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4.2 Data Access Commands
C141-C013 213
4.2 Data Access Commands
4.2.1 READ (08)
Bit
Byte
7 6 5 4 3 2 1 0
0 X'08'
1 0 0 0 Logical Block Address (MSB)
2 Logical Block Address
3 Logical Block Address (LSB)
4 Transfer Block Count
5 0 0 0 0 0 0 0 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 HDD,
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 HDD first corrects the data errors in the data buffer,
then transfers those data to the INIT.