On 06/09/10 18:25, Chuck Guzis wrote:
Much of what Jens does could now be handled with most
modern medium-
scale microcontrollers. I think that's what most of the other
products, such as the Deviceside do. All you need is a PWM-style
timer with a "capture" mode and the ability to address about 128K of
DRAM and a uC that runs at a sufficient speed to reduce aliasing
effects. There's really no magic involved at all.
Indeed -- the SPS guys are doing one (Kryoflux, google it) with an Atmel
SAM chip (if memory serves). Basically an ARM, Flash ROM and SRAM on a
single chip.
I'd be a little concerned about interrupt latency and jitter (the ARM is
a pipelined RISC design, interrupt timing tends not to be 100%
deterministic) but it's a really cool way to do it cheaply...
Given the
rather pedestrian nature of the job and the fast cheap uCs available
today, I doubt that a FPGA makes a lot of cost-effective sense in the
case of floppy work.
The reason I went with the FPGA was partly because I wanted it (the
DiscFerret) to be as flexible as possible. If all you want is floppy
disc reading and analysis, an Atmel AT91SAM chip should be plenty. If
you want to image hard drives (I do) then you NEED the raw speed and
programmability of an FPGA.
It's a feature not everyone will use, I'll admit, but I don't want to be
stuck making a "DiscFerret II" in a couple of years time, just because I
need to clone an MFM drive.
The other thing you can do on an FPGA is run an entire disc controller
IP core inside the GA, then use the microcontroller to pipe data in and
out. In this way, you could have (say) the Suska WD1771 controller core
running in the FPGA, reacting as a real WD1771 would when presented with
the same input data.
So not only can you read and write discs at bit-transition level, you
can see how a real disc controller would handle the discs. Assuming, of
course, you have an IP core for the disc controller in question
(apparently the Intel 8271 isn't hard to clone, the 1771 has already
been cloned, and I'm willing to bet someone's got an NEC 765 IP core)
And of course, one has to write the software to
interpret the
results.
But of course :)
Cheers,
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/