Update Process Image Partitions In The User Program - Siemens SIMATIC S7-1500/ET 200MP System Manual

Configuring
8.1 Configuring the CPU
8.1.3.2

Update process image partitions in the user program

Requirements
Alternatively, you can also use the following instructions to update process images:
• Instruction "UPDAT_PI"
• Instruction "UPDAT_PO"
You will find the instructions in STEP 7 in the "Instructions" task card under "Extended
instructions". The instructions 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 must not be assigned to any OB. This means the process
image partitions are not automatically updated.
Note
Update of PPI 0
PIP 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.
Isochronous mode interrupt OBs
In the isochronous mode interrupt OBs you use the instructions "SYNC_PI" and "SYNC_PO" to
update the process image partitions. Additional information on isochronous mode interrupt
OBs is available in the STEP 7 online help.
Direct I/O access to the inputs and outputs of the module
You also have direct read and write access to the I/O, as an alternative to access via the
process image, should direct access be required for programming reasons. A direct (write) I/O
access also writes the process image. This prevents the situation where a subsequent output
of the process image overwrites the value written via direct access again.
204
Automation system
System Manual, 01/2023, A5E03461182-AK