HB28D032MM2 datasheet(76/90 Pages) RENESAS

76 / 90 page

HB28H016/D032/B064/B128MM2

Rev.5.0, Jan. 2003, page 74 of 88

Cyclic Redundancy Check (CRC)

The CRC is intended for protecting MultiMediaCard commands, responses and data transfer against

transmission errors on the MultiMediaCard bus. One CRC is generated for every command and checked

for every response on the CMD line. For data blocks one CRC per transferred block is generated. The

CRC is generated and checked as described in the following.

• CRC7

The CRC7 check is used for all commands, for all responses except type R3, and for the CSD and CID

registers. The CRC7 is a 7-bit value and is computed as follows:

generator polynomial: G(x) = x

7 + x3 + 1

M(x) = (first bit) * x

n + (second bit) * xn-1 +...+ (last bit) * x0

CRC[6...0] = Remainder [(M(x) * x

7)/G(x)]

All CRC registers are initialized to zero. The first bit is the most left bit of the corresponding bitstring (of

the command, response, CID or CSD). The degree n of the polynomial is the number of CRC protected

bits decreased by one. The number of bits to be protected is 40 for commands and responses (n = 39), and

120 for the CSD and CID (n = 119).

• CRC16

The CRC16 is used for payload protection in block transfer mode. The CRC check sum is a 16-bit value

and is computed as follows:

generator polynomial: G(x) = x

16 + x12 +x5 + 1,

M(x) = (first bit) * x

n + (second bit) * xn-1 +...+ (last bit) * x0

CRC[15...0] = Remainder [(M(x) * x

16) / G(x)]

All CRC registers are initialized to zero. The first bit is the first data bit of the corresponding block. The

degree n of the polynomial denotes the number of bits of the data block decreased by one (e.g. n = 4095 for

a block length of 512 bytes). The generator polynomial G(x) is a standard CCITT polynomial. The code

has a minimal distance d=4 and is used for a payload length of up to 2048 Bytes (n <= 16383).

HB28D032MM2 Datasheet(PDF) 76 Page - Renesas Technology Corp