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

Configuring

7.8 Process images and process image partitions

7.8 Process images and process image partitions
7.8.1

Process image - overview

Process image input and process image output
The process image input and output is an image of the signal states. The CPU transfers the
values from the input and output modules to the process image input and output. At the start
of the cyclic program, the CPU transfers the process image output as a signal state to the
output modules. The CPU then transfers the signal states of the input modules to the
process image inputs.
Advantages of the process image
A process image accesses a consistent image of the process signals during cyclic program
execution. If a signal state at an input module changes during program execution, the signal
state is retained in the process image. The CPU does not update the process image until the
next cycle.
Consistency of the process image
When the process image is updated, the SIMATIC Drive Controller accesses the data of
each submodule as consistent data. This behavior is identical to the modular SIMATIC S7-
1500 CPUs.
The maximum data width that is accessed as consistent data for each submodule depends
on the IO system. For PROFINET IO, for example, this data width is 1024 bytes.
32 process image partitions
The CPU uses process image partitions to synchronize the updated inputs/outputs of
specific modules with specific parts of the user program.
With the SIMATIC Drive Controller, the overall process image is subdivided into up to 32
process image partitions (PIP).
The CPU automatically updates PIP 0 (automatic update) in each program cycle and assigns
it to OB 1.
You can assign other OBs to process image partitions PIP 1 to PIP 31 during configuration
of the IO devices.
Before the start of the OB, the CPU writes the outputs of the assigned process image
partition (PIPQ) straight to the peripheral outputs of the IO devices. The CPU then updates
the assigned process image partition for inputs (PIPI) and reads in the process signals.
The figure below illustrates the updating of a process image partition.
Figure 7-8
106
Updating a process image partition
SIMATIC Drive Controller
System Manual, 11/2019, A5E46600094-AA