In SX Microcontrollers, SX/B Compiler and SX-Key Tool, stamptrol wrote:

Ahmet,

     The chip itself is easy to use. Basically, all stations are in "listen" mode (RE/DE pulled low, I believe). When the master wants to talk, RE/DE is taken high and the data is sent to the chip on the D input. The other stations see the data on their R pins.

   Now, the MODBUS protocol is a bit complicated, especially the checksum generation. But, you'll only need to implement one or two command sequences and it is possible to hardcode the checksums required. MODBUS is still very popular, despite its age.

    Which PLC brand are you trying to communicate with? Some are easier to work with than others.
 
    I think I have some more details which I can dig out when I get home.

  Cheers,

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