Technical data

Testing with the Variable Table
20.7 Modifying Variables
Programming with STEP 7
Manual, 05/2010, A5E02789666-01 461
The following applies to trigger points when modifying variables:
• If you set "Once" as the trigger frequency, a message appears if the selected variables cannot
be modified.
• With the trigger frequency "Every cycle," no message appears.
Trigger Immediately
You can modify the values of selected variables using the menu command Variable > Activate
Modify Values. This command is taken to mean "trigger immediately" and is executed as quickly
as possible without reference to any point in the user program. This function is used mainly for
modifying in STOP mode.
Trigger Frequency
The following table shows the effect that the trigger condition set has on the modifying of variables:
Trigger frequency: Once Trigger frequency: Every cycle
Modify
Variables
Activate once
You can assign values to
variables once, independent of
the trigger point.
Modifying with a defined trigger
By assigning fixed values you can
simulate certain situations for your user
program and use this to debug the
functions you have programmed.