4.A2CCPU
-------------------
MELSEC·A
4.1.4
Timer processing and accuracy
The A2C uses up-timing timers which increase present value as measuring
I
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
END (of FEND)
instruction and
the
timer contacts close after
the
timer has
timed
out.
(a) 100 msec
and
10 msec 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) 100 msec 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) RST
T[
) instruction executed
When
the
timer is reset by the RST
T[
) instruction,
the
present value is •
reset to 0 and
the
timer contacts open. The retentive timers retain their
present value
and
contact status, and are reset using
the
RST
T[
)
instruction.
4-6
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