Example of frame in hexadecimal: 01 04 02 FF FF B8 80 (CRC-16-ANSI calculation from 01 to FF gives 80B8, which is transmitted least significant byte first). Polynomial: x 16 + x 15 + x 2 + 1 (CRC-16-ANSI also known as CRC-16-IBM, normal hexadecimal algebraic polynomial being 8005 and reversed A001). Modbus frame format (primarily used on 8-bit asynchronous lines like ) Name Length (bits) Function Start 28 At least 3 1⁄ 2 character times of silence (mark condition) Address 8 Station address Function 8 Indicates the function code e.g., read coils/holding registers Data n × 8 Data + length will be filled depending on the message type CRC 16 End 28 At least 3 1⁄ 2 character times of silence between frames Note about the.
All Modbus variants choose one of the following frame formats.
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