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Fastest Communications between PC and PLC


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I have  a customer that is looking to use a Unitronics PLC to add additional outputs to their existing system.  The main system runs on a .net application, so the PLC would be mainly used to set/reset a MB or Output at a particular time.  The response time needs to be pretty fast, likely a few milliseconds from PC send to output state change.

Which communication method would be the fastest or would they be roughly the same?


- .NET driver

- Custom protocol with short command sent from PC and received via FB protocol scan.

Just getting a feel on how I should build the PLC communications class.


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the .Net driver implements the PCOM.

There is a little overhead of the fact that it is written in .Net (Ctor, GC, JIT compilation, threads and locks), so I can't give you an accurate time on how much  it takes to send a message to the PLC (Assuming you already established a connection to the PLC).

It also depends on the channel (Serial or Ethernet, and if Ethernet then also the distance between the PC and PLC).


Modbus is also a fast protocol.

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