HITACHI Deskstar & CinemaStar 7K1000.B & Deskstar E7K1000 Hard Disk Drive specification 
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11.18.4  Command Error 
Table 109 defines the format of the Command Error data structure. 
 
Table 109 Command Error information 
 
The TAG field (Byte 0 Bits 4-0) contains the tag number corresponding to a queued command if the NQ bit is 
cleared. 
The NQ field (Byte 0 Bit 7) indicates whether the error condition was a result of a non-queued or not. If it is 
cleared the error information corresponds to a queued command specified by the tag number indicated in the 
TAG field. 
The bytes 1 to 13 correspond to the contents of Shadow Register Block when the error was reported. 
The Data Structure Checksum (Byte 511) contains the 2‘s complement of the sum of the first 511 bytes in the 
data structure. The sum of all 512 bytes of the data structure will be zero when the checksum is correct.