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The Primary Unit and the Secondary Unit must be configured separately. That is, the programming device should be connected directly to either the Primary or the Secondary Unit to configure that unit. When you have completed configuring that unit, disconnect the programmer from the configured unit and move it to the other unit and proceed with configuration of the second unit. Refer to Chapter 3, ºSystem Configurationº for details of configuring a Redundancy system
Definition of Terms
Several new or unfamiliar terms are used throughout this manual which are relevant to the discussions of CPU Redundancy. These terms are defined in the following table.
Term | Definition |
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ActiveUnit | The unit that is actively controlling the process. |
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Backup Unit | That unit that is synchronized with the active unit and able to take over the process. |
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CPURedundancy | A system with two PLC CPU units cooperating to control the same process. |
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CriticalComponent | A component whose failure causes the PLC (either active or backup) in which it resides to |
| stop. |
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Hot Standby | A feature of Genius blocks whereby the block prefers output data from the |
| Bus Controller at Serial Bus Address 31. When inputs from that Bus Controller are not |
| available, the block takes output data from the Bus Controller at Serial Bus Address30. |
| If inputs from neither Controller are available, the block places its outputs in the |
| designateddefaultstate. |
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LocalUnit | The RCM LEDs and %S status bits refer to the PLC in which they reside as |
| theºLocalUnitº. |
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Primary Unit | The unit in which the Genius Bus Controller's Serial Bus Address is 31. |
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Redundancy | A system feature that has multiple elements controlling the same process to provide alter- |
| nate functional channels in case of failure. |
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Remote Unit | The RCM LEDs and status bits refer to the other PLC as the ºRemote Unitº. |
| For example, the Primary Unit is the Remote Unit to the Secondary Unit and likewise |
| the Secondary Unit is the Remote Unit to the Primary Unit. |
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Secondary Unit | The unit in which the Genius Bus Controller's Serial Bus Address is 30. |
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Synchronized | A unit is considered to be synchronized when it has received the latest status information |
| from the Active unit and is running the PLC program in parallel. |
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Chapter 1 Introduction | 11 |
