Configuring the Island Bus
Island Fallback Scenarios
Introduction | In the event of a communications failure on the island or between the island and the |
| fieldbus, output data is put into a predefined fallback state so that the module’s |
| values are known when the system recovers from the failure. |
| When you use a basic NIM, you cannot change the fallback parameters of any |
| modules in the segment. All output channels on the modules go to a predefined |
| fallback value of 0. |
Fallback |
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There are several scenarios in which Advantys STB output modules go into their | |
Scenarios | fallback states: |
| loss of fieldbus |
| lost. |
| loss of island bus |
| communications error, indicated by a missing heartbeat message from either the |
| NIM or a module. |
| change of operating |
| switch from a running to a |
| In all of these fallback scenarios, the NIM disables the heartbeat message. |
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| Note: If a module fails, it needs to be replaced. The module may not go to its |
| fallback state. |
Heartbeat |
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The Advantys STB system relies on a heartbeat message to ensure the integrity and | |
Message | continuity of communications between the NIM and the island modules. The health |
| of island modules and the overall integrity of the Advantys STB system are |
| monitored through the transmission and reception of these periodic island bus |
| messages. |
| Because island I/O modules are configured to monitor the NIM’s heartbeat |
| message, output modules will go into their fallback states if they do not receive a |
| heartbeat message from the NIM within the defined interval. |
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34 | 890USE19600 April 2004 |