Filter
Top Products
1-4
1.5:
CRC
(Error
Checksum)
Algorithm
Q
The Cyclic Redundancy Check (CRC) field is an error checksum calculation that enables a Slave
device to determine if a request packet has been corrupted during transmission.
Q
Every request packet transmitted from Master to Slave includes a special 16-bit value derived from a
CRC-16 algorithm performed on the packet’s contents. When an EPM Slave receives a packet, it
performs a CRC-16 calculation and compares the value with the one included in the request packet.
If the two values do not match, the Slave will ignore the packet.
Q
The following is the pseudocode for calculating the 16-bit CRC:
Initialize a 16-bit register to FFFFH.
Initialize the generator polynomial to A001H.
Slave Address 01H Slave Address 01H
Function Code 10H Function Code 10H
Data Starting Address-Hi E0H Data Starting Address-Hi E0H
Data Starting Address-Lo 01H Data Starting Address-Lo 01H
Number of Setpoints-Hi 00H Number of Setpoints-Hi 00H
Number of Setpoints-Lo 03H Number of Setpoints-Lo 03H
Byte Count 06H CRC-Lo E6H
Data #1-Hi 00H CRC-Hi 08H
Data #1-Lo 01H
Data #2-Lo 00H
Data #2-Hi 01H
Data #3-Lo 00H
Data #3-Hi 01H
CRC-Lo 4DH
CRC-Hi 46H
Master Packet Slave Packet
Table 1.4: Function Code 10 Example