Program Execution According To The Oip Model - Siemens SIMATIC S7-1500 Function Manual

Programming isochronous mode

6.2 Program execution according to the OIP model

6.2 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 also in the OIP model, which
means it 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 6- 2
Step
46
Sequence according to the OIP model
Action
1 Output (O)
2 Read in (I)
3 Process (P)
Explanation
The SYNC_PO instruction outputs the data that was changed by the
user program in the previous cycle via the outputs of the process
image partition.
The SYNC_PI instruction reads in the inputs of the process image
partition of the current cycle and provides the inputs to the isochro-
nous mode interrupt OB.
The user program in the isochronous mode interrupt OB is executed.
Isochronous mode
Function Manual, 10/2018, A5E43884988-AA