Technical data

F flags
Characteristics Size
The flag area is a memory area which the user
program can access extremely quickly with certain
operations.
The flag area should be used ideally for working data
required often.
The following data types can be accessed:
- single bits,
- bytes,
- words,
- double words.
Single flag bytes can be used as
interprocessor
communication flags
(IPC flags) to exchange data
between the CPUs in the multiprocessor mode (refer
to Chapter 10). IPC flags are updated by the system
program at the end of the cycle via a buffer in the
coordinator or CP/IP.
2048 bits
S flags (extended flag area)
Characteristics Size
The CPU 928B also contains an additional flag area,
the S flag area. The user program can also access this
area extremely quickly as with the F flags.
S flags
cannot however by used as actual operands
with function block calls nor as IPC flags for data
exchange between the CPUs. The bit test operations
of the CPU 948 can also not be used with the S flags.
These flags can only be used with the PG system
software "S5-DOS" from version 3.0 upwards or
"S5-DOS/MT" from version 1.0 upwards.
8192 bits
Which Operands are available to the User Program?
CPU 928B Programming Guide
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