M32CSLASH8B datasheet(292/406 Pages) RENESAS

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Under development

M32C/8B Group

20. CRC Calculation

Preliminary specification

Specifications in this manual are tentative and subject to change.

REJ09B0450-0050 Rev.0.50 Oct 31, 2008

Page 275 of 385

Figure 20.3

CRC Calculation

CRC Calculation for M32C

CRC Calculation and Setup Procedure to Generate CRC Code for 80C4h

CRC code: a remainder of division,

Generator polynomial: X16 + X12 + X5 + 1 (1 0001 0000 0010 0001b)

CRCD register

Setting Steps

(1) Invert a bit position of 80C4h per byte by a program

80h

01h, C4h

23h

(2) Set 0000h (default value)

CRCIN register

(3) Set 01h

Bit position of the CRC code for 80h (9188h)

is inverted to 1189h, which is stored into the

CRCD register in the 3rd cycle.

(4) Set 23h

CRCD register

CRCIN register

Bit position of the CRC code for 80C4h

(8250h) is inverted to 0A41h, which is stored

into the CRCD register in the 3rd cycle.

CRCD register

Details of CRC Calculation

As shown in (3) above, bit position of 01h (00000001b) written to the CRCIN register is inverted to 10000000b.

Add 1000 0000 0000 0000 0000 0000b, as 10000000b plus 16 digits, to 0000h as the initial value of the CRCD

1 0001 0000 0010 0001 1000 0000 0000 0000 0000 0000

0001 0001 1000 1001b (1189h), the remainder 1001 0001 1000 1000b (9188h) with inversed bit position, can be

read from the CRCD register.

When going on to (4) above, 23h (00100011b) written in the CRCIN register is inverted to 11000100b.

Add 1100 0100 0000 0000 0000 0000b plus 16 digits, to 1001 0001 1000 1000b as a remainder of (3) left in the

CRCD register to perform the modulo-2 division.

0000 1010 0100 0001b (0A41h), the remainder with inverted bit position, can be read from CRCD register.

1189h

0A41h

Generator

polynomial

1000 1000

Data

1000 1000 0001 0000 1

1000 0001 0000 1000 0

1001 0001 1000 1000

Modulo-2 Arithmetic is

calculated on the law below

0 + 0 = 0

0 + 1 = 1

1 + 0 = 1

1 + 1 = 0

-1 = 1

1000 1000 0001 0000 1

CRC code

b15

value of the CRCIN register with inversed bit position

Generator polynomial

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