M32CSLASH86 datasheet(281/505 Pages) RENESAS

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Page 258

20. CRC Calculation

)

(

CRC Calculation and Setup Procedure to Generate CRC Code for "80C416"

CRC Code : a remainder of a division,

(1) Inverse a bit position of "80C416" per byte by program

(2) Set "000016" (default value)

CRCD register

CRCIN register

Generator Polynomial : X

+ X

+ 1 (1 0001 0000 0010 00012)

value of the CRCIN register with inversed bit position

generator polynomial

CRC Calculation for M32C

Setting Steps

Details of CRC Calculation

(3) Set "0116"

"8016"

"0116", "C416""2316"

Bit position of the CRC code for "8016"

(918816) is inversed to "118916", which is

stored into the CRCD register in 3rd cycle.

CRCD register

Generator Polynomial

data

0 + 0 = 0

0 + 1 = 1

1 + 0 = 1

1 + 1 = 0

- 1 = 1

CRCIN register

(4) Set "2316"

CRC Code

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

Bit position of the CRC code for "80C416"

(825016) is inversed to "0A4116", which is

stored into the CRCD register in 3rd cycle.

As shown in (3) above, bit position of "0116" (000000012) written to the CRCIN register is inversed and becomes

"100000002".

Add "1000 0000 0000 0000 0000 00002", as "100000002" plus 16 digits, to "000016" as the default value of the

CRCD register to perform the modulo-2 division.

"0001 0001 1000 10012 (118916)", the remainder "1001 0001 1000 10002 (918816)" with inversed bit position, can

be read from the CRCD register.

When going on to (4) above, "2316 (001000112)" written in the CRCIN register is inversed and becomes

"110001002".

Add "1100 0100 0000 0000 0000 00002", as "110001002" plus 16 digits, to "1001 0001 1000 10002" as a

remainder of (3) left in the CRCD register to perform the modulo-2 division.

"0000 1010 0100 00012 (0A4116)", the remainder with inversed bit position, can be read from CRCD register.

Modulo-2 Arithmetic is

calculated on the law below.

b15

118916

b15

0A4116

Figure 20.3 CRC Calculation

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