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4.13 Watchdog Timers (WDT)
4
FUNCTIONS
4.13 Watchdog Timers (WDT)
(1) Definition of watchdog timers (WDT)
The watchdog timers are internal timers of the C Controller module that are used to
detect hardware and user program errors of the C Controller module.
The C Controller module has the following two different watchdog timers.
(a) System watchdog timer
The system watchdog timer monitors the C Controller module system and is used
to detect hardware and system software errors.
(b) User watchdog timer
The user watchdog timer monitors the user program and is used to detect user
program errors.
(2) When watchdog timer has timed out
When the watchdog timer runs out, a watchdog timer error is detected and the
following processing is performed.
• The C Controller module turns off all the outputs.
• The RUN LED and MODE LED on the front of the C Controller module turn off,
and the ERR. LED flashes. (The MODE LED turns off only when a system
watchdog timer error occurs.)
(3) Setting and resetting watchdog timers
(a) Setting watchdog timers
1) System watchdog timer
The time of the system watchdog timer can be set and changed on the
<<System setting>> tab of the C Controller setting utility.
The system watchdog timer default is 1000ms. (It can be changed within the
range of 20ms to 2000ms (in 10ms units).)
2) User watchdog timer
The time of the user watchdog timer can be set by the QBF_StartWDT
function within the range of 100ms to 10000ms (in 10ms units).
(b) Resetting watchdog timers
1) System watchdog timer
The C Controller module periodically resets the watchdog timers in the
system.
The system watchdog timer runs out if the system processing is suspended for
a long time due to a C Controller module hardware fault, interrupt program
execution, etc.
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