SH7261 datasheet(1027/1348 Pages) RENESAS

1027 / 1348 page

Section 21 CD-ROM Decoder (ROM-DEC)

Rev. 2.00 Sep. 07, 2007 Page 995 of 1312

REJ09B0320-0200

Figure 21.7 shows a case of input stream data that has no padding (H'12345678). The upper and

lower 16 bits of data are swapped (H'56781234) for input to the CD-ROM decoder.

H'1234

H'1234 is input first.

H'5678 is input next.

H'5678

Core of CD-ROM decoder

BUFEND1[1:0] = 01

BYTEND = 0

H'1234

BUFEND0[1:0] = 10

H'5678

H'1234

H'5678

STRMDIN0, STRMDIN1

STRMDIN2, STRMDIN3

Figure 21.7 Example of Non-Padded Stream Data Control by the SSI Register

21.4.2

Sync Code Maintenance Function

Each sector of CD-ROM data consists of 2352 bytes starting with

H'00FFFFFFFFFFFFFFFFFFFF00 (sync code). However, a scratch on the disc or some other

factor might lead to erroneous recognition of the sync code sequence at the wrong time.

Conversely, a sync code might not be detected at a point where it should be detected. As a solution

to these problems, the CD-ROM decoder of this LSI has a sync-code maintenance function, which

operates to ignore sync codes detected at abnormal times and maintain the appearance of the sync

code at the expected times when it is not actually detected on the disc.

The operating modes of the sync-code maintenance function are listed below. For details on the

settings, refer to section 21.3.2, Sync Code-Based Synchronization Control Register (CROMSY0),

and table 21.2.

• Automatic sync maintenance mode

• External sync mode

• Interpolated sync mode

• Interpolated sync plus external sync mode

SH7261 Datasheet(PDF) 1027 Page - Renesas Technology Corp