Modbus RTU
- Input
- CRC-16/MODBUS hex: 01 03 00 00 00 0A
- Expected output
- CDC5
On the wire: 01 03 00 00 00 0A C5 CD.
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crc16 calculator modbus ccitt
The tool opens in "hex bytes" mode with the Modbus RTU frame 01 03 00 00 00 0A and the CRC-16/MODBUS model. Switch the model in the CRC selector to see how the other four popular CRC-16 variants handle the same frame.
On the wire: 01 03 00 00 00 0A C5 CD.
Initial 0xFFFF, no reflection.
Initial zero, no reflection.
Reflected, with final XOR 0xFFFF.
The "true CCITT": reflected 0x1021, initial zero.
On the wire: 01 03 00 00 00 01 84 0A, the classic one-register read example.
Yes. Text, files and HMAC secrets are processed directly in the browser without any upload.
Least significant byte first. For the CRC 0xCDC5, the wire carries C5 and then CD. The tool parameter panel shows the bytes in both orders.
They share the polynomial, 0x1021, but differ in the initial value (0xFFFF versus 0), so they give different results. Check the initial value in your device documentation.
You can. With Modbus and the CRC at the end (low byte first), an intact frame yields 0000. Any other value points to a transmission error or the wrong variant.
-Text, files and secrets are processed locally. Nothing is sent to the server.