Rockwell Automation 1772-LS_LSP,D17726.8.6 PROG/OPER MANUAL-MINI PLC-2/05 - Manual (Page 210)

Programming Techniques
Chapter 18
18-2
When bit 112/04 makes a false-to-true transition, the one-shot bit (bit
253/00) is set on for one scan. The length of time bit 112/04 remains on
does not affect the one-shot bit due to the next two rungs. Bit 011/14 is
latched when bit 112/04 is set or bit 011/14 is unlatched when 112/04 is
reset. During the next scan, either set of conditions prevents bit 253/00
from being set. The one-shot bit is set for another scan only when bit
112/04 makes a true-to-false and then a false-to-true transition.
Trailing Edge OneĆShot
A trailing edge one-shot 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. Figure 18.2 shows programming for a
trailing edge one-shot.
Figure 18.2
Trailing Edge OneĆShot
112
04
L
011
00
112
04
253
00
253
00
U
011
14
010
00
14
253
00
011
When bit 112/04 is set, bit 011/14 is latched. As soon as bit 112/04 makes
a true-to-false transition,the one-shot bit (bit 253/00 is set and bit 011/14 is
unlatched. Bit 153/00 remains on for only one scan. The input bit 112/04
makes a false-to-true transition then a true-to-false transition to set the
one-shot bit for another scan.
You can control start-up automatically when using the EEPROM memory
module. Anytime that an EEPROM to CMOS RAM memory transfer
occurs, bit 02701 in the data table is set by the processor. The program
must reset this bit. This allows the data table to be updated automatically
to the indicated machine position.
Automatic Restart