I am currently working with a customer who has a need to interface an Omron CJ1 PLC with existing building networks. The networks this customer requires communication with are BACnet MS/TP, BACnet/IP, and LONworks. I am still very new to the interfacing of building networks so I would like some help with getting more information on the protocol structure and checksum for BACnet MS/TP. I am primarily concerned with the checksum that is used for this network. The Omron PLC will be incorporated as a slave into the existing buidling network and will share minimal amounts of I/O data. I am already familiar with the ability to use Omron's protocol macro feature to enable an exchange of serial data. Since BACnet MS/TP is an RS-485 network, I would like to discover if Omron's protocol macro supports the same checksum used within BACnet MS/TP. I don't need help with the creation of the protocl macro, but I do need help to find the checksum for BACnet MS/TP. I've already spent much time researching with BACnet.org. Does anyone have this information easily available? Thanks!!