M32CSLASH8B datasheet(291/406 Pages) RENESAS

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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 274 of 385

20. CRC Calculation

The CRC (Cyclic Redundancy Check) calculation detects an error in data blocks. A generator polynomial of CRC -

CCITT (X16 + X12 + X5 + 1) generates CRC code.

The CRC code is a 16-bit code generated for a given length of the data block in bytes. The CRC code is stored in the

CRCD register every time one-byte data is transferred to the CRCIN register after a default value is written to the

CRCD register. CRC code generation for one-byte data is completed in two bus clock cycles.

Figure 20.1 shows a block diagram of the CRC circuit. Figure 20.2 shows CRC-associated registers. Figure 20.3

shows an example of the CRC calculation.

Figure 20.1

CRC Calculation Block Diagram

Figure 20.2

CRCD Register, CRCIN Register

CRCD register

High-order bits of data bus

Low-order bits of data bus

8 low-order bits

8 high-order bits

CRC code generation circuit

X16 + X12 + X5 + 1

CRCIN register

b15

Symbol

CRCD

Address

037Dh - 037Ch

After Reset

Undefined

Function

After an initial value is written to the CRCD register, the CRC code

can be read from the CRCD register by writing data to the CRCIN

value is read as the CRC code.

0000h to FFFFh

CRC Data Register

Setting Range

b8 b7

Symbol

CRCIN

Adddress

037Eh

Function

Data input.

Inverse bit position of data

00h to FFh

CRC Input Register

Setting Range

After Reset

Undefined

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