Automatically Updating Process Image Partitions; Update Process Image Partitions In The User Program - Siemens SIMATIC ET 200SP System Manual

6.2.3.2

Automatically updating process image partitions

You can assign one process image partition to each organization block. In this case, the user
program automatically updates the process image partition. The exceptions are PIP 0 and
isochronous OBs.
Updating the process image partition
The process image partition is divided into two parts:
● Process image partition of the inputs (PIPI)
● Process image partition of the outputs (PIPQ)
The CPU always updates/reads the process image partition of the inputs (PIPI) before
processing of 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 the process image partitions.
Figure 6-8
6.2.3.3

Update process image partitions in the user program

As an alternative to the automatic updating of process image partitions, you can update
process images with the "UPDAT_PI" instruction or the "UPDAT_PO" instruction. In STEP 7,
these instructions are available on the "Instructions" task card under "Extended instructions".
They can 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 are not allowed to be assigned to any OB, which means
they are not allowed to be automatically updated.
● PIP 0 (automatic update) can likewise not be updated with the "UPDAT_PI" and
"UPDAT_PO" instructions.
UPDAT_PI: Update the 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 the process image partition of the outputs
With this instruction you transfer the process image partition of the outputs to the output
modules.
Distributed I/O system
System Manual, 12/2015, A5E03576849-AF
Updating process image partitions
Configuring
6.2 Configuring the CPU
105