Mode Sense Data - Seagate ST32151W Product Manual

Hawk 2XL Product Manual, Rev. B 45
9.3.2

Mode Sense data

The Mode Sense command provides a means for the drive to report its operating parameters to the initiator.
The drive maintains four sets of Mode parameters, Default values, Saved values, Current values and Change-
able values.
Default values are hard coded in the drive firmware that is stored in flash EPROM nonvolatile memory on the
drive PCB. Default values can be changed only by downloading a complete set of new firmware into the flash
EPROM. An initiator can request and receive from the drive a list of Default values and use those in a Mode
Select command to set up new Current and Saved values, where the values are changeable.
Saved values are stored on the disk media using a Mode Select command. Only parameter values that are
allowed to be changed can be changed by this method. See "Changeable values" defined below. Parameters
in the Saved values list that are not changeable by the Mode Select command get their values from the Default
values storage.
Current values are volatile values currently being used by the drive to control its operation. A Mode Select
command can be used to change these values (only those that are changeable). Originally, they are installed
from Saved or Default values after a power on reset, hard reset, or Bus Device Reset message.
Changeable values form a bit mask, stored in nonvolatile memory, that dictates which of the Current values
and Saved values can be changed by a Mode Select command. A "one" allows a change to a corresponding
bit; a "zero" allows no change. For example, in Table 8a refer to Mode page 01, in the first row entitled "CHG".
These are hex numbers representing the changeable values for Mode page 01. Note in columns 1 and 2
(bytes 00 and 01), there is 00h, which indicates that in bytes 00 and 01 none of the bits are changeable. Note
also that bytes 04, 05, 06 and 07 are not changeable, because those fields are all zeros. In bytes 02, hex value
EF equates to the binary pattern 1110 1111. If there were a zero in any bit position in the field, it means that bit
is not changeable. Bits 7, 6, 5, 3, 2, 1 and 0 are changeable, because those bits are all ones. Bit 4 is not
changeable. In this particular example, it indicates 7 of 8 error recovery control bits are all changeable. FF in
column 4 indicates all bits in byte 3 are changeable.
The Changeable values list can only be changed by downloading new firmware into the flash EPROM.
On drives requiring unique Saved values, the required unique Saved values are stored into the Saved values
storage location on the media prior to shipping the drive. Some drives may have unique firmware with unique
Default values also.
On standard OEM drives the Saved values are taken from the Default values list and stored into the Saved val-
ues storage location on the media prior to shipping.
When a drive is powered up, it takes Saved values from the media and stores them to the Current values stor-
age in volatile memory. It is not possible to change the Current values (or the saved values) with a Mode
Select command before the drive is up to speed and is "ready." An attempt to do so results in a "Check Condi-
tion" status being returned.
Note.
Because there may be several different versions of drive control firmware in the total population of drives in the
field, the Mode Sense values given in the following tables may not exactly match those of some drives.