Siemens S5-135U/155U - Manual (Page 264)

6-2
System Manual
C79000-G8576-C199-06
6.1 Introduction
The S5-135U/155U is a member of the SIMATIC S5 family of programmable
(logic) controllers. The PLC can be used both in single and in multiprocessor
operation with up to four CPUs.
You can arbitrarily combine the CPUs in the central controller at the CPU
slots.
CPU Slot Requirement
CPU 948/CPU 928B/CPU 928 2 slots
CPU 922 1 slot
In multiprocessor operation, each CPU processes its individual user program
independently of the other CPUs.
The common S5 bus serves for data interchange with I/O modules, CPs, IPs
and other CPUs. In multiprocessor operation, access of the CPUs to the S5
bus is controlled by a coordinator. The functioning of this module is
described in Sections 6.5 and 6.6.
For an explanation of data interchange between CPUs in multiprocessor
operation and the arrangement of your STEP 5 program, please consult the
Programming Guide for your CPU.
A coordinator is required in multiprocessor operation. The following are
available for the S5-135U/155U PLC:
S
923A coordinator (COR A)
and
S
923C coordinator (COR C).
The coordinator allocates to the CPUs the time divisions in which they can
access the S5 bus (bus enable time), and contains the global memory for data
interchange between the CPUs via communication flags. Additionally, the
COR C contains another memory with four pages for the “multiprocessor
communication” function as well as a serial PG interface with PG
multiplexer function (PG MUX).
Slots Occupied
Coordinator
Multiprocessor Operation/Coordinators