Saia-Burgess Controls AG
User Manual Standby System
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Document 27-645
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Edition E
NG 02
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2017-04-26
Terminology
Standby System Overview
1-3
1
1.2
Terminology
The following definitions will provide a better understanding of the proper
-
ties and operating principles:
Standby Controller
The PCD3.M6880 controller which supports the standby
feature.
Primary PCD
The PCD which becomes the active device by default
when the system is powered up, depending on the
configuration.
Secondary PCD
The PCD which becomes the standby device on power
up, and only takes over active control in the event of
a fault on the active device.
Active PCD
The PCD whose CPU1 is in Active Mode, running the
redundant program and controlling the inputs/outputs
(PCD3.T668 RIOs).
Standby PCD
The PCD whose CPU1 is in Standby mode. It does not
run the redundant program and the outputs
(PCD3.T668 RIOs) are not controlled by this device.
Main CPU
CPU0 of the Primary or the Secondary PCD, which runs
the non-redundant program. This program may be
different on the Primary and Secondary devices.
Redundant CPU
CPU1 of the Primary or Secondary PCD, which contains
the Redundant program. This program must be the
same on the primary and Secondary devices. This CPU
is either in Active mode and running the Redundant
program, or in Standby mode and monitoring the Active
PCD.