Timers and Counters
Chapter 11
11-8
False
Accumulated value is retained.
Bit 14 - no action is taken.
Bit 15 - no action is taken.
Bit 17 is reset.
The Up Counter instruction retains its AC value when:
You change the mode to program or remote program.
The rung condition turns false.
A power outage occurs and memory backup is maintained.
Important: Bit 14 of the accumulated value word is set when the
accumulated value either overflows or underflows. When a down counter
preset is 000, the underflow bit 14 will not be set when the count goes
below 0.
The Down Counter instruction subtracts one from its accumulated value
for each false to true transition of its rung conditions. A count is only
added on a false to true transition, so rung conditions must go from true to
false and back to true before the next count is registered.
010
00
CTD
030
PR 150
AC 000
When the rung condition becomes:
True
Accumulated value decrements by 1.
Bit 14 is set when AC < 000.
Bit 15 is reset when AC < PR; counting continues.
Bit 16 is set and stays set until the rung goes false.
False
Accumulated value is retained.
Bit 14 - no action is taken.
Bit 15 - no action is taken.
Bit 16 is reset.
The Down Counter instruction retains its AC value when:
You change the mode to program or remote program.
The rung condition turns false.
A power outage occurs and memory backup is maintained.
Down Counter
