Mitsubishi Electric MELSEC-Q Series User Manual page 183

10 DEVICES
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(c) Multiple counters can be used within a single scan to achieve the maximum
counting speed.
In such cases, the direct access input (DX ) method should be used for
the counter input signals.
OUT
END
C
Sequence
program
(3) Resetting the counter
(a) Counter present values are not cleared even if the OUT C
switches OFF. Use the RST C
value and switch the contact OFF.
(b) The count value is cleared and the contact is switched OFF at the point
when the RST C
[Ladder example]
X0
[Counter reset timing]
END
Sequence
program
ON
OFF
X0
Execution
RST C0 OFF
instruction
Count value cleared & contact OFF
(4) Maximum counting speed
The counter can count only when the input condition ON/OFF time is longer than
the execution interval of the corresponding OUT C
The maximum counting speed is calculated by the following formula:
Maximum counting
speed (Cmax)
REMARK
1) 1: See Section 10.2.1 for details regarding direct access inputs.
2) 2: The "duty" is the count input signal's ON-OFF time ratio expressed as a
percentage value.
When T1 T2 n =
When T1 < T2 n =
Count input signal OFF
1
OUT OUT
END
C C
instruction to clear the counter's present
instruction is executed.
RST C0
RST C0 END
n 1
= [times/sec]
100 T
T1
100
T1+T2
T2
100
T1+T2
T1
ON
OUT OUT
C C
OUT C
RST C0 END
Count value cleared & contact OFF
instruction.
n: Duty(%) 2
T: Execution interval of the OUT C
T2
MELSEC-Q
execution intervals
instruction
RST C0
instruction
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