Allen-Bradley Logix5000

442 Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Chapter 10 Sequencer Instructions (SQI, SQO, SQL)
Execution:
Condition Relay Ladder Action
Prescan The .EN bit is set to prevent a false load when the program scan begins.
The rung-condition-out is set to false.
Rung-condition-in is false The .EN bit is cleared.
The rung-condition-out is set to false.
Postscan The rung-condition-out is set to false.
Rung-condition-in is true.
.LEN ≤ 0 or
.POS < 0
No
Yes
.DN bit is set.
.POS = .LEN
No
Yes
Examine .EN
bit.
.EN = 0
.EN = 1
.EN bit is set.
.ER bit is cleared.
.DN bit is set.
.POS ≥ .LEN
Yes
No
.POS = .POS + 1
.POS Value
rolls over
Yes
No
.ER bit is set.
Rung-condition-out is
set to true.
.DN bit is set.
.POS = .LEN
Yes
No
Destination = (Destination AND (NOT(Mask)))
OR (Array[control.POS] AND Mask)
.POS > .LEN
No
Yes
.POS = 1
Goto
Error
Error