Technical information

HGST Ultrastar C15K600 Hard Disk Drive Specification
190
Table 156 PM_BG_PRECEDENCE field
Code
Vendor Specific
00h
Vendor Specific – Background operations take precedence over maintaining low power conditions
(same as 01b)
01b
Performing background functions take precedence over maintaining low power conditions as follows:
a) if the logical unit is in a low power condition as the result of a power condition timer associated
with that condition expiring, then:
1) the logical unit shall change from that power condition, if necessary, to the power condition
required to perform the background function, when:
a) a timer associated with a background scan operation expires, and that function is enabled or
b) an event occurs to initiate a device specific background function, and that function is
enabled;
2) the logical unit shall perform the background function(s) based on the definitions in this standard
and other command standards (e.g., if the device server receives a command while performing a
background function, then the logical unit shall suspend the function to process the command);
3) if more than one condition is met to initiate a background function, then:
a) all initiated background functions shall be performed; and
b) the order of performing the functions is vendor specific; and
4) when all initiated background functions have been completed, the device server shall check to
see if any power condition timers have expired. If any power condition timer has
expired, then the
logical unit shall change to the power condition associated with the highest priority timer that has
expired;
or
b) if the logical unit is performing a background function, and a power condition timer expires, then
the logical unit shall perform all initiated background functions before the logical unit
changes to a
power condition associated with a timer has expired
10b
Maintaining low power conditions take precedence over performing background functions as follows:
a) if the logical unit is in a low power condition, then the logical unit shall not change from that power
condition to perform a background function;
b) the device server may perform any initiated and enabled background function based on the
definitions in this standard or other command standards, if all of the following are true:
A) a condition is met to initiate a background function;
B) that background function is enabled;
C) the logical unit changes to a power condition in which the background function may be performed
(e.g., the device server processes a medium access command causing the logical unit to change
its power condition to continue processing that command); and
D) all outstanding application client requests have been completed;
or
c) if the logical unit is performing a background function, and a power condition timer expires that
causes a change to a power condition in which the logical unit is unable to continue performing
the
background function, then the logical unit shall:
A) suspend the background function; and
B) change to the power condition associated with the timer that expired.
11b Reserved = 0