Denso AT27Q-SB User Manual page 76

Example of analysis for packet received
Data received (hexadecimal)
10H 02h 00h 13h 00h 00h 31h 32h 33h 34h 35h 36h 37h 38h 0Dh C4h 18h 10h 03h
Header Number of
data bytes
(1) Compare data lengths.
Data length received in packet: 0013h = 19 bytes
Data received in packet: 19 bytes
(2) Compare CRCs.
1) Initialize CRC to 0.
2) Retrieve the first data byte (00h).
3) Shift the current CRC value one bit to the left. If the shift produces overflow, XOR the result with 1021h.
4) Shift the data byte one bit to the left. If the shift produces overflow, XOR the current CRC value with 0001h.
5) Repeat steps 3) and 4) a total of 8 times.
6) Retrieve the second data byte (13h).
7) Repeat steps 3) and 4) a total of 8 times.
8) Repeat this calculation through to the final byte.
9) Finally repeat the calculation for the two bytes (C4h 18h) in the CRC storage area, but reverse them first
because the 16-bit CRC is stored in little-endian order.
Data
--
00h
13h
00h
00h
31h
32h
33h
34h
35h
36h
37h
38h
0Dh
18h
C4h
(3) A result of 0000h indicates a successful transfer; a nonzero one, an error.
Container Spare
number
CRC
0000h
0000h
1300h
0013h
221Ah
8EF9h
58C0h
F554h
2054h
2181h
A3A0h
92A9h
0059h
C244h
1CE2h
0000h
Transfer data
CRC
63
Terminator