Siemens SIMATIC S7-1200

Getting started with S7-1200
Getting Started, 11/2009, A5E02486791-01
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Use a watch table for monitoring
5
When you tested the latching circuit (Page 38), you used the physical switch
on the simulator and watched the
lights turn on and off on the front of the
CPU.
For this exercise, you will use the online functionality of STEP 7 Basic to
monitor the operation of your user program.
What is a "watch table"?
A watch table allows you to monitor or modify the values of tags while the CPU executes
your user program.
The "Modify" function allows you to change the value of a tag.
However, the "Modify" function does not work with inputs (I) or
outputs (Q) because the CPU updates the I/O, overwriting any
modified value before reading the modified value.
The watch table provides a "Force" function that allows you to
modify the values of the I/O. For this exercise, you will learn how
to force the input in the latch circuit on.