Example Calculation of The Fletcher Checksum
As an example, the checksum shall be calculated and verified for a byte stream of 0x01 0x02.
- C0_initial = 0
- C1_initial = 0
| Byte | C0 = C0prev + B | C1 = C1prev + C0 |
|---|---|---|
| 0x01 | 0x01 | 0x01 |
| 0x02 | 0x03 | 0x04 |
| −(C0 + C1) = 0xF9 | 0x03 + 0xF9 = 0xFC | 0x04 + 0xFC = 0x00 |
| −(C0 + C1) = 0x04 | 0xFC + 0x04 = 0x00 | 0x00 + 0x00 = 0x00 |
The checksum bytes are 0xF9 0x04. The transmitted byte stream is 0x01 0x02 0xF9 0x04. The receiver runs the checksum on all four bytes and calculates a passing checksum of 0x00 0x00.
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