Hitachi HDT725025VLA380 - Deskstar 0A33423 T7K500 250GB SATA 7200RPM 8MB Cache Hard Drive Specifications page 89

IDX Index. IDX=1 once per revolution. Because IDX=1 only for a very short time during each revolu-
tion, the host may not see it set to 1 even if the host is continuously reading the Status Register.
Therefore the host should not attempt to use IDX for timing purposes.
ERR Error. ERR=1 indicates that an error occurred during execution of the previous command. The
Error Register should be read to determine the error type. The device sets bit ERR=0 when the
next command is received from the host.
Deskstar T7K500 Hard Disk Drive Specification
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