ABB PM825 S800 Processor 3BSE010796R1

Processor unit redundancy is available for PM861, PM864, PM865, PM866, and PM891. In this case, the controller contains two processor units, each including memory for system and application software. One unit is acting as primary, the other is backup (hot stand-by). The primary processor unit controls the process. The backup stands by, ready to take over in case of a fault in the primary. The changeover is done bumplessly and in less than 10 ms. During the changeover, the process outputs are frozen. Following a changeover, the system operates as a system without redundancy with only one processor unit in operation. You can replace the malfunctioning processor unit while the system is running. After the replacement is carried out, the system once again has a redundant processor unit. If an error arises in the backup unit, you can also replace the backup unit while the

system is running.

Errors which occur in the backup unit can never affect the primary unit's operation.The primary unit and the backup unit are logically separated from one another.Hardware errors in the primary processor unit cause the system to perform a correct changeover. These hardware errors are single errors. The application programming and the communication are totally unaffected by the redundancy.