Hey Fernando,
I spoke with them also and they use ASCII commands, over serial 422 (485 will work too).
You can do the Translation in a PLC, I use ADC, in the ADC docs it give you the Hex equivelent of the ASCII characters, and it has built in "Converter Boxs" as well. Thus you can send the code you want from Mach from within a button or react to some data automatically, via brains and/or macro pump, as well as display the data. ALOT of the Translation that is Automatic will have to Live in the Macropump where you can have your VB code do the translation for dynamic stuff, like info from the control, or dynamic out to control.
Direct Serial: Mach can write OUT to direct serial, but not read in from my understanding, you will have to ask others about how to write to a serial port. I think "Graham" has done a lot of this, and would be a good resource.
Plug-IN: A plug-in can be done as well, that would do the Translations as discussed above, the advantage here would be the gain in speed, and you would not have to deal with the MacroPump!!
Scott