Modbus CRC Calculator
Online tool to calculate Modbus CRC16 checksums and generate RTU frames.
How Modbus CRC16 Works
Modbus RTU uses a Cyclic Redundancy Check (CRC) to ensure data integrity. The checksum is 2 bytes (16 bits) added to the end of the message. Unlike most data in Modbus which is Big Endian, the CRC is sent Low Byte First (Little Endian).
Example: For the command 01 03 00 00 00 02, the CRC calculation results in C4 0B. The final frame sent to the wire is 01 03 00 00 00 02 C4 0B.
Common Function Codes
| Code | Name | Description |
|---|---|---|
| 01 | Read Coils | Read digital outputs (0x) |
| 02 | Read Discrete Inputs | Read digital inputs (1x) |
| 03 | Read Holding Registers | Read analog outputs/parameters (4x) |
| 04 | Read Input Registers | Read analog inputs (3x) |
| 06 | Write Single Register | Change one value (4x) |
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