Special I/O Unit Data Exchange Error

What does A402.06 mean?

This fault indicates an error during data exchange between the CPU Unit and a Special I/O Unit. When this error occurs, the Special I/O Unit Error Flag (A402.06) is turned ON. The corresponding bit for the unit number (0-95) in A418 to A423 will also be set. The CPU Unit will continue operating, and the ERR/ALM indicator on the front of the CPU Unit will flash.

• Communication failure during data exchange with a Special I/O Unit (unit numbers 0-95).
• Physical connection issue with the Special I/O Unit.
• Faulty Special I/O Unit.

Click steps to track your progress.

1. 1

   Identify the faulty Special I/O Unit by checking the status of bits A418.00 to A423.15.

2. 2

   Inspect the physical connection and bus cables of the identified Special I/O Unit.

3. 3

   Verify the power supply to the Special I/O Unit.

4. 4

   Clear the error flag (A402.06) once the error condition is resolved.