Maxtor ATLAS 10K III - Manual (Page 232)

SCSI Description
5-168 Maxtor Atlas 10K III
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The TEST UNIT READY command returns GOOD status if the drive is ready to
receive medium access commands (that is, READ, WRITE, VERIFY, etc.). If the
drive is not ready to receive medium access commands, it returns CHECK
CONDITION status with the appropriate sense keys and qualifiers. The data format
is described in Table 5-209.
Table 5-209 TEST UNIT READY Command Descriptor Block-Data Format
$KV
$[VG
       
0 Operation Code (00h)
1 - 4 Reserved
5 Control