Fault on Primary and Secondary PLC

HA-CS31 system only takes care of the first fault. In case of a second fault the primary CPU remains primary CPU until the second fault occurs. This results in no further switch overs (manual switch overs included).

Example: If an error occurs on PLC A (primary) due to CS31 cable disconnection, the HA-CS31 system will switch over to PLC B (primary). If there is any cable disconnection happened in either PLC A (secondary) or PLC B (primary) the HA-CS31 system will remain in PLC B as primary.

In case of a second error generated in the HA-CS31 system, function block HA_CS31_CONTROL will generate an error with error code 16#2006.

If one fault occurs in both, CPU A and CPU B, error code 16#2006 occurs. This error code does not consider two faults on the same PLC. In the following the most common scenarios that trigger error code 16#2006 (named as wHA_ER_LOCAL_AND_REMOTE_FAULT) are listed:

• CS31 cable is removed from PLC A and PLC B (from same corresponding ports).
• CS31 cable is removed from PLC A and PLC B (from different ports).
• Cable of CS31 network is removed from any CI590-CS31-HA related to PLC A and afterwards it is removed from PLC B (coming from the same corresponding ports).
• Cable of CS31 network is removed from any CI590-CS31-HA related to PLC A and afterwards it is removed from PLC B (coming from different ports).
• PLC A is stopped and PLC B CS31 line is removed.
• PLC A CS31 line is removed and PLC B is stopped.
• PLC A is powered off and PLC B CS31 line is removed.
• PLC A CS31 line is removed and PLC B is powered off.
• PLC A CS31 line is removed and PLC B CI-590 is powered off.

All outputs on the remote modules keep on working properly as long as at least one CS31 line is active - regardless of CPU primary or secondary status. This is because of the self-primary action in CI590-CS31-HA module.