Process Images And Process Image Partitions; Process Image - Overview - Siemens SIMATIC S7-1500 System Manual

Configuring
6.1 Configuring the CPU
6.1.3

Process images and process image partitions

6.1.3.1

Process image - overview

Process image of the inputs and outputs
When the user program addresses the input (I) and output (O) operand areas, it does not
query the signal states directly from the I/O modules. Instead, it accesses a memory area of
the CPU. This memory area contains an image of the signal states and is called the process
image.
Advantages of the process image
A process image allows you to access a consistent image of 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 process image is not updated until the
next cycle.
32 process image partitions
In the S7-1500 automation system, the overall process image is subdivided into up to
32 process image partitions (PIP).
PIP 0 (automatic update) is automatically updated in each program cycle and is assigned to
OB 1.
Process image partitions PIP 1 through PIP 31 can be assigned to the other OBs. In
STEP 7, this assignment occurs during configuration of the I/O modules.
After the OB has been started, the assigned process image partition of inputs is updated by
the system and the process signals are read in. At the end of the OB the outputs of the
assigned process image partition are written directly to the peripheral outputs by the system
without having to wait for the termination of the cyclic program processing.
You can only assign the addresses of a module to a single process image partition.
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Automation system
System Manual, 12/2014, A5E03461182-AC