Change value in Modbus slave channel


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I've setup DAQFactory as a Modbus TCP slave. I can write values OK using an external Modbus TCP master. The problem I have is that I'm trying to replicate a certain PLC functionality as below:-

1. Master writes data to slave (DAQFActory/PLC)

2. Slave process the data

3. Slave indicates to master that data has been processed by setting data values to zero.

4. Master is reading registers and detects data has gone to zero so sends next set of data.

This works great on a PLC but I cannot fathom how to get a DAQFactory sequence to be able to set the RTU slave data channels to zero. Can you offer a solution please?


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Modbus Slave addresses are just assigned to channels and are holding registers, so your master should be able to both read and write to a single channel in DAQFactory.  So, your sequence should be able to monitor that channel and when it goes non-zero it does some processing, then it puts a zero into the channel.  It can stuff a zero in using addvalue:




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