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 Post subject: Modbus Slave Receive Timeout
PostPosted: Fri Dec 22, 2017 1:05 pm 

Joined: Thu Dec 13, 2012 2:07 pm
Posts: 16

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Is the Controller, Settings, Advanced configuration parameter Timeout (the number of milliseconds between retries when communication fails) applicable only to a Modbus Master?

If answer to above is yes, then, is there a way to specify a Modbus Slave receive timeout so that if the master stops sending requests, the slave will detect it? Will the SystemTagCommunicationErrors tag increment if the Modbus Slave receive timeout expires?


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 Post subject: Re: Modbus Slave Receive Timeout
PostPosted: Sat Dec 23, 2017 9:19 pm 

Joined: Mon Jun 11, 2012 2:10 pm
Posts: 120

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What type of Modbus slave are you using RTU or TCP? I have one project with a Modbus TCP slave and I know SystemTagCommunicationErrors incremented and the error message window would appear when no master was connected unless the command line options was set to "XDNCW".
Looking through the controller settings, it seems there is a "set digital signal" option for Modbus TCP slave that would set a Modbus coil in case of settable connection timeout. You could probably use this in conjunction with the system tag if you are using TCP.

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Adam M.
Controls Engineer
FlexEnergy


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 Post subject: Re: Modbus Slave Receive Timeout
PostPosted: Fri Jan 05, 2018 2:55 pm 

Joined: Thu Dec 13, 2012 2:07 pm
Posts: 16

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Thanks for the response. But I am using Modbus RTU so looks like will have to implement a heartbeat via a tag.


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