Process Images And Process Image Partitions; Process Image - Overview - Siemens SIMATIC S7-1500/ET 200MP System Manual

8.1.3

Process images and process image partitions

8.1.3.1

Process image - overview

Process image of the inputs and outputs
The process image of the inputs and outputs is an image of the signal states. The CPU
transfers the values from the input and output modules to the process image in this memory
area. At the start of the cyclic program, the CPU transfers the process image output as a
signal state to the output modules. The CPU then transfers the signal states of the input
modules to the process image inputs.
Advantages of the process image
A process image accesses a consistent image of the process signals during cyclic program
execution. If a signal state at an input module changes during program processing, the signal
state is retained in the process image. The CPU does not update the process image until the
next cycle.
Consistency of the process image
When the process image is updated, the S7-1500 accesses the data of each submodule as
consistent data. The maximum data width that is accessed as consistent data for each
submodule is dependent on the IO system. For PROFINET IO, for example, this data width is
1024 bytes.
32 process image partitions
By means of process image partitions, the CPU synchronizes the updated inputs/outputs of
particular modules with defined user program sections.
In the S7-1500 automation system, the overall process image is subdivided into up to 32
process image partitions (PIP).
The CPU automatically updates PIP 0 (automatic update) in each program cycle and assigns it
to OB 1.
You can assign the process image partitions PIP 1 to PIP 31 to the other OBs during
configuration of the input/output modules.
The CPU always reads the process image partition of the inputs (PIPI) before processing the
associated OB. The CPU outputs the process image of the outputs (PIPQ) at the end of the OB.
The figure below illustrates the updating of a process image partition.
Figure 8-9
Automation system
System Manual, 01/2023, A5E03461182-AK
process image
Configuring
8.1 Configuring the CPU
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