Design; Principle Of Operation; 923C Coordinator Module - Siemens S5-155U System Manual

Design

Principle of operation

System Manual
C79000-B8576-C199-03
The COR 923C is designed as a plug-in PCB in double Eurocard
format.
Two 48-way Series 2 blade connectors serve to connect the module to
the S5 bus in the subrack.
The front plate width is 1 1/3 standard plug-in stations.
A mode switch with three settings is fitted in the front plate for other
operator functions.
Faults are indicated by five small red LEDs.
There is a recess with cover in the upper third of the front plate. By
removing the cover, you can operate the DIL switches to set
parameters for the module.
You can connect the COR 923C via a 15-pin front connector to a
programmer, OP, operator control panel or the CP 530 and CP 143.
Bus arbitration
The COR 923C cyclically allocates a bus enable signal to each of the
two to four CPUs in the S5-135U/155U PLC. Only during this time
can the relevant CPU utilize the common S5 bus.
The assignment of bus enable signals takes place in time-division
multiplex operation. On the COR 923C, you set the number of CPUs
with DIL switches. The enable time for access to the S5 bus is preset
at 2 µs for all CPUs. If the bus enable signal has been emitted by the
coordinator for a CPU, this CPU can extend the enable time with the
bus lock signal. However, the user has no influence on this.

923C Coordinator Module

6 - 21
6