bit 0 : error bit. If this bit is set then an error has
occurred while executing the latest command. The error
status itself is to be found in the error register.
bit 1 : index pulse. Each revolution of the disk this bit is
pulsed to '1' once. I have never looked at this bit, I
do not even know if that really happens.
bit 2 : ECC bit. if this bit is set then an ECC correction on
the data was executed. I ignore this bit.
bit 3 : DRQ bit. If this bit is set then the disk either wants
data (disk write) or has data for you (disk read).
bit 4 : SKC bit. Indicates that a seek has been executed with
success. I ignore this bit.
bit 5 : WFT bit. indicates a write error has happened. I do
not know what to do with this bit here and now. I've
never seen it go active.
bit 6 : RDY bit. indicates that the disk has finished its
power-up. Wait for this bit to be active before doing
anything (execpt reset) with the disk. I once ignored
this bit and was rewarded with a completely unusable
disk.
bit 7 : BSY bit. This bit is set when the disk is doing
something for you. You have to wait for this bit to
clear before you can start giving orders to the disk.