Optical Drive and Library SCSI-2 Command Reference

SCSI-2 Drive Command Set
Read (Group 1) Command (28H)
Chapter 2 2-83
SCSI-2 Drive Commands
FUA A Force Unit Access bit of 1 indicates that data is read
directly from the disk.
A Force Unit Access bit of 0 indicates that the drive may
access the cache memory.
Rel Adr A relative address bit of one indicates that logical block
address specified is a two’s complement offset from the
last logical block address accessed.
A value of 0 indicates that the logical block address is an
absolute address.
Transfer
Length The Transfer Length field specifies the number of
contiguous logical blocks of data to be transferred.
A value of 0 indicates that no blocks will be transferred
and is not considered an error.
PBA A Physical Block Address bit of 1 indicates that physical
block addressing is used.
A PBA bit of 0 indicates that logical block addressing is
used.
NOTE For write-once media, blank checking is performed following a failed read.
If the sector is blank, the sense key/additional sense code will be set to
BLANK CHECK/Blank Sector Detected.
NOTE When this command is used with 14X 512 or 1024 byte/sector media,
setting the PBA bit will cause the drive to return a CHECK CONDITION
status. The sense key/additional sense code will be set to ILLEGAL
REQUEST/INVALID FIELD in CDB.