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Protocol & FramingModbus Term

CRC-16

A 2-byte cyclic redundancy check appended to every Modbus RTU frame.

Definition

CRC-16 (Cyclic Redundancy Check, 16-bit) is the error-detection method used in Modbus RTU. The transmitter computes a 2-byte checksum over the entire frame (slave address + PDU) and appends it in little-endian order. The receiver recalculates the CRC over the received bytes and compares it to the appended value — a mismatch means the frame is silently discarded. The Modbus CRC uses the polynomial 0xA001 (reflected CRC-16).

Quick Facts

Size2 bytes
Byte orderLow byte first (little-endian)
Polynomial0xA001 (reflected)
On mismatchFrame silently discarded

Related Terms

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ModPackQT Modbus Glossary · Updated 2026