HP C2488A Technical Reference Manual page 77

Mode Select, Mode Sense
Sense Data Length. This field specifies the length in bytes of the page data to be returned
during the Data In phase. The Sense Data Length field does not include itself nor does it
include the Block Descriptor length.
Media Type. Set to all zeros to indicate fixed disk.
WP (Write Protect). Indicates whether the drive is in the write protect mode: zero (0)
=
write protect disabled; one (1)
=
write protect enabled. The write protect mode is enabled
or disabled with bit 7 in the Mode Select command control byte: zero (0)
=
write protect
disabled; one (1)
=
write protect enabled.
DPOFUA. Indicates whether the target supports the cache control bits DPO (Disable Page
Out) and FUA (Force Unit Access) in the extended READ command. The target always
reports a zero (0) indicating that only the FUA bit is supported.
Device Specific Parameters. Not used. Set to all zeros.
Block Descriptor Length. This field specifies the length in bytes of the Block Descriptor, and
does not include the Parameter Pages. The block descriptor length will be either 0 or 8. The
Block Descriptor specifies the media characteristics for the entire Logical Unit.
Density Code. Not used. Set to zeros.
Number of Blocks. Set to all zeros by MODE SENSE indicating that all blocks are set to
same size. In MODE SELECT, used by the Set Capacity function to allow the Initiator to
modify the working capacity of the drive.
The Set Capacity function is performed by placing a value in the Number of Blocks field of
the 6- or lO-byte MODE SELECT Block Descriptor. The change to the working capacity of
the drive can be made non-volatile by setting the SP (Save Page) bit in the MODE SELECT
Command Descriptor Block to one (1).
Considerations for setting of Number of Block field:
If set to zero (0), the working capacity is not affected.
If set to FFFFFFh, the working capacity is set to maximum.
If set to a value greater than zero (0), but less than'or-equal to the maximum drive
capacity, the working capacity is adjusted to the number of blocks indicated.
If set to a value greater than the maximum drive capacity, the drive will set a Status of
CHECK CONDITION, a Sense Key oflLLEGAL REQUEST, and an additional Sense Key
of ILLEGAL LOGICAL BLOCK ADDRESS.
Attempting any access beyond the current working capacity of the drive will result in a Status
of CHECK CONDITION, a Sense Key of ILLEGAL REQUEST, and an Additional Sense Key
of ILLEGAL LOGICAL BLOCK ADDRESS. .
Block Length. Indicates logical block size; Set to user configuration in MODE SENSE. In
MODE SELECT, changing the Block Length (or changing the Data Bytes per Physical Sector
field in Mode Page 03H) will reset the working capacity to the maximum.
PS (Page Save). Indicates savable Mode Sense page when set to one (1). Ignored for Mode
Select.
Page Length. Indicates number of bytes remaining in specified page after Page Length field.
DRAFT SCSI Command Descriptions A·21
1/18/93 09:58