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SCP-PCS718-020-04H
Serial Communications Bus
The Serial Communications Bus (SCB) provides the means for the PAU/PMU to communicate with all other boards
in the shelf to allow:
•
Software downloads
•
Coordination of PMX equipment protection
•
Generation of status, alarm, and performance reports through the PG-Plus Console menus
•
Provisioning of each unit installed in the shelf through the PG-Plus Console menus
The serial bus operates in a master/slave polled environment with the PAU/PMU functioning as the SCB master. Each
COLU position has its own SCB connection to avoid conflict. The SCB acts as the "card present" line to notify the
PAU/PMU board that a line unit is present in the shelf. Figure 3 shows the communication line between the
PAU/PMU and any COLU. If a COLU is not installed, the line is pulled high to notify the PAU/PMU that a line unit
is not present and data should not be sent. When installed, each card pulls its line low.
Composite Clock Signals
Composite clock signals are a 64 kHz bipolar clock with 8 kHz bipolar violations. The 64 kHz clock and the 8 kHz
violations define the bit and byte boundaries of DDS data as it is transferred within a CO. In support of DDS
interfaces, PG-Plus defines two composite clock interfaces at the PAU or the PMU card slot. The PAU/PMU selects
the clock and translates it into bit and byte clocks, which it then distributes to the COLUs. Wire-wrap pins on the
backplane allow the composite clock source to be terminated or daisy-chained to another shelf.
Test Bus
The Test Bus provides a common Tip/Ring bus from the COLUs to the PAU/PMU. This bus allows the PAU/PMU
to provide a resistive signature to any of the tested subscriber circuits.
Communication Requests
The COTS provides communication requests from each of the cards to the PAU/PMU slot. These signals are used by
the COLU and PMX units to initiate communication with the PAU or the PMU.
Backplane Connections
Each shelf supports the connection of up to twelve COLUs, two PMX units, and one PAU/PMU. The backplane of
the COTS contains the connectors shown in Figure 4 and Table 1. Wiring external to the COTS should follow the
provisions of the current edition of the National Electrical Code and applicable local codes.
PCS-718 List 2
Figure 3 Communication Line Between PAU/PMU and COLU
January 6, 2003
Theory of Operation
3
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