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Timer and Counter Instructions Section 5-15
Flags ER: SV is not in BCD.
Indirectly addressed DM word is non-existent. (Content of *DM word
is not BCD, or the DM area boundary has been exceeded.)
Note The timer set value must be BCD between #0000 and #9999. Operation will
be as follows if #0000 or #0001 is set.
• If #0000 is set, the Completion Flag will turn ON as soon as the timer’s
execution condition turns ON.
• If #0001 is set, the Completion Flag may turn ON as soon as the timer’s
execution condition turns ON because timer accuracy is 0 to –0.1 s.
Consider the timer accuracy (0 to –0.1 s) when determining the proper set
value.
5-15-2 COUNTER – CNT
Limitations Each TC number can be used as the definer in only one TIMER or COUNTER
instruction. TC numbers run from 000 through 511 in the CQM1 PCs and from
000 through 127 in the CPM1/CPM1A/SRM1 PCs.
Description CNT is used to count down from SV when the execution condition on the
count pulse, CP, goes from OFF to ON, i.e., the present value (PV) will be
decremented by one whenever CNT is executed with an ON execution condi-
tion for CP and the execution condition was OFF for the last execution. If the
execution condition has not changed or has changed from ON to OFF, the PV
of CNT will not be changed. The Completion Flag for a counter is turned ON
when the PV reaches zero and will remain ON until the counter is reset.
CNT is reset with a reset input, R. When R goes from OFF to ON, the PV is
reset to SV. The PV will not be decremented while R is ON. Counting down
from SV will begin again when R goes OFF. The PV for CNT will not be reset
in interlocked program sections or by power interruptions.
N: TC number
#
Ladder Symbol
Definer Values
SV: Set value (word, BCD)
IR, SR, AR, DM, HR, LR, #
Operand Data Areas
CP
R
CNT
SV
N
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