《MODBUS application protocol specification》.pdf
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MODBUS Application Protocol Specification MODBUS.ORG
Content 1 Introduction 2
1.1 Scope of this document 2
1.2 References 2
2 Abbreviations 3
3 Context 3
4 General description 5
4.1 Protocol description 5
4.2 Data Encoding 7
4.3 MODBUS data model 7
4.4 Define MODBUS Transaction 9
5 Function Code Categories 11
5.1 Public Function Code Definition 12
6 Function codes descripitons 12
6.1 01 (0x01) Read Coils 12
6.2 02 (0x02) Read Discrete Inputs14
6.3 03 (0x03) Read Holding Registers 17
6.4 04 (0x04) Read Input Registers 18
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