5. IDE Command Descriptions
40
error condition to the host. With the exception of disabling retries (retry count = 0), the
retry count of 128 is currently not changeable.
When the read/write heads are switched or a seek is completed the drive will attempt an
offtrack read when less than 200
µ
inches from the center of the track. If this attempt is
successful 17 ms of latency is saved and seek performance of the drive will exceed the
specification. When this attempt is not successful the drive will read the sector on the
next pass as in a normal read operation (100
µ
inches) and the seek specification is met.
Header Retry Algorithm
When an ECC error is detected while reading the header field, 20 read retries are
attempted before a header error is returned to the host. If a header is successfully read
before the 20 retries are completed, the header retry counter is reset and the data field
is processed. For a hard error in the data field the total amount of time for 20 retries is
0.34 seconds (17 ms * 20 = 340 ms). Header retries cannot be disabled from the
interface, nor can the header retry count be changed.
ERROR REPORTING
In general, errors are detected in the following fashion by the drive microprocessor. At
the start of execution of a command the command register is checked for conditions
that would lead to an aborted command. The operation is then attempted. Any
subsequent error terminates the command at the point of discovery. Errors valid for
each command are summarized in the "Error Reporting Matrix" table following. Any
subsequent error terminates the command at the point of discovery.
The following abbreviations are used in the matrix, where V means the error type is
valid for this command:
BBK
bad block detected
UNC
non-correctable data error
IDNF
requested ID not found
ABRT
aborted command error
TKO
track 0 not found error
DRDY
disk drive not ready detected
DWF
disk drive write fault detected
DSC
disk drive seek complete not detected
CORR
corrected data error
ERR
error bit in the status register
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
