The READ SUB-CHANNEL command requests that the target return the requested sub-channel data plus the state of audio play operations.

Note: If a READ SUB CHANNEL command is issued to request the media catalog number (UPC/EAN Bar Coding), the drive should return the UPC code in ASCII format as specified in the SCSI-2 specification. Some drives return the UPC code in BCD. It should be converted to ASCII prior to returning. All other sub-channel data is returned in binary format.