Abstract: Communication protocol software is employed to perform communication among devices,systems and diffe-rent parts of them to exchange data and share information in automation projects．Its reliability and scalability would significantly affect the quality and implementation of the projects．In this paper the data and operations in the communication protocol software are explored and then divided according to the function stage．By introducing the transaction concept,some principles for the communication protocol software are suggested,which help enhance the independence of the communication protocol software,thus improve its reliability and scalability,and as a result contribute to the quality and implementation of automation projects.

Key words: Communication protocol software,Independence,Transaction