Siemens S5-135U/155U appendix 923A Coordinator Module Technical Description, Bus arbitration

Multiprocessor Operation/Coordinators

6.4923A Coordinator Module

6.4.1Technical Description

This section contains information on the application, design and principle of operation of the 923A coordinator.

Application	The 923A coordinator module is intended for operation in the S5-135U/155U
	PLC. It is required in multiprocessor operation and has the following
	functions:
	S	Bus arbitration
		To coordinate multiprocessor operation, i.e. the simultaneous use of two
		to four CPUs (CPU 928B, CPU 928 or CPU 922).
	S	Communication memory
		for the interchange of data between CPUs via communication flags.

Note

The 923A coordinator module cannot be used in multiprocessor operation if a CPU 948 is fitted in the 135U/155U PLC. If you execute global memory access in multiprocessor operation (I/O area with addresses 0000H-EFFFH) with the CPU 928B and/or the CPU 928, you must use the COR 923C as the coordinator.

Design	The COR 923A is designed as a plug-in PCB of double Eurocard format.
	Two 48-way Series 2 blade connectors serve to connect the PCB to the S5
	bus in the subrack.
	The front plate width is 1 1/3 standard plug-in stations.
	A three-position mode switch is fitted in the front plate for operator
	functions.

System Manual	6-15
C79000-G8576-C199-06