Chapter 11
Program Control Instructions (JMP, LBL, JSR, RET, SBR, JXR, TND, MCR, UID, UIE, AFI, NOP, EOT, SFP, SFR, EVENT)
User Interrupt Disable (UID)
User Interrupt Enable (UIE)
UID();
Description:
470
The UID instruction and the UIE instruction work together to prevent a small
number of critical rungs from being interrupted by other tasks.
Operands:
Relay Ladder
None
Structured Text
None
You must enter the parentheses () after the instruction mnemonic, even though
there are no operands.
When the rung-condition-in is true, the:
· UID instruction prevents higher-priority tasks from interrupting the current
task but does not disable execution of a fault routine or the Controller Fault
Handler.
· UIE instruction enables other tasks to interrupt the current task.
Follow these steps to prevent a series of rungs from being interrupted.
1. Limit the number of rungs that you do not want interrupted to as few as
possible.
Disabling interrupts for a prolonged period of time can produce
communication loss.
2. Above the first rung that you do not want interrupted, enter a rung and a
UID instruction.
3. After the last rung in the series that you do not want interrupted, enter a
rung and a UIE instruction.
4. If required, you can nest pairs of UID/UIE instructions.
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011