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CDU-541 CD-ROM DRIVE SCSI INTERFACE MANUAL
The Sub-channel
Q
data contains the following:
4 bits Reserved
4 bits Control Field
8 bits Track Number Field in bcd format
8 bits Index Number Field in bcd format
8 bits Relative Minute Field in bcd format
8 bits Relative Second Field in bcd format
8 bits Relative Frame Field in bcd format
8 bits Absolute Minute Field in bcd format
8 bits Absolute Second Field in bcd format
8 bits Absolute Frame Field in bcd format
72 bits total sub-channel
Q
data
The data symbols make up the block of data that is returned to the user
during a read operation.
A block of data is made up of 98 frames, so there
are (98 x 24) 2352 bytes of data in a block.
A block of data contains the
following if the CD-ROM Mode field has a value of one:
12 bytes Synchronization
4 bytes CD-ROM data header
Absolute Minute Field in bcd format
Absolute Second Field in bcd format
Absolute Frame Field in bcd format
CD-ROM Mode Field
2048 bytes user defined data
-
4 bytes Error Detection Code
8 bytes zero
276 bytes Layered Error Correction Code
A block of data contains the following if the CD-ROM Mode field has a value
of two:
12 bytes Synchronization
4 bytes CD-ROM data header
Absolute Minute Field in bcd format
Absolute Second Field in bcd format
Absolute Frame Field in bcd format
CD-ROM Mode Field
2336 bytes user defined data
NOTE:
Many drives are capable of returning CD-ROM Mode one data in a
00-
ROM Mode two format.
This allows the user to investigate the error
detection and error correction codes.
However if the data is encoded as
CD-ROM Mode two it cannot be read as CD-ROM mode one data.
The address in the CD-ROM Header field is usually the same as the address in
the sub-channel
Q
data for a particular sector.
However a tolerance of
+
one
second is allowed.
The address in the TOC for the start of user data in track has a tolerance
of
+
0 second.
5-3
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