M30620FCAFP datasheet(181/615 Pages) RENESAS

181 / 615 page

Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

CRC

1-162

b15

(1) Setting 000016

CRC data register

CRCD

[03BD16, 03BC16]

b15

(2) Setting 0116

CRC input register

CRCIN

[03BE16]

2 cycles

After CRC calculation is complete

CRC data register

CRCD

[03BD16, 03BC16]

118916

Stores CRC code

b15

(3) Setting 2316

CRC input register

CRCIN

[03BE16]

After CRC calculation is complete

CRC data register

CRCD

[03BD16, 03BC16]

0A4116

Stores CRC code

The code resulting from sending 0116 in LSB first mode is (1000 0000). Thus 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.

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 in the CRC operation

circuit built in the M16C, switch between the LSB side and the MSB side of the input-holding bits, and carry out the CRC

operation. Also switch between the MSB and LSB of the result as stored in CRC data.

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

LSB

MSB

LSB

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

Figure 1.19.3. Calculation example using the CRC calculation circuit

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