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~DU-5ql
CD-ROM DRIVE SCSI INTERFACE MANUAL
5.5.
C"D-ROM Glossary
CD-ROM - Compact Disc Read Only Memory The CD-ROM was developed by
N.V. Philips
&
Sony Corporation.
The 'RED BOOK' and 'YELLOW BOOK'
documents describe the medium.
Sub-Channel - The signal from the compact disc consists of a main channel and
a sub-channel.
The sub-channel is divided into three parts.
The P sub-
channel is part one and is used with CD-Audio.
The Q sub-channel is part
three and contains useful information. such as the control field and MSF
address.
-The R. S.T,U, V and W sub-channels collectively are treated as
part three.
Control Field - Four bits in the Q sub-channel data that indicate whether the
track is CD-ROM or CD-Audio.
If the track is CD-Audio then three bits are
used to indicate use of
pre~emphasis,
copy protection, and whether the
audio is two or four channel.
TNO - Track Number.
A disc has logical segments
track numbers range from one to ninety-nine.
always of the same type.
A track can contain
data.
A disc can start at any track number.
which are called tracks. The
The data within a track is
either CD-ROM or CD-Audio
TOe - The Table Of Contents has information on the
t~~e
of each track and the
starting address of the user data in a tracks.
This information is encoded
in the Sub-Q channel during tne lead-in area of the compact disc.
MSF Address - The address on the disc in minutes, seconds and frame number.
All three must be specified to determine a physical location on the disc .
Absolute MSF Address
- The address encoded in the sub-channel (and header of
CD-ROM) which is the elapsed time from the start of disc.
Relative MSF Address
The address encoded in the sub-channel which is the
elapsed time from the start of a track.
Frame - One frame is equal to
1/75
second of elapsed time.
Block - A block commonly refers to the data contained in one frame.
However
there are other meanings attached to this term within the world of compact
disc.
Hold Track State - When the drive enters the hold track state the optical
pick-up of jumps one track towards the inside of the disc at the specified
Sub-Q address.
The optical pick-up traces the groove of the disc until
detecting the address and again jumps one track towards the inside of the
disc.
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END OF DOCUMENT
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CDSCSI.WS6
5-79
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