Ras Function; Program Monitoring (Wdt) Function - Mitsubishi Electric MELSEC iQ-R C User Manual

1.3

RAS Function

Program Monitoring (WDT) Function

This function monitors and detects errors on hardware and a user program by using the watchdog timer (WDT), an internal
timer of a C intelligent function module.
Program monitoring (WDT) type
■System watchdog timer
A timer to monitor the system of a C intelligent function module.
Use this to detect an error in hardware and system software.
■User watchdog timer
A timer to monitor a user program.
Use this to detect an error in a user program.
Monitoring time setting and reset
■System watchdog timer
The monitoring time of the system watchdog timer is 2000 ms (fixed value).
The system of a C intelligent function module resets it every cycle (2000 ms).
■User watchdog timer
Set a monitoring time for the user watchdog timer within the range of 100 ms to 10000 ms (in 10 ms units) by using the C
intelligent function module dedicated function (CITL_StartWDT).
Monitoring starts by executing the C intelligent function module dedicated function (CITL_StartWDT), and the monitoring time
is reset by executing the C intelligent function module dedicated function (CITL_ResetWDT).
Timeout of watchdog timer
When the watchdog timer times out, an error indicating that the monitoring time set in the watchdog timer setting has been
exceeded (watchdog timer error) occurs. If a system watchdog timer error occurs, the RUN LED turns OFF and the ERR LED
turns ON. If a user watchdog timer error occurs, the ERR LED starts flashing.
■System watchdog timer
In case of failure of a C intelligent function module hardware and interrupt program execution, timeout will occur as the system
processing has been suspended for a long time.
■User watchdog timer
If a user program cannot complete processing within the time specified by using the C intelligent function module dedicated
function (CITL_StartWDT), and also cannot reset by using the C intelligent function module dedicated function
(CITL_ResetWDT), a timeout will occur.
Precautions
When using the following functions, a user watchdog timer error occurs easily since the CPU utilization by a system task with
high priority increases.
• Shell command
• Connection with CW Workbench and Wind River Workbench
• Mounting and unmounting an SD memory card
• File access
• Ethernet communication
• NFS server communication
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1.3 RAS Function