4.
AZCCPU
/MELSEC-A
4.1.4
Timer
processing
and
accuracy
The
A2C
uses up-timing timers which increase present value as
measuring time increases. Three kinds of timers are provided; 100
msec timer, 10 msec timer and 100 msec retentive timer.
100
msec timers
...
setting range: 0.1 to
3276.7
sec
in
100
msec
increments
10 msec timers
...
setting range:
0.01
to
327.67
sec in
10
msec
increments
100 msec retentive timers
...
setting range: 0.1 to
3276.7
sec in
100 msec increments.
Processing when the coil is turned off differs from the
processing of
100
msec timers.
The following paragraphs explain timer processing.
(1)
Timer present value and contact status update
With continuity in front of a timer coil, the timer present value
and contact status are updated after the execution of the
I=]
(or
FEND)
instruction and the timer contacts close after
the timer has timed out.
(a) 100ms and 1Oms timers
When the continuity is removed from in front of the timer coil,
the present value is reset to
0
and the timer contacts open.
(b)
100ms retentive timer
When the continuity is removed from in front of the timer
coil, the present value update is stopped but the present
value is retained.
(2)
w]
T[:l instruction executed
When the timer
is
reset by the instruction, the
present value is reset to
0
and
the timer contacts open.
The retentive timers retain
is jumped after the timer has
started timing,
it
continues to time. The contacts are closed
when the timer times out.
0
END
0
END
0
Timer contact status updated
Fig.
4.2
Timer
Processing
piGF-l
Accuracy
of
timers when external inputs are used is within
0
to
+2
from the scan
time.
For timer timing and accuracy, read the
ACPU
Programming Manual
(Fun-
damentals).
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