MS/TP Token Pass Timeout
The MS/TP master holds a token and must pass it to the next station. Token pass timeout occurs when no valid Pass Token frame is received within the slot time, indicating trunk or node issues.
Common Causes
- Faulty or offline node between current master and next address
- Wiring fault causing Pass Token frames to be lost or corrupted
- Slot time too short for network propagation delay
- Duplicate MAC addresses causing confusion in token rotation
Fix Steps
- Identify the next MAC in token rotation; verify that device is online and wired correctly.
- Test RS-485 trunk: check voltage, termination, and continuity.
- Increase slot time (default 50 ms) if network has long propagation delay.
- Scan for duplicate MAC addresses; resolve conflicts.
- Power-cycle the trunk or reset master to force token ring rebuild.