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CLICK PLC Serial Flow Control

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  • CLICK PLC Serial Flow Control

    In the configuration of the COM Ports there isn't an option for Flow Control. Is this because there is only one option and if so what is it or is there another reason?

  • #2
    PLC's typically don't use flow control. There are pins for hardware flow control (RTS/CTS), but they are rarely used and usually jumpered together.

    PLC communications tends to be with one master device and one or more slave devices. Since the master device controls the data flow, there just isn't much need for flow control since the slave devices are assumed to be always ready.
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    • #3
      I should have added in my initial post that I am using Port 2 [on the CLICK PLC] to communicate with a home automation controller that only supports ASCII. The home automation controller is essentially a custom PC.

      Based on your reply though I assume I would be able to use hardware (RTS/CTS) flow control if my other hardware supported it.

      Thanks for the follow-up.


      • #4
        Usually RS-232 flow control (hardware or software) are required when the baud rate is higher than reliable comm's can take place. If a baud rate is faster than the receiving end can process it, not just receive it, then flow control is needed.

        The classic example is a serial printer. Even at 4800 baud, the printer can not keep up with the serial data arriving. I have a small Citizen serial (4.8K baud) interfaced to a DL260 rs-232 port and it simply must have flow control. I can't even get through the first line of print with out the flow control using the printer Busy signal.