M16C26A Datasheet, PDF (232/352 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/Tiny SERIES

M16C/26A Group (M16C/26A, M16C/26B, M16C/26T)
15. CRC Calculation Circuit
b15
(1) Setting 000016 (initial value)
b7
(2) Setting 0116
b15
118916
b0
CRD data register CRCD
[03BD16, 03BC16]
b0
CRC input register CRCIN
[03BE16]
2 cycles
After CRC calculation is complete
b0
CRD data register CRCD
[03BD16, 03BC16]
Stores CRC code
The code resulting from sending 0116 in LSB first mode is (10000 0000).This the CRC code in the generating polynomial,
(X¹⁶ + X¹² + X⁵ + 1), becomes the remainder resulting from dividing(1000 0000)X¹⁶ by ( 1 0001 0000 0010 0001) in
conformity with the modulo-2 operation.
LSB
1 0001 0000 0010 0001
1000 1000
1000 0000 0000 0000 0000 0000
1000 1000 0001 0000 1
1000 0001 0000 1000 0
1000 1000 0001 0000 1
1001 0001 1000 1000
LSB
MSB
MSB
Modulo-2 operation is
operation that complies
with the law given below.
0+0=0
0+1=1
1+0=1
1+1=0
-1 = 1
98
11
Thus the CRC code becomes ( 1001 0001 1000 1000). Since the operation is in LSB first mode, the (1001 0001 1000 1000)
corresponds to 118916 in hexadecimal notation. If the CRC operation in MSB first mode is necessary, set the CRC mode
selection bit to "1". CRC data register stores CRC code for MSB first mode.
(3) Setting 2316
b7
b15
0A4116
b0
CRC input register CRCIN
[03BE16]
After CRC calculation is complete
b0
CRD data register CRCD
[03BD16, 03BC16]
Stores CRC code
Figure 15.3. CRC Calculation
Rev. 2.00 Feb.15, 2007 page 215 of 329
REJ09B0202-0200