Siemens Simatic S7-1500R System Manual page 148

UPDAT_PI: Updates the process image partition of the inputs
With this instruction, you read the signal states from the input modules of the IO devices to
the process image partition of the inputs (PIPI).
UPDAT_PO: Updates the process image partition of the outputs
With this instruction, you transfer the process image partition of the outputs of the IO devices
to the output modules.
Direct I/O access to the inputs and outputs of the IO devices
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. Direct (write) I/O
access also writes to the process image. This prevents a subsequent output of the process
image from again overwriting the value written by direct access.
Note
Avoid direct I/O access. Each instance of direct I/O access is synchronized in the RUN-
Redundant system state and results in a higher cycle time. Recommendation: Access the
inputs and outputs of the IO devices over the process image.
Reference
You can find more information on process image partitions in the Cycle and response times
(http://support.automation.siemens.com/WW/view/en/59193558) function manual.
S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA
6.5 Process images and process image partitions
Configuration
147