Measuring Input - Siemens SIMATIC S7-1500 Manual

8 Example Application
8.3 Programming of the processing stations
The individual processing units therefore work totally independent from each other.
The following principle applies:

If there is no difference between the read index of the unit and the write index
the measuring input unit, there is no product for processing and the respective
process remains in the dormant phase.

If there is a difference between the indices, the respective unit has to be
started and the product has to be processed.
Note
This approach even supports several products on the conveyor belt. The
respective process is started until write and read index point to the same array
element of the "PositionTable" again.
Note It has to be ensured that the product does not reach the processing station
before the processing process was started.
8.3.3

Measuring input

Since the "MC_MeasuringInputCyclic" technology function can only be used in
connection with a real measuring input, i.e. a "real hardware input", the measuring
input functionality in the example application with virtual axis via the
"GetMeasuringInput_Simulation" function block is simulated.
Triggering the measurement input is communicated to the block via the
"GetPosition" input, which is influenced via the interface of the example application.
As soon as a rising edge is detected on this input, the temporary
"tempLatchProductPosition" tag is set.
//+++ Control machine function +++
//Check function block interface
#tempLatchProductPosition := False;
IF ((#GetPosition = True)
AND (#statGetPositionOld = False))
THEN
#tempLatchProductPosition := True;
END_IF;
If the temporary "tempLatchProductPosition" tag is set, the current axis position of
the conveyor belt is entered in the table and the write index is set to the next index.
TOs of S7-1500(T)
Entry ID: 109743134, V1.0, 05/2017
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