Handling Modbus Slaves going offline

[bdiesel]

All,

Is there an elegant way to handle the situation when modbus slaves are not online.  In this situation dcaf fails.  Since this is a fairly common occurrence in a network, how should one handle this situation?  The controller should then re-connect when the slave becomes available again.

Bruce

[BeCeGa]

Hi Bruce when you say DCAF fails what do you mean? You can configure what you want to do based on error code classification when you are configuring the module in the engine, you could change the behavior to just restart the module when connected. How often are you loosing connection. How long are the periods of time you are expecting the slaves to be disconnected? Is this serial MODBUS or TCP?

Best Regards

[bdiesel]

Hi Benjamin,

Apologies for the slow response - I have been tied up trying to get a plant commissioned.

The plant we are working on has around 30 modbus slaves in the network.  When one of the slaves isn't available on dcaf startup, I get a Labview TCP error and dcaf stops.  If a slave goes off the network while dcaf is running, I get the error code on the dcaf front panel, but I am not clear on how to get it to re-connect?

Bruce

[BeCeGa]

Hi Bruce by default most modules will prevent the engine form starting if there is an error. But as this is a common issue with MODBUS there is an extra option you can use. In the module settings for the engine there is a Continue on Initialization Error. Using this option will allow the engine and the modules to start if there is a problem.

In order to reconnect you can set the error classification to recover module.  

Best Regards