Transcription of Modbus Protocol Reference Guide - M-System
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1 Modbus Protocol Reference GuideEM-5650 Protocol Reference GuideContents1. Introduction .. 42. Modbus Protocol .. Description .. Message Framing .. 5 ASCII Framing .. 5 RTU Framing .. 5 Address Field .. 5 Function Field .. 5 Data Field .. 5 Error Checking Field .. 6 LRC Checking .. 6 CRC Checking .. Modbus Function Formats .. 7 Data Address .. 7 Coil .. 7 Input Status .. 7 Input Register .. 7 Holding Register .. Contents in Modbus Messages ..83. Modbus Function Codes .. Coil Status (01) .. Input Status (02) .. Holding Register (03) .. Input Register (04) .. Single Coil (05) .. Single Register (06) .. (08) .. Communication Event Counter (11, 0x0B) .. Communication Event Log (12, 0x0C) .. Force Multiple Coils (15, 0x0F) .. Multiple Registers (16, 0x10) .. Report Slave ID (17, 0x11) .. 202 Modbus Protocol Reference GuideEM-5650 Diagnostic Subfunctions (08) .. Query Data (00) .. Communications Option (01) .. Diagnostics Register (02).
Standard Code for Information Interchange) or RTU (Remote Terminal Unit). The mode must be the same for all devices on a Modbus network. In ASCII mode, each 8-bit byte in a message is sent as two ASCII characters. In RTU mode, each 8-bit byte in a message contains two 4-bit hexadecimal characters.
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