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....................................................................................................................9
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................................................................................................15
4.3 上位机通信软件的设计................................................................................................16
4.3.1 通信协议设计..........................................................................................................17
4.3.2 多机传输..................................................................................................................18
4.3.3 差错控制..................................................................................................................19
