10.1.3
Exchanging Data via IPC
Flags
Interprocessor communication (IPC) flags are available for cyclic
exchange of binary data. They are used mainly for transmitting
information byte by byte.
Data is transferred as follows:
CPU(s) ↔ CPU(s)
CPU(s) ↔ Communications processor(s)
The system program transfers IPC flags once per cycle. For data
transfer between CPUs, the IPC flags are buffered physically on the
coordinator.
IPC flags are bytes that are transferred. You define them in DB 1 for
each CPU as IPC input or output flags. If, for example, you have
defined flag byte 50 on the CPU 1 as an IPC output flag byte, its
signal state is transferred cyclically via the coordinator to the CPU on
which the flag byte F 50 is defined as an IPC input flag byte.
Note
There is no error message when the IPC flag byte exists
physically but is only written by one CPU and never read out and
vice-versa.
Memory area
With the CPU 948 the memory area for the IPC flags in the
coordinator and the CPs covers the addresses F F200H to F F2FFH.
On a CPU/communications processor there are 256 available IPC flag
bytes.
Jumper settings
To avoid double assignments you must group the 256 available IPC
flag bytes on the COR or CP modules. Fields of 32 bytes can be
enabled or disabled (your system manual contains information about
setting the jumpers).
Multiprocessor Mode
CPU 948 Programming Guide
C79000-G8576-C848-04
10 - 5
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