Experimental Physics and
Industrial Control System

Ø  Does this mean that, whatever the modbus device is that i am communicating, i can always substitute my 'field(SCAN, "1 Second")' to 'field(SCAN, "I/O Intr")' and go out unpunished?

 

Yes, that is true.  This assumes that you are not using the “absolute” addressing option, because in that case there is no poller thread.  When you are not using absolute addressing then the poller thread is constantly reading a block of Modbus registers.  If your record has SCAN=1 second, for example, then it calls the driver and retrieves the most recent poll value.  It does not cause a Modbus transaction to occur.  If you use SCAN=I/O Intr then your record will only process when the driver finds that the value has changed.  This will be much more efficient for bits and registers that rarely change state.

 

Ø  Will this work against me in the future?

 

No, it is the recommended way to run.

 

Mark

 

 

 

 

 

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