More than a master from the Modbus communication protocol of wireless communications Industrial control -

The scheme can be applied to more than 3 units of Siemens PLC controller S7 - Or S7-200 200 smart implementation more than a master from the Modbus communication protocol of wireless communications.

apply PLC controller models: S7 - And S7-200 200 smart

communication protocol: the Modbus - RTU

communication relationship: a main 8 from the communication distance:

5 km

communications, digital encryption wireless transmission:

wireless communication terminal DTD434MC Siemens PLC controller special wireless communication terminal

add

S7 - MODBUS library file 200 PLC Modbus communication, Siemens itself is not directly related instructions, so you need to provide Siemens STEP7 to add official Modbus library file. After add good library files will be shown below. It opens at

' Library 】 Will appear as shown in figure

open respectively associated with Modbus folder will appear as shown in figure can be directly call instructions

master station program host program we use time-sharing cycle collection way to read and write in turn eight from the station. Programming using millisecond timer 【 T32】 As a system of communication acquisition cycle. Our size parameters can be adjusted according to actual needs. If use GPRS communication way, out of respect for the traffic cost, need to adjust the communication cycle according to actual condition, in order to avoid unnecessary late fees. From standing program

from station program only need according to the main communication format set consistent, then from standing response command to normal communication. Eight from station communication program, in addition to the address is not the same, other parameters are the same, later period can be adjusted according to actual usage.

instruction calls description

' Modbus主Port0 ( v1。 2) 】 Communication port 0 as the Modbus master station used in instruction.

【 MBUS_MSG】 Communication port 0 Modbus master station instruction in reading and writing.

【 Modbus主端口1 ( v1。 2) 】 Communication port 1 used as Modbus master station instructions.

【 MBSU_CTRL_P1】 Communication port 1 Modbus master station initialization instructions.

【 MBUS_MSG_P1】 Communication port 1 Modbus master station instruction in reading and writing.

【 Modbus Slave Port0（ v1。 0) 】 Communication port 0 as the Modbus use instructions from the station.

【 MBUS_SLAVE】 Communication port 0 as the Modbus from standing response host, speaking, reading and writing instruction.

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