Relay Ladder - Allen-Bradley Logix5000 Reference Manual

Chapter 11 Program Control Instructions (JMP, LBL, JSR, RET, SBR, JXR, TND, MCR, UID, UIE, AFI, NOP, EOT, SFP, SFR, EVENT)
Arithmetic Status Flags:
Fault Conditions:
Condition
Prescan
Rung-condition-in is false
Rung-condition-in is true
EnableIn is set
Instruction execution
Postscan
482
The controller does not clear the bits of the Status attribute once they are set.
· To use a bit for new status information, you must manually clear the bit.
· Use a Set System Value (SSV) instruction to set the attribute to a different
value.
Not affected
None
Execution:
Relay Ladder Action
The rung-condition-out is set to false.
The rung-condition-out is set to false.
The instruction executes.
The rung-condition-out is set to true.
N/A
The instruction triggers one execution of the specified event task
The rung-condition-out is set to false.
Example 1:
A controller uses multiple programs but a common shut down procedure. Each
program uses a program-scoped tag named Shut_Down_Line that turns on if the
program detects a condition that requires a shut down. The logic in each program
executes as follows:
If Shut_Down_Line = on (conditions require a shut down) then
Execute the Shut_Down task one time

Relay Ladder

Program A
Program B
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Structured Text Action
No action taken.
N/A
N/A
EnableIn is always set.
The instruction executes.
No action taken.