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Western Digital Hard Disk Drive OEM Specification
Sector Count Previous
PRIO (bits 7-6)
The Priority (PRIO) value shall be assigned by the host based on the priority of the
command issued. The device makes a best effort to complete High priority requests in
a more timely fashion than Normal and isochronous priority requests. The device tries
to complete isochronous requests prior to its associated deadline. The Priority values
are defined as follows:
00b Normal priority
01b Isochronous
– deadline dependent priority
10b High priority
Sector Number Current
LBA (7:0)
Sector Number Previous
LBA (31:24)
Cylinder Low Current
LBA (15:8)
Cylinder Low Previous
LBA (39:32)
Cylinder High Current
LBA (23:16)
Cylinder High Previous
LBA (47:40)
ZCICC
The Isochronous Command Completion (ICC) field is valid when PRIO is set to a
value of 01b. It is assigned by the host based on the intended deadline associated
with the command issued. When a deadline has expired, the device continues to
complete the command as soon as possible. The host can modify this behavior if the
device supports the NCQ NON-DATA command (see 11.15 NCQ NON-DATA (63h))
and supports the Deadline Handling subcommand (see 11.15.2 Deadline handling
Subcommand (1h)). This subcommand allows the host to set whether the device
aborts commands that have exceeded the time set in ICC.
There are several parameters encoded in the ICC field: Fine or Coarse timing, Interval
and the Max Time. The Interval indicates the time units of the Time Limit parameter.
If ICC Bit 7 cleared to zero, then the time interval is fine-grained.
Interval = 10msec
Time Limit = (ICC[6:0] + 1) * 10 msec
If ICC Bit 7 is set to one (coarse encoding), then the time interval is coarse grained.
Interval = 0.5 sec
Time Limit = (ICC[6:0] + 1) * 0.5 sec
Device/Head
FUA (bit 7)
When the FUA bit is set to 1, the requested data is always retrieved from the media
regardless of whether the data are held in the sector buffer or not.
When the FUA bit is set to 0, the data may be retrieved from the media or from the
cached data left by previously processed Read or Write commands.
Input Parameters From The Device
Sector Number (HOB=0)
LBA (7:0) of the address of the first unrecoverable error.
Sector Number (HOB=1)
LBA (31:24) of the address of the first unrecoverable error.
Cylinder Low (HOB=0)
LBA (15:8) of the address of the first unrecoverable error.
Cylinder Low (HOB=1)
LBA (39:32) of the address of the first unrecoverable error.
Cylinder High (HOB=0)
LBA (23:16) of the address of the first unrecoverable error.
Cylinder High (HOB=1)
LBA (47:40) of the address of the first unrecoverable error.