Monitor The Status In The Lad Editor; Force An Input To A Specific Value - Siemens SIMATIC S7-1200 Getting Started

Use a watch table for monitoring

5.3 Monitor the status in the LAD editor

5.3 Monitor the status in the LAD editor
You can also monitor the status of the tags in the LAD editor. Use the editor bar to display
the LAD editor. The editor bar allows you to change the view between the open editors
without having to open or close the editors.
With all of the switches on the simulator turned off, notice that the "On" input is not green
because it is off (or "false"). Notice also that there is no power flow going to the "Off"
contact. However, the normally closed contact "Off" itself is green. "Off" being green does
not in itself generate power flow, but means that if power were to flow into the "Off" contact,
then the power flow would be passed on to the "Run" coil.
Using the simulator, turn the switch for I0.0 on and watch the power flow across the
network. Now, turn I.0.0 off and see how the latching circuit works!
5.4

Force an input to a specific value

A watch table provides a "force" function that overwrites the value for an input or output
point to a specified value for the peripheral input or peripheral output address. The CPU
applies this forced value to the input process image prior to the execution of the user
program and to the output process image before the outputs are written to the modules.
Because you cannot force an input (or "I" address), you must change the address for "On"
input to access the peripheral input. In the "Address" or "Name" cell for "On", append a ":P"
to the address ("On:P").
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In the toolbar of the LAD editor, click the "Monitoring on/off" button to display the
status of your user program.
Click the LAD editor.
Use the editor bar to open the watch table.
The LAD editor displays power
flow in green.
Now turn the switch for I0.1 off to
remove power flow from the "Run"
coil (Q0.0).
Getting started with S7-1200
Getting Started, 11/2009, A5E02486791-01