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Command Specifications
The "Parameter length" field of the CDB specifies the total byte length of the
MODE SELECT parameters transferred from the INIT by this command. If zero
is specified in the "Parameter length" field, this command is terminated normally
without data transfer being executed with the INIT. The MODE SELECT
parameters have specifically defined formats and lengths, as explained by the
descriptions of each page descriptor in this item, and the INIT must always specify
(transfer) those formats and lengths.
If a "Header," "Block Descriptor" or any "Page Descriptor" cannot be transferred
with all the defined length because the total defined length of the MODE SELECT
parameters actually transferred from the INIT do not match the value specified in
the "Parameter List Length" field, or if the total of the MODE SELECT
parameter's defined length transferred from the INIT exceeds the value specified in
the "Parameter list length" field, this command is terminated with a CHECK
CONDITION status (ILLEGAL REQUEST [=5] / Invalid field in CDB [=24-00])
and all the MODE SELECT parameters transferred in the command are disabled.
Three types of values exist in the MODE SELECT parameters, "Current," "Save"
and "Default" values. "Current" values are parameters which actually control the
HDD's operation, and the parameters specified by this command are converted to
"Current" values. "Save" values are parameter values specified by this command
which are preserved on the disk. And "Default" values are values which the HDD
uses as "Current" values during the time until reading of "Save" values is
completed after the HDD's power is switched on, or when no "Save" values exist
and no MODE SELECT command is being issued.
The HDD has a common set of "Current", "Save" and "Default" values of all the
MODE SELECT parameters for all the INITs.
When the HDD's power is switched on, when HARD RESET is received,
LOGICAL UNIT RESET TASK is received, the "Current" MODE SELECT
parameter values are changed to the "Save" parameter values, if they exist, and are
changed to the "Default" parameter values if the "Save" values do not exist.
When any of the variable parameters of this command are changed, the unit
attention condition is generated for (Mode parameters changed [= 2A-01]) for all
the INITs except the one that has issued this command.
Figure 4.1 shows the relation between the three types of parameters, "Current,"
"Save" and "Default".
154 C141-C013