valid standby ref
&
[main ref invalid or
(higher-priority ref valid
& in revertive mode) or
out of lock >100s]
(13) no valid standby ref
&
(main ref invalid
or out of lock >100s)
(14) all refs evaluated
&
at least one ref valid
Reference sources are flagged as valid when
active, in-band and have no phase alarm set.
All sources are continuously checked for
activity and frequency
Only the main source is checked for phase.
A phase lock alarm is only raised on a
reference when that reference has lost phase
whilst being used as the main reference. The
micro-processor can reset the phase lock
alarm.
A source is considered to have phase locked
when it has been continuously in phase lock
for between 1 and 2 seconds.
F8525D_018AutoModeContStateDia_01
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Pre-locked2 Mode
This state is very similar to the Pre-locked state. It is
entered from the Digital Holdover state when an input
SEC has been selected and applied to the phase locked
loop. It is also entered if the device is operating in
Revertive mode and a higher-priority SEC is restored.
Upon applying a SEC to the phase locked loop, the
ACS8525 will enter the Locked state in a maximum of
100 seconds, as defined by GR-1244-CORE[13]
specification, if the selected SEC is of good quality. If the
device cannot achieve lock within 100 seconds, it reverts
to Digital Holdover mode and another SEC is selected.
Local Oscillator Clock
The Master system clock on the ACS8525 should be
provided by an external clock oscillator of frequency
12.800 MHz. W ander on th e local oscillator c lock will not
have a significant effect on the output clock whilst in
Locked mode. In Free-Run or Holdover mode wander on
the crystal is more significant. Variation in crystal
temperature or supply voltage both cause drifts in
operating frequency, as does ageing. The se effect s must
be limited by careful selection of a suitable component for
the local oscillator. Please contact Semtech for
information on crystal oscillator suppliers.
Crys tal Frequency Calibration
The absolute crystal frequency accuracy is less important
than the stability since any frequency offset can be
compensated by adjustment of register values in the IC.
This allows for calibration and compensation of any
crystal frequency variation away from its nominal value.
± 50 ppm adjustment would be sufficient to cope with
most crystals, in fact the range is an order of magnitude
larger due to the use of two 8-bit register locations. The
setting of the cnfg_nominal_frequency register allows for
this adjustment. An increase in the register value
increases the output frequencies by 0.0196229 ppm for
each LSB step.
Note...The default register value (in decimal) = 39321
(9999 hex) = 0 ppm offset. The minimum to maximum offset
range of the register is 0 to 65535 (dec), giving an adjustment
range of -771 ppm to +514 ppm of the output frequencies, in
0.0196229 ppm steps.
Example: If the crystal was oscillating at 12.800 MHz + 5 ppm,
then the calibration value in the register to g i ve a - 5 p p m
adjustment in output frequencies to compensate for the
crystal inaccuracy, would be:
39321 - (5 / 0.0196229) = 39066 (dec) = 989A (hex).
Status Reporting and Phase Measurement
Input Status Interrupts
Status interrupts are provided for the following events:
zChanged status on SEC input (one interrupt per input)
(Reg. 05)
zChange of Operating mode (Reg. 0 6)
zDPLL1 Main reference Failure (Reg. 06)
zFrame Sync alarm limit reached (Reg. 08)
These interrupts are flagged on pin INTREQ.
Input Status Information
Status information can be read from the following Status
Registers:
sts_operating_mode (Reg. 09)
sts_priority_table (Reg. 0A and 0B)
sts_current_DPLL_frequency (Reg. 0C, 0D, and 07)
sts_sources_valid (Reg. 0E and 0F)
sts_reference_sources (Reg. 11, 12 and 14)
Refer to “Register Ma p” on page 38 and associated
Register Descriptions for more details.
DPLL Frequency Reporting
The registers sts_current_DPLL_frequency (Reg. 0C,
Reg. 0D and Reg. 07) report the frequency of DPLL1 or
DPLL2 with respect to the external crystal XO frequency
(after calibration via Reg. 3C, 3D if used). The selection of
DPLL2 or DPLL1 reporting is made via Reg. 4B, Bit 4. The
value is a 19-bit signed number with one LSB
representing 0.0003068 ppm (range of ±80 ppm). This
value is actually the integral path value in the DPLL, and
as such corresponds to an averaged measurement of the
input frequency, with an averaging ti me inversely
proportional to the DPLL bandwidth setting. Reading this
regularly can show how the currently locked source is
varying in value e.g. due to frequency wander on its input.
The input phase, as seen at the DPLL phase detector, can
be read back from register sts_current_phase, Reg. 77
and 78. DPLL1 or DPLL2 phase detector reporting is
again controlled by Reg. 4B, Bit 4. One LSB corresponds
to 0.707° phase difference. For DPLL1 this will be
reporting the phase diffe rence between the input and the
internal feedback clock. The phase resu lt is internally
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ACS8525 LC/P
averaged or filtered with a -3 dB attenuation point at
approximately 100 Hz.
Measuring Phase Between Master and
Slave/Stand-by SEC Sources
The phase can be measured between the selected SEC
input to DPLL1 and either of the other two SEC inputs by
a using the Phase and Frequency detector of DPLL2. This
special configuration requires manual selection of
DPLL2’s selected source (by altering the Priorities).
The DPLL2 PFD compares two inputs (usually the
feedback and reference input) with each other and
performs some filtering. This filtering has a bandwidth of
approx. 100 Hz. This will result in a digital number
represent ing the filtered phas e difference be tween these
two signals being available (normally used for the digital
synthesis).
Under normal circumstances the frequency of the inputs
to the PFD are determined by the input frequency
selection and the pre-divider settings such as lock8k and
DivN. The appropriate feed bac k freq uen cy is
automatically selected from the supported spot
frequencies to match the input r eference frequency (post
division if necessary).
The phase difference is reported in units of 0.707
degrees of the actual locking frequency. When direct
locking to high frequency input, the actual time is then
scaled down and will give resolution down to e.g. 110 ps
at 19.44 MHz in direct locking mode compared with
245 ns with Lock8K mode enabled with the same
19.44 MHz input. The two inputs to the PFD have to be
very close in frequency to give an accurate phase
measurement.
Reg. 65, Bit 7 is used to switch one input to the DPLL2
phase detector over to the current DPLL1 input. The other
phase detector input becomes connected to a second
input source. The second input source can be changed via
the DPLL2 priority (Reg. 19 to 1C), when Reg. 4B,
Bit 4 = 1).
The phase difference measurement is held in the 16-bit
register, sts_current_phase Reg. 77 and 78. The register
is updated on a 204.8 MHz cycle.
When measuring the relative phase error between the
selected inputs, the user must ensure that the settings
and frequency are the same for the two inputs to be
measured. Enabling this phase measurement feature
replaces the DPLL2 feedback signal to the DPLL2 PFD
with the DPLL1 PFD input reference signal. Reading the
current phase register fr om DPLL2 will yield the filtered
phase difference between the two inputs. If there is jitter
or wander present on either or both inputs, then this will
have an effect on the measured phase . The extent of this
effect will depend on the frequency of the jitter/wander
compared to the 100 Hz bandwidth of the phase filter.
With the input selections in the examples below, a
meaningful result for phase measurement will be
obtained from Example 1 only.
Example 1
SEC1 19.44 MHz input, direct locking
SEC2 19.44 MHz input, direct locking
Example 2
SEC1 19.44 MHz input, direct locking
SEC2 19.44 MHz input, Lock8K
The phase reported in degrees of the locking frequency.
Direct locking to the highest frequency gives the most
meaningful result, as the actual time is scaled down and
will give a resolution in picoseconds, for example: 101 ps
@19.44 MHz, Direct locking on SEC1 and SEC2. With
Lock8K enabled instead of direct locking, a result can be
measured but the phase error will have a much lower
resolution of 245 nanoseconds.
Sync Reference Sources
The ACS8525 provides the facility to have a Sync
reference source associated with each SEC. The Sync
inputs (SYNC1, SYNC2 and SYNC3) are used for Frame
Sync output alignment and can be 2, 4 or 8 kHz
(automatically detected frequency). In the ACS8525
device, the Sync is treated as an additional part of the SEC
clock. The failure of a Sync input will never cause a source
disqualification. The Sync input is used to internally align
the generation of the output 2 kHz and 8 kHz Sync pulses.
On the ACS8525, the presence of a Sync input associated
with any particular SEC input is optional. If a Sync input is
not present, or it fails, the 2 kHz and 8 kHz outputs will
simply continue to be generated with the same
relationship to the SEC output. This also applies to a
source switch from a reference with a Sync input to a
reference without a Sync input. The Sync outputs are
always divided from the SEC outputs and will never
free-run.
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Figure 9 External Sync Input Phase Control (Reg.7B Bits [1:0])
As with all frequencies generated at the outputs of the
ACS8525, the Sync outputs are falling edge aligned.
However, the Sync outputs can be inverted. They can also
be selected to have a number of different pulse widths. In
addition to these controls on the outputs, the input Sync
phases with respect to their associated SEC can be
configured (separately for each Sync). Nominally, the Sync
input is expected to b e fa lling edge aligned with the SEC.
Therefore it is sampled on the rising edge of the SEC. This
gives a tolerance to offset between the SEC and the Sync
input of ±0.5 UI of the SEC clock. If the Sync is delayed or
advanced with respect to the SEC the expected position of
the edge can be moved by 0.5 UI early or late. The
tolerance is always ±0 .5 UI of the SEC fr om the expe cted
position. Figure 9 summarizes these points and
Sync_phase_SYNC1 (Reg. 7B, Bits [1:0]) provides the
controlling configuration.
Aligning Phase of MFrSync and FrSync Outputs to
Phase of Sync Inputs
The selected Sync input (which is selected by SEC
selection) is monitored by the ACS8525 for consistent
phase and correct frequency compared with the SEC
input, and if it does not pass these quality checks, an
alarm flag is raised (Reg. 08, Bit 7 and Reg. 09, Bit 7). The
check for consistent phase involves checking that each
input edge is within an expected timing window. The
window size is set by Reg. 7C, Bits [6:4]. An internal
detector senses that a correct Sync signal is present and
only then allows the signal to resynchronize the internal
dividers that generate the 8 kHz FrSync an d 2 kHz
MFrSync outputs. This sequence avoids spurious
resynchronizations that may otherwise occur with
connections and disconnections of the Sync input.
The Sync input will normally be a 2 kHz frequency, only its
falling edge is used. It can however be at a frequencies of
4kHz or 8kHz without any change to the register setups.
However the 2 kHz Sync output alignment can only be
achieved when aligning to a 2 kHz SEC.
Safe sampling of the selected Sync input is achieved by
using the “locked-to” SEC, with which it is paired, to do the
input sampling. Phase Build-out mode should be off
(Reg. 48, Bit 2 = 0). The Sync input is norm ally sampled
on the rising edge of the current input reference clock, in
order to provide the most margin. As mentioned earlier,
modification of the expected timing of the selected Sync
input with respect to its SEC can be achieve d via Reg. 7B,
Bits [1 :0].
A different sampling resolution is used depending on the
input reference frequency and the setting of Reg. 7B Bit 6,
cnfg_sync_phase. With this bit Low, the Sync input
sampling has a 6.48 MHz resolution. When Bit 6 is High
the selected Sync can have a sampling resolution of
F8525_030ExtSyncPhasCntl_01
Sync Input
On Target
SEC Output
Sync Input
Sync Output
SEC Input
Sync Input
0.5 UI Early
Sync Input
0.5 UI Late
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ACS8525 LC/P
either 19.44 MHz (when the current locked to reference is
19.44 MHz) or 38.88 MHz (all other frequencies). This
would allow, for instance, a 19.44 MHz and 2 kHz pair to
be used for Line Card synchronization.
Reg. 7B Bit 7, Indep_FrSync/MFrSync controls whether
the 2kHz MFrSync and 8kHz FrSync outputs keep their
precise alignment with the othe r output clocks. When
Indep_FrSync/MFrSync Reg. 7B Bit 7 is Low the FrSyncs
and the oth er higher rate clocks are not independent and
their alignment on the falling 8kHz edge is maintained.
This means that when bit Sync_OC-N_rates is High, the
OC-N rate dividers and clocks are also synchronized by the
Sync input. On a change of phase position of the Sync, this
could result in a shift in phase of the 6.48 MHz output
clock when a 19.44 MHz precision is used for the Sync
input. To avoid disturbing any of the output clocks and
only align the MFrSync and FrSync outputs, at the chosen
level of precision, Independent Frame Sync mode can be
used (Reg. 7B, Bit 7 = 1). Edge al ignment of the FrSync
output with other clocks outputs may then change
depending on the selected Sync sampling precision used.
For example with a 19.44 MHz reference input clock and
Reg. 7B Bits 6 & 7 both High (independent mode and
Sync OC-N rates), then the FrSync output will still align
with the 19.44 MHz output but not with the 6.48 MHz
output clock.
The FrSync and MFrSync outputs always come from
DPLL1. 2 kHz and 8 kHz outputs can also be produced at
the O1 to O2 outputs. These can come from either the
DPLL1 or from the DPLL2, controlled by Reg. 7A, Bit 7.
Power-On Reset
The Power-On Reset (PORB) pin resets the device if forced
Low. The reset is asynchronous, the minimum Low pulse
width is 5 ns. Reset is needed to initialize all of the
register values to their defaults. Reset must be asserted
at power on, and may be re-asserted at any time to restore
defaults. This is implemented simply using an external
capacitor to GND along with the internal pull-up resistor.
The ACS8525 is held in a reset state for 250 ms after the
PORB pin has been pulled High. In normal operation PORB
should be held High.
Serial Interface
The ACS8525 device has a serial interface which can be
SPI compatible. The Motorola SPI Convention is such that
address and data is transmitted and received MSB first.
On the ACS8525 address and data are transmitted and
received LSB first. Address, read/write control and data
on the SDI pin are latched into the device on the rising
edge of the SCLK. During a read operation, serial data
output on the SDO pin can be read out of the device on
either the rising or falling edge of the SCLK depending on
the logic level of CLKE. For standard Motorola SPI
compliance, data should be clocked out of the SDO pin on
the rising edge of the SCLK so that it may be latched into
the microprocessor on the falling edge of the SCLK.
Figure 10 and Figure 1 1 show the timing diagrams of
read and write accesses for this interface.
The serial interface clock (SCLK) is not required to run
between accesses (i.e., when CSB = 1).
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ACS8525 LC/P
Figure 10Read Access Timing for SERIAL Interface
Table 13 Read Access Timing for SERIAL Interface (For use with Figure 10)
Symbol Parameter MIN TYP MAX
tSU1 Setup SDI valid to SCLKrising edge 4 ns - -
tSU2 Setup CSBfalling edge to SCLKrising edge 14 ns - -
td1 Delay SCLKrising edge (SCLKfalling edge for CLKE = 1) to SDO valid - - 18 ns
td2 Delay CSBrising edge to SDO high-Z - - 16 ns
tpw1 SCLK Low time 22 ns - -
tpw2 SCLK High time 22 ns - -
th1 Hold SDI valid after SCLKrising edge 6 ns - -
th2 Hold CSB Low after SCLKrising edge, for CLKE = 0
Hold CSB Low after SCLKfalling ed ge, for CLKE = 1 5 ns - -
tpTime between consecutive accesses (CSBrising edge to CSBfalling edge)10 ns - -
F8526D_013ReadAccSerial_01
SCLK
CSB
CLKE = 0; SDO data is clocked out on the rising edge of SCLK
CLKE = 1; SDO data is clocked out on the falling edge of SCLK
R/W
Output not driven, pulled low by internal resistor
SDI
SDO
tsu2
tsu1 th1 tpw1
tpw2
_A0 A1 A2 A3 A4 A5 A6
D0 D1 D2 D3 D4 D5 D6 D7
th2
td2
td1
SCLK
CSB
R/W
Output not driven, pulled low by internal resistor
SDI
SDO
_A0 A1 A2 A3 A4 A5 A6
D0 D1 D2 D3 D4 D5 D6 D7
th2
td2
td1
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ACS8525 LC/P
Figure 11Write Access Timing fo r SERIAL Interface
Table 14 Write Access Timing for SERIAL Interface (For use with Figure 11)
Symbol Parameter MIN TYP MAX
tsu1 Setup SDI valid to SCLKrising edge 4 ns - -
tsu2 Setup CSBfalling edge to SCLKrising edge 14 ns - -
tpw1 SCLK Low time 22 ns - -
tpw2 SCLK High time 22 ns - -
th1 Hold SDI valid after SCLKrising edge 6 ns - -
th2 Hold CSB Low after SCLKrising edge 5 ns - -
tpTime between consecutive accesses (CSBrising edge to CSBfalling edge)10 ns - -
SCLK
CSB
R/W
Output not driven, pulled low by internal resistor
SDI
SDO
tsu2
tsu1 th1 tpw1
tpw2
_A0 A1 A2 A3 A4 A5 A6
th2
D0 D1 D2 D3 D4 D5 D6 D7
F8525D_014WriteAccSerial_01
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ACS8525 LC/P
Each Register, or register group, is described in the
following Register Map (Table 15) and subsequent
Register Description Tables.
Register Organization
The ACS8525 LC/P uses a total of 91 eight-b it register
locations, identified by a Register Name and
correspond ing hexadecimal Register Address. They are
presented here in ascending order of Reg. address and
each Register is organized with the most-significant bit
positioned in the left-most bit, with bit significance
decreasing towards the right-most bit. Some registers
carry several individual data fields of various sizes, from
single-bit values (e.g. flags) upwards. Several data fields
are spread across multiple registers, as shown in the
Register Map,
Table 15. Shaded areas in the map are “don’t care” and
writing either 0 or 1 will not affect any function of the
device. Bits labelled “Set to 0” or “Set to 1” must be set
as stated during initialization of the device, either
following power- up, or after a power-on reset (POR).
Failure to correctl y set these bi ts may result in the dev ice
operating in an unexpected way.
CAUTION! Do not write to any undefined register
addresses as this may cause the device to operate in a
test mode. If an undefined register has been
inadvertently addressed, the device should be reset to
ensure the undefined registers are at default values.
Multi-word Registers
For Multi-word Registers (e.g. Reg. 0C and 0D), all the
words have to be written to their separate addresses, and
without any other access taking place, before their
combined value can take effect. If the sequence is
interrupted, the sequence of write s will be ignored.
Reading a multi-word address freezes the other address
words of a multi-word address so that the bytes all
correspond to the same complete word.
Register Access
Most registers are of one of two types, configuration
registers or status registers, the exceptions being the
chip_id and chip_revision registers. Configuration
registers may be written to or read from at any time (the
complete 8-bit register must be written, even if only one
bit is being modified). All status registers may be read at
any time and, in some status registers (such as the
sts_interrupts register), any individual data field may be
cleared by writing a 1 into each bit of the field (writing a 0
value into a bit will not affect the value of the bit).
Configuration Registers
Each configuration register rever ts to a default value on
power-up or following a reset. Most default values are
fixed, but some can be pin-set. All configuration registers
can be read out over the microprocessor port.
Status Registers
The Status Registers contain readable registers. They may
all be read from outside the chip but are not writeable
from outside the ch ip (except for a clearing operation) . All
status registers are read via shadow registers to avoid
data hits due to dynamic operation. Each individual status
register has a unique location.
Interrupt Enable and Clear
Interrupt requests ar e flagged on pin INTREQ; the active
state (High or Low) is programmable and the pin can
either be driven, or set to high impedance when non-
active (Reg 7D refers).
Bits in the interrupt status register are set (High) by the
following conditions;
1. Any SEC becoming valid or going invalid.
2. A change in the operating state e.g. Locked, Holdover.
3. A brief loss of the currently selected SEC.
All interrupt sources, see Reg. 05, Reg. 06 and Reg. 08,
are maskable via the mask register, each one being
enabled by writing a 1 to the appropriate bit. Any
unmasked bit set in the interrupt status register will cause
the interrupt request pin to be asserted. All interrupts are
cleared by writing a 1 to the bit (s) to be cleared in the
status register. When all pending unmasked interrupts
are cleared the interrupt pin will go inactive.
Defaults
Each Register is given a defined default value at reset and
these are listed in the Map and Description Tables.
However, some read-only status registers may not
necessarily show the same default values after reset as
those given in the tables. This is because they reflect the
status of the device which may have changed in the time
it takes to carry out the read, or through reasons of
configuration. In the same way, the default values given
for shaded areas could also take different values to those
stated.
Register Map
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ACS8525 LC/P
Table 15 Register Map
Register Name
Address
(hex)
Default
(hex)
Data Bit
RO = Read Only
R/W = Read/Write 7 (MSB)6543210 (LSB)
chip_id (RO) 00 4D chip_id[7:0], 8 LSBs of Chip ID
01 21 chip_id[15:8], 8 MSBs of Chip ID
chip_revision (RO) 02 00 chip_revision[7:0]
test_register1 (R/W) 03 14 Phase_alarm Disable_180 Resync_
analog Set to 0 8K Edge
Polarity Set to 0 Set to 0
test_register2 (R/W) 04 12 Do not use
sts_interrupts (R/W) 05 FF status_SEC2_
DIFF status_SEC1_
DIFF status_SEC2_
TTL status_SEC1_
TTL
06 3F operating_
mode DPLL1_main_
ref_failed status_SEC3
sts_current_DPLL_frequency,
see OC/OD 07 00 Bits [18:16] of sts_current_DPLL_frequency
sts_interrupts (R/W) 08 10 Sync_alarm_
int
sts_operating_mode (RO) 09 01 Sync_alarm DPLL2_Lock DPLL1_freq_
soft_alarm DPLL2_freq_
soft_alarm DPLL1_operating_mode
sts_priority_table (RO) 0A 00 Highest priority validated source Currently selected source
0B 00 3rd highest priority validated source 2nd highest priority validated source
sts_current_DPLL_frequency[7:0] 0C 00 Bits [7:0] of sts_current_DPLL_frequency
(RO) [15:8] 0D 00 Bits [15:8] of sts_current_DPLL_frequencyy
[18:16] 07 00 Bits [18:16] of sts_current_DPLL_frequency
sts_sources_valid (RO) 0E 00 SEC2 DIFF SEC1 DIFF SEC2 TTL SEC1 TTL
0F 00 SEC3
sts_reference_sources (RO)
Alarm Status on inputs:
SEC1 & SEC2 TTL 11 22 No Activity
SEC2 TTL Phase Lock
SEC2 TTL No Activity
SEC1 TTL Phase Lock
SEC1 TTL
SEC1 & SEC2 DIFF 12 22 No Activity
SEC2 DIFF Phase Lock
SEC2 DIFF No Activity
SEC1 DIFF Phase Lock
SEC1 DIFF
SEC3 14 22 No Activity
SEC3 Phase Lock
SEC3
cnfg_ref_selection_pr ior ity (R/ W )
SEC1 & SEC2 TTL 19 32 programmed_priority_SEC2_TTL programmed_priority_SEC1_TTL
SEC1 & SEC2 DIFF 1A 00 programmed_priority_SEC2_DIFF programmed_priority_SEC1_DIFF
SEC3 1C 04 programmed_priority_SEC3
cnfg_ref_source_frequency_
<input> (R/W), where <input> =
SEC1 TTL 22 00 divn_SEC1 TTL lock8k_SEC1
TTL Bucket_id_SEC1 TTL reference_source_frequency_SEC1 TTL
SEC2 TTL 23 00 divn_SEC2 TTL lock8k_SEC2
TTL Bucket_id_SEC2 TTL reference_source_frequency_SEC2 TTL
SEC1 DIFF 24 03 divn_SEC1
DIFF lock8k_SEC1
DIFF Bucket_id_SEC1 DIFF reference_source_frequency_SEC1 DIFF
SEC2 DIFF 25 03 divn_SEC2
DIFF lock8k_SEC2
DIFF Bucket_id_SEC2 DIFF reference_source_frequency_SEC2 DIFF
SEC3 28 03 divn_SEC3 lock8k_SEC3 Bucket_id_SEC3 reference_source_frequency_SEC3
cnfg_operating_mode (R/W) 32 00 DPLL1_operating_mode
force_select_reference_source
(R/W) 33 0F forced_select_SEC_input
cnfg_input_mode (R/W) 34 CA auto_extsync_
en phalarm_
timeout XO_ edge extsync_en ip_sonsdhb reversion_
mode
cnfg_DPLL2_path (R/W) 35 A0 DPLL2_dig_
feedback
cnfg_differential_inputs (R/W) 36 03 SEC2_DIFF_
PECL SEC1_DIFF_
PECL
cnfg_dig_outputs_sonsdh (R/W) 38 04 dig2_sonsdh dig1_sonsdh
cnfg_digtial_frequencies (R/W) 39 08 digital2_frequency digital1_frequency
cnfg_differential_output (R/W) 3A C2 Output O1 _LVDS_PECL
cnfg_auto_bw_sel 3B 98 auto_BW_sel DPLL1_lim_int
cnfg_nominal_frequency [7:0] 3C 99 Bits[7:0] of cnfg_nominal_frequency
(R/W) [15:8] 3D 99 Bits[15:8] of cnfg_nominal_frequency
cnfg_DPLL_freq_limit (R/W) [7:0] 41 76 Bits[7:0] of cnfg_DPLL_freq_limit
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ACS8525 LC/P
cnfg_DPLL_freq_limit (R/W) [9:8] 42 00 Bits[9:8] of
cnfg_DPLL_freq_limit
cnfg_interrupt_mask (R/W) [7:0] 43 00 Set to 0 Set to 0 SEC2 DIFF SEC1 DIFF SEC2 TTL SEC1 TTL
[15:8] 44 00 operating_
mode main_ref_
failed Set to 0 SEC3
[23:16] 45 00 Sync_ip_alarm
cnfg_freq_divn (R/W) [7:0]. 46 FF divn_value [7:0] (divide Input frequency by n)
[13:8] 47 3F divn_value [13:8] (divide Input frequency by n)
cnfg_monitors (R/W) 48 04 los_flag_on_
TDO ultra_fast_
switch ext_switch PBO_freeze PBO_en
cnfg_registers_source_select
(R/W) 4B 00 DPLL1_DPLL2
_select
cnfg_freq_lim_ph_loss 4D freq_lim_ph_
loss
cnfg_upper_threshold_0 (R/W) 50 06 upper_threshold_0_value (Activity alarm, Config. 0, Leaky Bucket - set threshold)
cnfg_lower_threshold_0 (R/W) 51 04 lower_threshold_0_value (Activity alarm, Config. 0, Leaky Bucket - reset threshold)
cnfg_bucket_size_0 (R/W) 52 08 Bucket_size_0_value (Activity alarm, Config. 0, Leaky Bucket - size)
cnfg_decay_rate_0 (R/W) 53 01 decay_rate_0_value (Activity
alarm, Config. 0, Leaky Bucket -
leak rate)
cnfg_upper_threshold_1 (R/W) 54 06 upper_threshold_1_value (Activity alarm, Config. 1, Leaky Bucket - set threshold)
cnfg_lower_threshold_1 (R/W) 55 04 lower_threshold_1_value (Activity alarm, Config. 1, Leaky Bucket - reset threshold)
cnfg_bucket_size_1 (R/W) 56 08 Bucket_size_1_value (Activity alarm, Config. 1, Leaky Bucket - size)
cnfg_decay_rate_1 (R/W) 57 01 decay_rate_1_value (Activity
alarm, Config. 1, Leaky Bucket -
leak rate)
cnfg_upper_threshold_2 (R/W) 58 06 upper_threshold_2_value (Activity alarm, Config. 2, Leaky Bucket - set threshold)
cnfg_lower_threshold_2 (R/W) 59 04 lower_threshold_2_value (Activity alarm, Config. 2, Leaky Bucket - reset threshold)
cnfg_bucket_size_2 (R/W) 5A 08 Bucket_size_2_va lue (Activity alarm, Config. 2, Leaky Bucket - size)
cnfg_decay_rate_2 (R/W) 5B 01 decay_rate_2_value (Activity
alarm, Config. 2, Leaky Bucket -
leak rate)
cnfg_upper_threshold_3 (R/W) 5C 06 upper_threshold_3_value (Activity alarm, Config. 3, Leaky Bucket - set threshold)
cnfg_lower_threshold_3 (R/W) 5D 04 lower_threshold_3_value (Activity alarm, Config. 3, Leaky Bucket - reset threshold)
cnfg_bucket_size_3 (R/W) 5E 08 Bucket_size_3_value (Activity alarm, Config. 3, Leaky Bucket - size)
cnfg_decay_rate_3 (R/W) 5F 01 decay_rate_3_value (Activity
alarm, Config. 3, Leaky Bucket -
leak rate)
cnfg_output_frequency (R/W)
(Output O2) 61 06 output_freq_O2
(Output O1) 62 80 output_freq_O1
(MFrSync/FrSync) 63 C0 MFrSync_en FrSync_en
cnfg_DPLL2_frequency (R/W) 64 00 DPLL2_frequency
cnfg_DPLL1_frequency (R/W) 65 01 DPLL2_meas_
DPLL1_ph APLL2_for_
DPLL1_E1/
DS1
DPLL1_freq_to_APLL2 DPLL1_frequency
cnfg_DPLL2_bw (R/W) 66 00 DPLL2_bandwidth
cnfg_DPLL1_locked_bw (R/W) 67 10 DPLL1_locked_bandwidth
cnfg_DPLL1_acq_bw (R/W) 69 11 DPLL1_acquisition_bandwidth
cnfg_DPLL2_damping (R/W) 6A 13 DPLL2_PD2_gain_alog_8k DPLL2_damping
cnfg_DPLL1_damping (R/W) 6B 13 DPLL1_PD2_gain_alog_8k DPLL1_damping
cnfg_DPLL2_PD2_gain (R/W) 6C C2 DPLL2_PD2_
gain_enable DPLL2_PD2_gain_alog DPLL2_PD2_gain_digital
cnfg_DPLL1_PD2_gain (R/W) 6D C2 DPLL1_PD2_
gain_enable DPLL1_PD2_gain_alog DPLL1_PD2_gain_digital
cnfg_phase_offset (R/W) [7:0] 70 00 phase_offset_value [7:0]
[15:8] 71 00 phase_offset_value[15:8]
cnfg_PBO_phase_offset (R/W) 72 00 PBO_phase_offset
cnfg_phase_loss_fine_limit (R/W) 73 A2 fine_limit_en noact_ph_loss narrow_en phase_loss_fine_limit
Table 15 Register Map (cont...)
Register Name
Address
(hex)
Default
(hex)
Data Bit
RO = Read Only
R/W = Read/Write 7 (MSB)6543210 (LSB)
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ACS8525 LC/P
cnfg_phase_loss_coarse_limit
(R/W) 74 85 coarse_lim_
phaseloss_en wide_range_
en multi_ph_resp phase_loss_coarse_limit
cnfg_ip_noise_window (R/W) 76 06 ip_noise_
window_en
sts_current_phase (RO) [7:0] 77 00 current_phase[7:0]
[15:8] 78 00 current_phase[15:8]
cnfg_phase_alarm_timeout
(R/W) 79 32 timeout_value (in two-second intervals)
cnfg_sync_pulses (R/W) 7A 00 2k_8k_from_
DPLL2 8k_invert 8k_pulse 2k_invert 2k_pulse
cnfg_sync_phase (R/W ) 7B 00 Indep_FrS ync/
MFrSync Sync_OC-N_
rates Sync_phase_SYNC3 Sync_phase_SYNC2 Sync_phase_SYNC1
cnfg_sync_monitor (R/W) 7C 2B ph_offset_
ramp Sync_monitor_limit
cnfg_interrupt (R/W) 7D 02 Interrupt
GPO_en Interrupt
tristate_en Interrupt
int_polarity
cnfg_protection(R/W) 7E 85 protection_value
Table 15 Register Map (cont...)
Register Name
Address
(hex)
Default
(hex)
Data Bit
RO = Read Only
R/W = Read/Write 7 (MSB)6543210 (LSB)
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ACS8525 LC/P
Register Descriptions
Address (hex): 00
Register Name chip_id Description (RO) 8 least significant bits of the
chip ID. Default Value 0100 1101
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
chip_id[7:0], 8 LSBs of Chip ID
Bit No. Description Bit Value Value Description
[7:0] chip_id
Least significant byte of the 2-byte device ID. 48 (hex)
Address (hex): 01
Register Name chip_id Description (RO) 8 most significant bits of the
chip ID. Default Value 0010 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
chip_id[15:8], 8 MSBs of Chip ID
Bit No. Description Bit Value Value Description
[7:0] chip_id
Most significant byte of the 2-byte device ID. 21 (hex)
Address (hex): 02
Register Name chip_revision Description (RO) Silicon revision of the device. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
chip_revision[7:0]
Bit No. Description Bit Value Value Description
[7:0] chip_revision
Silicon revision of the device. 00(hex)
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ACS8525 LC/P
Address (hex): 03
Register Name test_register1 Description (R/W) Register containing various
test controls (not normally used). Default Value 0001 0100
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
phase_alarm disable_180 resync_analog Set to 0 8k Edge Polarity Set to 0 Set to 0
Bit No. Description Bit Value Value Description
7phase_alarm (phase alarm (R/O))
Instantaneous result from DPLL1. 0
1DPLL1 reporting phase locked.
DPLL1 reporting phase lost.
6disable_180
Normally the DPLL will try to lock to the nearest
edge (±180°) for the first 2 seconds when locking to
a new reference. If the DPLL does not determine
that it is phase locked after this time, then the
capture range reverts to ±360°, which corresponds
to frequency and phase locking. Forcing the DPLL
into frequency locking mode may reduce the time to
frequency lock to a new reference by up to two
seconds. However, this may cause an unnecessary
phase shift of up to 360° when the new and old
references are very close in frequency and phase.
0
1
DPLL1 automatically determines frequency lock
enable.
DPLL1 forced to always frequency and phase lock.
5Not used. --
4resync_analog (analog dividers re-synchron ization)
The analog output dividers include a
synchronization mechanism to ensure phase lock at
low frequencies between the input and the output.
0
1
Analog divider only synchronized during first 2
seconds after power-up.
Analog dividers always synchronized.This keeps the
clocks divided down from the APLL output, in sync
with equivalent frequency digital clocks in the DPLL.
Hence ensuring that 6.48 MHz output clocks, and
above, are in sync with the DPLL even though only a
77.76 MHz clock drives the APLL.
3Set to 0
Test Control. Leave unchanged or set to 0. 0-
28k Edge Polarity
When lock 8k mode is selected for the current input
SEC, this bit allows the system to lock on either the
rising or the falling edge of the input clock.
0
1Lock to falling clock edge.
Lock to rising clock edge.
1Set to 0
Test Control. Leave unchanged or set to 0. 0-
0Set to 0
Test Control. Leave unchanged or set to 0. 0-
Address (hex): 04 test_register2 Do not use. Only zero should be written to this address.
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ACS8525 LC/P
Address (hex): 05
Register Name sts_interrupts Description (R/W) Bits [7:0] of the interrupt
status register. Default Value 1111 1111
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
status_SEC2_
DIFF status_SEC1_
DIFF status_SEC2_
TTL status_SEC1_
TTL
Bit No. Description Bit Value Value Description
[7:6] Not used. - -
5status_SEC2_DIFF
Interrup t indicatin g th a t input SEC2 DIFF
has become valid (if it was invalid), or invalid (if it
was valid). Latched until reset by software writing a
1 to this bit.
0
1
Input SEC2 DIFF has not changed status (valid/
invalid).
Input SEC2 DIFF has changed status (valid/invalid).
Writing 1 resets the interrupt to 0.
4status_SEC1_DIFF
Interrup t indicating that input SEC1 DIFF has
become valid (if it was invalid), or invalid (if it was
valid). Latched until reset by software writing a 1 to
this bit.
0
1Input SEC1 DIFF has not changed status (valid/
invalid).
Input SEC1 DIFF has changed status (valid/invalid).
Writing 1 resets the interrupt to 0.
3status_SEC2_TTL
Interrupt indicating that input SEC2 TTL has become
valid (if it was invalid), or invalid (if it was valid).
Latched until reset by software writing a 1 to this bit.
0
1
Input SEC2 TTL has not changed status (valid/
invalid).
Input SEC2 TTL has changed status (valid /invalid).
Writing 1 resets the interrupt to 0.
2status_SEC1_TTL
Interrupt indicating that input SEC1 TTL has become
valid (if it was invalid), or invalid (if it was valid).
Latched until reset by software writing a 1 to this bit.
0
1Input SEC1 TTL has not changed status (valid/
invalid).
Input SEC1 TTL has changed status (valid /invalid).
Writing 1 resets the interrupt to 0.
[1:0] Not used. - -
Address (hex): 06
Register Name sts_interrupts Description (R/W) Bits [15:8] of the interrupt
status register. Default Value 0011 1111
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
operating_
mode DPLL1_
main_ref_failed status_SEC3
Bit No. Description Bit Value Value Description
7operating_mode
Interrupt indicating that the operating mode has
changed. Latched until reset by software writing a 1
to this bit.
0
1Operating mode has not changed.
Operating mode has changed.
Writing 1 resets the interrupt to 0.
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6DPLL1_main_ref_failed
Interrupt indicating that input to the DPLL1 has
failed. This interrupt will be raised after 2 missin g
input cycles. This is much quicker than waiting for
the input to become invalid. This input is not
generated in Free-run or Holdover modes. Latched
until reset by software writing a 1 to this bit.
0
1Input to DPLL1 is valid.
Input to DPLL1 has failed.
Writing 1 resets the interrupt to 0.
[5:1] Not used. - -
0status_SEC3
Interrupt indicating th a t input SEC3 has b e come
valid (if it was invalid), or invalid (if it was valid).
Latched until reset by software writing a 1 to this bit.
0
1Input SEC3 has not changed status (valid/invalid).
Input SEC3 has changed status (valid/invalid).
Writing 1 resets the interrupt to 0.
Address (hex): 07
Register Name sts_current_DPLL_frequency
[18:16] Description (RO) Bits [18:16] of the current
DPLL frequency. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Bits [18:16] of sts_current_DPLL_frequency
Bit No. Description Bit Value Value Description
[7:3] Not used. - -
[2:0] Bits [18:16] of sts_current_DPLL_frequency
When Bit 4 (DPLL1_DPLL2_select) of Reg. 4B
(cnfg_registers_source_select) = 0 the frequency
for DPLL1 is reported.
When this Bit 4 = 1 the frequency for DPLL2 is
reported.
- See register description of
sts_current_DPLL_frequency at Reg. 0D.
Address (hex): 06 (cont...)
Register Name sts_interrupts Description (R/W) Bits [15:8] of the interrupt
status register. Default Value 0011 1111
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
operating_
mode DPLL1_
main_ref_failed status_SEC3
Bit No. Description Bit Value Value Description
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Address (hex): 08
Register Name sts_interrupts Description (R/W) Bits [ 23:16] of the interrupt
status register. Default Value 0001 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Sync_alarm_ int
Bit No. Description Bit Value Value Description
7Sync_alarm_int
Interrupt indicating that the selected Sync input
monitor has hit its alarm limit. Latched until reset by
software writing a 1 to this bit.
0
1Input Sync alarm has not occurred.
Input Sync alarm has occurred.
Writing 1 resets the input to 0.
[6:0] Not used. - -
Address (hex): 09
Register Name sts_operating_mode Description (RO) Current operating state of
the device’s internal state
machine.
Default Value 0000 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Sync_alarm DPLL2_Lock DPLL1_freq_
soft_alarm DPLL2_freq_
soft_alarm DPLL1_operating_mode
Bit No. Description Bit Value Value Description
7Sync_alarm
Reports current interrupt status of the selected
Sync input monitor.
0
1External Sync. monitor not in alarm condition.
External Sync. monitor in alarm condition.
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6DPLL2_Lock
Reports current phase lock status of DPLL2. DPLL2
does not have the same state machine as DPLL1,
as it does not support all the features of DPLL1. It
can only report its state as locked or unlocked.
The bit indicates that the DPLL2 is locked by
monitoring the DPLL2 phase loss indicators, which
potentially come from four sources. The four phase
loss indicators are enabled by the same registers
that enable them for the DPLL1, as follows: the fine
phase loss detector enabled by Reg. 73 Bit 7, the
coarse phase loss detector enabled by Reg. 74 Bit
7, the phase loss indication from no activity on the
input enabled by Reg. 73 Bit 6 and phase loss from
the DPLL being at its minimum or maximum
frequency limits enabled by Reg. 4D Bit 7.
For the DPLL2 lock indicator (at Reg. 09 Bit 6) the
bit will latch an indication of phase lost from the
coarse phase lock detector such that when an
indication of phase lost (or not locked) is set it stays
in that phase lost or not locked state (so Reg. 09 Bit
6 =0).
For this bit to give a correct current reading of the
DPLL2 locked state, then the coarse phase loss
detector should be temporarily disabled (set
Reg. 74 Bit 7 = 0), then the DPLL2 locked bit can be
read (Reg. 09 Bit 6), then the coarse phase loss
detector should be re-enabled again (set
Reg. 74 Bit 7 = 1).
Once the bit is indicating “locked” (Reg. 09 Bit 6=1),
it is always a correct indication and no change to
the coarse phase loss detector enable is required. If
at any time any cycle slips occur that trigger the
coarse phase loss detector (which monitors cycle
slips) then this information is latched so that the
lock bit (Reg. 09 Bit 6) will go low and stay low,
indicating that a problem has occurred. It is then a
requirement that the coarse phase loss detector's
disable/re-enable sequence is performed during a
read of t h e DPLL2 lock e d b it, in orde r to get a
current indication of whether the DPLL2 is locked.
0
1DPLL2 not phase locked to SEC.
DPLL2 phase locked to SEC.
Address (hex): 09 (cont...)
Register Name sts_operating_mode Description (RO) Current operating state of
the device’s internal state
machine.
Default Value 0000 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Sync_alarm DPLL2_Lock DPLL1_freq_
soft_alarm DPLL2_freq_
soft_alarm DPLL1_operating_mode
Bit No. Description Bit Value Value Description
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5DPLL1_freq_soft_alarm
DPLL1 has a programmable frequency limit and
“soft” alarm limit. The frequency limit is the extent
to which it will track a reference before limiting. The
“soft” limit is the point beyond which the DPLL
tracking a referen ce will cause an alarm. This bit
reports the status of the “soft” alarm.
0
1
DPLL1 tracking its reference within the limits of the
programmed “soft” alarm.
DPLL1 tracking its reference beyond the limits of
the programmed “soft” alarm.
4DPLL2_freq_soft_alarm
DPLL2 has a programmable frequency limit and
“soft” alarm limit. The frequency limit is the extent
to which it will track a reference before limiting. The
“soft” limit is the point beyond which the DPLL
tracking a referen ce will cause an alarm. This bit
reports the status of the “soft” alarm.
0
1
DPLL2 tracking its reference within the limits of the
programmed “soft” alarm.
DPLL2 tracking its reference beyond the limits of
the programmed “soft” alarm.
3Not used. --
[2:0] DPLL1_operating_mode
This field is used to report the state of the internal
finite state machine controlling DPLL1.
000
001
010
011
100
101
110
111
Not used.
Free Run.
Holdover.
Not used.
Locked.
Pre-locked2.
Pre-locked.
Phase Lost.
Address (hex): 09 (cont...)
Register Name sts_operating_mode Description (RO) Current operating state of
the device’s internal state
machine.
Default Value 0000 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Sync_alarm DPLL2_Lock DPLL1_freq_
soft_alarm DPLL2_freq_
soft_alarm DPLL1_operating_mode
Bit No. Description Bit Value Value Description
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Address (hex): 0A
Register Name sts_priority_table Description (RO) Bits [7:0] of the validated
priority table. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Highest priority validated source Currently selected source
Bit No. Description Bit Value Value Description
[7:4] Highest priority validated source
Reports the input channel number of the highest
priority validated sour ce.
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010 to 1111
No valid source available .
Not used.
Not used.
Input SEC1 TTL is the highest priority valid source.
Input SEC2 TTL is the highest priority valid source.
Input SEC1 DIFF is the highest priority valid source.
Input SEC2 DIFF is the highest priority valid source.
Not used.
Not used.
Input SEC3 is the highest priority valid source.
Not used.
[3:0] Currently selected source
Reports the input channel number of the currently
selected source. When in Non-revertive mode, this
is not necessarily the same as the highest priority
validated source.
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010-1111
No source currently selected.
Not used.
Not used.
Input SEC1 TTL is the currently selected source.
Input SEC2 TTL is the currently selected source.
Input SEC1 DIFF is the currently selected source.
Input SEC2 DIFF is the currently selected source.
Not used.
Not used.
Input SEC3 is the currently selected source.
Not used.
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Address (hex): 0B
Register Name sts_priority_table Description (RO) Bits [15:8] of the validated
priority table. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
3rd highest priority validated source 2nd highest priority validated source
Bit No. Description Bit Value Value Description
[7:4] 3rd highest priority validated source
Reports the input channel number of the 3rd highest
priority validated sour ce.
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010-1111
Less than 3 valid sources availab le.
Not used.
Not used.
Input SEC1 TTL is the 3rd highest priority valid
source.
Input SEC2 TTL is the 3rd highest priority valid
source.
Input SEC1 DIFF is the 3rd highest priority valid
source.
Input SEC2 DIFF is the 3rd highest priority valid
source.
Not used.
Not used.
Input SEC3 is the 3rd highest priority valid source.
Not used.
[3:0] 2nd highest priority validated
Reports the input channel number of the 2nd
highest priority validated source.
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010-1111
Less than 2 valid sources availab le.
Not used.
Not used.
Input SEC1 TTL is the 2nd highest priority valid
source.
Input SEC2 TTL is the 2nd highest priority valid
source.
Input SEC1 DIFF is the 2nd highest priority valid
source.
Input SEC2 DIFF is the 2nd highest priority valid
source.
Not used.
Not used.
Input SEC3 is the 2nd highest priority valid source.
Not used.
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Address (hex): 0C
Register Name sts_current_DPLL_frequency
[7:0] Description (RO) Bits [7:0] of the current DPLL
frequency. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Bits [7:0] of sts_current_DPLL_frequency
Bit No. Description Bit Value Value Description
[7:0] Bits [7:0] of sts_current_DPLL_frequency
*When Bit 4 (DPLL1_DPLL2_select) of Reg. 4B
(cnfg_registers_source_select) = 0 the frequency
for DPLL1 is reported.
When this Bit 4 = 1 the frequency for DPLL2 is
reported.
- See register description of
sts_current_DPLL_frequency at Reg. 0D.
Address (hex): 0D
Register Name sts_current_DPLL_frequency
[15:8] Description (RO) Bits [15:8] of the current
DPLL frequency. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Bits [15:8] of sts_current_DPLL_frequency
Bit No. Description Bit Value Value Description
[7:0] Bits [15:8] of sts_current_DPLL_frequency
The value in this register is combined with the value
in Reg. 0C and Reg. 07 to represent the current
frequency offset of the DPLL.
*When Bit 4 (DPLL1_DPLL2_select) of Reg. 4B
(cnfg_registers_source_select) = 0 the frequency
for DPLL1 is reported.
When this Bit 4 = 1 the frequency for DPLL2 is
reported.
- In order to calculate the ppm offset of the DPLL with
respect to the crystal oscillator frequency, the value
in Reg. 07, Reg. 0D and Reg. 0C need to be
concatenated. This value is a 2’s complement
signed integer. The value multiplied by
0.0003068 dec will give the value in ppm offset
with respect to the XO frequency, allowing for any
crystal calibration that has been performed, via
cnfg_nominal_frequency, Reg. 3C and 3D. The
value is actually the DPLL integral path value so it
can be viewed as an average frequency, where the
rate of change is related to the DPLL bandwidth. If
Bit 3 of Reg. 3B is High then this value will freeze if
the DPLL has been pulled to its min or max
frequency.
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Address (hex): 0E
Register Name sts_sources_valid Description (RO) 8 least significant bits of the
sts_sources_valid register. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
SEC2 DIFF SEC1 DIFF SEC2 TTL SEC1 TTL
Bit No. Description Bit Value Value Description
[7:6] Not used. - -
5SEC2 DIFF
Bit indicating if SE C2 DIFF is valid. The input is valid
if it has no outstanding alarms.
0
1Input SEC2 DIFF is invalid.
Input SEC2 DIFF is valid.
4SEC1 DIFF
Bit indicating if SE C1 DIFF is valid. The input is valid
if it has no outstanding alarms.
0
1Input SEC1 DIFF is invalid.
Input SEC1 DIFF is valid.
3SEC2 TTL
Bit indicating if SEC2 TTL is valid. The input is valid if
it has no outstanding alarms.
0
1Input SEC2 TTL is invalid.
Input SEC2 TTL is valid.
2SEC1 TTL
Bit indicating if SEC1 TTL is valid. The input is valid if
it has no outstanding alarms.
0
1Input SEC1 TTL is invalid.
Input SEC1 TTL is valid.
[1:0] Not used. - -
Address (hex): 0F
Register Name sts_sources_valid Description (RO) 8 most significant bits of the
sts_sources_valid reg ister. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
SEC3
Bit No. Description Bit Value Value Description
[7:1] Not used. - -
0SEC3
Bit indicating if SEC3 is valid. The input is valid if it
has no outstanding alarms.
0
1Input SEC3 is invalid.
Input SEC3 is valid.
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Address (hex): 11
Register Name sts_reference_sources
SEC1 & SEC2 TTL Description (RO except for test when R/W)
Reports any alarms active on
inputs.
Default Value 0010 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Reg. 11: Status of SEC2 TTL Input Reg. 11: Status of SEC1 TTL Input
Reg. 12: Status of SEC2 DIFF
Input Reg. 12: Status of SEC1 DIFF
Input
Reg. 14: Status of SEC3 Input
Bit No. Description Bit Value Value Description
[7:6] & [3:2] Not Used - -
5 & 1 Input Activity Alarm
Alarm indication from the activity monitors. 0
1No alarm.
Input has an active “no activity” alarm.
4 & 0 Phase Lock Alarm
If the DPLL cannot indicate that it is phase locked
onto the current source within 100 seconds this
alarm will be raised.
0
1No alarm.
Phase lock alarm.
Address (hex): 12 As Reg. 11, but for sts_reference_sources, Inputs: SEC1 & SEC2 DIFF
Address (hex): 14 As Reg. 11, but for sts_reference_sources, Input: SEC3
Address (hex): 19
Register Name cnfg_ref_selection_priority
SEC1 & SEC2 TTL Description (R/W) Configures the relative
priority of input sources SEC1 TTL
and SEC2 TTL.
Default Value 0011 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
programmed_priority_SEC2 TTL programmed_priority_SEC1 TTL
Bit No. Description Bit Value Value Description
[7:4] programmed_priority_SEC2 TTL
This 4-bit value represents the relative priority of
input SEC2 TTL. The smaller the number, the higher
the priority; zero disables the input.
*When the priority of this input is set to >0, the
priority of SEC2 DIFF is set to 0 (disabled).
0000
0001-1111 Input SEC2 TTL unavailable for automatic select ion.
Input SEC2 TTL priority value.
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[3:0] programmed_priority_SEC1 TTL
This 4-bit value represents the relative priority of
input SEC1 TTL. The smaller the number, the higher
the priority; zero disables the input.
*When the priority of this input is set to >0, the
priority of SEC1 DIFF is set to 0 (disabled).
0000
0001-1111 Input SEC1 TTL unavailable for automatic select ion.
Input SEC1 TTL priority value.
Address (hex): 1A
Register Name cnfg_ref_selection_priority
SEC1 & SEC2 DIFF Description (R/W) Configures the relative
priority of input sources SEC1
DIFF and SEC2 DIFF.
Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
programmed_priority_SEC2 DIFF programmed_priority_SEC1 DIFF
Bit No. Description Bit Value Value Description
[7:4] programmed_priority_SEC2 DIFF
This 4-bit value represents the relative priority of
input SEC2 DIFF. The smaller the number, the
higher the priority; zero disables the input.
*When the priority of this input is set to >0, the
priority of SEC2 TTL is set to 0 (disabled).
0000
0001-1111
Input SEC2 DIFF unavailable for automatic
selection.
Input SEC2 DIFF priority value.
[3:0] programmed_priority_SEC1 DIFF
This 4-bit value represents the relative priority of
input SEC1 DIFF. The smaller the number, the
higher the priority; zero disables the input.
*When the priority of this input is set to >0, the
priority of SEC1 TTL is set to 0 (disabled).
0000
0001-1111
Input SEC1 DIFF unavailable for automatic
selection.
Input SEC1 DIFF priority value.
Address (hex): 19 (cont...)
Register Name cnfg_ref_selection_priority
SEC1 & SEC2 TTL Description (R/W) Configures the relative
priority of input sources SEC1 TTL
and SEC2 TTL.
Default Value 0011 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
programmed_priority_SEC2 TTL programmed_priority_SEC1 TTL
Bit No. Description Bit Value Value Description
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Address (hex): 1C
Register Name cnfg_ref_selection_priority
SEC3 Description (R/W) Configures the relative
priority of input source SEC3. Default Value 0000 0100
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
programmed_priority_SEC3
Bit No. Description Bit Value Value Description
[7:4] Not used. - -
[3:0] cnfg_ref_selection_priority_9
This 4-bit value represents the relative priority of
input SEC3. The smaller the number, the higher the
priority; zero disa bl es the input.
0000
0001-1111 Input SEC3 unavailable for automatic selection.
Input SEC3 priority value.
Address (hex): 22
Register Name cnfg_ref_source_frequency
<input>
For Reg. 22, <input> =
SEC1 TTL
Description (R/W) Configuration of the
frequency and input monitoring
for input <input>.
Default Value SEC1 TTL=
0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
divn_<input> lock8k_<input> Bucket_id_<input> reference_source_frequency_<input>
Bit No. Description Bit Value Value Description
7divn_<input>
This bit selects whether or not input SEC1 TTL is
divided in the programmable pre-divider prior to
being input to the DPLL and frequency monitor- see
Reg. 46 and Reg. 47 (cnfg_freq_divn).
0
1Input <input> fed directly to DPLL and monitor.
Input <input> fed to DPLL and monitor via pre-
divider.
6lock8k_<input>
This bit selects whether or not input SEC1 TTL is
divided in the preset pre-divider prior to being input
to the DPLL. This results in the DPLL locking to the
reference after it has been divided to 8 kHz. This bit
is ignored when divn_<input> is set (bit =1).
0
1Input <input> fed directly to DPLL.
Input <input> fed to DPLL via preset pre-divider.
[5:4] Bucket_id_<input>
Every input has its own Leaky Bucket used for
activity monitoring. There are four possible
configurations for each Leaky Bucket- see Reg. 50
to Reg. 5F. This 2-bit field selects the configuration
used for input <input>.
00
01
10
11
Input <input> activity monitor uses Leaky Bucket
Configuration 0.
Input <input> activity monitor uses Leaky Bucket
Configuration 1.
Input <input> activity monitor uses Leaky Bucket
Configuration 2.
Input <input> activity monitor uses Leaky Bucket
Configuration 3.
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[3:0] reference_source_frequency_<input>
Programs the frequency of the SEC connected to
input <input>. If divn_<input> is set, then this value
should be set to 0000 (8 kHz).
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011-1111
8 kHz.
1544/2048 kHz (dependant on Bit 2 (ip_sonsdhb)
in Reg. 34).
6.48 MHz.
19.44 MHz.
25.92 MHz.
38.88 MHz.
51.84 MHz.
77.76 MHz.
155.52 MHz.
2 kHz.
4 kHz.
Not used.
Address (hex): 23 Use description for Reg. 22, but use <input> = SEC2 TTL Default = 0000 0000
Address (hex): 24 Use description for Reg. 22, but use <input> = SEC1 DIFF Default = 0000 0011
Address (hex): 25 Use description for Reg. 22, but use <input> = SEC2 DIFF Default = 0000 0011
Address (hex): 28 Use description for Reg. 22, but use <input> = SEC3 Default = 0000 0011
Address (hex): 32
Register Name cnfg_operating_mode Description (R/W) Register to force the state
of DPLL1 controlling state
machine.
Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL1_operating_mode
Bit No. Description Bit Value Value Description
[7:3] Not used. - -
Address (hex): 22 (cont...)
Register Name cnfg_ref_source_frequency
<input>
For Reg. 22, <input> =
SEC1 TTL
Description (R/W) Configuration of the
frequency and input monitoring
for input <input>.
Default Value SEC1 TTL=
0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
divn_<input> lock8k_<input> Bucket_id_<input> reference_source_frequency_<input>
Bit No. Description Bit Value Value Description
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[2:0] DPLL1_operating_mode
This field is used to control the state of the internal
finite state machine controlling DPLL1. A value of
zero is used to allow the finite state machine to
control itself. Any other value will force the state
machine to jump into that state. Care should be
taken when forcing the state machine. Whilst it is
forced, the internal monitoring functions cannot
affect the internal state machine, therefore, the
user is responsible for all monitoring and control
functions required to achieve the desired
functionality.
000
001
010
011
100
101
110
111
Automatic (internal state machine controlled).
Free Run.
Holdover.
Not used.
Locked.
Pre-locked2.
Pre-locked.
Phase Lost.
Address (hex): 33
Register Name force_select_reference_source Description (R/W) Register used to force the
selection of a particular SEC for
DPLL1.
Default Value 0000 1111
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
forced_select_SEC_input
Bit No. Description Bit Value Value Description
[7:4] Not used. - -
[3:0] forced_select_SEC_input
Value representing the SEC to be selected by
DPLL1. Value of 0 hex will leave the selection to the
automatic control mechanism within the device.
Using this mechanism will bypass all the monitoring
functions assuming the selected input to be valid. If
the device is not in state “Locked” then it will
progress to state locked in the usual manner. If the
input fails, the device will not change state to
Holdover, as it is not allowed to disqualify the
source. The effect of this register is simply to raise
the priority of the selected input to “1” (highest). To
ensure selection of the programmed input
reference under all circumstances, revertive mode
should be enabled (Reg. 34 bit 0 set to “1”).
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010-1111
Automatic state machine source selection
Not used.
Not used.
DPLL1 forced to select input SEC1 TTL.
DPLL1 forced to select input SEC2 TTL.
DPLL1 forced to select input SEC1 DIFF.
DPLL1 forced to select input SEC2 DIFF.
Not used.
Not used.
DPLL1 forced to select input SEC3.
Not used.
Address (hex): 32 (cont...)
Register Name cnfg_operating_mode Description (R/W) Register to force the state
of DPLL1 controlling state
machine.
Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL1_operating_mode
Bit No. Description Bit Value Value Description
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Address (hex): 34
Register Name cnfg_input_mode Description (R/W) Register controlling various
input modes of the device. Default Value 1100 1010*
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
auto_extsync_
en phalarm_time-
out XO_edge extsync_en ip_sonsdhb reversion_mode
Bit No. Description Bit Value Value Description
7auto_extsync_en
Bit to automatically disable the external Frame Sync
input following a source switch.
0
1
External Frame Sync enabled/disabled according to
extsync_en.
External Fr ame Sync en abled if extsync_en = 1 until
a source switch. After this it is only re-enabled by
writing “1” to extsync_en again.
6phalarm_timeout
Bit to enable the automatic timeout facility on phase
alarms. When enabled, any source with a phase
alarm set will have its phase alarm cancelled after
128 seconds.
0
1
Phase alarms on sources only cancelled by
software.
Phase alarms on sources automatically time out.
5XO_edge
If the 12.800 MHz oscillator module connected to
REFCLK has one edge faster than the other, then for
jitter performance reasons, the faster edge should
be selected. This bit allows either the rising edge or
the falling edge to be selected.
0
1
Device uses the rising edge of the external
oscillator.
Device uses the falling edge of the external
oscillator.
4Not used. --
3extsync_en
Bit to select whether or not DPLL1 will look for a
reference Sync pulse on the SYNC1/2/3 input pins.
Even though this bit may enable the external Sync
reference, it may be disabled according to
auto_extsync_en.
0
1
No External Frame Sync signal on selected Sync
input- SYNC1/2/3 pins ignored.
External Sync derived from selected Sync input-
SYNC1/2/3 pin- according to auto_extsync_en.
2ip_sonsdhb
Bit to configure input frequencies to be either
SONET or SDH derived. This applies only to
selections of 0001 (bin) in the
cnfg_ref_source_frequency registers when the
input frequency is either 1544 kHz or 2048 kHz.
*The default value of this bit is taken from the value
of the SONSDHB pin at power-up.
0
1SDH- inputs set to 0001 expected to be 2048 kHz.
SONET- inputs set to 0001 expected to be
1544 kHz.
1Not used. --
0reversion_mode
Bit to select Revertive/Non-revertive mode. When in
Non-revertive mode, the device will not
automatically switch to a higher priority source,
unless the current source fails. When in Revertive
mode the device will always select the highest
priority source.
0
1Non-revertive mode.
Revertive mode.
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Address (hex): 35
Register Name cnfg_DPLL2_path Description (R/W) Register to configure the
feedback mode of DPLL2. Default Value 1010 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL2_dig_
feedback
Bit No. Description Bit Value Value Description
7Not used. --
6DPLL2_dig_feedback
Bit to select digital feedback mode for DPLL2. 0
1DPLL2 in analog feedback mode.
DPLL2 in digital feedback mode.
[5:0] Not used. - -
Address (hex): 36
Register Name cnfg_differential_inputs Description (R/W) Configures the differential
inputs to be PECL or LVDS type
inputs.
Default Value 0000 0011
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
SEC2_DIFF_
PECL SEC1_DIFF_
PECL
Bit No. Description Bit Value Value Description
[7:2] Not used. - -
1SEC2_DIFF_PECL
Configures the SEC2 DIFF input to be compatible
with either 3 V LVDS or 3 V PECL electrical levels.
0
1SEC2 DIFF input LVDS compatible.
SEC2 DIFF input PECL compatible (Default).
0SEC1_DIFF_PECL
Configures the SEC1 DIFF input to be compatible
with either 3 V LVDS or 3 V PECL electrical levels.
0
1SEC1 DIFF input LVDS compatible.
SEC1 DIFF input PECL compatible (Default).
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Address (hex): 38
Register Name cnfg_dig_outputs_sonsdh Description Configures Digital1 and Digital2
output frequencies to be SONET
or SDH compatible frequencies.
Default Value 0000 0100*
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
dig2_sonsdh dig1_sonsdh
Bit No. Description Bit Value Value Description
7Not used. --
6dig2_sonsdh
Selects whether the frequencies generated by the
Digital2 frequency generator are SONET derived or
SDH.
*Default value of this bit is set by the SONSDHB pin
at power-up.
1
0
Digital2 can be selected from 1,544/3,088/6,176/
12,352 kHz.
Digital2 can be selected from 2,048/4,096/8,192/
16,384 kHz.
5dig1_sonsdh
Selects whether the frequencies generated by the
Digital1 frequency generator are SONET derived or
SDH.
*Default value of this bit is set by the SONSDHB pin
at power-up.
1
0
Digital1 can be selected from 1,544/3,088/6,176/
12,352 kHz.
Digital1 can be selected from 2,048/4,096/8,192/
16,384 kHz.
[4:0] Not used. - -
Address (hex): 39
Register Name cnfg_digtial_frequencies Description (R/W) Configures the actual
frequencies of Digital1 & Digital2. Default Value 0000 1000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
digital2_frequency digital1_frequency
Bit No. Description Bit Value Value Description
[7:6] digital2_frequency
Configures the frequency of Digital2. Whether this is
SONET or SDH based is configured by Bit 6
(dig2_sonsdh) of Reg. 38.
00
01
10
11
Digital2 set to 1,544 kHz or 2,048 kHz.
Digital2 set to 3,088 kHz or 4,096 kHz.
Digital2 set to 6,176 kHz or 8,192 kHz.
Digital2 set to 12,353 kHz or 16,384 kHz.
[5:4] digital1_frequency
Configures the frequency of Digital1. Whether this is
SONET or SDH based is configured by Bit 5
(dig1_sonsdh) of Reg. 38.
00
01
10
11
Digital1 set to 1,544 kHz or 2,048 kHz.
Digital1 set to 3,088 kHz or 4,096 kHz.
Digital1 set to 6,176 kHz or 8,192 kHz.
Digital1 set to 12,353 kHz or 16,384 kHz.
[3:0] Not used.
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Address (hex): 3A
Register Name cnfg_differential_output Description (R/W) Configures the electrical
compatibility of the differential
output driver to be 3 V PECL or
3V LVDS.
Default Value 1100 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Output O1_LVDS_PECL
Bit No. Description Bit Value Value Description
[7:2] Not used. - -
[1:0] Output O1_LVDS_PECL
Selection of the electrical compatibility of Output O1
between 3 V PECL and 3 V LVDS.
00
01
10
11
Output O1 disabled.
Output O1 3 V PECL compatible.
Output O1 3 V LVDS compatible.
Not used.
Address (hex): 3B
Register Name cnfg_auto_bw_sel Description (R/W) Register to select
automatic BW selection for DPLL1
path.
Default Value 1001 1000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
auto_BW_sel DPLL1_lim_int
Bit No. Description Bit Value Value Description
7auto_BW_sel
Bit to select locked bandwidth (Reg. 67) or
acquisition bandwidth (Reg. 69) for DPLL1.
1
0
Automatically selects either locked or acquisition
bandwidth as appropriate.
Always selects locked bandwidth.
[6:4] Not used. - -
3 DPLL1_lim_int
When set to 1 the integral path value of DPLL1 is
limited or frozen when DPLL1 reaches either min. or
max. frequency. This can be used to minimise
subsequent overshoot when the DPLL is pulling in.
Note that when this happens, the reported
frequency value, via current_DPLL_freq (Reg. 0C,
0D and 07) is also frozen.
1
0DPLL value frozen.
DPLL not frozen.
[2:0] Not used. - -
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Address (hex): 3C
Register Name cnfg_nominal_frequency
[7:0] Description (R/W) Bits [7:0] of the register
used to calibrate the crystal
oscillator used to clock the
device.
Default Value 1001 1001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
cnfg_nominal_frequency_value[7:0]
Bit No. Description Bit Value Value Description
[7:0] cnfg_nominal_frequency_value[7:0]. - See register description of Reg. 3D
(cnfg_nominal_frequency_value[15:8]).
Address (hex): 3D
Register Name cnfg_nominal_frequency
[15:8] Description (R/W) Bits [15:8] of the register
used to calibrate the crystal
oscillator used to clock the
device.
Default Value 1001 1001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
cnfg_nominal_frequency_value[15:8]
Bit No. Description Bit Value Value Description
[7:0] cnfg_nominal_frequency_value[15:8]
This register is used in conjunction with Reg. 3C
(cnfg_nominal_frequency_value[7:0].) to be able to
offset the frequency of the crystal oscillator by up to
+514 ppm and –771 ppm. The default value
represents 0 ppm offset from 12.800 MHz.
This value is an unsigned integer.
The value in Reg. 3C/3D is used within the DPLL to
offset the frequency value used in the DPLL only.
This means that the value programmed will affect
the value reported in the
sts_current_DPLL_frequency (Reg. 07/0D/0C). IIt
will also affect the value programmed into the DPLL
frequency offset limit .
- In order to program the ppm offset of the crystal
oscillator frequency, the value in Reg. 3C and
Reg. 3D need to be concatenated. This value is an
unsigned integer. The value multiplied by
0.0196229 dec will give the value in ppm. To
calculate the absolute value, the default 39321
(9999 hex) needs to be subtracted.
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Address (hex): 41
Register Name cnfg_DPLL_freq_limit
[7:0] Description (R/W) Bits [7:0] of the DPLL
frequency limit register. Default Value 0111 0110
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Bits[7:0] of cnfg_DPLL_freq_limit
Bit No. Description Bit Value Value Description
[7:0] Bits [7:0] of cnfg_DPLL_freq_limit
This register defines the extent of frequency offset
to which either the DPLL1 or DPLL2 will track a
source before limiting- i.e. it represents the pull-in
range of the DPLLs. The offset of the device is
determined by the frequency offset of the DPLL
when compared to the offset of the external crystal
oscillator clocking the device. If the oscillator is
calibrated using cnfg_nominal_frequency Reg. 3 C
and 3D, then this calibration is automatically taken
into account. The DPLL frequency limit limits the
offset of the DPLL when compared to the calibrated
oscillator frequency.
- In order to calculate the frequency limit in ppm,
Bits [1:0] of Reg. 42 and Bits [7:0] of Reg. 41 need
to be concatenated. This value is a unsigned integer
and represents limit both positive and negative in
ppm. The value multiplied by 0.078 will gi ve the
value in ppm.
Address (hex): 42
Register Name cnfg_DPLL_freq_limit
[9:8] Description (R/W) Bits [9:8] of the DPLL
frequency limit register. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Bits [9:8] of cnfg_DPLL_freq_limit
Bit No. Description Bit Value Value Description
[7:2] Not used. - -
[1:0] Bits [9:8] of cnfg_DPLL_freq_limit. - See Reg. 41 (cnfg_DPLL_freq_limit) for details.
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Address (hex): 43
Register Name cnfg_interrupt_mask
[7:0] Description (R/W) Bits [7:0] of the interrupt
mask register. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
SEC2 DIFF SEC1 DIFF SEC2 TTL SEC1 TTL Set to 0 Set to 0
Bit No. Description Bit Value Value Description
[7:6] Not used. - -
5SEC2 DIFF
Mask bit for input SEC2 DIFF interrupt. 0
1Input SEC2 DIFF cannot generate interrupts.
Input SEC2 DIFF can generate interrupts.
4SEC1 DIFF
Mask bit for input SEC1 DIFF interrupt. 0
1Input SEC1 DIFF cannot generate interrupts.
Input SEC1 DIFF can generate interrupts.
3SEC2 TTL
Mask bit for input SEC2 TTL interrupt. 0
1Input SEC2 TTL cannot generate interrupts.
Input SEC2 TTL can generate interrupts.
2SEC1 TTL
Mask bit for input SEC1 TTL interrupt. 0
1Input SEC1 TTL cannot generate interrupts.
Input SEC1 TTL can generate interrupts.
[1:0] Set to 0. 0 Set to 0.
Address (hex): 44
Register Name cnfg_interrupt_mask
[15:8] Description (R/W) Bits [15:8] of the interrupt
mask register. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
operating_
mode main_ref_failed Set to 0 SEC3
Bit No. Description Bit Value Value Description
7operating_mode
Mask bit for operating_mode interrupt. 0
1Operating mode cannot generate inte rrupts.
Operating mode can generate interrupt s.
6main_ref_failed
Mask bit for main_ref_failed interrupt. 0
1Main reference failure cannot generate interrupts.
Main reference failure can generate interrupts.
[5:3] Not used. - -
2 Set to 0. 0 Set to 0.
1Not used. --
0SEC3
Mask bit for input SEC3 interrupt. 0
1Input SEC3 cannot generate interrupts.
Input SEC3 can generate interrupts.
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Address (hex): 45
Register Name cnfg_interrupt_mask
[23:16] Description (R/W) Bits [23:16] of the interrupt
mask register. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Sync_ip_alarm
Bit No. Description Bit Value Value Description
7Sync_ip_alarm
Mask bit for Sync_ip_alarm interrupt. 0
1The external Sync input cannot generate interrupts.
The external Sync input can generate interrupts.
[6:0] Not used. - -
Address (hex): 46
Register Name cnfg_freq_divn
[7:0]. Description (R/W) Bits [7:0] of the division
factor for inputs using the DivN
feature.
Default Value 1111 1111
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
divn_value [7:0] (divide Input frequency by n)
Bit No. Description Bit Value Value Description
[7:0] divn_value[7:0]. - See Reg. 47 (cnfg_freq_divn {13:8]) for details.
Address (hex): 47
Register Name cnfg_freq_divn
[13:8] Description (R/W) Bits [13:8] of the division
factor for inputs using the DivN
feature.
Default Value 0011 1111
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
divn_value [13:8] (divide input frequency by n)
Bit No. Description Bit Value Value Description
[7:6] Not used. - -
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[5:0] divn_value[13:8]
This register, in conjunction with Reg. 46
(cnfg_freq_divn) represents the integer value by
which to divide inputs that use the DivN pre-divider.
The DivN feature supports input frequencies up to a
maximum of 100 MHz; therefore, the maximum
value that should be w r itte n to this register is 30D3
hex (12499 dec). Use of higher DivN values may
result in unreliable behaviour.
- The input frequency will be divided by the value in
this register plus 1. i.e. to divide by 8, program a
value of 7.
Address (hex): 48
Register Name cnfg_monitors Description (R/W) Configuration register
controlling several input
monitoring and switching options.
Default Value 0000 0100*
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
los_flag_on_
TDO ultra_fast_
switch ext_switch PBO_freeze PBO_en
Bit No. Description Bit Value Value Description
7Not used. --
6los_flag_on_TDO
Bit to select whether the main_ref_fail interrupt
from DPLL1 is flagged on the TDO pin. If enabled
this will not strictly conform to the IEEE 1149.1 JTAG
standard for the function of the TDO pin. When
enabled the TDO pin will simply mimic the state of
the main_ref_fail interrupt status bit.
0
1Normal mode, TDO complies with IEEE 1149.1.
TDO pin used to indicate the state of the
main_ref_fail interrupt status. This allows a system
to have a hardware indication of a source failure
very rapidly.
5ultra_fast_switch
Bit to enable ultra-fast switching mode. When in this
mode, the device will disqualify a locked-to source
as soon as it detects a few missing input cycles.
0
1
Currently selected source only disqualified by Leaky
Bucket or frequency monitors.
Currently selected source disqualified after less
than 3 missing input cycles.
Address (hex): 47 (cont...)
Register Name cnfg_freq_divn
[13:8] Description (R/W) Bits [13:8] of the division
factor for inputs using the DivN
feature.
Default Value 0011 1111
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
divn_value [13:8] (divide input frequency by n)
Bit No. Description Bit Value Value Description
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4ext_switch
Bit to enable external switching mode. When in
external switching mode, the device is only allowed
to lock to a pair of sources. If the programmed
priority of input SEC1 TTL is non-zero, then when the
SRCSW pin is High, the device will be forced to lock
to input SEC1 TTL regardless of the signal present
on that input. If the programmed priority of input
SEC1 TTL is zero, then it will be forced to lock to
input SEC1 DIFF instead. If the programmed priority
of input SEC2 TTL is non-zero, then when the
SRCSW pin is Low, the device will be forced to lock
to input SEC2 TTL regardless of the signal present
on that input. If the programmed priority of input
SEC2 TTL is zero, then it will be forced to lock to
input SEC2 DIFF instead.
* The default value of this bit is dependent on the
value of the SRCSW pin at power-up.
0
1Normal operation mode.
External source switching mode enabled. Operating
mode of the device is always forced to be “locked”
when in this mode.
3PBO_freeze
Bit to control the freezing of Phase Build-out
operation. If Phase Build-out has been enabled and
there have been some source switches, then the
input-output phase relationship of DPLL1 is
unknown. If Phase Build-out is no longer required,
then it can be frozen. This will maintain the current
input-output phase relationship, but not allow
further Phase Build-out events to tak e plac e. Simp ly
disabling Phase Build-out could cause a phas e shift
in the output, as DPLL1 re-locks the phase to zero
degrees.
0
1Phase Build-out not frozen.
Phase Build-out frozen, no further Phase Build-out
events will occur.
2PBO_en
Bit to enable Phase Build-out events on source
switching. When enabled a Phase Build-out event is
triggered every time DPLL1 selects a new source-
this includes exiting the Holdover or Free-run states.
0
1
Phase Build-out not enabled. DPLL1 locks to zero
degrees phase.
Phase Build-out enabled on source switching.
1Not used. --
Address (hex): 48 (cont...)
Register Name cnfg_monitors Description (R/W) Configuration register
controlling several input
monitoring and switching options.
Default Value 0000 0100*
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
los_flag_on_
TDO ultra_fast_
switch ext_switch PBO_freeze PBO_en
Bit No. Description Bit Value Value Description
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Address (hex): 4B
Register Name cnfg_registers_source_select Description (R/W) Register to select the
source of many of the registers. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL1_DPLL2_
select
Bit No. Description Bit Value Value Description
[7:5] Not used. - -
4DPLL1_DPLL2_select
Bit to select between many of the registers
associated with DPLL1 or DPLL2 e.g. frequency
registers.
0
1DPLL1 registers selected.
DPLL2 registers selected.
[3:0] Not used. - -
Address (hex): 4D
Register Name cnfg_freq_lim_ph_loss Description (R/W) Register to enable the
phase lost indication when DPLL
hits its hard frequency limit.
Default Value 1000 1110
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
freq_lim_ph_
loss
Bit No. Description Bit Value Value Description
7freq_lim_ph_loss
Bit to enable the phase lost indication when the
DPLL hits its hard frequency limit as programmed in
Reg. 41 and Reg. 42 (cnfg_DPLL_freq_limit). This
results in the DPLL entering the phase lost state any
time the DPLL tracks to the extent of its hard limit.
0
1Phase lost/locked determined normally.
Phase lost forced when DPLL tracks to hard limit.
[6:0] Not used. - -
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Address (hex): 50
Register Name cnfg_upper_threshold_0 Description (R/W) Register to program the
activity alarm setting limit for
Leaky Bucket Configuration 0.
Default Value 0000 0110
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
upper_threshold_0_value (Activity alarm, Config. 0, Leaky Bucket - set threshold )
Bit No. Description Bit Value Value Description
[7:0] upper_threshold_0_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 53 (cnfg_decay_rate_0), in
which this does not occur, the accumulator is
decremented by 1.
When the accumulator count reaches the value
programmed as the upper_threshold_0_value, the
Leaky Bucket raises an input inactivity alarm.
- Value at whic h the Leaky Bucket will raise an
inactiv ity alarm.
Address (hex): 51
Register Name cnfg_lower_threshold_0 Description (R/W) Register to program the
activity alarm resetting limit for
Leaky Bucket Configuration 0.
Default Value 0000 0100
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
lower_threshold_0_value (Activity alarm, Config. 0, Leaky Bucket - reset threshold)
Bit No. Description Bit Value Value Description
[7:0] lower_threshold_0_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 53 (cnfg_decay_rate_0), in
which this does not occur, the accumulator is
decremented by 1.
The lower_threshold_0_value is the value at which
the Leaky Bucket will reset an inactivity alarm.
- Value at whic h the Leaky Bucket will reset an
inactiv ity alarm.
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Address (hex): 52
Register Name cnfg_bucket_size_0 Description (R/W) Register to program the
maximum size limit for Leaky
Bucket Configuration 0.
Default Value 0000 1000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
bucket_size_0_value (Activity alarm, Con fig. 0, Leaky Bucket - size)
Bit No. Description Bit Value Value Description
[7:0] bucket_size_0_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 53 (cnfg_decay_rate_0), in
which this does not occur, the accumulator is
decremented by 1.
The number in the Bucket cannot exceed the value
programmed into this regi ster .
- Value at whic h the Leaky Bucket will stop
incrementing, even with further inactive periods.
Address (hex): 53
Register Name cnfg_decay_rate_0 Description (R/W) Register to program the
“decay” or “leak” rate for Leaky
Bucket Configuration 0.
Default Value 0000 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
decay_rate_0_value (Activity
alarm, Config. 0, Leaky Bucket -
leak rate)
Bit No. Description Bit Value Value Description
[7:2] Not used. - -
[1:0] decay_rate_0_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in this register, in which this does not
occur, the accumulator is decremented by 1.
The Leaky Bucket can be programmed to “leak” or
“decay” at the same rate as the “fill” cycle, or
effectively at one half, one quarter, or one eighth of
the fill rate.
00
01
10
11
Bucket decay rate of 1 every 128 ms.
Bucket decay rate of 1 every 256 ms.
Bucket decay rate of 1 every 512 ms.
Bucket decay rate of 1 every 1,024 ms.
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Address (hex): 54
Register Name cnfg_upper_threshold_1 Description (R/W) Register to program the
activity alarm setting limit for
Leaky Bucket Configuration 1.
Default Value 0000 0110
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
upper_threshold_1_value (Activity alarm, Config. 1, Leaky Bucket - set threshold )
Bit No. Description Bit Value Value Description
[7:0] upper_threshold_1_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 57 (cnfg_decay_rate_1), in
which this does not occur, the accumulator is
decremented by 1.
When the accumulator count reaches the value
programmed as the upper_threshold_1_value, the
Leaky Bucket raises an input inactivity alarm.
- Value at whic h the Leaky Bucket will raise an
inactiv ity alarm.
Address (hex): 55
Register Name cnfg_lower_threshold_1 Description (R/W) Register to program the
activity alarm resetting limit for
Leaky Bucket Configuration 1.
Default Value 0000 0100
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
lower_threshold_1_value (Activity alarm, Config. 1, Leaky Bucket - reset threshold)
Bit No. Description Bit Value Value Description
[7:0] lower_threshold_1_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 57 (cnfg_decay_rate_1), in
which this does not occur, the accumulator is
decremented by 1.
The lower_threshold_1_value is the value at which
the Leaky Bucket will reset an inactivity alarm.
- Value at whic h the Leaky Bucket will reset an
inactiv ity alarm.
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Address (hex): 56
Register Name cnfg_bucket_size_1 Description (R/W) Register to program the
maximum size limit for Leaky
Bucket Configuration 1.
Default Value 0000 1000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
bucket_size_1_value (Activity alarm, Con fig. 1, Leaky Bucket - size)
Bit No. Description Bit Value Value Description
[7:0] bucket_size_1_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 57 (cnfg_decay_rate_1), in
which this does not occur, the accumulator is
decremented by 1.
The number in the Bucket cannot exceed the value
programmed into this regi ster .
- Value at whic h the Leaky Bucket will stop
incrementing, even with further inactive periods.
Address (hex): 57
Register Name cnfg_decay_rate_1 Description (R/W) Register to program the
“decay” or “leak” rate for Leaky
Bucket Configuration 1.
Default Value 0000 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
decay_rate_1_value (Activity
alarm, Config. 1, Leaky Bucket -
leak rate)
Bit No. Description Bit Value Value Description
[7:2] Not used. - -
[1:0] decay_rate_1_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in this register, in which this does not
occur, the accumulator is decremented by 1.
The Leaky Bucket can be programmed to “leak” or
“decay” at the same rate as the “fill” cycle, or
effectively at one half, one quarter, or one eighth of
the fill rate.
00
01
10
11
Bucket decay rate of 1 every 128 ms.
Bucket decay rate of 1 every 256 ms.
Bucket decay rate of 1 every 512 ms.
Bucket decay rate of 1 every 1,024 ms.
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Address (hex): 58
Register Name cnfg_upper_threshold_2 Description (R/W) Register to program the
activity alarm setting limit for
Leaky Bucket Configuration 2.
Default Value 0000 0110
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
upper_threshold_2_value (Activity alarm, Config. 2, Leaky Bucket - set threshold )
Bit No. Description Bit Value Value Description
[7:0] upper_threshold_2_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 5B (cnfg_decay_rate_2), in
which this does not occur, the accumulator is
decremented by 1.
When the accumulator count reaches the value
programmed as the upper_threshold_2_value, the
Leaky Bucket raises an input inactivity alarm.
- Value at whic h the Leaky Bucket will raise an
inactiv ity alarm.
Address (hex): 59
Register Name cnfg_lower_threshold_2 Description (R/W) Register to program the
activity alarm resetting limit for
Leaky Bucket Configuration 2.
Default Value 0000 0100
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
lower_threshold_2_value (Activity alarm, Config. 2, Leaky Bucket - reset threshold)
Bit No. Description Bit Value Value Description
[7:0] lower_threshold_2_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 5B (cnfg_decay_rate_2), in
which this does not occur, the accumulator is
decremented by 1.
The lower_threshold_2_value is the value at which
the Leaky Bucket will reset an inactivity alarm.
- Value at whic h the Leaky Bucket will reset an
inactiv ity alarm.
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Address (hex): 5A
Register Name cnfg_bucket_size_2 Description (R/W) Register to program the
maximum size limit for Leaky
Bucket Configuration 2.
Default Value 0000 1000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
bucket_size_2_value (Activity alarm, Con fig. 2, Leaky Bucket - size)
Bit No. Description Bit Value Value Description
[7:0] bucket_size_2_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 5B (cnfg_decay_rate_2), in
which this does not occur, the accumulator is
decremented by 1.
The number in the Bucket cannot exceed the value
programmed into this regi ster .
- Value at whic h the Leaky Bucket will stop
incrementing, even with further inactive periods.
Address (hex): 5B
Register Name cnfg_decay_rate_2 Description (R/W) Register to program the
“decay” or “leak” rate for Leaky
Bucket Configuration 2.
Default Value 0000 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
decay_rate_2_value (Activity
alarm, Config. 2, Leaky Bucket -
leak rate)
Bit No. Description Bit Value Value Description
[7:2] Not used. - -
[1:0] decay_rate_2_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in this register, in which this does not
occur, the accumulator is decremented by 1.
The Leaky Bucket can be programmed to “leak” or
“decay” at the same rate as the “fill” cycle, or
effectively at one half, one quarter, or one eighth of
the fill rate.
00
01
10
11
Bucket decay rate of 1 every 128 ms.
Bucket decay rate of 1 every 256 ms.
Bucket decay rate of 1 every 512 ms.
Bucket decay rate of 1 every 1,024 ms.
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Address (hex): 5C
Register Name cnfg_upper_threshold_3 Description (R/W) Register to program the
activity alarm setting limit for
Leaky Bucket Configuration 3.
Default Value 0000 0110
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
upper_threshold_3_value (Activity alarm, Config. 3, Leaky Bucket - set threshold )
Bit No. Description Bit Value Value Description
[7:0] upper_threshold_3_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 5F (cnfg_decay_rate_3), in
which this does not occur, the accumulator is
decremented by 1.
When the accumulator count reaches the value
programmed as the upper_threshold_3_value, the
Leaky Bucket raises an input inactivity alarm.
- Value at whic h the Leaky Bucket will raise an
inactiv ity alarm.
Address (hex): 5D
Register Name cnfg_lower_threshold_3 Description (R/W) Register to program the
activity alarm resetting limit for
Leaky Bucket Configuration 3.
Default Value 0000 0100
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
lower_threshold_3_value (Activity alarm, Config. 3, Leaky Bucket - reset threshold)
Bit No. Description Bit Value Value Description
[7:0] lower_threshold_3_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 5F (cnfg_decay_rate_3), in
which this does not occur, the accumulator is
decremented by 1.
The lower_threshold_3_value is the value at which
the Leaky Bucket will reset an inactivity alarm.
- Value at whic h the Leaky Bucket will reset an
inactiv ity alarm.
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Address (hex): 5E
Register Name cnfg_bucket_size_3 Description (R/W) Register to program the
maximum size limit for Leaky
Bucket Configuration 3.
Default Value 0000 1000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
bucket_size_3_value (Activity alarm, Con fig. 3, Leaky Bucket - size)
Bit No. Description Bit Value Value Description
[7:0] bucket_size_3_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in Reg. 5F (cnfg_decay_rate_3), in
which this does not occur, the accumulator is
decremented by 1.
The number in the Bucket cannot exceed the value
programmed into this regi ster .
- Value at whic h the Leaky Bucket will stop
incrementing, even with further inactive periods.
Address (hex): 5F
Register Name cnfg_decay_rate_3 Description (R/W) Register to program the
“decay” or “leak” rate for Leaky
Bucket Configuration 3.
Default Value 0000 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
decay_rate_3_value (Activity
alarm, Config. 3, Leaky Bucket -
leak rate)
Bit No. Description Bit Value Value Description
[7:2] Not used. - -
[1:0] decay_rate_3_value
The Leaky Bucket operates on a 128 ms cycle. If,
during a cycle, it detects that an input has either
failed or has been erratic, then for each cycle in
which this occurs, the accumulator is incremented
by 1, and for each period of 1, 2, 4, or 8 cycles, as
programmed in this register, in which this does not
occur, the accumulator is decremented by 1.
The Leaky Bucket can be programmed to “leak” or
“decay” at the same rate as the “fill” cycle, or
effectively at one half, one quarter, or one eighth of
the fill rate.
00
01
10
11
Bucket decay rate of 1 every 128 ms.
Bucket decay rate of 1 every 256 ms.
Bucket decay rate of 1 every 512 ms.
Bucket decay rate of 1 every 1024 ms.
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Address (hex): 61
Register Name cnfg_output_frequency
(Output O2) Description (R/W) Register to configure and
enable the frequencies available
on Output O2.
Default Value 0000 0110
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
output_freq_O2
Bit No. Description Bit Value Value Description
[7:4] Not used. - -
[3:0] output_freq_O2
Configuration of the output frequency available at
Output O2. Many of the frequencies available are
dependent on the frequencies of the APLL1 and the
APLL2. These are configured in Reg. 64 and
Reg. 65. For more detail see the detailed section on
configuring the output frequencies.
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
Output disabled.
2 kHz.
8 kHz.
Digital2 (Reg. 39 cnfg_digital_frequencies).
Digital1 (Reg. 39 cnfg_digital_frequencies).
APLL1 frequency/48.
APLL1 frequency/16.
APLL1 frequency/12.
APLL1 frequency/8.
APLL1 frequency/6.
APLL1 frequency/4.
APLL2 frequency/64.
APLL2 frequency/48.
APLL2 frequency/16.
APLL2 frequency/8.
APLL2 frequency/4.
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Address (hex): 62
Register Name cnfg_output_frequency
(Output O1) Description (R/W) Register to configure and
enable the frequencies available
on Output O1.
Default Value 1000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
output_freq_O1
Bit No. Description Bit Value Value Description
[7:4] output_freq_O1
Configuration of the output frequency available at
Output O1. Many of the frequencies available are
dependent on the frequencies of the APLL1 and the
APLL2. These are configured in Reg. 64 and
Reg. 65. For more detail see the detailed section on
configuring the output frequencies.
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
Output disabled.
2 kHz.
8 kHz.
APLL1 frequency/2.
Digital1 (Reg. 39 cnfg_digital_frequencies).
APLL1 frequency.
APLL1 frequency/16.
APLL1 frequency/12.
APLL1 frequency/8.
APLL1 frequency/6.
APLL1 frequency/4.
APLL2 frequency/64.
APLL2 frequency/48.
APLL2 frequency/16.
APLL2 frequency/8.
APLL2 frequency/4.
[3:0] Not used. - -
Address (hex): 63
Register Name cnfg_output_frequency
(MFrSync/FrSync) Description (R/W) Register to configure and
enable the frequencies available
on outputs MFrSync and FrSync.
Default Value 1100 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
MFrSync_en FrSync_en
Bit No. Description Bit Value Value Description
7MFrSync_en
Register bit to enable the 2 kHz Sync output
(MFrSync).
0
1Output MFrSync disabled.
Output MFrSync enabled.
6FrSync_en
Register bit to enable the 8 kHz Sync output
(FrSync).
0
1Output FrSync disabled.
Output FrSync enabled.
[5:0] Not used. - -
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Address (hex): 64
Register Name cnfg_DPLL2_frequency Description (R/W) Register to configure
DPLL2 Frequency. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL2_frequency
Bit No. Description Bit Value Value Description
[7:4] Not used. - -
[2:0] DPLL2_frequency
Register to configure the frequency of operation of
DPLL2. The frequency of DPLL2 will also affect the
frequency of the APLL2 which, in turn, affects the
frequencies available at outputs O1 and O2 see
Reg. 61 - Reg. 63. It is also possible to not use
DPLL2 at all, but use the APLL2 to run directly from
DPLL1 output, see Reg. 65
(cnfg_DPLL1_frequency). If any frequencies are
required from the APLL2 then DPLL2 should not be
squelched, as the APLL2 input is squelched and the
APLL2 will free run.
000
001
010
011
100
101
110
111
DPLL2 mode = squelched (clock off).
DPLL2 mode = 77.76 MHz (OC-N rates), giving
APLL2 frequency = 311.04 MHz.
DPLL2 mode = 12E1, giving APLL2 output
frequency (before dividers) = 98.304 MHz.
DPLL2 mode = 16E1, giving APLL2 output
frequency (before dividers) = 131.072 MHz.
DPLL2 mode = 24DS1, giving APLL2 output
frequency (before dividers) = 148.224 MHz.
DPLL2 mode = 16DS1, giving APLL2 output
frequency (before dividers) = 98.816 MHz.
DPLL2 mode = E3, giving APLL2 output frequency
(before dividers) = 274.944 MHz.
DPLL2 mode = DS3, giving APLL2 output frequency
(before dividers) = 178.944 MHz.
Address (hex): 65
Register Name cnfg_DPLL1_frequency Description (R/W) Register to configure
DPLL1 and several other
parameters.
Default Value 0000 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL2_meas_
DPLL1_ph APLL2_for_
DPLL1_E1/DS1 DPLL1_freq_to_APLL2 DPLL1_frequency
Bit No. Description Bit Value Value Description
7DPLL2_meas_DPLL1_ph
Register bit to control the feature where DPLL2 is
used to measure phase offset between the SEC
input selected by DPLL1 and either of the other two
SEC Inputs. Refer to the Section “Measuring Phase
Between Master and Slave/Stand-by SEC Sources”
on page 33.
0
1Normal- DPLL2 normal operation.
DPLL2 disabled, DPLL2 phase detector used to
measure phase between selected DPLL1 input and
selected DPLL2 input.
6APLL2_for_DPLL1_E1/DS1
Register bit to select whether the APLL2 takes its
input from DPLL2 or DPLL1. If DPLL1 is selected
then the frequency is controlled by Bits [5:4],
DPLL1_freq_to_APLL2.
0
1APLL2 takes its input from DPLL2.
APLL2 takes its input from DPLL1.
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[5:4] DPLL1_freq_to_APLL2
Register to select the frequency/mode of DPLL1
which is driven to the APLL2 when selected by Bit 6,
APLL2_for_DPLL1_E1/DS1.
Register to select DPLL1’s frequency driven to the
APLL2 (DPLL1 mode*) when selected by Bit 6,
APLL2_for_DPLL1_E1/DS1 ; and consequently the
APLL output frequency in the T4 path.
*Note that this is not the operating frequency of
DPLL1 itself - which is fixed at outputting
77.76 MHz - but is the multiplied output from the LF
Output DFS block. See Figure 5 “PLL Block
Diagram” on page 15.
00
01
10
11
DPLL1 mode = 12E1, giving APLL2 output
frequency (before dividers) = 98.304 MHz.
DPLL1 mode = 16E1, giving APLL2 output
frequency (before dividers) = 131.072 MHz.
DPLL1 mode = 24DS1, giving APLL2 output
frequency (before dividers) = 148.224 MHz.
DPLL1 mode = 16DS1, giving APLL2 output
frequency (before dividers) = 98.816 MHz.
3Not used. --
[2:0] DPLL1_frequency
Register to configure the frequency driven to APLL1
(DPLL1 mode*) and consequently the APLL output
frequency in the T0 path. This register affects the
frequencies available at outputs O1 and O2, see
Reg. 61 - Reg. 63.
*Note that this is not the operating frequency of the
DPLL1 itself - which is fixed at outputting
77.76 MHz - but is the multiplied output from the LF
Output DFS block. See Figure 5 “PLL Block
Diagram” on page 15.
Note...001 is the only selection tha t does not
bypass APLL3. All other selections use digital
feedback.
000
001
010
011
100
101
110
111
DPLL1 mode = 77.76 MHz, digital feedback, APLL1
output frequency (before dividers) = 311.04 MHz.
DPLL1 mode = 77.76 MHz, analog feedback, APLL1
output frequency (before dividers) = 311.04 MHz.
DPLL1 mode = 12E1, giving APLL1 output
frequency (before dividers) = 98.304 MHz.
DPLL1 mode = 16E1, giving APLL1 output
frequency (before dividers) = 131.072 MHz.
DPLL1 mode = 24DS1, giving APLL1 output
frequency (before dividers) = 148.224 MHz.
DPLL1 mode = 16DS1, giving APLL1 output
frequency (before dividers) = 98.816 MHz.
Not used.
Not used.
Address (hex): 65 (cont...)
Register Name cnfg_DPLL1_frequency Description (R/W) Register to configure
DPLL1 and several other
parameters.
Default Value 0000 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL2_meas_
DPLL1_ph APLL2_for_
DPLL1_E1/DS1 DPLL1_freq_to_APLL2 DPLL1_frequency
Bit No. Description Bit Value Value Description
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Address (hex): 66
Register Name cnfg_DPLL2_bw Description (R/W) Register to configure the
bandwidth of DPLL2. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL2_bandwidth
Bit No. Description Bit Value Value Description
[7:2] Not used. - -
[1:0] DPLL2_bandwidth
Register to configure the bandwidth of DPLL2. 00
01
10
11
DPLL2 18 Hz bandwidth.
DPLL2 35 Hz bandwidth.
DPLL2 70 Hz bandwidth.
Not used.
Address (hex): 67
Register Name cnfg_DPLL1_locked_bw Description (R/W) Register to configure the
bandwidth of DPLL1, when phase
locked to an input.
Default Value 0001 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL1_locked_bandwidth
Bit No. Description Bit Value Value Description
[7:2] Not used. - -
[1:0] DPLL1_locked_bandwidth
Register to configure the bandwidth of DPLL1 when
locked to an input reference. Reg. 3B Bit 7 is used
to control whether this bandwidth is used all of the
time or automatically switched to when phase
locked.
11
00
01
10
DPLL1, 18 Hz locked bandwidth.
DPLL1, 35 Hz locked bandwidth.
DPLL1, 70 Hz locked bandwidth.
Not used.
Address (hex): 69
Register Name cnfg_DPLL1_acq_bw Description (R/W) Register to configure the
bandwidth of DPLL1, when not
phase locked to an input.
Default Value 0001 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL1_acquisition_bandwidth
Bit No. Description Bit Value Value Description
[7:4] Not used. - -
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[3:0] DPLL1_acquisition_bandwidth
Register to configure the bandwidth of DPLL1 when
acquiring phase lock on an input reference. Reg. 3B
Bit 7 is used to control whether this bandwidth is
not used or automatically switched to when not
phase locked.
11
00
01
10
DPLL1, 18 Hz acquisition bandwidth.
DPLL1, 35 Hz acquisition bandwidth.
DPLL1, 70 Hz acquisition bandwidth.
Not used.
Address (hex): 6A
Register Name cnfg_DPLL2_damping Description (R/W) Register to configure the
damping factor of DPLL2, along
with the gain of Phase Detector 2
in some modes.
Default Value 0001 0011
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL2_PD2_gain_alog_8k DPLL2_damping
Bit No. Description Bit Value Value Description
7Not used. --
[6:4] DPLL2_PD2_gain_alog_8k
Register to control the gain of the Phase Detector 2
when locking to a reference of 8 kHz or less in
analog feedback mode. This setting is only used if
automatic gain selection is enabled in Reg. 6C Bit 7,
cnfg_DPLL2_PD2_gain.
- Gain value of the Phase Detector 2 when locking to
an 8 kHz reference in analog feedback mode.
3Not used. --
Address (hex): 69 (cont...)
Register Name cnfg_DPLL1_acq_bw Description (R/W) Register to configure the
bandwidth of DPLL1, when not
phase locked to an input.
Default Value 0001 0001
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL1_acquisition_bandwidth
Bit No. Description Bit Value Value Description
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[2:0] DPLL2_damping
Register to configure the damping factor of DPLL2.
The bit values correspond to different damping
factors, depending on the bandwidth selected.
The Gain Peak for the Damping Factors given in the
Value Description (right) are tabulated below:
Damping Factor
for Bandwidth
of 18 Hz:
Damping Factor
for Bandwidth
of 35 Hz:
Damping Factor
for Bandwidth
of 70 Hz:
001 1.2 1.2 1.2
010 2.5 2.5 2.5
011555
Damping Factor Gain Peak 100 5 10 10
1.2
2.5
5
10
20
0.4 dB
0.2 dB
0.1 dB
0.06 dB
0.03 dB
101 5 10 20
Address (hex): 6B
Register Name cnfg_DPLL1_damping Description (R/W) Register to configure the
damping factor of DPLL1, along
with the gain of the Phase
Detector 2 in some modes.
Default Value 0001 0011
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL1_PD2_gain_alog_8k DPLL1_damping
Bit No. Description Bit Value Value Description
7Not used. --
[6:4] DPLL1_PD2_gain_alog_8k
Register to control the gain of the Phase Detector 2
when locking to a reference of 8 kHz or less in
analog feedback mode. This setting is only used if
automatic gain selection is enabled in Reg. 6D Bit 7,
cnfg_DPLL1_PD2_gain.
- Gain value of the Phase Detector 2 when locking to
an 8 kHz reference in analog feedback mode.
3Not used. --
Address (hex): 6A (cont...)
Register Name cnfg_DPLL2_damping Description (R/W) Register to configure the
damping factor of DPLL2, along
with the gain of Phase Detector 2
in some modes.
Default Value 0001 0011
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL2_PD2_gain_alog_8k DPLL2_damping
Bit No. Description Bit Value Value Description
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[2:0] DPLL1_damping
Register to configure the damping factor of DPLL1.
The bit values correspond to different damping
factors, depending on the bandwidth selected.
The Gain Peak for the Damping Factors given in the
Value Description (right) are the same as those
tabulated in the description for Reg. 6A.
Damping Factor
for Bandwidth
of 18 Hz:
Damping Factor
for Bandwidth
of 35 Hz:
Damping Factor
for Bandwidth
of 70 Hz:
001 1.2 1.2 1.2
010 2.5 2.5 2.5
011555
100 5 10 10
101 5 10 20
Address (hex): 6C
Register Name cnfg_DPLL2_PD2_gain Description (R/W) Register to configure the
gain of Phase Detector 2 in some
modes for DPLL2.
Default Value 1100 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL2_PD2_
gain_enable DPLL2_PD2_gain_alog DPLL2_PD2_gain_digital
Bit No. Description Bit Value Value Description
7DPLL2_PD2_gain_enable 0
1DPLL2 Phase Detector 2 not used.
DPLL2 Phase Detector 2 gain enabled and choice of
gain determined according to the locking mode:
- digital feedback mode
- analog feedback mode
- analog feedback at 8 kHz.
[6:4] DPLL2_PD2_gain_alog
Register to control the gain of Phase Detector 2
when locking to a reference, higher than 8 kHz, in
analog feedback mode. This setting is not used if
automatic gain selection is disabled in Bit 7,
DPLL2_PD2_gain_enable.
- Gain value of Phase Detector 2 when locking to a
high frequency reference in analog feedback mode.
3Not used. --
Address (hex): 6B (cont...)
Register Name cnfg_DPLL1_damping Description (R/W) Register to configure the
damping factor of DPLL1, along
with the gain of the Phase
Detector 2 in some modes.
Default Value 0001 0011
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL1_PD2_gain_alog_8k DPLL1_damping
Bit No. Description Bit Value Value Description
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[2:0] DPLL2_PD2_gain_digital
Register to control the gain of Phase Detector 2
when locking to a reference in digital feedback
mode. This setting is always used if automatic gain
selection is disabled in Bit 7,
DPLL2_PD2_gain_enable.
- Gain value of Phase Detector 2 when locking to any
reference in digital feedback mode.
Address (hex): 6D
Register Name cnfg_DPLL1_PD2_gain Description (R/W) Register to configure the
gain of Phase Detector 2 in some
modes for DPLL1.
Default Value 1100 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL1_PD2_
gain_enable DPLL1_PD2_gain_alog DPLL1_PD2_gain_digital
Bit No. Description Bit Value Value Description
7DPLL1_PD2_gain_enable 0
1
DPLL2 Phase Detector 2 not used.
DPLL2 Phase Detector 2 gain enabled and choice of
gain determined according to the locking mode:
- digital feedback mode
- analog feedback mode
- analog feedback at 8 kHz
[6:4] DPLL1_PD2_gain_alog
Register to control the gain of Phase Detector 2
when locking to a reference, higher than 8 kHz, in
analog feedback mode. This setting is not used if
automatic gain selection is disabled in Bit 7,
DPLL1_PD2_gain_enable.
- Gain value of Phase Detector 2 when locking to a
high frequency reference in analog feedback mode.
3Not used. --
Address (hex): 6C (cont...)
Register Name cnfg_DPLL2_PD2_gain Description (R/W) Register to configure the
gain of Phase Detector 2 in some
modes for DPLL2.
Default Value 1100 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL2_PD2_
gain_enable DPLL2_PD2_gain_alog DPLL2_PD2_gain_digital
Bit No. Description Bit Value Value Description
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[2:0] DPLL1_PD2_gain_digital
Register to control the gain of Phase Detector 2
when locking to a reference in digital feedback
mode. Automatic gain selection must be enabled
(Bit 7, DPLL1_PD2_gain_enable), for
DPLL1_PD2_gain_digital to have any effect.
- Gain value of Phase Detector 2 when locking to any
reference in digital feedback mode.
Address (hex): 70
Register Name cnfg_phase_offset
[7:0] Description (R/W) Bits [7:0] of the phase
offset control register. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
phase_offset_value[7:0]
Bit No. Description Bit Value Value Description
[7:0] phase_offset_value[7:0]
Register forming part of the phase offset control. - See Reg. 71, cnfg_phase_offset[15:8] for more
details.
Address (hex): 6D (cont...)
Register Name cnfg_DPLL1_PD2_gain Description (R/W) Register to configure the
gain of Phase Detector 2 in some
modes for DPLL1.
Default Value 1100 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
DPLL1_PD2_
gain_enable DPLL1_PD2_gain_alog DPLL1_PD2_gain_digital
Bit No. Description Bit Value Value Description
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Address (hex): 71
Register Name cnfg_phase_offset
[15:8] Description (R/W) Bits [15:8] of the phase
offset control register. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
phase_offset_value[15:8]
Bit No. Description Bit Value Value Description
[7:0] phase_offset_value[15:8]
Register forming part of the phase offset control. If
the phase offset register is written to when the DPLL
is locked to an input, then it is possible that some
internal signals become out of synchronisation. In
order to avoid this, the phase offset is automatically
“ramped” to the new value. If the phase offset is
only ever adjusted when the device is in Holdover,
then this is not necessary, and this automatic
“ramping” can be disabled, see Reg. 7C,
cnfg_sync_monitor.
This register is ignored and has no affect when
Phase Build-out is enabled in either Reg. 48 or
Reg. 76.
- The value in this register is to be concatenated with
the contents of Reg. 70 cnfg_phase_offset[7:0].
This value is a 16-bit 2’s complement signed
number. The value multiplied by 6.279 represents
the extent of the applied phase offset in
picoseconds.
The phase offset register is not a control to a
“traditional” delay line. This number 6.279 actually
represents a fractional portion of the period of an
internal 77.76 MHz cycle and can, therefore, be
represented more accurately as follows. Each bit
value of the register represents the period of the
internal 77.76 MHz clock divided by 211.
If, for example, the DPLL is locked to a reference
that is +1 ppm in frequency with respect to a perfect
oscillator, then the period, and hence the phase
offset, will be decreased by 1 ppm. Programming a
value of 1024 into the phase offset register will
produce a complete inversion of the 77.76 MHz
output clock.
Note...The exact period of the internal 77.76 MHz
clock is determined by the current state of the DPLL
i.e. in Locked mode its accuracy depends on that of
the locked to input, in Holdover or Free-run it
depends on the accuracy of the external oscillator.
Address (hex): 72
Register Name cnfg_PBO_phase_offset Description (R/W) Register to offset the mean
time error of Phase Build-out
events.
Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
PBO_phase_offset
Bit No. Description Bit Value Value Description
[7:6] Not used. - -
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[5:0] PBO_phase_offset
Each time a Phase Build-out event is triggered,
there is an uncertainty of up to 5 ns introduced
which translates to a phase hit on the output. The
mean error over a large number of events is
designed to be zero. This register can be used to
introduce a fixed offset into each PBO event. This
will have the effect of moving the mean error
positive or negative in time.
- The value in this register is a 6-bit 2’s complement
number. The value multiplied by 0.101 gives the
programmed offset in nanoseconds. Values greater
than +1.4 ns or less than -1.4 ns should NOT be
used as they may cause internal mathematical
errors.
Address (hex): 73
Register Name cnfg_phase_loss_fine_limit Description (R/W) Register to configure some
of the parameters of the DPLL
phase detectors.
Default Value 1010 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
fine_limit_en noact_ph_loss narrow_en phase_loss_fine_limit
Bit No. Description Bit Value Value Description
7fine_limit_en
Register bit to enable the phase_loss_fine_limit
Bits [2:0]. When disabled, phase lock/loss is
determined by the other means within the device.
This must be disabled when multi-UI jitter tolerance
is required, see Reg. 74,
cnfg_phase_loss_course_limit.
0
1Phase loss indication only triggered by other means.
Phase loss triggered when phase error exceeds the
limit programmed in phase_loss_fine_limit,
Bits [2:0].
6noact_ph_loss
The DPLL detects that an input has failed very
rapidly. Normally, when the DPLL detects this
condition, it does not consider phase lock to be lost
and will phase lock to the nearest edge (±180º)
when a source becomes available again, hence
giving tolerance to mis si n g cycles . If pha se loss is
indicated, then frequency and phase locking is
instigated (±360º locking). This bit can be used to
force the DPLL to indicate phase loss immediately
when no activity is detected.
0
1
No activity on reference does not trigger phase lost
indication.
No activity triggers phase lost indication .
Address (hex): 72 (cont...)
Register Name cnfg_PBO_phase_offset Description (R/W) Register to offset the mean
time error of Phase Build-out
events.
Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
PBO_phase_offset
Bit No. Description Bit Value Value Description
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5narrow_en (test control bit)
Set to 1 (default value). 0
1Set to 1.
[4:3] Not used. - -
[2:0] phase_loss_fine_limit
When enabled by Bit 7, this register coarsely sets
the phase limit at which the device indicates phase
lost or locked. The default value of 2 (010) gives a
window size of around ±90 - 180º. The phase
position of the inputs to the DPLL has to be within
the window limit for 1 – 2 seconds before the device
indicates phase lock. If it is outside the window for
any time then phase loss is immediately indicated.
For most cases the default value of 2 (010) is
satisfactory. The window size changes in proportion
to the value, so a value of 1 (001) will give a narrow
phase acceptance or lock window of approximately
±45 - 90º.
000
001
010
011
100
101
110
111
Do not use. Indicates phase loss continuously.
Small phase window for phase lock indication.
Recommended value.
)
)
) Larger phase window for phase lock indication.
)
)
Address (hex): 74
Register Name cnfg_phase_loss_coarse_limit Description (R/W) Register to configure some
of the parameters of DPLL phase
detectors.
Default Value 1000 0101
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
coarse_lim_
phaseloss_en wide_range_en multi_ph_resp phase_loss_coarse_limit
Bit No. Description Bit Value Value Description
7coarse_lim_phaseloss_en
Register bit to enable the coarse phase detector,
whose range is determi ned by
phase_loss_coarse_limit Bits [3:0]. This register
sets the limit in the number of input clock cycles (UI)
that the input phase can move by before the DPLL
indicates phase lost.
0
1
Phase loss not triggered by the coarse phase lock
detector.
Phase loss triggered when phase error exceeds the
limit programmed in phase_loss_coarse_limit,
Bits [3:0].
Address (hex): 73 (cont...)
Register Name cnfg_phase_loss_fine_limit Description (R/W) Register to configure some
of the parameters of the DPLL
phase detectors.
Default Value 1010 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
fine_limit_en noact_ph_loss narrow_en phase_loss_fine_limit
Bit No. Description Bit Value Value Description
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6wide_range_en
To enable the device to be tolerant to large amounts
of applied jitter and still do direct phase locking at
the input frequency rate (up to 77.76 MHz), a wide
range phase detector and phase lock detector is
employed. This bit enables the wide range phase
detector. This allows the device to be tolerant to,
and therefore keep track of, drifts in input phase of
many cycles (UI). The range of the phase detector is
set by the same register used for the phase loss
coarse limit (Bits [3:0]).
0
1Wide range phase detector off.
Wide range phase detector on.
5multi_ph_resp
Enables the phase result from the coarse phase
detector to be used in the DPLL algorithm. Bit 6
should also be set when this is activated. The
coarse phase detector can measure and keep track
over many thousands of input cycles, thus allowing
excellent jitter and wander tolerance. This bit
enables that phase result to be used in the DPLL
algorithm, so that a large phase measurement gives
a faster pull-in of the DPLL. If this bit is not set then
the phase measurement is limited to ±360º which
can give a slower pull-in rate at higher input
frequencies, but could also be used to give less
overshoot.
Setting this bit in direct locking mode, for example
with a 19.44 MHz input, w oul d give the same
dynamic response as a 19.44 MHz input used with
8 k locking mode, where the input is divided down
internally to 8 kHz first.
0
1
DPLL phase detector limited to ±360º (±1 UI).
However it will still remember its original phase
position over many thousands of UI if Bit 6 is set.
DPLL phase detector also uses the full coarse
phase detector result. It can now measure up to:
±360º x 8191 UI = ±2,948,760º.
4Not used. --
Address (hex): 74 (cont...)
Register Name cnfg_phase_loss_coarse_limit Description (R/W) Register to configure some
of the parameters of DPLL phase
detectors.
Default Value 1000 0101
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
coarse_lim_
phaseloss_en wide_range_en multi_ph_resp phase_loss_coarse_limit
Bit No. Description Bit Value Value Description
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[3:0] phase_loss_coarse_limit
Sets the range of the coarse phase loss detector
and the coarse phase detector.
When locking to a high frequency signal, and jitter
tolerance greater than 0.5 UI is required, then the
DPLL can be configured to track phase errors over
many input clock periods. This is particularly useful
with very low bandwidths. This register configures
how many UI over which the input phase can be
tracked. It also sets the range of the coarse phase
loss detector, which can be used with or without the
multi-UI phase capture range capability.
This register value is used by Bits 6 and 7.
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100-1111
Input phase error tracked over ±1 UI.
Input phase error tracked over ±3 UI.
Input phase error tracked over ±7 UI.
Input phase error tracked over ±15 UI.
Input phase error tracked over ±31 UI.
Input phase error tracked over ±63 UI.
Input phase error tracked over ±127 UI.
Input phase error tracked over ±255 UI.
Input phase error tracked over ±511 UI.
Input phase error tracked over ±1023 UI.
Input phase error tracked over ±2047 UI.
Input phase error tracked over ±4095 UI.
Input phase error tracked over ±8191 UI.
Address (hex): 76
Register Name cnfg_ip_noise_window Description (R/W) Register to configure the
noise rejection function for low
frequency inputs.
Default Value 0000 0110
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
ip_noise_
window_en
Bit No. Description Bit Value Value Description
7ip_noise_window_en
Register bit to enable a window of 5% tolerance
around low-frequency inputs (2, 4 and 8 kHz). This
feature ensures that any edge caused by noise
outside the 5% window where the edge is expected
will not be considered within the DPLL. This reduces
any possible phase hit when a low-frequency
connection is removed and contact bounce is
possible.
0
1DPLL considers all edges for phase locking.
DPLL ignores input edges outside a 95% to 105%
window.
[6:0] Not used. - -
Address (hex): 74 (cont...)
Register Name cnfg_phase_loss_coarse_limit Description (R/W) Register to configure some
of the parameters of DPLL phase
detectors.
Default Value 1000 0101
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
coarse_lim_
phaseloss_en wide_range_en multi_ph_resp phase_loss_coarse_limit
Bit No. Description Bit Value Value Description
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Address (hex): 77
Register Name sts_current_phase
[7:0] Description (RO) Bits [7:0] of the current
phase register. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
current_phase[7:0]
Bit No. Description Bit Value Value Description
[7:0] current_phase
Bits [7:0] of the current phase register. See Reg. 78
sts_current_phase [15:8] for details.
- See Reg. 78 sts_current_phase [15:8] for details.
Address (hex): 78
Register Name sts_current_phase
[15:8] Description (RO) Bits [15:8] of the current
phase register. Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
current_phase[15:8]
Bit No. Description Bit Value Value Description
[7:0] current_phase
Bits [15:8] of the current phase register. This
register is used to read either from the phase
detector of either DPLL1 or DPLL2, according to
Reg. 4B Bit 4 DPLL2_DPLL1_select. The value is
averaged in the phase averager before being made
available.
- The value in this register should be concatenated
with the value in Reg. 77 sts_current_phase [7:0].
This 16-bit value is a 2’s complement signed
integer. The value multiplied by 0.707 is the
averaged value of the current phase error, in
degrees, as measured at the DPLL’s phase
detector.
Address (hex): 79
Register Name cnfg_phase_alarm_timeout Description (R/W) Register to configure how
long before a phase alarm is
raised on an input.
Default Value 0011 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
timeout_value (in two-second intervals)
Bit No. Description Bit Value Value Description
[7:6] Not used. - -
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[5:0] timeout_value
Phase alarms can only be raised on an input when
DPLL1 is attempting to lock to it. Once an input has
been rejected due to a phase alarm, there is no way
to measure whether it is good again, becau se it is
no longer selected by the DPLL. The phase alarms
can either remain until reset by software, or timeout
after 128 seconds, as selected in Reg. 34 Bit 6,
phalarm_timeout.
- This 6-bit unsigned integ e r represents the length of
time before a phase alarm will be raised on an
input. The value multiplied by 2 gives the time in
seconds. This time value is the time that the
controlling state machine will spend in Pre-locked,
Pre-locked2 or Phase-lost modes before setting the
phase alarm on the selected input.
Address (hex): 7A
Register Name cnfg_sync_pulses Description (R/W) Register to configure the
Sync outputs available from
FrSync and MFrSync and select
the source for the 2 kHz and
8 kHz outputs from O1 and O2.
Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
2k_8k_from_
DPLL2 8k_invert 8k_pulse 2k_invert 2k_pulse
Bit No. Description Bit Value Value Description
72k_8k_from_DPLL2
Register to select the source (DPLL1 or DPLL2) for
the 2 kHz and 8 kHz outputs available from O1 and
O2.
0
1
2/8 kHz on O1 and O2 generated from DPLL1.
2/8 kHz on O1 and O2 generated from DPLL2.
[6:4] Not used. - -
38k_invert
Register bit to invert the 8 kHz output from FrSync. 0
18 kHz FrSync output not inverted.
8 kHz FrSync output inverted.
28k_pulse
Register bit to enable the 8 kHz output from FrSync
to be either pulsed or 50:50 duty cycle. Output 02
must be enabled to use “pulsed output” mode on
the FrSync output, and then the pulse width on the
FrSync output will be equal to the period of the
output programmed on O2.
0
18 kHz FrSync output not pulsed.
8 kHz FrSync output pulsed.
Address (hex): 79 (cont...)
Register Name cnfg_phase_alarm_timeout Description (R/W) Register to configure how
long before a phase alarm is
raised on an input.
Default Value 0011 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
timeout_value (in two-second intervals)
Bit No. Description Bit Value Value Description
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12k_invert
Register bit to invert the 2 kHz output from
MFrSync.
0
12 kHz MFrSync output not inverted.
2 kHz MFrSync output inverted.
02k_pulse
Register bit to enable the 2 kHz output from
MFrSync to be either pulsed or 50:50 duty cycle.
Output O2 must be enabled to use “pulsed output”
mode on the MFrSync output, and then the pulse
width on the MFrSync output will be equal to the
period of the output programmed on O2.
0
12 kHz MFrSync output not pulsed.
2 kHz MFrSync output pulsed.
Address (hex): 7B
Register Name cnfg_sync_phase Description (R/W) Register to configure the
behaviour of the synchronisation
for the external frame reference.
Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Indep_FrSync/
MFrSync Sync_OC-N_
rates Sync_phase_SYNC3 Sync_phase_SYNC2 Sync_phase_SYNC1
Bit No. Description Bit Value Value Description
7Indep_FrSync/MrSync
This allows the option of either maintaining
alignment of FrSync and other clock outputs during
synchronisation from the selected Sync input, or
whether to not maintain alignment to all clocks and
so not disturb any of the output clocks.
0
1
MFrSync & FrSync outputs are always aligned with
other output clocks.
MFrSync & FrSync outputs are independent of other
output clocks.
Address (hex): 7A (cont...)
Register Name cnfg_sync_pulses Description (R/W) Register to configure the
Sync outputs available from
FrSync and MFrSync and select
the source for the 2 kHz and
8 kHz outputs from O1 and O2.
Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
2k_8k_from_
DPLL2 8k_invert 8k_pulse 2k_invert 2k_pulse
Bit No. Description Bit Value Value Description
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6Sync_OC-N_rates
This allows the selected Sync input to synchronize
the OC-3 derived clocks in order to maintain
alignment between the FrSync output and output
clocks and allo w a finer sampling pr ecision of the
selected Sync input of either 19.44MHz or
38.88MHz.
0
1
The OC-N rate clocks are not affected by the
selected Sync input. The selected Sync input is
sampled with a 6.48 MHz precision . 6.48MHz
should be provided as the input reference clock.
Allows the selected Sync input to operate with a
19.44 MHz or 38.88 MHz input clock reference.
Input sampling and output alignment to 19.44 MHz
is used when the current clock input is 19.44 MHz,
otherwise 38.88 MHz sampling precision is used.
[5:4] Sync_phase_SYNC3
Register to control the sampling of the external Sync
input. Nominally the falling edge of the input is
aligned with the falling edge of the reference clock.
The margin is ±0.5 U.I. (Unit Interval).
00
01
10
11
On target.
0.5 U.I. early.
1 U.I. late.
0.5 U.I. late.
[3:2] Sync_phase_SYNC2
Register to control the sampling of the external Sync
input. Nominally the falling edge of the input is
aligned with the falling edge of the reference clock.
The margin is ±0.5 U.I. (Unit Interval).
00
01
10
11
On target.
0.5 U.I. early.
1 U.I. late.
0.5 U.I. late.
[1:0] Sync_phase_SYNC1
Register to control the sampling of the external Sync
input. Nominally the falling edge of the input is
aligned with the falling edge of the reference clock.
The margin is ±0.5 U.I. (Unit Interval).
00
01
10
11
On target.
0.5 U.I. early.
1 U.I. late.
0.5 U.I. late.
Address (hex): 7B (cont...)
Register Name cnfg_sync_phase Description (R/W) Register to configure the
behaviour of the synchronisation
for the external frame reference.
Default Value 0000 0000
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Indep_FrSync/
MFrSync Sync_OC-N_
rates Sync_phase_SYNC3 Sync_phase_SYNC2 Sync_phase_SYNC1
Bit No. Description Bit Value Value Description
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Address (hex): 7C
Register Name cnfg_sync_monitor Description (R/W) Register to configure the
external Sync input monitor. It
also has a bit to control the phase
offset automatic ramping feature.
Default Value 0010 1011
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
ph_offset_ramp Sync_monitor_limit
Bit No. Description Bit Value Value Description
7ph_offset_ramp
Register bit to force an internal phase offset
calibration routine. See also Reg. 71,
Cnfg_Phase_Offset. The calibration routine puts the
device into Holdover while it internally ramps the
phase offset to zero, then resets all internal output
and feedback dividers, then ramps the phase offset
to the current value from Regs 70 and 71, and then
turns Holdover off. The routine is transparent to the
outside with no visible change in output phase
offset.
0
1
Phase offset automatically ramped on from old
value to new value when there is a change in Reg
70 or 71.
Start phase offset internal phase offset calibration
routine.
[6:4] Sync_monitor_limit
An alternative to allowing the external Sync input to
synchronize the outputs, is to use the Sync monitor
block to alarm when the external Sync input does
not align with the output within a certain number of
input clock cycles. This register defines the limit in
UI of the selected SEC. If the external Sync does not
occur within this limit, then Sync alarm will be
raised, see Reg. 09 Bit 7.
000
001
010
011
100
101
110
111
Sync alarm raised beyond ±1 UI.
Sync alarm raised beyond ±2 UI.
Sync alarm raised beyond ±3 UI.
Sync alarm raised beyond ±4 UI.
Sync alarm raised beyond ±5 UI.
Sync alarm raised beyond ±6 UI.
Sync alarm raised beyond ±7 UI.
Sync alarm raised beyond ±8 UI.
[3:0] Not used. - -
Address (hex): 7D
Register Name cnfg_interrupt Description (R/W) Register to configure
interrupt output. Default Value 0000 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Interrupt
GPO_en Interrupt
tristate_en Interrupt
int_polarity
Bit No. Description Bit Value Value Description
[7:3] Not used. - -
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ACS8525 LC/P
2Interrupt GPO_en
(Interrupt General Purpose Output). If the interrupt
output pin is not required, then setting this bit will
allow the pin to be used as a general purpose
output. The pin will be driven to the state of the
polarity control bit, int_polarity.
0
1Interrupt output pin used for interrupts.
Interrupt output pin used for GPO purpose.
1Interrupt tristate_en
The interrupt can be configured to be either
connected directly to a processor, or wired together
with other sources.
0
1Interrupt pin always driven when inactive.
Interrupt pin only driven when active, high-
impedance when inactive.
0Interrupt int_polarity
The interrupt pin can be configured to be active
High or Low.
0
1
Active Low - pin driven Low to indicate active
interrupt.
Active High - pin driv en High to indicate active
interrupt.
Address (hex): 7E
Register Name cnfg_protection Description (R/W) Pro tection register to
protect against erroneous
software writes.
Default Value 1000 0101
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
protection_value
Bit No. Description Bit Value Value Description
[7:0] protection_value
This register can be used to ensure that the
software writes a specific value to this register,
before being able to modify any other register in the
device. Three modes of protection are offered,
(i) protected,
(ii) fully unprotected,
(iii) single unprotected.
When protected, no other register in the device can
be written to. When fully unprotected, any writeable
register in the device can be written to. When single
unprotected, only one register can be written before
the device automatically re-protects itself.
Note...This register cannot be protected.
0000 0000 –
1000 0100
1000 0101
1000 0110
1000 0111 –
1111 1111
Protected mode.
Fully unprotected.
Single unprotected.
Protected mode.
Address (hex): 7D (cont...)
Register Name cnfg_interrupt Description (R/W) Register to configure
interrupt output. Default Value 0000 0010
Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Interrupt
GPO_en Interrupt
tristate_en Interrupt
int_polarity
Bit No. Description Bit Value Value Description
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ACS8525 LC/P
JTAG
The JTAG connections on the ACS8525 allow a full
boundary scan to be made. The JTA G impleme ntation is
fully compliant to IEEE 1149.1[4], with the following minor
exceptions, and the user should refer to the standard for
further information.
1. The output boundary scan cells do not captu re data
from the core, and so do not support INTEST. However
this does not affect board testing.
2. In common with some other manufacturers, pin TRST
is internally pulled Low to disable JTAG by default. The
standard is to pull High. The polarity of TRST is as the
standard: TRST High to enable JTAG boundary scan
mode, TRST Low for normal operation.
The JTAG timing diagram is shown in Figure 12.
Over-voltage Protection
The ACS8525 may require Over-voltage Protection on
input reference clock ports according to ITU
recommendation K.41[10]. Semtech protection devices
are recommended for this purpose (see separate
Semtech data book).
ESD Protection
Suitable precautions should be taken to protec t against
electrostatic damage during handling and assembly. This
device incorporates ESD protection structures that
protect the device against ESD damage at ESD input
levels up to at least +/2kV using the Human Body Model
(HBD) MIL-STD-883D Method 3015.7, for all pins.
Latchup Protection
This device is protected against latchup for input current
pulses of magnitude up to at least ±100 mA to JEDEC
Standard No. 78 August 1997.
Figure 12JTAG Timing
Electrical Specifications
Table 16 JTAG Timing (for use with Figure 12)
Parameter Symbol Minimum Typical Maximum Units
Cycle Time tCYC 50 - - ns
TMS/TDI to TCK rising edge time tSUR 3--ns
TCK rising to TMS/TDI hold time tHT 23 - - ns
TCK falling to TDO valid tDOD --5ns
F8110D_022JTAGTiming_01
T
CK
T
MS
TDI
t
SUR
t
HT
T
DO
t
DOD
t
CYC
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ACS8525 LC/P
Maximum Ratings
Important Note: The Absolute Maximum Ratings, Table 17, are stress ratings only, and functional operation of the
device at conditions other than those indicated in the Operating Conditions sections of this specification are not
implied. Exposure to the absolute maximum ratings for an extended period may reduce the reliability or useful lifetime
of the product.
Operating Conditions
DC Characteristics
Table 17 Absolute Maximum Ratings
Parameter Symbol Minimum Maximum Units
Supply Voltage VDD1, VDD2, VDD3, VDD4,
VDD5, VDD6, VDD7, VD1+, VD2+,VD3+,
VA1+, VA2+, VA 3+, VDD_DIFF
VDD -0.5 3.6 V
Power Supply (DC Voltage) VDD5V VDD5V 5.5 V
Input Voltage (non-supply pins) VIN -5.5V
Output Voltage (non-supply pins) VOUT -5.5V
Ambient Operating Temperature Range TA-40 +85 oC
Storage Temperature TSTOR -50 +150 oC
Table 18 Operating Conditions
Parameter Symbol Minimum Typical Maximum Units
Power Supply (DC Voltage)
VDD1, VDD2, VDD3, VDD4, VDD5, VDD6,
VDD7, VD1+, VD2+,VD3+, VA1+, VA2+,
VA3+, VDD_DIF
VDD 3.0 3.3 3.6 V
Power Supply (DC Voltage) VDD5V VDD5V 3.0 3.3/5.0 5.5 V
Ambient Temperature Range TA-40 - +85 oC
Supply Current
(Typical - one 19 MHz output) IDD 110 200 mA
Total Power Dissipation PTOT 360 720 mW
Table 19 DC Characteristics: TTL Input Port
Across all operating conditions, unless otherwise stated
Parameter Symbol Minimum Typical Maximum Units
VIN High VIH 2--V
VIN Low VIL --0.8V
Input Current IIN --10µA
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ACS8525 LC/P
Table 20 DC Characteristics: TTL Input Port with In ternal Pull-up
Across all operating conditions, unless otherwise stated
Parameter Symbol Minimum Typical Maximum Units
VIN High VIH 2--V
VIN Low VIL --0.8V
Pull-up Resistor PU 25 - 95 kΩ
Input Current IIN - - 120 µΑ
Table 21 DC Characteristics: TTL Input Port with In ternal Pull-down
Across all operating conditions, unless otherwise stated
Parameter Symbol Minimum Typical Maximum Units
VIN High VIH 2--V
VIN Low VIL --0.8V
Pull-down Resistor (except TCK input) PD 25 - 95 kΩ
Pull-down Resistor (TCK input only) PD 12.5 - 47.5 kΩ
Input Current IIN - - 120 µA
Table 22 DC Characteristics: TTL Output Port
Across all operating conditions, unless otherwise stated
Parameter Symbol Minimum Typical Maximum Units
VOUT Low (lOL = 4mA) VOL 0-0.4V
VOUT High (lOL = 4mA) VOH 2.4 - - V
Drive Current ID - - 4 mA
Table 23 DC Characteristics: PECL Input/Output Port
Across all operating conditions, unless otherwise stated
Parameter Symbol Minimum Typical Maximum Units
PECL Input Low Voltage
Differential Inputs (Note ii) VILPECL VDD-2.5 - VDD-0.5 V
PECL Input High Voltage
Differential Inputs (Note ii) VIHPECL VDD-2.4 - VDD-0.4 V
Input Differential Voltage VIDPECL 0.1 - 1.4 V
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ACS8525 LC/P
Notes: (i) Unused differential input ports should be left floating and set in LVDS mode, or the positive and negative inputs tied to VDD and GND
respectively.
(ii) Assuming a differential input voltage of at least 100 mV.
(iii) Unused differential input terminated to VDD - 1.4 V.
(iv) With 50
Ω
load on each pin to VDD - 2 V, i.e. 82
Ω
to GND and 130
Ω
to VDD.
Figure 13Recommended Line Termination for PECL Input/Output Ports
PECL Input Low Voltage
Single-ended Input (Note iii) VILPECL_S VDD-2.4 - VDD-1.5 V
PECL Input High Voltage
Single-ended Input (Note iii) VILPECL_S VDD-1.3 - VDD-0.5 V
Input High Current
Input Differential Voltage VID = 1.4V IIHPECL -10 - +10 µΑ
Input Low Current
Input Differential Voltage VID = 1.4V IILPECL -10 - +10 µA
PECL Output Low Voltage (Note iv) VOLPECL VDD-2.10 - VDD-1.62 V
PECL Output High Voltage (Note iv) VOHPECL VDD-1.25 - VDD-0.88 V
PECL Output Differential Voltage (Note iv) VODPECL 580 - 900 mV
Table 23 DC Characteristics: PECL Input/Output Port (cont...)
Across all operating conditions, unless otherwise stated
Parameter Symbol Minimum Typical Maximum Units
SEC2POS
SEC2NEG
SEC1NEG
SEC1POS
F8595D_024PECL_01
n x 8 kHz,
1.544/2.048 MHz,
6.48 MHz,
19.44 MHz,
38.88 MHz,
51.84 MHz,
77.76 MHz or
155.52 MHz
n x 8 kHz,
1.544/2.048 MHz,
6.48 MHz,
19.44 MHz,
38.88 MHz,
51.84 MHz,
77.76 MHz or
155.52 MHz
01POS
01NEG
Fully
Programmable
Output Frequencies
ZO = Transmission line Impedance
VDD = +3.3 V
n = Integer 1 to 12,500
ZO = 50Ω
ZO = 50Ω
VDD
GND
130 Ω
82Ω
130 Ω
82 Ω
ZO = 50Ω
ZO = 50Ω
VDD
GND
130 Ω
82Ω
130 Ω
82 Ω
ZO = 50Ω
ZO = 50Ω
VDD
GND
130 Ω
82Ω
130 Ω
82 Ω
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ACS8525 LC/P
Notes: (i) With 100
Ω
load between the differential outputs.
Figure 14Recommended Line Termination for LVDS Input/Output Ports
Table 24 DC Characteristics: LVDS Input/Output Port
Across all operating conditions, unless otherwise stated
Parameter Symbol Minimum Typical Maximum Units
LVDS Input Voltage Range
Differential Input Voltage = 100 mV VVRLVDS 0-2.40V
LVDS Differential Input Threshold VDITH -100 - +100 mV
LVDS Input Differential Voltage VIDLVTSDS 0.1 - 1.4 V
LVDS Input Termination Resistance
Must be placed externally across the LVDS
± input pins of ACS8525. Resistor should
be 100 Ω with 5% tolerance
RTERM 95 100 105 Ω
LVDS Output High Volt age
(Note (i)) VOHLVDS --1.585V
LVDS Output Low Voltage
(Note (i)) VOLLVDS 0.885 - - V
LVDS Differential Output Voltage VODLVDS 250 - 450 mV
LVDS Change in Magnitude of Differential
Output Voltage for complementary States
(Note (i))
VDOSLVDS --25mV
LVDS Output Offset Voltage
Temperature = 25oC (Note (i)) VOSLVDS 1.125 - 1.275 V
SEC2POS
SEC2NEG
SEC1NEG
SEC1POS
F8595D_025LVDS_01
n x 8 kHz,
1.544/2.048 MHz,
6.48 MHz,
19.44 MHz,
38.88 MHz,
51.84 MHz,
77.76 MHz or
155.52 MHz
n x 8 kHz,
1.544/2.048 MHz,
6.48 MHz,
19.44 MHz,
38.88 MHz,
51.84 MHz,
77.76 MHz or
155.52 MHz 01POS
01NEG
Fully
Programmable
Output Frequencies
ZO = 50Ω
ZO = 50Ω100 Ω
ZO = 50Ω
ZO = 50Ω100 Ω
ZO = 50Ω
ZO = 50Ω100 ΩZO = Transmission line Impedance
VDD = +3.3 V
n = integer 1 to 12,500
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ACS8525 LC/P
Jitter Performance
Output jitter generation me asured over 60 second interval, UI p-p max measured using C-MAC E2747 12.800 MHz
TCXO on ICT Flexacom tester.
Table 25 Output Jitter Generation at 35 Hz bandwidth and 8 kHz Input
Test Definition Jitter Spec ACS8525 Jitter
Specification Filter UI UI (TYP)
G813[8] for 155 MHz o/p option 1 65 kHz - 1.3 MHz 0.1 p-p 0.073 p-p
G813[8] & G812[7] for 2.048 MHz option 1 20 Hz - 100 kHz 0.05 p-p 0.012 p-p
G813[8] for 155 MHz o/p option 2 12 kHz - 1.3 MHz 0.1 p-p 0.069 p-p
G812[7] for 1.544 MHz o/p 10 Hz - 40 kHz 0.05 p-p 0.011 p-p
G812[7] for 155 MHz electrical 500 Hz - 1.3 MHz 0.5 p-p 0.083 p-p
G812[7] for 155 MHz electrical 65 kHz - 1.3 MHz 0.075 p-p 0.073p-p
ETS-300-462-3[2] for 2.048 MHz SEC o/p 20 Hz - 100 kHz 0.5 p-p 0.012 p-p
ETS-300-462-3[2] for 2.048 MHz SEC o/p 49 Hz - 100 kHz 0.2 p-p 0.012 p-p
ETS-300-462-3[2] for 2.048 MHz SSU o/p 20 Hz - 100 kHz 0.05 p-p 0.012 p-p
ETS-300-462-5[3] for 155 MHz o/p 500 Hz - 1.3 MHz 0.5 p-p 0.083 p-p
ETS-300-462-5[3] for 155 MHz o/p 65 kHz - 1.3 MHz 0.1 p-p 0.073 p-p
GR-253-CORE[11] net i/f, 51.84 MHz o/p 100 Hz - 0.4 MHz 1.5 p-p 0.038 p-p
GR-253-CORE[11] net i/f, 51.84 MHz o/p 20 kHz to 0.4 MHz 0.15 p-p 0.019 p-p
GR-253-CORE[11] net i/f, 155 MHz o/p 500 Hz - 1.3 MHz 1.5 p-p 0.083 p-p
GR-253-CORE[11] net i/f, 155 MHz o/p 65 kHz - 1.3 MHz 0.15 p-p 0.073 p-p
GR-253-CORE[11] cat II elect i/f, 155 MHz 12 kHz - 1.3 MHz 0.1 p-p 0.069 p-p
0.01 rms 0.009 rms
GR-253-CORE[11] cat II elect i/f, 51.84 MHz 12 kHz - 400 kHz 0.1 p-p 0.008 p-p
0.01 rms 0.004 rms
GR-253-CORE[11] DS1 i/f, 1.544 MHz 10 Hz - 40 kHz 0.1 p-p 0.001 p-p
0.01 rms <0.001 rms
AT&T 62411[1] for 1.544 MHz 10 Hz - 8 kHz 0.02 rms <0.001 rms
AT&T 62411[1] for 1.544 MHz 8 Hz - 40 kHz 0.025 rms <0.001 rms
AT&T 62411[1] for 1.544 MHz 10 Hz - 40 kHz 0.025 rms <0.001 rms
AT&T 62411[1] for 1.544 MHz Broadband 0.05 rms <0.001 rms
G-742[6] for 2.048 MHz DC - 100 kHz 0.25 rms 0.012 rms
G-742[6] for 2.048 MHz 18 kHz - 100 kHz 0.05 p-p 0.012 p-p
G-736[5] for 2.048 MHz 20 Hz - 100 kHz 0.05 p-p 0.012 p-p
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ACS8525 LC/P
Note...This table is only for comparing the ACS8525 output jitter performance against values and quoted in various specifications for given
conditions. It should not be used to infer compliance to any other aspects of these specifications.
GR-499-CORE[12] & G824[9] for 1.544 MHz 10 Hz - 40kHz 5.0 p-p 0.001 p-p
GR-499-CORE[12] & G824[9] for 1.544 MHz 8 kHz - 40kH z 0.1 p-p 0.001 p-p
GR-1244-CORE[13] for 1.544 MHz > 10 Hz 0.05 p-p 0.001 p-p
Table 25 Output Jitter Generation at 35 Hz bandwidth and 8 kHz Input (cont...)
Test Definition Jitter Spec ACS8525 Jitter
Specification Filter UI UI (TYP)
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ACS8525 LC/P
Input/Output Timing
Figure 15Input/Output Timing with Phase Build-out Off (Typical Conditions)
F8525D_021IP_OPTiming_02
Input/Output Delay Output Min/Max Phase Alignment
(FrSync Alignment switched on)
8 kHz input
8 kHz output
6.48 MHz input
6.48 MHz output
19.44 MHz input
25.92 MHz input
38.88 MHz input
51.84 MHz input
77.76 MHz input
19.44 MHz output
38.88 MHz output
51.84 MHz output
77.76 MHz output
25.92 MHz output
+8.2 ± 1.5 ns
+4.7 ± 1.5 ns
+4.3 ± 1.5 ns
+4.7 ± 1.5 ns
+4.6 ± 1.5 ns
+3.0 ± 1.5 ns
+5.3 ± 1.5 ns
8 kHz
MFrSync (2 kHz)
FrSync (8 kHz)
2 kHz
DS1 (1.544 MHz)
E1 (2.048 MHz)
6.48 MHz
19.44 MHz
25.92 MHz
38.88 MHz
51.84 MHz
77.76 MHz
155.52 MHz
-1.2 ± 0.5 ns
-0.4 ± 0.5 ns
DS3 (44.736 MHz)
E3 (34.368 MHz)
155.52 MHz input
155.52 MHz output +5.3 ± 1.5 ns
311.04 MHz
-0.0 ± 0.5 ns
-1.2 ± 1.25 ns
-1.2 ± 1.25 ns
-3.75 ± 1.25 ns
-3.75 ± 1.25 ns
-3.75 ± 1.25 ns
-3.75 ± 1.25 ns
-3.75 ± 1.25 ns
-3.75 ± 1.25 ns
-3.75 ± 1.25 ns
-3.75 ± 1.25 ns
-3.75 ± 1.25 ns
-3.75 ± 1.25 ns
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ACS8525 LC/P
Figure 16LQFP Package
Package Information
Table 26 64 Pin LQFP Package Dimension Data (for use with Figure 16)
Dimensions
in mm D/E D1/
E1 A A1 A2 e AN1 AN2 AN3 AN4 R1 R2 L L1 S b b1 c c1
Min. - - 1.40 0.05 1.35 - 11o11o0o0o0.08 0.08 0.45 - 0.20 0.17 0.17 0.09 0.09
Nom. 12.00 10.00 1.50 0.10 1.40 0.50 12o12o-3.5
o- - 0.60 1.00
(ref) - 0.22 0.20 - -
Max. - - 1.60 0.15 1.45 - 13o13o-7
o- 0.20 0.75 - - 0.27 0.23 0.20 0.16
E
D
AA2
A1 b
e
b1
b
cc1
L
L1
AN4
AN3
AN2
S
AN1 R2
Section A-A
Section B-B
AA
Seating plane
1
2
3
4
5
6
D1
E1
1
1
2
3
7
7
7
78
Notes
1
2
3
4
5
6
7
8
R1
B
B
The top package body may be smaller than the bottom package body by as much as 0.15 mm.
To be determined at seating plane.
Dimensions D1 and E1 do not include mold protrusion. Allowable protrusion is 0.25 mm per side.
D1 and E1 are maximum plastic body size dimensions including mold mismatch.
Details of pin 1 identifier are optional but will be located within the zone indicated.
Exact shape of corner s can vary.
A1 is defined as the distance from the seating plane to the lowest point of the package body.
These dimensions apply to the flat section of the lead between 0.10 mm and 0.25 mm fro m the lead tip.
Shows plating.
123
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ACS8525 LC/P
Thermal Conditions
The device is rated for full temperature range when this package is used with a 4 layer or more PCB. Copper coverage
must exceed 50%. All pins must be soldered to the PCB. Maximum operat ing temperature must be reduced when the
device is used with a PCB with less than these requireme nts.
Figure 17Typical 64-Pin LQFP Package Landing Pattern
Notes: (i) Solderable to this limit.
(ii) Square package - dimensions apply in both X and Y directions.
(iii) Typical example. The user is responsible for ensuring compatibility with PCB manufacturing process, etc.
10
10
.6 mm
mm
13
13
.0 mm (
(
1)
14
14
.3 mm
Pitch 0.5 m
ch 0.5 m
m
Widt
idt
h
h
0.3
.3
m
m
m
1.85
1.85
mm
F8525D_029LQFootprt64
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ACS8525 LC/P
Figure 18Simplified Application Schematic
Application Information
F8525D_031SimpleApp_02
1nF
C13
C15
100nF
100nF
C9 100nF
C10
100nF
C14
10R
R1
10R
R2
100nF
C6
100nF
C8
100nF
C7
C17
100nF
100nF
C12
C2
100uF
C3
100nF
C4
10uF_TANT
100nF
C5
C11
100nF
SEC2PMFrSync O1P SEC1P SEC1N SEC2N SYNC3
OP 5
NC
1
NC
2
NC
3
GND 4
NC
6
NC
7
NC
8
VS
9
GNDb
10
12.8MHz
C-MAC
E2747_
X1
term_connect
P1
BZV90C-5.6v
ZD1
VIN
3
GND
1VOUT 2
IC2
EZ1086CM-3.3
SEC2SEC1SYNC1O1NFrSync SYNC2
AGND1
1
IC1
2
AGND2
3
VA1+
4
REFCLK
6
DGND1
7
VD1+
8
VD2+
9
DGND2
10
DGND3
11
VD3+
12
VA2+
14
AGND3
15
IC2
16
FrSync
17
MFrSync
18
O1POS
19
O1NEG
20
GND_DIFF
21
VDD_DIFF
22
SEC1POS
23
SEC1NEG
24
SEC2POS
25
SEC2NEG
26
VDD5V
27
SYNC1
28
SEC1
29
SEC2
30
DGND4
31
VDD1
32
SYNC2 33
SEC3 34
SYNC3 35
VDD2 36
TRST 37
VDD3 38
VDD4 39
DGND5 40
TMS 41
CLKE 42
SDI 43
CSB 44
VDD5 45
VDD6 46
SCLK 47
PORB 48
TCK
49
TDO
50
TDI
51
SDO
52
DGND6
53
VDD7
54
NC1
55
O2
56
VA3+
57
AGND4
58
NC2
59
IC3
60
IC4
61
IC5
62
IC6
63
SONSDHB
64
INTREQ
5
SRCSW
13
IC1
ACS8525
SEC3
AGND
AGND
AGND
AGND
DGND
VDDA
VDD2
DGND2
DGND
VDD
DGND
DGND
DGND2
DGND
DGND
VDD
VDDA
DGND3
VDD3
DGND DGND
VDD VDD
DGND
VDD
DGND
DGND3
DGND2
VDDA
VDD5v
VDD
VDD3
VDD2
VDD5v
PORB
SrcSwit
CSB
SDI
SC/0
SDOINTRE1
O2
5v
0v
234 2 34
O5tion678Proce99or
Inter:6ce8connection9
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ACS8525 LC/P
APLL Analogue Phase Locked Loop
BITS Building Integrated Timing Supply
DFS Digital Frequency Synthesis
DPLL Digital Phase Locked Loop
DS1 1544 kbit/s interface rate
DTO Discrete Time Oscillator
E1 2048 kbit/s int erface rate
I/O Input - Output
LQFP Low profile Quad Flat Pack
LVDS Low Voltage Differential Signal
MTIE Maximum Time Interval Error
PBO Phase Build-out
PD2 Phase Detector 2
PECL Positive Emitter Coupled Logic
PFD Phase and Frequency Detector
PLL Phase Locked Loop
POR Power-On Reset
ppb parts per billion
ppm parts per million
p-p peak-to-peak
R/W Read/Write
RO Read Only
RoHS Restrictive Use of Certain Hazardous
Substances (directive)
rms root-mean-square
SDH Synchronous Digital Hierarchy
SEC SDH/SONET Equipment Clock
SETS Synchronous Equipment Timing source
SONET Synchronous Optical Network
SSU Synchronization Supply Unit
STM Synchronous Transport Module
TDEV Time Deviation
TCXO Temperature Compensated Crystal
Oscillator
UI Unit Interval
WEEE Waste Electrical and Electronic
Equipment (directive)
XO Crystal Oscillator
[1] AT & T 62411 (12/1990)
ACCUNET® T1.5 Service description and Interface
Specification
[2] ETSI ETS 300 462-3, (01/1997)
Transmission and Multiplexing (TM); Generic
requirements for synchronization networ ks; Part 3: The
control of jitter and wander within synchronization
networks
[3] ETSI ETS 300 462-5 (09/1996)
Transmission and Multiplexing (TM); Generic
requirements for synchronization networks; Part 5: Timing
characteristics of slave clocks suitable for operation in
Synchronous Digital Hierarchy (SDH) equipment
[4] IEEE 1149.1 (1990)
Standard Test Access Port and Boundary-Scan
Architecture
[5] ITU-T G.736 (03/1993)
Characteristics of a synchronous digital multiplex
equipment operating at 2048 kbit/s
[6] ITU-T G.742 (1988)
Second order digital multiplex equipment operating at
8448 kbit/s, and using positive justification
[7] ITU-T G.812 (06/1998)
Timing requirements of slave clocks suitable for use as
node clocks in synchronization networks
[8] ITU-T G.813 (08/1996)
Timing characteristics of SDH equipment slave clocks
(SEC)
[9] ITU-T G.824 (03/2000)
The control of jitter and wander within digital networks
which are based on the 1544 kbit/s hierarchy
[10] ITU-T K.41 (05/1998)
Resistibility of internal interfaces of telecommunication
centres to surge overvoltages
[11] Telcordia GR-253-CORE, Issue 3 (09/ 2000)
Synchronous Optical Network (SONET) Transport
Systems: Common Generic Criteria
[12] Telcordia GR-499-CORE, Issue 2 (12/1998)
Transport Systems Generic Requirements (TSGR)
Common requirements
[13] Telcordia GR-1244-CORE, Issue 2 (1 2/2000)
Clocks for the Synchronized Network: Common Generic
Criteria
Abbreviations References
ADVANCED COMMUNICATIONS FINAL DATASHEET
Revision 3.01/August 2005 © Semtech Corp. Page 110 www.semtech.com
ACS8525 LC/P
Semtech and the Semtech S logo are registered
trademarks of Semtech Corporation.
ACCUNET® is a registered trademark of AT & T.
C-MAC is a registered trademark of
C-MAC MicroTechnology - a division of Solectron
Corporation.
ICT Flexacom is a registered trademar k of ICT Electronics.
Motorola is a registered trademark of Motorola, Inc.
Telcordia is a registered trademark of Telcordia
Technologies.
Trademark Acknowledgements Notes
ADVANCED COMMUNICATIONS FINAL DATASHEET
Revision 3.01/August 2005 © Semtech Corp. Page 111 www.semtech.com
ACS8525 LC/P
The Revision Status of the datasheet, as shown in the
center of the datasheet header bar, may be TARGET,
PRELIMINARY, or FINAL, and refers to the status of the
Device (not the datasheet) within the design cycle.
TARGET status is used when the design is being realized
but is not yet physically available, and the datasheet
content reflects the intention of the design. The datasheet
is raised to PRELIMINARY status when initial prototype
devices are physically available, and the datasheet
content more accurately represents the realization of the
design. The datasheet is only raised to FINAL status after
the device has been fully characterized, and the
datasheet content updated with measu red, rather than
simulated parameter values.
This is a FINAL release (Revision 3.01) of the ACS8525
datasheet. Changes made for this document revision are
given in Table 27, together with a summary of previous
revisions. For specific changes between earlier revisions,
refer (where available) to those earlier revisions. Always
use the current version of the datasheet.
Revision Status/History
Table 27 Revision History
Revision Reference Description of Changes
1.00/May 2002 All pages First full release.
1.01/August 2002 See Rev 1.01 Minor release.
2.00/January 2003 All pages Major revision with product at FINAL status.
3.00/September 2003 All Pages. Major revision. For details see previous revision.
3.01/August 2005 Front and back pages and
“Abbreviations” on page 109. New references for lead (Pb)-free package variants.
Back page Address change: former PO Box removed as mail is now del iv e red to
Camarillo office at the street address only.
Figure 13, Figure 14 Updated to show transmi ssion line impedance.
page 18 “Patent pending” changed to “patented” multiphase detector.
Table 17, Table 18 Rows added for VDD5V.
Figure 5 Title and description changed to indicate diagram is reference to DPLL1
only, and note added to explain the states of DPLL2.
Figure 18 New simplified application schematic diagram.
“Input to Output Phase
Adjustment” on page 20 Phrase in first line, first para: “(including Auto-PBO on phase
transients)” removed.
Reg. 34, Reg. 3D, Reg. 64,
Reg. 65, Reg. 79 Register descriptions (and register map where appropriate) updated.
“Trademark Acknowledgements”
on page 110 Reference to “Semtech Corp.”as a registered trademark now removed.
“Configuration Registers” on
page 38 Paragraph changed.
All pages Abbreviation “pk-pk” changed to “p-p” throughout. Header bar updated
(for Internation AG variant only) stating “ADVANCED
COMMUNICATIONS”.
Register Description pages
onwards Layout chang e s an d repagination to end of docume n t .
ADVANCED COMMUNICATIONS FINAL DATASHEET
Revision 3.01/August 2005 © Semtech Corp. Page 112 www.semtech.com
ACS8525 LC/P
Disclaimers
Life support- This product is not designed or intended for use in life support equipment, devices or systems, or other critical
applications, and is not authorized or warranted for su ch use.
Right to change- Changes may be made to this product without notice. Customers are advised to obtain the latest version of the
relevant information before placing orders.
Compliance to relevant standards- Operation of this device is subject to the User’s implementation and design practices. It is the
responsibility of the User to ensure equipment using this device is compliant to any relevant standards.
Ordering Information
Table 28 Parts List
Part Number Description
ACS8525 Line Card Protec tion Switch for SONE T/SDH Systems.
ACS8525T Lead (Pb)-free packaged version of ACS8525; RoHS and WEEE compliant.
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