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3.2 Data Access Commands
C141-E167
3 - 67
3.2.3 WRITE (0A)
Bit
Byte
76543210
0X‘0A’
1 LUN Logical Block Address (MSB)
2 Logical Block Address
3 Logical Block Address (LSB)
4 Transfer Block Count
5 0000000Link
This command transfers the number of blocks of data specified in the "Transfer block count" field
from the INIT and writes them in continuous logical data blocks 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 writing 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 writing of data to the disk media is not executed.
The IDD does not perform data transfer immediately after receiving the CDB, but after performing
automatic disconnect processing once, it executes pre-fetching of data. If disconnect processing is
permitted, the IDD either completes transfer of all the data specified in the command or, at the point
when the empty space in the data buffer runs out, disconnect processing is executed. Positioning of
the specified data blocks is performed in parallel with this data transfer, and writing of data from the
data buffer to the disk media is executed immediately after positioning is completed. See Section
2.1 "Data Buffer" for details of data buffer operation and control of the timing for starting
reconnection processing by the MODE SELECT parameter (buffer empty ratio).
If the write cache function is enabled, the IDD reports a status byte at the point when reception of all
the data transferred from the INIT is completed. If an error occurs while data are being written to
the disk media, a CHECK CONDITION status is reported for the command to be executed next. If
the write cache function is disabled, a status byte is reported after writing to the disk media of all the
data transferred from the INIT is completed, then execution of the command is terminated.