Rockwell Automation Publication 2080-UM002K-EN-E - March 2019 277
Quickstarts Appendix C
Forcing I/Os
Inputs are logically forced. LED status indicators do not show forced values, but
the inputs in the user program are forced.
Forcing is only possible with I/O and does not apply to user defined variables and
non-I/O variables, and special functions such as HSC and Motion which execute
independently from the User Program scan. For example, for motion, Drive
Ready input cannot be forced.
Unlike inputs, outputs are physically forced. LED status indicators do show
forced values and the user program does not use forced values.
The following diagram illustrates forcing behavior.
Checking if Forces (locks) are Enabled
If Connected Components Workbench is available, check the Variable Monitor
while debugging online. Forcing is performed by first Locking an I/O variable
and then setting the Logical Value for Inputs and Physical Value for Outputs.
User Program
Logical
Inputs
Logical
Outputs
Normal
Variables
Force
Motion
HSC
Physical
Inputs
Force
Physical
Outputs
• LED status indicators always match the physical value of I/O
• Normal, non-physical internal variables cannot be forced
• Special functions such as HSC and Motion cannot be forced
ATTENTION: Forcing variable can result in sudden
machine movement, possibly injuring personnel or
equipment. Use extreme caution when forcing variables.
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