5 Feb
2009
5 Feb
'09
11:21 a.m.
I been "listening" to most of this thread so, forgive me if I already mention an
idea that someone has already brought up...
I seem to recollect that when I was working on hard sector floppy drives back in the
Northstar Horizon system days, that the controller only wrote a block of data for each
sector with basically nothing in between. It saw an index hole, wrote the block and then
waited for the next index hole to write the next sector. If you want to recreate index
holes for reading a hard sectored floppy, it seems you could detect the end of data from
the previous sector and then generate a accurate index hole for the upcoming sector. Use
the single index to reset the sector count if you are keeping track of that.
Obviously, this is only a solution for reading the disk
best regards, Steve Thatcher
Hi Chris
I was recently looking at my Teac drive's index pulse to see how it
worked relative to the drive going ready ( the problem of trying to
find a way to recreate the /Ready signal ).
One thing I noticed was that the leading edge of the index pulse
was as accurate as my scope could show but the trailing edge was
all over the place.
My thinking is that the drive is controlled by a servo loop.
The leading edge is when a crystal clock says the pulse is suppose
to start and the trailing edge is when the actual edge is detected.
If one timed the length of time between the two edges, one would
then know the corrective response of the loop.
As an example, if the pulse was long, you'd keep a similar software
wheel rotating that you apply a correction to by the amount the
pulse was long.
It would be this internal software generated wheel that you'd use
to create the index pulses from.
You need the code to watch the drive to determine the parameters
of the control system, gain, dampening and intertia.
If done this way, I suspect that one could get very close to
the right index pulse spacing.
Dwight
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