## Storage Device Driver Reference

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### READ (08h) and READ (028h)

The READ (6-byte) and READ (10-byte) commands request that the target transfer data to the initiator.

The Adapter Device Driver should return with a sense key error of 08h ( Blank Check) and additional sense code of 064h (illegal mode for this track ) if any of the following events occur.

1.If the requested logical block address is in an audio track and the drive does not support reading raw 2352 byte CD-DA data.
2.If the requested logical block address is a mode 2 sector and the drive does not support reading mode 2 sectors.

Refer to the ANSI SCSI-2 specification for a detailed description of this command.

Reading Mode-2 Sectors

If the CD-ROM drive supports the reading of Mode 2 Form 1 and Mode 2 Form 2 sectors, the Adapter Device Driver should mask the complexity of reading the target sector and return successfully, even if the mode of the target sector does not match the currently specified mode for the drive.

Some drives require the drive be set to the proper mode of the target sector prior to issuing the read. For those drives, the Adapter Device Driver should issue the original read, and if the read fails with an error indicating the current drive mode does not match the mode of the target sector, the adapter device driver must issue the mode select to set the proper mode and then re-issue the read request.

It is the responsibility of the CD-ROM Device Manager to ensure the proper block length is specified via the Mode Select command prior to issuing the read command. So, for Mode 2 Form 1 sectors, the device manager will issue a Mode Select command to set the block length to 2048 bytes. For a Mode 2 Form 2 sector, the device manager will issue a Mode Select to set the block length to 2340 or 2352 bytes, depending on the max block length the drive supports. See the Mode Select command section MODE SELECT (15h).