Rockwell Automation 1772-LV Mini-PLC - 2/15 Programmable Controller (Series B) Programming and Operations - Manual (Page 159)

Special Programming Techniques
Chapter 11
11Ć12
Figure 11.4
Leading Edge OneĆShot
112 011
04
One-shot storage
253
00 14 bit
253
00
011
14
L
112
04
011
14
U
253
00
One-shot output
When bit 11204 makes a transition, the one-shot bit (bit 25300) is set on for one
scan. The length of time bit 11204 remains on does not affect the one-shot bit
due to the next two rungs. Bit 01114 will be latched on when bit 11204 is on or
bit 01114 will be unlatched when 11204 is off. During the next scan, either set
of conditions will prevent bit 25300 from being set on. The one-shot bit is set
on for another scan only when bit 11204 makes a true-to-false and then a
false-to-true transition.
Trailing Edge OneĆShot
A trailing edge one-shot programming technique sets a bit for one scan when its
input condition has made a true-to-false transition. The true-to-false transition
represents the trailing edge of the input pulse. Programming for a trailing edge
one-shot is shown in Figure 11.5.
Figure 11.5
Trailing Edge OneĆShot
112
04
011
14
L
253
00
011
14
U
112 011
04
253
00 14
253
00
One-shot storage
bit
One-shot output