Forcing the Values of Variables

While connected or simulating, force or override the values of variables. These variables can be user-defined or directly represented. The behavior of a variable is defined by its logical value, physical value, lock state, and direction. When forcing the values of variables, the value to overwrite depends on the direction of the variable. Force the values of variables from the
Dictionary
, language containers, and the
Watch
window.
Locking and unlocking operates only on elementary data types for variables, array elements, and structure elements that are wired.
For locked variables, the values displayed in the
Logical Value
 and
Physical Value
 columns differ depending on their direction:
Input Variable (Read) Behavior
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Example: To force the temperature reading from a sensor.
Output Variable (Write) Behavior
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Example: To force the closing of an actuator valve.
TIP: When you force variable values, the computer running
AADvance-Trusted SIS Workstation software
 or AADvance Standalone OPC server sends an IXL write message to the controller.
If the IXL write message is processed right after
Execute target independent code (TIC)
 in the application execution loop (step 4 in Execution Rules), the forced value is used for the producer binding, wired output, or retained variable.
If the IXL write message is processed right after
Save retain variables
 in the current application execution loop (step 8 in Execution Rules), the step
Execute target independent code (TIC)
 in the next application execution loop may overwrite the forced value with a different value for the producer binding, wired output, or retained variable.
To help achieve deterministic behavior, avoid forcing an:
  • internal variable that is bound as a producer or retained (internal variables cannot be locked)
  • unlocked output variable
To force the values of variables
  1. From the
    Dictionary
    instance, locate the required variable.
  2. Write the required value in the respective value column:
    • For an input variable, write the value in the
      Logical Value
       column.
    • For an output variable, write the value in the
      Physical Value
       column if the variable is locked and write the value in the
      Logical Value
       column if the variable is unlocked.
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