FPGA VAX update

[Peter C. Wallace]

On Sat, 5 Nov 2005, Tony Duell wrote:
>
>> Unfortunately, many of the more interesting TTLs are now no longer
>> easily available (you find lots of octal
>> drivers and registers,  but almost none of ALUs, multifunction chips,
>> RAMs - even the classical
>> 7490,7491,7492,7493 combo of counters for any purpose is reduced to
>> 7490/7493 - noone
>> needs to divide by 6 ('92) any more - you don't build digital clocks in
>> TTL) - you have to seek for
>> them in specialized mail-order shops. This is no issue for us old farts
>> who play with such stuff for
>> long time, but it is another hurdle for starters. A kit with all parts
>> is much easier to acquire - but then,
>
> Waht somebody needs to do (and it can't be me for obvious reasons) is to
> select some CPLDs/FPGAs where the download protocol is documented (that
> is, you can progam the chip, given the binary file, without a proprietary
> programmer), and use the tools (that's why it can't be me) to make some
> useful logic functions -- things like an <n> bit universal shift
> register, <n> bit ALU, counters, even JK flip-flops, gates, etc. Make the
> binary files available for free download.>
> Anyone wanting to experiment with logic and not wanting to use the
> horrible CAD tools under an even worse OS, can then program up some chips
> with the appropriate files and use the resulting devices like the TTL of old.
>
> -tony
>

I think that most if not all of the ISP (In System Programmable) CPLDs have 
documented download protocols so that they can be reprogrammed by 
microcontrollers. Xilinx even has a smaller binary varient of SVF files (XSVF) 
just for this purpose.

Only problem is most of the newer, easy to program parts are in surface mount 
packages, though PLCC 44s are not too bad. A Xilinx 9536XL in that package is 
about a dollar, a 9572XL about $2. I Believe someone has made a complete CPU 
(but no memory) in a chip somewhat smaller than the 9536...

Peter Wallace