18. CRC Calculation Circuit
puorG92/C61M
page 315
854fo7002,03.raM21.1.veR
2110-1010B90JER
Figure 18.3. CRC Calculation
(1) Setting 0000
16
(initial value)
b15 b0
1 0001 0000 0010 0001
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
1000 1000
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
The code resulting from sending 01
16
in LSB first mode is (10000 0000).This the CRC code in the generating polynomial,
(X
16
+ X
12
+ X
5
+ 1), becomes the remainder resulting from dividing (1000 0000)X
16
by ( 1 0001 0000 0010 0001) in
conformity with the modulo-2 operation.
(2) Setting 01
16
b0b7
b15
b0
1189
16
2 cycles
After CRC calculation is complete
Thus the CRC code becomes ( 1001 0001 1000 1000). Since the operation is in LSB first mode, the (1001 0001 1000 1000)
corresponds to 1189
16
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.
CRD data register CRCD
[03BD
16
, 03BC
16
]
CRC input register CRCIN
[03BE
16
]
CRD data register CRCD
[03BD
16
, 03BC
16
]
CRC input register CRCIN
[03BE
16
]
(3) Setting 23
16
b0b7
b15 b0
0A41
16
After CRC calculation is complete
CRD data register CRCD
[03BD
16
, 03BC
16
]
98 11
MSB
LSB
LSB
Stores CRC code
Stores CRC code
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