4.A2CCPU
--------------------
MELSEC·A
I
WDT error occurs If the
WOT counter value exceeds
the
.etting
I
Sequence program
operat1ion
1
~ND
pro6eSsing time
Scan time (WDT counting value)
I
o END
1 I
L WDT reset
(WDT
Is reset
when END is executed)
END 0 END
==1.-I=======I-t=======-
Fig. 4.7
Resetting
Watch
Dog
Timer
(4) Watch
dog
timer error processing
Do one of the following if
the
scan time of a sequence program is greater
than
the
watch
dog
timer setting.
(a) Change
the
sequence program so
that
the operation time is within
the
watch dog timer setting.
(b) Change the watch
dog
timer setting.
Setting
range:
0 to 2000 msec
(c) Reset
the
watch
dog
timer with
the
worinstruction in
the
sequence
program.
The watch
dog
timer is reset at the time the WOT instruction is
executed and it begins counting again from "0·.
Note
that
the
scan time values registered in
09017
to
09019
are not
reset when
the
WOT instruction is executed.
•
POINTI
(1) The watch dog timer setting must be as indicated below if constant
scan (see Section 4.2.1) is set.
IConstant scan setting + 10 msec s Watch
dog
timer setting I
(2) When the A2C stops communication with a remote terminal module.
the output state of the remote module is as
follows:
(a) A2C I/O module : all turns OFF
(b) Remote I/O module
for
MINI-53:
depends
on EC mode setting
4-12
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