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Programming Considerations
There are several features in the operation of the Redundancy CPU which are not supported or are different then operation of other CPUs. These features are listed below and are described in detail in Chapter 4, ºSystem Operationº.
The following features are not available with the Redundancy CPU (CPU 780):
HI/OInterrupts
HTimed Interrupts
HVME Integrator Rack
HSTOP/IOSCAN mode
HFlash memory operation
The operation of the following features is different with the CPU 780 than with other
Series
HRUN/DISABLEDmode
HConfiguration of fault actions
HSTOP to RUN mode
HDefault Background Window Time
Configuration Requirements
The Redundancy CPU and the Redundancy Communications Module must be configured into the redundancy system. There are several additional parameters (other than the normal CPU parameters) that must be configured with the Logicmaster
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| The time to wait on a failed active PLC before switching to |
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| the backup CPU. The default value is 60 ms. |
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| Control Strategy | The control strategy for the current configuration. Config- |
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| ured as a |
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| CPU Redundancy). The default value is GHS (currently |
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| the only value that is valid). |
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| Shared I/O References | The references within the control of the Redundancy sys- |
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| tem; up to 20 KBytes of Input data and 28 KBytes of Out- |
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| put data is transferred. The references which may be used |
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| as shared I/O are %I, %Q, %AI, %AQ, %R, and %M. |
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| Redund Type | Whether the CPU being configured is the Primary or Sec- |
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| ondary CPU in the Redundancy system. Redund Type |
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| has three possible values: PRIMARY, SECONDARY, or |
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| SIMPLEX. SIMPLEX (not supported in this release of the |
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| product) indicates a non±redundant system. The default |
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| value is PRIMARY. |
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10 | Series |
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