29 Nov
2008
29 Nov
'08
4:34 a.m.
On 28 Nov 2008 at 19:39, Philip Pemberton wrote:
I suppose you could do what the Catweasel does and
save the time between flux
transitions, but that opens up a whole other can of worms when you want to
write back to the disc...
You could even do something like a Catweasel without incurring the
worms. Since there is a certain minimum time/distance between
transitions, you can sample adequately by storing a
byte/nibble/quantum of information at a rate only slightly faster
than this minimum time. The value reflects either no transition or
the time of the transition from the edge of the sampling frame.
Suppose this minimum distance between transitions is 200 nsec. You
need only read or store sample every 150 nsec or so. The only high-
speed part of the device is a counter that runs at whatever
oversample rate you're using. Start the counter at zero at the
beginning of every sample frame and store the value when a transition
occurs during writing; generate one using a comparator to generate a
pulse if a match is found between the value of this counter and the
stored sample value.
I feel awkward trying to explain this with words and no whiteboard,
but I hope you get the idea.
No need to bother with shift registers.
And no worms.
Cheers,
Chuck