Sony CDU-541 - Page 24

CDU-541 CD-ROM DRIVE SCSI INTERFACE MANUAL
Each disc has a table of contents (TOC). The TOe contains information on
the number of tracks on a disc, and the starting location of the user
information within the track. The starting location is given in MSF or LBA
address format. The TOe also indicates which tracks are audio and which
tracks are data. Note though, that the TOC does not contain information to
distinguish between CD-ROM Mode one and CD-ROM Mode two data.
The recovery of the TOC data is necessary before a drive is ready and data
can be read from the disc. The TOC data is written several times in the area
set up for TOC data. The exact number of repetitions depends on the number of
tracks on a disc.
The drive attempts to recover the TOC as soon as a caddy is successfully
loaded. The time maximum time to recover a TOC that is read without error is
approximately five seconds. The repeated TOC data can be up to two minutes
long.
A frame has 588 bits. A frame must be EFM decoded by the drive before the
bit stream contains recognizable data. Fourteen bits are used to represent
each eight-bit byte. Three merging bits are added to each fourteen bits.
A block contains 98 frames.
FRAME BYTES
============================
1 (24 +
3)
Synchronization
1 (14
+ 3)
Sub-Channels
24 (14
+
3)
Data Symbols
8
(14 +
3)
CIRC Symbols
-----------
---------------
588 bits total
============================
=-) 1 eight-bit sub-channel P,Q,R,S,T,U,V,W
--) 24 eight-bit bytes of data
Cross Interleaved Reed Solomon Code
The
sub-channel byte is assigned one bit for each sub-channel. One byte
contains a bit for sub-channels P,Q.R,S,T,U,V,W. Sub-channel P is used for
audio muting control. Sub-channels R,S,T,U,V,W are not used in CD-ROM. Sub-
channel Q contains the following:
2 bits Sync
4 bits Control
4 bits ADR
72 bits Sub-channel Q data (9 bytes)
16 bits CRC
98 bits total (one bit from the sub-channel byte of each frame in a block).
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