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Command Specifications
3 - 20 C141-E167
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 IDD'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 IDD uses as "Current" values during the time until reading of "Save" values is
completed after the IDD's power is switched on, or when no "Save" values exist and no MODE
SELECT command is being issued.
The IDD has a common set of "Current", "Save" and "Default" values of all the MODE SELECT
parameters for all the INITs.
When the IDD's power is switched on, when a RESET condition occurs or when the IDD receives a
BUS DEVICE RESET message, 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 parameters related to the data format on the disk media (Block Descriptor, Format
parameters: Page 3, and Drive parameters: Page 4), parameters related to the segment buffer
(Caching parameters: Page 8, byte 13) and parameters related to command queuing (Control mode
parameters: Page A, byte 3) is changed by this command, a UNIT ATTENTION condition (Mode
parameters changed [=2A-01]) is generated for all the INITs other than the INIT that issued this
command.
When the RESERVE command is issued which specifies the Third Party Reserve function, the
"Current" values of MODE SELECT parameters of the INIT that issued the RESERVE command
are copied to "Current" values for a third party device specified by the RESERVE command.
Details of this function are described in Section 3.1.11, "RESERVE (16)."
Followings show the relation between the three types of parameters, "Current," "Save" and
"Default".