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Sense Data and Error Recovery Methods
384 C141-C013
judges that correction is possible, it regards verification as being successful and
continues processing of subsequent data blocks.
(5) Other internal HDD errors
If an irrecoverable error other than those in items (1) to (4) above is detected internally
in the HDD, the HDD terminates the command that is currently being executed with a
CHECK CONDITION status. The sense key in the sense data at this time is
"HARDWARE ERROR [=4]."
6.3.2 Auto alternate block allocation processing
The HDD is equipped with a function which automatically executes alternate
block allocation processing for defective data blocks detected during execution of
the READ and READ EXTENDED commands.
(1) Auto alternate block allocation processing during a read operation
This function is enabled by specifying "1" in the ARRE flag in the MODE
SELECT parameters. Furthermore, this function is applicable to the following
commands only.
• READ command
• READ EXTENDED command
When this function is permitted, if, during read processing to the data area, an error
which is an object of retry processing is detected, and which it is impossible to recover
from even when reading is retried (see Section 6.3.1(3)) the number of times specified
in the "Number of Retries during Read" field in the MODE SELECT parameters, the
HDD allocates an alternate block for that data block and executes copying of the
alternate block to the data area. Alternate block allocation processing is the same as
processing with the REASSIGN BLOCKS command. Furthermore, recovered data
copied to the alternate block are data which are read out, skipping the ID area, if there
is an ID area, or they are data which have been corrected through the ECC.
This function is applied once only during execution of one command. Alternate
block allocation processing and copying are executed for the first defective data
block to be detected during execution of a command, but if a second defective
data block is detected, the command that is being executed at that point is
terminated with an error. However, by the INIT's reissuing the same command,
auto alternate block allocation is applied sequentially and error recovery can be
attempted.
Remark:
1. When this function is specified (ARRE = "1"), the EER flag's specification in
the MODE SELECT parameter is made invalid and Read retry processing is
performed up to the number of times specified in the "Number of Retries
during Read" parameter. If "0" is specified in the DCR flag, correction
processing of the data is performed afterward (see Section 6.3.1 (3)). When
"1" is specified in the DCR flag, ECC correction processing is prohibited, so