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Changes in execution conditions, the Completion Flag, and the PV are illus-
trated below. PV line height is meant only to indicate changes in the PV.
Execution condition
on count pulse (CP)
Execution condition
on reset (R)
ON
OFF
ON
OFF
Completion Flag
ON
OFF
PV
SV
SV – 1
SV – 2
0002
0001
0000
SV
Precautions Program execution will continue even if a non-BCD SV is used, but the SV will
not be correct.
Jumps
Never program CNT between JMP(04) 00 and JME(05) 00 with an SV of #0000.
The Completion Flag will turn ON even when the execution condition for
JMP(04) 00 is ON (i.e., even when the program section with CNT is jumped).
CNT can be programmed successfully between JMP(04) and JME(05) as long
as a jump number between 01 and 99 is used.
Step Instructions
Never program CNT between STEP(08) and SNXT(09) with an SV of #0000.
The Completion Flag will turn ON even when the step containing CNT is reset.
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.)
In the following example, the PV will be decremented whenever both 00000 and
00001 are ON provided that 00002 is OFF and either 00000 or 00001 was OFF
the last time CNT 004 was executed. When 150 pulses have been counted down
(i.e., when PV reaches zero), 00205 will be turned ON.
00000
CP
R
CNT 004
#0150
00002
00001
00205
CNT 004
Address Instruction Operands
00000 LD 00000
00001 AND 00001
00002 LD 00002
00003 CNT 0004
# 0150
00004 LD CNT 004
00005 OUT 00205
Here, 00000 can be used to control when CNT is operative and 00001 can be
used as the bit whose OFF to ON changes are being counted.
Example 1:
Basic Application
Timer and Counter Instructions Section 5-14