Forcing I/O Variable Values (NI Scan Engine)

You can use an I/O variable probe to force I/O variable values. Forcing an I/O variable causes the input or output and all associated aliases of the variable to assume the forced value until you unforce the value. If an input from hardware returns an error, and the associated I/O variable is forced, System Manager does not display the error. However, if the error results in a fault, LabVIEW registers the fault. If an output returns an error, System Manager displays the error.

Note  If you link several I/O variables in a chain of aliases and force one of the I/O variables in the chain, the forced value applies to all I/O variables in the chain.

Enabling I/O Variable Forcing

Complete the following steps to enable and disable I/O variable forcing on a target with the NI Scan Engine installed.

  1. Click a scan-enabled target in the system tree to display a target probe in the Auto View. You also can right-click a target and select Probe to display a target probe in a separate window.
  2. The Scan Engine page of a real-time target probe displays the Forcing Enabled LED indicator, which indicates whether I/O variable forcing is enabled on the controller.
  3. Use the Enable Forcing button to enable forcing. Use the Disable Forcing button to disable forcing and unforce all forced I/O variable values. Use the Clear Forcing button to clear forcing on all I/O variables.
Note  If you disable forcing and then enable forcing again, all previously-forced I/O variables return to their last forced value, unless you have cleared those values using the Clear Forcing button.

Forcing I/O Variable Values

Complete the following steps to force and unforce I/O variable values.

  1. Click an I/O variable in the system tree to display an I/O variable probe in the Auto View or right-click an I/O variable and select Probe to display an I/O variable probe in a separate window.
  2. In the New Value section of the I/O variable probe, enter or select the new value for the I/O variable.
  3. Click the Force button to force the I/O variable to the value you specified.
  4. Click the Unforce button to unforce the I/O variable value.
Note  Individual I/O variable forcing applies only if forcing is enabled on the target. Use the Enable Forcing and Disable Forcing buttons to enable and disable forcing on the target.

Batch Forcing I/O Variable Values

Complete the following steps to perform batch forcing on a set of I/O variables.

  1. Disable forcing on the target.
  2. Force each I/O variable to the desired value.
  3. Enable forcing on the target.