Author Topic: Cant connect to COM3 (RS485)  (Read 3695 times)


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Cant connect to COM3 (RS485)
« on: April 20, 2004, 11:20:45 AM »
Im using a T100MD to communicate with a modem.
I have some problems and need to online-monitor the program while the modem is connected.
I want to monitor via com3 (rs485) and have connected a rs232/485 converter to the PC

I have set the baudrate in the plc -> setbaud 3,$H04 and tls server can connect to com1 using the same settings.
This is the converter:
And this is the manual:
My questions:
Do I need a terminating resitor, my cable is about 1 meter long.?
Witch pins shall i use on the converter ?
How shall i posistion the DIP switches ?
I hope that you can help even though it is not a converter you sell :-)
Regards from Denmark
Anders Kj?r


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Re:Cant connect to COM3 (RS485)
« Reply #1 on: April 20, 2004, 08:32:26 PM »
Much as we like our products to work with as many third party products as possible it is not practical for us to try to support every available converter on the market, especially when the question has to do with configuring the converter using DIP switches etc. Please refer to the manual of your converter and try to set it to the configuration as described below.

Basically, your converter must work on two wire, half-duplex mode RS485 and the transmitter in the RS485 driver must turnaround either automatically or controlled by the RTS signal of the RS232 interface.

The TRiLOGI program try to control the RS485 converter using the /RTS signal on the RS232 pin but since Windows is not very deterministic you can't really switch the converter at very precise moment. A wrong delay may cause a communication message to fail because the RS485 switches too quickly or too slowly.  So an auto-turnaround converter will work best.

Tel: 1-877-TRI-PLCS