In order for me to help we will need:
1) Please provide a more detailed description of the problem and its history.
2) Details on the communications port or converter (brand name, part number etc.).
3) Screen shots of the following screens (Use Print Screen and Paste into a document such as a Word file):
Setup/Communications
Setup/Communications/Setup Modbus Adapters
Setup/Define Loops
Help/About/About Commander
4) Please supply the complete Model/Part number for the controls (P610x/Zxxxx/xxxx as marked on the controller housing)
5) Configuration Mode Parameters:
Communication Protocol (Prot)
Bit Rate (bAud)
Communications Address (Addr) (must be different on each control)
Communications Write Enable (CoEn)
6) Window operating system. XP, 7, 8?
The above parameters relate to the P6100 controller. If your control is an older N6100 series then Protocol will not be present and some of the other parameters have different parameter designations.