On the ECOM 100, when your setting it up, put your module as 192.168.0.2, and put your gateway as 192.168.0.1 (this is what you assign your Ether card too in your PC, also in your PC, got to advanced, WINS and enable NetBios over TCP. Assign a 1 to your ECOM module, and set your TCP modbus setup to 192.168.0.2, and device #1. (subnet mask on both is obvioulsy 255.255.255.0).
One other issue that will save you some hair pulling...... the "Bit of Word" in Brians no-worky...... So you will have to shuffle one entire word per discrete bit, Use the Bit of Word functions in your PLC i.e. B1200.0, B1201.0 etc.1 for stuff comming in from Mach3, and B1400.0 and B1401.0 etc. In the TCP modbus make both your input and outputs to be holding registers.
NOTE: if you use an Analog module, DON't use the lower ranges, use something like the V6000 range, the 1200's in the analog get into the counters and it stops your ana module from working............
scott