Internet PLC Forum

I used the RS232 cable I bought from TRIPLC. I run the utility provided with the software and set up the COMM1 port parameters- 9600,N,8,1. The PC COM port is set with identical values - 9600,N,8,1.  The switchws SW1-4 are set to "ON". When I send "IR*" or any other string or even just a <CR>, the utility software times out. "No response from PLC". So I did some hardware debug. The Tx line from the PC shows -10V to +12V signals when the cable is not connected to the PLC COMM1. (the data is "05 Hex [ENQ]"). When the cable is connected to  the COMM1, there is no signal. The manual says the COMM1 is configured as a DCE, and the cable is a straight 1:1 cable. Writing the PLC program and simulating it was the easy part.