基于RS485总线的BACnet MS/TP状态机实现

Design of BACnet MS/TP state machine based on RS485 bus

对主从/令牌传递协议(BACnet MS/TP)的工作流程和工作状态转换过程由浅入深地进行了描述。该协议属于BACnet数据链路层协议,运行于RS485总线之上。通过对协议工作状态转换的深入分析,给出了MS/TP状态机的实现方法。经验证表明,基于该状态机采用C语言设计的软件在总线设备数量为60个,RS485波特率为38.4 kbps的条件下,工作稳定。

The work process and work state transition of the master-slave / token passing protocol （BACnetMS/TP）were described developmentally in this paper. This protocol belongs to the BACnet data link layerprotocol, and runs on the RS485 bus. The realization method of MS/TP state machine was worked out throughanalyzing the work state transition of the protocol. After verification, a conclusion was obtained： the state machinedesigned using C language had a stable work performance under the condition of 60 bus devices and 38.4 kbps.