Assign Process Image Partitions To An Ob; Update Process Image Partitions In The User Program - Siemens Simatic S7-1500/ET 200MP System Manual

Configuring
7.1 Configuring the CPU
7.1.3.2

Assign process image partitions to an OB

Update process image partition
You can assign a process image partition to an OB. In this case, the process image partition
is automatically updated.
The CPU always reads the process image partition of the inputs (PIPI) before processing of
the associated OB and always outputs the process image partition of the outputs (PIPO) at
the end of the OB.
The following figure illustrates the updating of a process image partition.
Figure 7-10
7.1.3.3

Update process image partitions in the user program

Requirements
As an alternative to methods already described, you can use the instruction "UPDAT_PI" or
the instruction "UPDAT_PO" at the start or the at the end of the respectively assigned OB to
update the process image. In STEP 7, these instructions are available on the "Instructions"
Task Card under "Extended instructions" and may be called from any point in the program.
Requirements for updating process image partitions with the "UPDAT_PI" and "UPDAT_PO"
instructions:
● The process image partitions cannot be assigned to any OB, i.e. they cannot be
automatically updated.
Note
Update of PPI 0
PPI 0 (automatic update) cannot be updated with the "UPDAT_PI" and "UPDAT_PO"
instructions.
UPDAT_PI: Update process image partition of the inputs
With this instruction you read the signal states from the input modules into the process
image partition of the inputs (PIPI).
UPDAT_PO: Update process image partition of the outputs
With this instruction you transmit the process image partition of the outputs to the output
modules.
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Update process image partitions
Automation system
System Manual, 12/2017, A5E03461182-AE