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6.Command Specification
Note: If the Page Code is ZERO, the drive will only return the four-byte header and the one eight-byte block
descriptor and terminate the command with GOOD status.
Allocation Length: The Allocation Length specifies the number of bytes that the HOST has allocated for returned
MODE SENSE data. An Allocation Length of ZERO means that the drive will return no MODE SENSE data. This is
not considered an error and GOOD status will be returned. Any other value indicates the maximum number of bytes
that can be transferred. The drive terminates the DATA IN phase when the Allocation Length bytes have been
transferred or when all available MODE SENSE data has been transferred to the initiator, whichever is less. The
Allocation Length must fall on header or block descriptor boundaries. If the Allocation Length does not fall on these
boundaries then the drive returns CHECK CONDITION status with the ILLEGAL REQUEST sense key set, unless
the value is greater than that required for the specified page.
If the Page Code is ZERO, the Host requires MODE SENSE to only return the four-byte header the one eight-byte
block descriptor, therefore the Allocation Length must be set to 0Ch. The value of the Page Control Field is then not
checked by the drive and may be set to any value.
If the Allocation Length is non ZERO, it must be set to 4 or more. If the Allocation length is non ZERO and less than
4, the drive will return CHECK CONDITION status, and ILLEGAL REQUEST sense key.
If the drive does not support Data Compression and a Mode Sense Page is received the drive will return CHECK
CONDITION status, and sense key will set to ILLEGAL REQUEST.
The MODE SENSE data contains a four-byte header, followed by one eight-byte block descriptor, followed by ZERO
or more variable length pages, depending on the Page Code and the Allocation Length.
Bit
7
Byte
0
1
2
WP
3
4
5
(MSB)
6
7
8
9
(MSB)
10
11
Mode Data Length: The mode data length specifies the length in bytes of the following mode sense data that is
available to be transferred during the DATA IN phase. The mode data length does not include itself but does include
the total length of all requested MODE SENSE pages.
Media Type: The media value will be ZERO as only one media type is supported.
WP: A Write Protected bit of ZERO indicates that the tape is write enabled. A Write Protected bit of one indicates that
the tape is write protected.
Buffered Mode: if this bit is set to ZERO, the drive will not report a GOOD status on WRITE commands until the data
blocks are actually written on the tape. If set, the drive is in buffered mode and may report a GOOD status on WRITE
commands as soon as the data block has been transferred to the drive's buffer. One or more blocks may be buffered
prior to writing to the tape.
Speed Field: will return ZERO as the drive only supports one speed.
Block Descriptor Length: returns a value of 8, which specifies the length in bytes of the following Block Descriptor.
The drive only returns a single Block Descriptor.
Destiny Code: The drive returns 32h in the Density Code field.
6-58
Table 6-47: MODE SENSE data
6
5
4
Mode Data Length
Medium Type (00h)
Buffered Mode
Block Descriptor Length (08h)
Density Code (32h)
Number of Blocks (00 00 00h)
3
2
Reserved
Block Length
SONY AIT-2 Turbo drive SDX-550V series Ver.1.0
MODE SENSE
1
0
Speed (00h)
(LSB)
(LSB)
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