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4.1 Control/Sense Commands
4.1.4 MODE SELECT (15)
Bit
Byte
7 6 5 4 3 2 1 0
0 X'15'
1 0 0 0 PF 0 0 0 SP
2 0 0 0 0 0 0 0 0
3 0 0 0 0 0 0 0 0
4 Parameter List Length
5 0 0 0 0 0 0 0 0
This command performs setting and changing of each type of parameter related to
disk drive physical attributes, data format, timing of SAS interface transferring
processing and error recovery procedures, etc. The INIT can know the types of
parameters, the current settings of each parameter and the types of parameters
which can be changed, and the ranges for such changes, etc. by using the MODE
SENSE or MODE SENSE EXTENDED command.
The data (MODE SELECT parameters) transferred from the INIT to the HDD by
this command, are configured from a "Header," "Block Descriptor" and one or
more "Page Descriptors" which describe each parameter, each of which will be
explained later.
When the "PF (page format)" bit in CDB byte 1 is "1," it indicates that the MODE
SELECT parameters transferred from the INIT by this command are in the "Page
Descriptor" format. The HDD disregards the value specified in this bit and regards
the MODE SELECT parameters transferred from the INIT as being in the "Page
Descriptor" format and executes this command.
The "SP (save pages)" bit in CDB byte 1 specifies whether or not to save the
MODE SELECT parameters specified in this command on the disk. It is possible
for the HDD to save all the MODE SELECT parameters described in the "Page
Descriptor" (except for those on page C), but this bit's specification is valid only
for parameters other than "Format parameters (Page 3)" and "Drive parameters
(Page 4)."
If "1" is specified in the "SP" bit, the parameters transferred from the INIT are
saved to the disk when this command is executed, except for "Format parameters
(Page 3)" and "Drive parameters (Page 4)." When the "SP" bit is "0," these
parameters are not saved to the disk. On the other hand, as for "Format parameters
(Page 3)" and "Drive parameters (Page 4)," regardless of the specification of the
"SP" bit when this command is executed, these parameters are always saved to the
disk when the FORMAT UNIT command is executed.
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