Design of multi-host communication protocol module of RS485 based on class token ring

In view of problems of bad real-time performances, no plug-and-play function and low communication efficiency existed in poll calling mode of main control computer for communication nodes used by RS485 bus of current coal mine safety monitoring and control system, a multi-host communication protocol module of RS485 based on class token ring was designed. Token information is included in frame head of each frame, it is frame end mark in 4 byte time of RS485 bus idle state, it is snatching sending time of key devices in 4~5 byte time of RS485 bus idle state, and it is snatching sending time of common devices in 5~6 byte time of RS485 bus idle state. Communication modes exchange data with main control computer by turns according to token order under normal condition. While one device needs snatch to send data under emergency condition, it can snatch RS485 bus in snatching sending time. Test analysis shows that the module has good application effect under conditions that RS485 bus has little capacity and channel interference.