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Rockwell Automation Publication 2080-UM002N-EN-E - November 2022
Appendix C User Interrupts
STI Function Status Information
STI Function status bits can be monitored either in the User Program, or in the Connected
Components Workbench software, in Debug mode.
STI User Interrupt Executing (STI0.EX)
The EX (User Interrupt Executing) bit is set whenever the STI mechanism completes timing and
the controller is scanning the STI POU. The EX bit is cleared when the controller completes
processing the STI subroutine.
The STI EX bit can be used in the control program as conditional logic to detect if an STI
interrupt is executing.
STI User Interrupt Enable (STI0.Enabled)
The User Interrupt Enable bit is used to indicate STI enable or disable status.
STI User Interrupt Lost (STI0.LS)
The LS is a status flag that indicates an interrupt was lost. The controller can process 1 active
and maintain up to 1 pending user interrupt conditions before it sets the lost bit.
This bit is set by the controller. It is up to the control program to utilize, track, the lost
condition if necessary.
STI User Interrupt Pending (STI0.PE)
The PE is a status flag that represents an interrupt is pending. This status bit can be
monitored or used for logic purposes in the control program if you need to determine when a
subroutine cannot execute immediately.
This bit is automatically set and cleared by the controller. The controller can process 1 active
and maintain up to 1 pending user interrupt conditions before it sets the lost bit.
Sub-Element Description
Data Format
User Program Access
EX - User Interrupt Executing
binary (bit)
read only
Sub-Element Description
Data Format
User Program Access
Enabled - User Interrupt Enable
binary (bit)
read only
Sub-Element Description
Data Format
User Program Access
LS - User Interrupt Lost
binary (bit)
read/write
Sub-Element Description
Data Format
User Program Access
PE - User Interrupt Pending
binary (bit)
read only