Pioneer SCSI-2 Reference Manual page 120

Audio Status indicates the status of an audio play operation. The status of audio commands are
listed in Table 2-23C on the opposite page.
Sub Channel Data Length should be set 0, 12, 20, 28 or 44 bytes and does not include the Sub
Channel Header.
ADR codes are defined in Table 2-23D
Control bits are defined in Table 2-23E
Track Number specifies the current Track Number
Index Number specifies the current index number in the current track.
Absolute CD-ROM Address returns the current location relative to the logical beginning of the
media. If the MSF bit in the CDB is zero, this field is a logical block address. If the MSF bit in
the CDB is one, this field is an Absolute MSF address.
Track Relative CD-ROM Add returns the current location relative to the logical beginning of
the current track. If the MSF bit is zero, this field is a track relative logical block address. If the
current block is in the pre-gap area of a track, this address will be a negative value, expressed as a
two's complement number. If the MSF bit is one, this field is an absolute MSF address.
MCV
If the MCV bit is one, the media catalog number field is valid.
There are identify numbers according to the UPC/EAN cording in the media catalog
number field. If all data in this field is ASCII 0, there is no media catalog number in the
field.
TCV
If the TCV bit is one, the ISRC field is valid. In this field, there are identify numbers
according to the ISRC standard. (DIN-31-621)
When the Sub-Q bit in the CDB is set to zero, the drive returns the Sub Channel Header with no
other data.
Audio status values 13h and 14h return information on previous audio operations; they are
returned only once after the condition has occurred. If another audio play operation is not
requested, the audio status returned for subsequent READ SUB-CHANNEL commands is 15h.
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Read Sub-Channel