Case 369

[James]

Question:
The RMS-HCD Modbus RTU communication is not clear. It explains the ordering of the bytes for the Checksum (LSB, MSB in the CRC).

Possible Root Cause:

1. No example of the order of the bytes for the Checksum.

Solution:
Hex format: 01 04 00 00 00 04 f1 c9

1. 01 device address
2. 04 command id
3. 00 not used
4. 00 start address, init16
5. 00 not used
6. 04 number of data = 4, init 16
7. f1 > CRC 16bit Modbus (LSB)
8. c9 > CRC 16 bit Modbus (MSB)

Additional Information:
The PCD includes this example with the LSB, MSB in the CRC. It explains the ordering of the bytes for the Checksum.
https://service.rotronic.com/manual/modbus2.html.