[sebhc] hard sector substitute

Dave Dunfield dave04a at dunfield.com
Wed Jun 30 06:55:22 CDT 2004

>if you put the device on each drive, you would also have to "switch off"
>the input and output lines. The index hole output will go "off" when the
>drive is deselected which means that you would have to keep all drives
>(that had been accessed recently) selected to keep them synched. You also
>would not want the direction and step control to be "seen" by drives that
>should be deselected. Not a problem just something that would have to be
>done by an added device.


I guess I was not clear - I think it would be best to modify the drive so
that these signals are available to our adapter even when the drive is
deselected. If you use the traditional "Motor ON" control line instead of
the "Motor on select", you can keep the drive running even when it's not
selected - by attaching to the index sensor BEFORE the drive select logic,
we should be able to read it even if the drive is deselected.

As for the index output - you would have to gate that externally with select
anyway because we have to generate pulses that the drive does not generate,
Again if you were modifying the drive, you could do this by injecting the
additional sector pulses BEFORE the drive select logic.

dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools: www.dunfield.com
com             Vintage computing equipment collector.

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