RS-232C Port Timeout Error
Omron · SYSMAC CJ2 CPU Unit
What does A528.05 mean?
This flag turns ON when a timeout error occurs during RS-232C communication. This indicates that a response from the connected device was not received within the expected timeframe after a transmission. This error is valid in Serial Gateway mode, NT Link mode, and for both Polling and Polled Units in Serial PLC Link Mode.
Common Causes
- The connected device is not responding or is offline
- Communication cable issues (disconnection, damage)
- Incorrect communication protocol or addressing settings
- Timeout parameter set too short for network latency or device response time
Repair Steps & Checklist
Click steps to track your progress.
- 1
Verify the connected device is powered ON and operating correctly
- 2
Inspect the RS-232C cable for continuity and proper connection at both ends
- 3
Check communication parameters, including device address and protocol settings, on both the PLC and the connected device
- 4
Adjust the communication timeout parameter in the PLC configuration if the connected device has a slower response time
- 5
Restart the RS-232C port by turning ON the Serial Port Restart Bit (A526.00) from OFF to ON