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(d) Maximum counting speed
The counter can count only when the on/off time of the input condition is longer than the execution interval of
the corresponding OUT C instruction.
The maximum counting speed is calculated by the following expression:
*1: Duty (n) is the ON-OFF time ratio of count input signal, and is expressed as a percentage
value.
The maximum counting speed can be increased by placing multiple counters within one scan.
At this time, use the direct access input (DX )( Section 3.8.2) for the counter input signal.
(4) Precautions
(a) When counting processing is suspended
If an interrupt occurs during execution of the processing shown below, counting is suspended until the
execution of each processing is completed.
• Each instruction on the sequence program
• Interrupt program
• Fixed scan execution type program
Upon completion of the processing, the counting restarts.
However, if the same interrupt occurs again during each processing, these interrupts are counted as once.
n: Duty (%)
*1
T: Execution interval of the OUT C instruction (sec)
Figure 9.36 Duty ratio
Figure 9.37 Ladder example for increasing the maximum counting speed
n
100 T
Maximum counting
speed (Cmax)
[times/s]
1
=
OFF
ON
T1 T2
T2
T1
When T1 T2, n = 100%
100%When T1 < T2, n =
T1+T2
T1+T2
Count input signal
Execution interval of the
OUT C instruction
END END
OUT
C
OUT
C
OUT
C
OUT
C
OUT
C
Sequence
program