CHAPTER 25:Programmable CRC
S6J3200 Series Hardware Manual Document Number: 002-04852 Rev. *G
965
3.3.
CRC Calculation Example
Consider the following values for calculating 8-bit CRC checksum value.
Input data = 0x0F (Hex)
Seed = 0xFF (Hex)
Final XOR = 0x00 (Hex)
The coefficients of the polynomial are arranged in .
Table 3-4 Coefficients of the Polynomial
x8
x7
x6
x5
x4
x3
x2
x1
x0
1
0
0
0
0
0
1
1
1
The highest order coefficient x8 provides the degree of the CRC polynomial and the checksum length,
respectively. It must not be set to "1" while configuring CRCn_POLY register, instead CRCn_CFG:LEN
should be configured (here it is CRCn_CFG:LEN = 8). Therefore, the value of the polynomial that is
written to CRCn_POLY register in accordance with above coefficients is 0x07 (Hex).
The input/output bit reflection is disabled in this example.
The Programmable CRC registers should be configured as follows for the given values:
The CRC configuration register is configured by considering 8-bit input data size and 8-bit
polynomial/checksum length as follows.
CRCn_CFG = 0x00080000 (Hex)
CRCn_POLY = 0x00000007 (Hex)
CRCn_SEED = 0x000000FF (Hex)
CRCn_FXOR = 0x00000000 (Hex)
CRCn_WR = 0x0000000F (Hex)
The final result of CRC checksum calculation is 0xDE (Hex), which gets available after 10 clock cycles
(once CRCn_WR is written) in the CRCn_RD register.
If another input data is given to the CRC module, then "preliminary checksum #1" (0xDE) is used as the
initial seed value.
If the new CRC calculation should start from the seed value instead of from the last CRC result, then the
CRCn_SEED register needs to be re-written (even if it is the same seed value as before).
Polynomial
8
2
1
+
+
+
=
Содержание S6J3200 Series
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