Read Sub-Channel

2.27Read Sub-Channel (42h)

Operation Code is (42h).

MSF

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.

Sub Q

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.

Track Number

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. The sense key and additional sense code are set to ILLEGAL REQUEST/INVALID FIELD in CDB.

Allocation Length

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.

Format Code

 

Sub-Channel Data Block

00h

:

Q Sub-code Data

01h

:

CD-ROM Current Position

02h

:

Media Catalog Number (UPC/Bar Code)

03h

:

Track International Standard Recording Code (ISRC)

04h-FFh

:

Reserved

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.

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