Siemens SIMATIC ET 200AL, System Manual

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Functions
5.7 Isochronous mode
PROFINET with STEP 7
Function Manual, 05/2021, A5E03444486-AL
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5.7.5.3 Program execution according to the OIP model
Use the OIP model in the case of execution cycles of the isochronous mode interrupt OB of
different lengths, if the application cycle is greater than data cycle T_DC.
The data exchange with the process is always deterministic in the OIP model, i.e. takes place
at a precisely specified time.
Programming according to the OIP model in the isochronous mode interrupt OB
For programming according to the OIP model:
1.
Call the SYNC_PO instruction at the start of the isochronous mode interrupt OB.
2. Then call the SYNC_PI instruction.
3. Then call the actual user program.
Table 5- 4 Programming according to the OIP model
Step Action Explanation
1 Output (O) The SYNC_PO instruction outputs the data that was changed by the
user program in the previous cycle via the outputs of the process im-
age partition.
2 Read in (I) The SYNC_PI instruction reads in the inputs of the process image parti-
tion of the current cycle and provides the inputs to the isochronous
mode interrupt OB.
3 Process (P) You program the actual user program of the isochronous mode inter-
rupt OB.