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

 

There are several scenarios in which Advantys STB output modules go into their

Scenarios

fallback states:

 

loss of fieldbus communications—Communications with the fieldbus master are

 

lost.

 

loss of island bus communications—There is an internal island bus

 

communications error, indicated by a missing heartbeat message from either the

 

￿NIM or a module.

 

change of operating state—The NIM may command the island I/O modules to

 

switch from a running to a non-running (stopped or reset) state.

 

In all of these fallback scenarios, the NIM disables the heartbeat message.

 

 

 

Note: If a module fails, it needs to be replaced. The module may not go to its

 

fallback state.

Heartbeat

 

 

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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890USE19600 April 2004

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Schneider Electric 890USE19600 Version 1.0 manual Island Fallback Scenarios, Heartbeat, Message