13 Nov
2011
13 Nov
'11
1:30 p.m.
On Nov 13, 2011, at 1:13 PM, Tony Duell wrote:
As far as I know there is no complete open FPGA (or
even CPLD). By
'completely open' I mean that there is sufficient docuemtation available
(without an NDA) to go from a design (be that as a schematic, a wirelist,
VHDL, whatever) to the necessary data to program into the chip, and be
able to actually program that data into the chip.
This is in contract to microcontrollers where in many cases the machine
code (and special-purpose registers, I/O ports, etc) is fully documented,
as is the way to get the object code into the chip (e.g. by ysing a JTAG
interface). It is quite possible to write an aassembler (or programmer)
and program loader for such devices.
I should point out, too, that FPGAs are a comparatively young field. The first ones were
released in 1992 IIRC... CPLDs are a bit older and have a lot more in common with PALs,
which in turn have a lot more in common with ROMs. It's not impossible for the
industry to change tracks in the future (certainly something I'd like to see).
I'd love
to get into FPGA hacking. But not nearly enough so to
tolerate something as abusive towards their users as "you have to run
our closed-source code". :-=FE
From a _hobbyist_ perspective, I am not sure you're missing much. I've
designed with FPGas as part of a job, and didn't enjoy it much. It is
very different from designing logic cirucitry the old-fashioned way for a
start.
For a one-off design, where size is no real issue, I much prefer to grab
a handful of TTL pacakges and start soldering. From that standpoint, I'd say you'd have almost
as much fun with simulation as with the real hardware. The real hardware is a much bigger
headache than simulation, because unlike simulation and a board full of TTL chips, you
can't go in and probe specific nodes without rebuilding the design.
That said, I do FPGAs for a living and I enjoy working on them from a hobbyist
perspective, but largely because I don't have a huge library of TTL parts at my
disposal (and it's expensive to acquire them all at once, and decent wire-wrap boards
are hard to come by at least in the US, etc).
The availability of nice FPGA eval boards (like the Terasic ones, which I absolutely love)
make it attractive to me. I'm still working on my 68000 SBC, but it's mostly in
concept only until I can find a decent source of wire wrap boards (the kind with traces,
not just bare phenolic) around here.
- Dave