Protocols

Difference between SNP, SNPX and Modbus Protocol

SNP and SNPX are GE protocols. SNPX is a stripped-down version of SNP that is not supported on the Rx3i and Rx7i platforms. Modbus is a more universally supported protocol. When devices from two different manufacturers need to communicate with each other, Modbus is quite often the protocol they both support.

Just to elaborate on Steve's accurate answer.

The main differences in SNPx over SNP are:
1. In SNP when the master connects to a slave they use a "null" character which many telephone modems use to initiate a modem command. (SNPx eliminates this.)
2. In SNP Every time the master sends a message to a slave it must [Connect]-[Send]/[Receive]-[Disconnect]. This is not very efficient.
SNPx [Connects]and stays connected until the master loses connection or is told to [Disconnect].

For Modbus details go here: http://modbus.org/