2.27 Read Sub-Channel (42h)
Operation Code is (42h).
If "1", the CD-ROM address field of the returned sub-channel data is in MSF format. The
returned M,S and F fields are specified in hex. If "0", the CD-ROM address field of the
returned sub-channel data is in logical address format.
The Sub Q bit set to one requests the target return the Q sub-Channel data. Set to zero
requests that no sub-channel data will be returned.
Sub Channel Data Format
The Sub Channel Data Format Field specifies the returned Sub Channel Data. The format
codes are listed below.
The track number field specifies the track number from which the ISRC Code is
transferred. This field must have the value between 01h and 63h (99 bcd), and is valid only
when the Sub Channel Data Format field is 03h. In this case, the target returns the ISRC
Code of the track if it is detected. In other cases (i.e. Sub Channel Data Format Field not
equal to 03h), the drive will return Check Condition status if the Track Number Field is not
equal to 00h.
REQUEST/INVALID FIELD in CDB.
The READ SUB-CHANNEL command requests that the target return the requested sub-channel
data of the current block plus the status of an audio play operation.
The returned sub-channel data consists of a four-byte header followed by a sub-channel data
block. The header contains the audio status byte and the sub-channel data length field. If the
Sub-Q bit in byte 2 of the CDB is zero, the target will not return the sub-channel data block. In
this case the sub-channel data length is 0.
The sense key and additional sense code are set to ILLEGAL
Sub-Channel Data Block
Q Sub-code Data
CD-ROM Current Position
Media Catalog Number (UPC/Bar Code)
Track International Standard Recording Code (ISRC)
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