ACS8510 Semtech, ACS8510 Datasheet - Page 44

• Manufacturer Part Number: ACS8510
• Manufacturer: Semtech

Specifications of ACS8510

• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (min): 3V
• Operating Supply Voltage (max): 3.6/5.5V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Package Type: LQFP
• Mounting: Surface Mount
• Pin Count: 100
• Lead Free Status / Rohs Status: Not Compliant

during Holdover, the Master device's 6.48 MHz
output is fed into the Slave device on its <I_11>
pin, whilst the Multi-Frame Sync (2 kHz) output
is fed to the Sync2k input of the Slave. In this
way, the Slave locks to the master's output
and remains locked whilst the Master moves
between operating states. Only when the
Master fails does the Slave use its own
reference inputs - should the Master have been
in the Holdover state, the Slave device will see
the same lack of reference sources and also
enter the Holdover state. This scheme also
provides a convenient way to phase-align all
T
and also to detect the failure of the Master
device.
If a Master device fails, the Slave has to take
over responsibility for the generation of the
output clocks, including the 8 kHz and 2 kHz
Frame and Multi-Frame clocks. The Slave device
is also given responsibility for building the priority
table and performing the reference switching
operations. The Slave device, therefore, adopts
a more active role when the Master has failed.
The cnfg_mode register 34 (Hex) Bit 1 contains
the ‘Master/Slave’ control bit to determine the
designation of the device.
To restore redundancy protection, the Master
has to be repaired and replaced. When this
occurs, the new Master cannot immediately
adopt its normal role because it must not cause
phase hits on the output clocks. It has,
therefore, to adopt a subordinate role to the
active Slave device, at least until such time as
it has acquired alignment to the 8 kHz and
2 kHz frame and Multi-Frame clocks and the
priority table of the Slave device; then, when a
switch-back (restoration) is ordered, the Master
can take over responsibility. These activities, in
Master or Slave operation, are summarized in
Table 12 and described in detail in Application
Note AN-SETS-2.
Revision 2.00/September 2003
ADVANCED COMMUNICATIONS
OUT0
output clocks in Master and Slave devices,
Semtech Corp.
44
Alignment of Priority Tables in Master and Slave
Alignment of Priority Tables in Master and Slave
Alignment of Priority Tables in Master and Slave
Alignment of Priority Tables in Master and Slave
Alignment of Priority Tables in Master and Slave
A C S 8 5 1 0
A C S 8 5 1 0
A C S 8 5 1 0
A C S 8 5 1 0
A C S 8 5 1 0
Correct protection will only be achieved by
connecting individual reference sources to the
same input ports on each device and priority
tables in each device must be aligned to each
other.
The Master device must take account of the
availability of each reference source seen by
another device and a Slave device must adopt
the same order of priority as the Master device
(except that the Slave's highest-priority input is
<I_11>). Both devices monitor the reference
sources and decide the availability of each
source; if the failure of a reference source is
seen by both devices, they will both update
their priority tables - however, if the reference
source failure is only seen by one device and
not by both, the priority tables could get out of
step: this could be catastrophic if it resulted in
two devices choosing different reference
sources since any slight differences in frequency
variation over time (e.g. wander) would mis-align
the phase of the 8 kHz Frame and 2 kHz Multi-
Frame clocks produced by the individual
devices, resulting in phase hits on switch-over.
It is therefore important that the same priority
table be built by each device, using the
reference source availability seen by each
device.
The monitoring of the reference sources
performed by a Master ACS8510 results in a
list of available sources being placed in a
sts_valid_sources register. This information is
used within the device as one of the masks
used to build the device's priority table. The
information is passed to the Slave device and
used to configure the cnfg_sts_remote_
sources_valid register so that it can use it as a
mask in building its own priority tables. The
information is passed between devices using
the microprocessor port.
ACS8510 Rev2.1 SETS
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