Force I/O variables

Forcing variables might result in sudden machine movement, possibly injuring personnel or equipment. Use extreme caution when forcing variables.
Only I/O variables can be forced. Consider the following rules when forcing variables:
  • User-defined variables and non-I/O variables cannot be forced.
  • Special functions, such as HSC and Motion that execute independently from the user program scan, cannot be forced. For example, for motion, Drive Ready input cannot be forced.
  • LED status indicators always match the physical value of I/Os.
  • Normal and non-physical internal variables cannot be forced.
  • Outputs, unlike inputs, are physically forced. LED status indicators show the forced values, but the user program does not use forced values.
  • When the controller is turned off, all I/O forces are cleared from memory.
Forcing behavior
A diagram that illustrates the forcing behavior of I/O variables
Prerequisites
  • The controller is online.
To force I/O variables
  1. In the variable monitor, locate the variable you want to force.
  2. Select the
    Force
     checkbox for the variable.
  3. Enter the value in the respective value column.
    • For an Input variable, enter the
      Value
      .
    • For an Output variable, enter the
      Physical Value
      .
Forced variable examples
For variables, the values displayed in the
Value
 and
Physical Value
 columns differ depending on whether the variable is an Input or Output variable.
  • Input variable (Read) behavior - Force the temperature reading from a sensor
    A diagram that shows how to force the temperature reading from a sensor
  • Output variable (Write) behavior - Force the closure of an actuator valve
    A diagram that shows how to force the closure of an actuator valve
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