3 Mar
2008
3 Mar
'08
7:22 a.m.
From: mcguire at neurotica.com
On Mar 1, 2008, at 10:39 AM, dwight elvey wrote:
Why not just build that bus interface and put a floppy controller
chip (WD2797, 765, etc) on the other side of it? I suppose the DSP
chip would give you much greater flexibility in terms of being able to
download new code into it to support different formats (even different
types of modulation), but it's much more complex.
Hmm. Now that I think about it, a DSP-based floppy controller would
be amazingly flexible. Wow..
Hi
I like the DSP over the PIC because it has several feature that make
it easier to handle this application.
My thinking is that the SPI port makes a great way to sample the
bit stream from the drive. I'd still add a flipflop in front so that one
doesn't have to sample the pulse width, only the spacing between
pulses.
The DSP comes with an efficient barral shifter that would be great
to align data for pattern matching. It is designed to talk to a host
computer with minimal external circuits and contains enough RAM
to buffer the results of a track of data. The circuit would have almost
no external components being that most of the work was software.
The code could even be easily down loaded from the PC to select
differing formats.
With a PIC is it either a bit banging or adding external components
to handle these operations.
Dwight
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How about
a PCI floppy controller board? Maybe with some supplementary
logic to allow raw track reads? Possibly a BIOS to boot from? An
external
floppy drive connector?
Just wondering how complicated such a thing would be. Thanks!
It would be relatively easy if you did most of the work in a DSP chip.
For the floppy end, you need a parallel port to read status and
write controls.
For reading raw data, a 7474 flipflop, an adjustable clock
and a DSP chip, such as a ADSP2118 or similar.
Then you'd need a bus interface to the PCI bus.