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MODE SELECT
Bit
7
Byte
0
1
2
Reserved
3
4
5
(MSB)
6
7
8
9
(MSB)
10
11
Buffered Mode: Buffered Mode is the mechanism by which the drive implements Immediate Reporting on WRITE
commands.
If the field is ZERO, then the drive does not report a GOOD status on WRITE commands until the data blocks are
actually written to tape (not support).
If the Buffered Mode field is one, then the drive reports GOOD status on WRITE commands as soon as the data
block has been transferred to the buffer. This field should be set to ONE.
Speed: The drive only supports one speed, the default speed. Because of this, this field must be set to ZERO. Any
other value will cause a CHECK CONDITION status with an ILLEGAL REQUEST sense key is returned.
Block Descriptor Length: This specifies the length in bytes of all the block descriptors. Since the drive only allows
one block descriptor, this value must be eight. Any other value will cause a CHECK CONDITION status with an
ILLEGAL REQUEST sense key to be returned.
Note: The block descriptor specifies the media characteristics for the SDX drive. The block descriptor contains the
density code, number of blocks and block length fields.
Density Code: The supported values for the density code field are defined in the following table.
Note: 00h - Default: The use of the word "Default" is SCSI specific. It instructs the drive to use its default or only
density.
Code Value
00h
30h
31h
32h
33h
7Fh
Number of Blocks: A MODE SENSE field which will be returned as ZERO, indicating that all of the remaining
logical blocks on the media will have the medium characteristics specified by the block descriptor, or until a
subsequent MODE SELECT command changes those parameters. This field must be set to ZERO on a MODE
SELECT otherwise a CHECK CONDITION status will be returned with an ILLEGAL REQUEST sense key.
Block length: The Block Length field specifies the length in bytes of each logical block transferred over the SCSI
bus. A block length of ZERO indicates that the length is variable. Any other value indicates the number of bytes per
block that the drive must handshake over the bus. This establishes block length such that the transfer length for
read, write type commands will be a block count not a byte count.
Note: It is value of this field together with the Fixed Bit Field in the READ, or WRITE commands that determine
whether the drive is in Fixed or Variable block mode.
SONY AIT-4 drive SDX-900V series Ver.2.1
Table 6-36: MODE SELECT parameter list
6
5
4
Buffered Mode (001b)
Block Descriptor Length (08h)
Density Code
Number of Blocks (00 00 00h)
Block Length
Table 6-37: Sequential-Access Density Codes
Code Value
Default Format
AIT-1
Format
AIT-2
Format
AIT-3
Format
AIT-4
Format
No change from previous density
3
2
Reserved
Reserved
Speed (00h)
Reserved
6.Command Specification
1
0
(LSB)
(LSB)
6-39
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