Delta Electronics AH500 Manual page 139

A H 5 00 M o ti on C on tr ol M od ul e Ma nua l
API Instruction code
07 WDT

E xp la nat io n


E xa mple

A dditio nal
re mark

Operand
─
P
Pulse instruction

The instruction WDT is used to reset the watchdog timer in a motion
control module. If the scan time in a motion control module exceeds 200
milliseconds, the error LED indicator of the motion control module will be
ON, and users will have to disconnect the motion control module. After
the users connect the motion control module again, the module control
module will judge its state according to the setting of the "RUN-STOP"
switch. If there is no "RUN-STOP" switch, the module will stop running
automatically.
The points when a watchdog timer acts are as follows.
 The system is abnormal.
 The execution of a program takes much time, and therefore the scan
time is greater than the setting value in D1000. There are two ways
users can use to improve the situation.
1. Using the instruction WDT
O100
2. Changing the value in D1000 (The default setting is 200
milliseconds.)
Suppose the scan time is 300 milliseconds. After the program is divided
into two parts, and the instruction WDT is inserted between these two
parts, the time it takes to scan either the first part of the program or the
second part of the program will be less than 200 milliseconds.
300ms pr ogram
M102
150ms pr ogram
X0.0
WDT
150ms pr ogram
M102
T he instruction WDT is executed when a condition is met. Users can
make the instruction WDT executed only in one scan cycle by writing a
program. They can use the pulse instruction WDTP.
The default setting of a watchdog timer is 200 milliseconds. Users can
set a watchdog timer by means of D1000.
Function
Watchdog timer
16-bit instruction (1 step) 32-bit instruction

M102
WDT
T2
T1
T he program is divided into two par ts .
T he time it takes to s can either the fi rst
part of the program or the s econd part
of the pr ogr am is less than 200 mil liseconds.
T he watc hdog ti mer is r eset.
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