Hello,
   I'm trying to get a modbus connection between my PLC (DL205 w/ D2-250 CPU) and Mach4.  I've got a cable made and it's tested good.  I've got the PLC's port 2 setup for modbus.  In the Mach modbus configuration I keep getting "timeout" responses from the PLC. 

   Art mentioned having to have a special program running on the PLC to setup modbus addresses for IO points.  I need help, I'm so out of ideas...  Thanks.

The error that Art had in his DL05 was that he didn't have an (END) rung at the end of the program...

I know that there is supposed to be an end rung at the end of a program.  Does there HAVE to be a program loaded on the PLC to simply connect to it via modbus?

   More specificly, does there have to be program that enables modbus communications and configures the IO points to modbus addresses (beyond simply configuring port 2 for modbus)?

If so, am I supposed to use RX and WX read/write from network instructions in this program?

Art doesn't know about this stuff, and PLC guys don't know about Mach, and there is SQUAT for documentation.  I have to get this running.  I appreciate your help in pointing me in the right direction.

I think the best thing that I can do for you is post an example program. The program will send a16bit register that represents 16points of I/O. and to do this in Directsoft you do the following command (B2000.0)| |-------------(OUTY0) The B2000 is register V2000 and the .0 is saying close this contact if bit 0 is a one. The same thing is done on the input (X0)| |-------------------------------(OUT B2100.0) this will turn bit 0 in register V2100 to a 1 and Mach3 will read this as the switch is on....

This should get you on the right page and I will give you a program that I use on the DL06

The mod bus config page should be set up like the Pic