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CDU-541 CD-ROM DRIVE SCSI INTERFACE MANUAL
5. CD-ROM Devices
This section has five parts; a model of the CD-ROM, a command set used to
control the drive, a part detailing the implemented pages, a part listing the
additional sense codes, and a glossary.
5.1. CD-ROM Model
IMPLEMENTORS NOTE:
The model described is based on CD-ROM technology,
however the command set is designed to be usable by all read-only devices.
The model is provided as a means to understand the implementation of the
command set.
As such the model description does not impose any mandatory
requirements.
CD-ROM drives are designed to work with any disc that meets the Sony-Philips
"red-book" or "yellow-book" documents at the current revision level.
Most
drives will read CD-ROM data discs in mode one or mode two, digital audio
discs, and combined-mode discs (i.e. some tracks are audio, some tracks are
data) .
The CD-ROM disc has the same physical size and properties as the CD-AUDIO
disc.
The discs have two sizes, 120 millimeter diameter and 80 millimeter
diameter.
These correspond to 5-1/4 inch and 3-1/2 inch footprint drives.
The disc is single sided containing approximately 600 megabytes of data or
74
minutes of audio in the larger diameter.
The smaller diameter has a
capacity of 200 megabytes of data or 23 minutes of audio.
A disc may contain
both audio and data, a so called combined mode disc.
A disc contains from one to ninety-nine tracks.
Each change in the type of
information on the disc (audio or data) requires a change in track number.
A
-~-
disc containing both audio and data would have at least two tracks, one for
audio and one for data.
A track has a
m~n~mum
length of four seconds or 300 sectors.
The first
track number on a disc may be any track number from one to ninety-nine.
The
following track numbers, if any, are in contiguous and ascending order.
A transition area occurs between each track.
Seek operations can be
performed to the transition area.
However read or play operations cannot be
performed in the transition area.
The transition area is structured and the
logical addressing sequence continues to increment through the transition area.
There also exits a lead-in and a lead-out area on the disc.
This allows for
overshoot during seek operations.
These areas are outside of the user defined
area as reported in the READ CAPACITY data.
Each track can be subdivided by indexes.
Every track has at least index
one, and may have up to ninety-nine indexes.
The user information starts at
index one within a track.
The index numbers are contiguous and ascending.
5-1
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