Calculation method of CRC check code for Modbus RTU

The CRC is calculated using only 8 data bits, starting bit and stop bit, if parity bit also includes parity bit , do not participate in CRC calculation.

The CRC is calculated by:

1. Load a 16-bit register with a value of 0XFFFF, which is the CRC register.

2, the first 8-bit binary data (that is, the first byte of the communication information frame) and the 16-bit CRC register is different or, the result is still stored in the CRC register.

3, the CRC register the contents of the right one bit, with 0 to fill the highest bit, and detect the shift out of the bit is 0 or 1.

4. If the move-out bit is zero, repeat the third step (move right one bit again), or if the 1,CRC register is different from the 0xa001.

5, repeat steps 3 and 4, until the right shift 8 times, so that the entire 8-bit data are all processed.

6, repeat steps 2 and 5, the processing of the next byte of the communication information frame.

7, the communication information frame all bytes according to the above steps, the resulting 16-bit CRC register high and low byte to Exchange

8, the final CRC register content is: CRC check Code

Calculation method of CRC check code for Modbus RTU