Broken Wire or Noise (Subsequent Unit)

What does ALM LED Blink (1:1) mean?

The red ALM LED blinks with a 1:1 duty cycle (0.5s ON / 0.5s OFF), indicating a broken wire or poor cable connection between the unit of interest (JD1A connector) and a subsequent unit (JD1B connector). Electromagnetic noise around the cable is also a potential contributing factor to this communication issue.

• A broken wire or significant electrical noise is disrupting communication with a subsequent unit or module.
• The signal integrity on the communication bus to a connected device (e.g., I/O expander, remote axis) has been compromised.
• This could be due to damaged cabling, poor shielding, or interference from external electrical sources.
• The control system is unable to reliably receive or transmit data from the affected downstream unit.

Click steps to track your progress.

1. 1

   Check for a defective cable or a poor cable connection between JD1A on the unit of interest and JD1B on a unit subsequent to that unit.

2. 2

   Check to see if there is noise present around the cable.