Common Parameters For Instructions - Siemens S7-1200 System Manual
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Communication
10.2 PROFINET
10.2.2.10
Common parameters for instructions
REQ input parameter
Many of the Open User Communication instructions use the REQ input to initiate the
operation on a low to high transition. The REQ input must be high (TRUE) for one execution
of an instruction, but the REQ input can remain TRUE for as long as desired. The instruction
does not initiate another operation until it has been executed with the REQ input FALSE so
that the instruction can reset the history state of the REQ input. This is required so that the
instruction can detect the low to high transition to initiate the next operation.
When you place one of these instructions in your program, STEP 7 prompts you to identify
the instance DB. Use a unique DB for each instruction call. This ensures that each
instruction properly handles inputs such as REQ.
ID input parameter
This is a reference to the "Local ID (hex)" on the "Network view" of "Devices and networks"
in STEP 7 and is the ID of the network that you want to use for this communication block.
The ID must be identical to the associated parameter ID in the local connection description.
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S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
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