Applicable Systems
PLC
Symptoms
The PLC reports a watchdog timeout fault. The system watchdog timer expired without receiving the expected communication or task completion signal.
Possible Causes
- Host controller communication interrupted or stopped
- Application task execution exceeded the watchdog timeout period
- Watchdog timeout setting too short for the actual task cycle time
Troubleshooting Steps
- Step 1: Check the host controller communication link status in the drive
Communication link is active and stable - Step 2: Review the task execution time and compare with the watchdog setting
Task completes within the watchdog period - Step 3: Increase the watchdog timeout if the task legitimately requires more time
Watchdog timeout accommodates the task cycle
How to Reset
To reset: Restore communication or fix the task timing, then reset.
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Source: B&R Automation System Manual, B&R Industrial Automation
Category: PLC & VFD
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