Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 71)

Introduction to Programming
Chapter 4
4Ć7
by an Output Unlatch instruction. If power is lost and back-up battery for
CMOS RAM memory is maintained, all latched bits will remain on.
The Output Unlatch instruction is used to de-energize a memory bit
that has been latched on. The Output Unlatch instruction addresses the
same memory bit that has been latched on (Figure 4.8). When the rung
conditions for the Output Unlatch instruction go true, the addressed
memory bit is reset to zero (off) (Figure 4.9). The output unlatch is also
retentive. This means that once the rung conditions go false, the unlatched
bit remains off.
Figure 4.8
Latch/Unlatch Instructions
|ą|
04
( L )
00
113 010
|ą|
05
( U )
00
113 010
Figure 4.9
Latch/Unlatch Timing Diagram
True
False
ЗЗЗЗ
ЗЗЗЗ
ЗЗЗЗ
ЗЗЗЗ
True
False
ЗЗЗЗЗ
ЗЗЗЗЗ
On
Off
ЗЗЗЗЗЗЗЗ
ЗЗЗЗЗЗЗЗ
ЗЗЗЗ
ЗЗЗЗ
Latch
Rung
Unlatch
Rung
Output
Bit
01000