4.A2CCPU
--------------------
... MELSEC·A
4.1.5 Counter processing and maximum counting speed
The A2C uses up-timing counters which increase
their
present values on
the
leading edge of an
input
signal.
Counters are used by incorporating in
the
main routine programs or
sub
routine programs.
(1) Counter present value and contact status update
Counter coil Is switched on and off by
the
OUT C[ I instruction. The
counter
present value is
updated
on
the
leading
edge
of
the
coil signal
after
the
END (FEND) instruction is executed. The counter contacts
close after
the
counter has counted out. The counters retain their
present value and contact status even if the counter coil is switched off.
(2) RST C[
I instruction executed
When the counter is reset by the RST C[
I instruction, the present value
is reset to 0 and the counter contacts open.
I
o
END
o
END
o
Counter present value updated
Counter contact status updated
Fig. 4.3
Counter
Processing
IREMARKSI
The maximum counting speed of the counter depends on the scan time. Counting Is only
possible if the input condition is on for more than one scan time. For further details, see the
ACPU Programming Manual.
Maximum counting speed Cmax
=
1~O
x
~
(times/sec)
where. n =
duty
(%)
Duty is the ratio of the input signal's on time to off
time
as a percentage.
ON
Count input signal
OFF
If T1 s T2
lin>
T2
T1
n =
Tf+T2X
100 (%)
T2
n =
Tf+T2x
100 (%)
ts : Program scan time (sec)
4-8
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