3.2 Data Access Commands; Read (08) - Fujitsu MAX3073NC - SCSI,80, Dell DC961,Hard Drive Scsi Logical Interface Specifications

3.2 Data Access Commands
3.2.1

READ (08)

Bit
7
Byte
0
1
2
3
4
5 0
This command reads the number of blocks of data in continuous logical data blocks specified in the
"Transfer block count" field with the logical data block on the disk media specified in the "Logical block
address" field in the CDB as the top.
The transfer block count can be specified up to a maximum of 256 logical data blocks. When zero is
specified in the "Transfer block count" field in byte 4 of the CDB, it specifies transfer of 256 logical data
blocks and when a value other than zero is specified, it specifies the number of logical data blocks that
should be transferred.
When transfer of multiple data blocks is instructed by this command, when the data blocks which are to
be processed come to a track boundary, cylinder boundary or zone boundary, a head switch or cylinder
switch is executed automatically and reading of the specified number of blocks is performed.
When the specifications in the "Logical block address" field and "Transfer block count" field in the CDB
exceed the maximum logical block address in the IDD, that command is terminated with a CHECK
CONDITION status (ILLEGAL REQUEST [=5] / Logical block address out of range [=21-00]) and the
reading of data from the disk media is not executed.
Error recovery processing during execution of this command can be specified by the MODE SELECT
parameter. If retry processing and data correction processing are not prohibited, when this command is
completed normally, or when it is completed with a "RECOVERED ERROR [=1]" sense key report, the
data transferred to the INIT by this command are error free. When a correctable error check is detected,
the IDD first corrects the data errors in the data buffer, then transfers those data to the INIT.
When disconnect processing is permitted, the starting timing for reconnection processing in order to
execute data transfer on the SCSI bus can be specified by the MODE SELECT parameter (buffer full
ratio). Also, if the Look-Ahead cache feature is permitted, a caching operation is performed using the
IDD's data buffer by this command. See Chapter 2, "Data Buffer Management," concerning details of
data buffer operation and the Look-Ahead cache feature.
C141-C010
6 5 4
LUN
Logical Block Address
Logical Block Address (LSB)
Transfer Block Count
0 0 0

3.2 Data Access Commands

3 2
X'08'
Logical Block Address (MSB)
0 0
1 0
0 Link
3-71