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6.1 Sense Data
C141-C013 361
6.1.2 Sense data basic information
Bytes 0 to 17 of the sense data are basic information which show the contents of
the error that has occurred. The INIT can know the contents of the error and the
key information that is necessary for recovery processing by analyzing this basic
information. Each field and the meanings of bits in the sense data basic
information are explained below.
(1) Valid
When this bit is "1," it indicates that the values shown in the information field
(bytes 3 to 6) are valid. On the other hand, when this bit is "0", it indicates that
the information field does not contain valid information.
(2) Error code
This field shows the format and type of sense data. The HDD always displays X
'70' (current error) or X '71' (deferred error), which has the meaning "expanded
sense data format" in this field.
(3) ILI (incorrect length indicator)
When this bit is "1," it indicates that the transfer byte length requested in the
command did not coincide with the data block length on the disk media. In the
HDD, the only commands that it reports "1" in this bit for are the READ LONG
command and the WRITE LONG command. For details, refer to the descriptions
of these commands (Sections 4.4.5 and 4.4.6).
(4) Sense key
This field shows the cause of the sense data being generated. More details
reasons are indicated in the additional sense code field (Byte 12) and the
additional sense code qualifier field (Byte 13). Table 6.3 shows a list of the
meanings of sense keys.
(5) Information
This field shows information related to the error that has been detected and is
valid only when the Valid bit is "1." Depending on the command where the error
occurred, additional information other than the information in this field may be
indicated in the command inherent information field. The information shown in
this field has the following meanings depending on the value of the "ILI" bit.
a) When the "ILI" bit is "0," the logical block address of the data block where
the error occurred is indicated.
b) When the "ILI" bit is "1," the difference between the transfer byte length
requested by the command and the actual data block length on the disk media is
indicated. If the difference is a minus value, (if the request transfer byte count is
smaller), it is expressed as a complement of 2. In the HDD, only the READ
LONG command and the WRITE LONG command display this information. For
details, see the descriptions of these commands (Sections 4.4.5 and 4.4.6).