
Functions of the IM 151-7 CPU
8-13
ET 200S IM 151-7 CPU Interface Module
A5E00058783-04
Working memory
The working memory is integrated on the CPU and cannot be expanded. It is used
to process the codes and data of the user program. Program processing is only
performed at the working memory and system memory.
The working memory of the CPU is retentive if the MMC is inserted.
Your data in the working memory is saved on the MMC if the power supply is
interrupted.
System memory
The system memory is integrated on the CPU and cannot be expanded.
It contains
the address areas ”memory markers”, ”timers” and ”counters”
the process images of the inputs and outputs
the local data
For memory markers, timers and counters, you can configure (Properties of the
CPU, Retentivity tab) which parts are to be retentive and which parts are to be
initialized with ”0” when a complete restart (warm restart) is performed.
The diagnostic buffer, MPI address (and transmission rate) as well as the run-time
meter are generally stored in the retentive memory area on the CPU. Retentivity of
the MPI address and transmission rate ensures that your CPU is still able to
communicate following a power failure, a memory reset or the loss of
communication parameters (by removing the MMC or erasing the communication
parameters).
Retentivity
The IM 151-7 CPU has a retentive memory. The retentivity is provided on the MMC
and CPU.
The retentivity means that the content of the retentive memory is retained even
following POWER OFF and a restart (warm restart).
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