USB Universal Floppy Disk controller

Paul Koning pkoning at equallogic.com
Fri Mar 11 12:17:43 CST 2005


>>>>> "Jules" == Jules Richardson <julesrichardsonuk at yahoo.co.uk> writes:

 Jules> On Fri, 2005-03-11 at 07:51 +0000, Philip Pemberton wrote:
 >> ...
 >> Shift register + counter + high speed RAM. Could even do it with
 >> an FPGA if you wanted.  Buffering an entire track with 8x
 >> oversampling is going to be hellishly memory intensive though.

 Jules> Well if worst-case is 1mbps data rate at 300rpm and 8x
 Jules> oversample, isn't that (8 * 10240 * 1024) / 5 = 1677722 bits
 Jules> of memory maximum needed?

 Jules> (div by 5 because 300rpm gives you a whole track in 1/5 of a
 Jules> second)

 Jules> So 256KBytes of RAM should always be enough to buffer a whole
 Jules> track, regardless of what physical drive or media you use.

Even if you want 8 bits per sample, that's still only 1.5 MB, and the
data rate is 7.5 MB/s (since a track is 200 ms by your calculation).

That's a trivial bandwidth requirement; anything better than antique
DRAM will do the job easily, and the space requirement is tiny, too.

I'm wondering if you can do this job with a microcontroller similar to
a PIC, running the sampling loop in software.  If not quite, it should
be pretty close.

   paul




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