Modbus TCP学习笔记

1. 功能码列表：     

            0x01 读线圈状态（Read Coils）
            0x02 读离散输入状态（Read Discrete Inputs ）            
            0x03 读保持寄存器（Read Holding Registers ）                 
            0x04 读输入寄存器（Read Input Registers）            
            0x05 写单线圈（Write Single Coil ）            
            0x06 写单寄存器（Write Single Register）            
            0x07 读取异常状态（限串行线）（Read Exception Status (Serial Line only) ）        
            0x08 通信系统诊断（限串行线）（Diagnostics (Serial Line only) ）    
            0x09-0x0A无    
            0x0B 获取串行通信事件计数器（Get Comm Event Counter (Serial Line only) ）    
            0x0C 获取串行通信事件日志 （ Get Comm Event Log (Serial Line only) ）    
            0x0D-0x0E无    
            0x0F 写多个线圈（Write Multiple Coils）    
            0x10 写多个寄存器（Write Multiple registers）    
            0x11 报告服务器ID（仅串行线）（Report Server ID (Serial Line only) ）    
            0x12-0x13无    
            0x14 读文件记录（Read File Record ）    
            0x15 写文件记录（Write File Record）    
            0x16 带屏蔽字写入寄存器（Mask Write Register ）    
            0x17 读/写多个寄存器（Read/Write Multiple registers）    
            0x18 读取先进先出（FIFO）队列（Read FIFO Queue）    
            0x19-0x2A无        
            0x2B 封装接口传输（Encapsulated Interface Transport .）

2. 分主站，从站，主站是客户端，从站是服务端。启动时先启动从站（服务端），然后主站再连上从站，获取信息。

3. Device and Modbus 地址表（最大地址看设备）

Device address	Modbus address	Description	Function	R/W	Comments
1...10000	address-1	Coils(outputs)	01	Read/Write	05 and 15
10001...20000	address-10001	Discrete Inputs	02	Read
40001...50000	address-40001	Holding Registers	03	Read/Write	06,16,22 and 23
30001...40000	address-30001	Input Registers	04	Read