Schneider Electric 840 USE 106 0 manual Standby on Logic Mismatches, Mismatch Hazard

Using a Quantum 984 HSBY System

Standby on Logic Mismatches

Logic Program To function properly, the Primary and the Standby controller in a Hot Standby system must be solving an identical logic program, which is updated on every scan by a state RAM data transfer between the two controllers.

By default, the Standby controller is set to go offline if a mismatch is detected between its user logic and that of the Primary controller. Switchover cannot occur while the Standby controller is Offline.

The radio buttons provide you with the option to override this default. If you change the parameter in this field from Offline to Running, the Standby controller remains online if a logic mismatch is detected between its logic program and that of the Primary controller.

CAUTION

Mismatch Hazard

A mismatch in the I/O map or configuration is not allowed under any circumstances.

Failure to follow this precaution can result in injury or equipment damage.

CAUTION

Switchover Hazard

If switchover occurs when the radio button is set to Running and there is a logic mismatch between the two controllers, the Standby controller will assume Primary responsibilities and will start solving a different logic program from the previous Primary controller.

Failure to follow this precaution can result in injury or equipment damage.

92 840 USE 106 00 January 2003