30 Nov
2011
30 Nov
'11
3:33 p.m.
On 30 Nov 2011 at 22:30, Philip Pemberton wrote:
On 30/11/2011 21:48, Chuck Guzis wrote:
Exactly what I was (trying to say)/saying. At 30 MHz every 33nsec
window is used to sample for a pulse occurring within the window.
You run a counter that counts between such transitions--and store the
accumulated count when a transition happens. What the catweasel and
countless others have been doing for years. I suspect that the
Kyroflux and Deviceside devices do likewise.
It can be done with almost any modern microcontroller; no fancy FPGAs
needed as most modern microcontrollers contain counters with a
"capture" facility triggered automatically. For example, a lowly
ATMega running at 16MHz is more than sufficient to get accurate
samples to decode a high-density floppy. Similarly, the PWM facility
on most microcontrollers is sufficient to simulate a high-density
floppy.
All you need is a counter, some way to trigger it and some memory to
store the counts in. It's not rocket science--in fact, it's mostly
software.
My apologies if I'm not communicating well.
--Chuck
On 30 Nov 2011 at 11:38, Richard wrote:
It doesn't work like that...
Acquiring data like that is wasteful -- the width of the pulse which
the drive outputs when a flux transition is detected is basically
irrelevant and carries no useful information. However, if we know the
time between the leading (active-going) edges of the pulses, we can
reconstruct the transition stream. Since ST-506 is a digital interface, is there any
point to
digitizing the digital signals as if they were analog signals?
Sorry for the confusion. I was referring to the acquisition rate.
In other words, did a read pulse occur in this 33nsec window
(30MHz)? Recording each even in terms of ticks of a 30MHz clock from
the previous event..