前 言 ............................................................................................................................................. 0 1 RS-485与RS-422性能指标及其标准 ......................................................................................... 0 2 RS-485与RS-422器件及材料说明 ............................................................................................. 1 3 RS-485与RS-422设计原理 ......................................................................................................... 1 3.1 基本原理 ..................................................................................................................... 1 3.1.1 RS-485与RS -232电路的区别与优势 ................................................................... 1 3.1.2 长短连接的判断标准、物理表现与应对措施 ..................................................... 3 3.1.3 RS-485与RS-422典型应用电路与选择方法 ..................................................... 4 3.1.4 485总线上处理竞争的方法 ............................................................................... 7 3.2 可靠性的设计 ............................................................................................................. 8 3.2.1 网络配置 ............................................................................................................. 8 3.2.2 总线匹配 ............................................................................................................. 8 3.2.3 引出线 ............................................................................................................... 10 3.2.4 失效保护 ........................................................................................................... 10 3.2.5 地线与接地 ....................................................................................................... 11 3.2.5.1 共模干扰问题 ...................................................................
