4. IDE Interface
25
DRDY—Drive Ready
DRDY indicates that the drive is ready to accept a command. When an error occurs this
bit remains unchanged until the host reads the status register, then again indicates that
the drive is ready. At power-on this bit should be cleared until the drive is up to speed
and ready to accept a command.
DWF—Drive Write Fault
When an error occurs this bit remains unchanged until the status register is read, then
again indicates the current write fault status.
DSC—Drive Seek Complete
This bit is set after the completion of a seek and when the head has settled over a track.
When an error occurs this bit remains unchanged until the host reads the status
register, at which time it will again indicate the current seek complete status.
DRQ—Data Request
This bit indicates that the drive is ready to transfer a word or byte of data from the host
to the data port.
CORR—Corrected Data
This bit is set when the drive encounters and corrects a data error. This condition does
not terminate a multisector read operation.
IDX—Index
This bit is set when the drive detects the index mark during each revolution of the disk.
ERR—Error
This bit indicates that the previous command ended in an error. The error register and
other status register bits contain further information as to its cause.
Command Register
(1F7h, Write - 8 bits)
The host CPU sends commands to the drive via an 8-bit code written to the command
register. Some drives have additional commands that are a superset of the original AT
command set. Consult the drive manufacturer's manual for additional information. The
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