目录
摘要 ............................................................................................................................................I
Abstract ....................................................................................................................................II
第一章 绪论..............................................................................................................................1
1.1 研究背景及意义.........................................................................................................1
1.2 RS485 总线通信系统研究现状..................................................................................2
第二章 RS485 介绍...................................................................................................................4
2.1 RS485 标准..................................................................................................................4
2.2 MAX485 芯片介绍........................................................................................................4
2.3 RS485 总线组网方式..................................................................................................5
2.4 RS485 方式构成的多机通信原理..............................................................................5
第三章 系统协议及硬件设计..................................................................................................7
3.1 RS485 通信协议设计..................................................................................................7
3.1.1 物理层设计......................................................................................................7
3.1.2 数据链路层设计..............................................................................................8
3.1.3 应用层设计......................................................................................................8
3.1.4 通信协议..........................................................................................................8
3.2 系统硬件设计...........................................................................................................10
3.2.1 PC 与 RS485 总线的接口...............................................................................10
3.2.2 RS485 方式构成的多机通信.........................................................................10
3.2.3 单片机与 PC 机串行通信系统构成..............................................................11
第四章 系统的软件实现........................................................................................................12
4.1 上下位机的关系.......................................................................................................13
4.2 下位机通信软件的设计...........................................................................................14
4.3 上位机通信软件的设计...........................................................................................16
4.3.1 通信协议设计................................................................................................16
4.3.2 多机传输........................................................................................................17
4.3.3 差错控制........................................................................................................18