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44
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. "Changeable values" are 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 com-
mand 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 8 refer to Mode page 01, in the first row titled "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 byte 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 change-
able. 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 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 Condition" sta-
tus 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.
Elite 23 Product Manual, Rev. A
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