Checksum (Crc16) - ECOLAB Versatronic Modbus Beschreibung

Modbus protocol description
3.7

Checksum (CRC16)

Calculation principle
Transmission errors are detected with the aid of the checksum (CRC16). If an error is
detected during evaluation, the device concerned does not respond.
CRC = 0xFFFF
while (not all BytesOfMessage processed);
NOTICE!
The low byte of the checksum is transmitted first!
Example:
The CRC16 checksum CC DD is transmitted and represented in the
sequence DD CC.
Example
Query the binary value of the wash timer 1 at address 0x14E5:
Instruction: Read one word from address 0x14E5
01
Slave
Response (CRC16 = 0x8479)
01
Slave
Word 1 = 1 means that the binary value of wash timer 1 = 1.
417102397 Rev. 1-10.2019
CRC = CRC XOR ByteOfMessage
For (1 to 8)
03 14 E5
Function Adresse
03 02
Function Number of bytes
24
CRC = SHR(CRC)
if (flag shifted to the right = 1)
then CRC = CRC XOR
0xA001
00 01
Read one word
00 01
Word 1
else
90 0D
CRC
79 84
CRC