S7-1200 Modbus-TCP 通讯配置向导说明
https://zhuanlan.zhihu.com/p/133828790
S7-1200PLC与上位机ModbusTCP通信
https://www.cnblogs.com/xiketang/p/13540698.html
s7-1200DB块地址和ModbusRTU地址是怎么对应的
https://www.zhaoplc.com/plc165659.html
西门子官方 Modbus TCP V4.0指令
https://www.ad.siemens.com.cn/productportal/Prods/S7-1200_PLC_EASY_PLUS/SmartSMS/1002.html