Fujitsu MAN3735 Manuale Utente
C141-E124-01EN
3 - 75
3.2
Data Access Commands
3.2.1
READ (08)
Bit
Byte
Byte
7
6
5
4
3
2
1
0
0
X‘08’
1
LUN
Logical Block Address (MSB)
2
Logical Block Address
3
Logical Block Address (LSB)
4
Transfer Block Count
5
0
0
0
0
0
0
Flag
Link
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" 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.
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.
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.
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.
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.
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.