FPGA VAX update

[Scott Stevens]

On Fri, 4 Nov 2005 20:31:25 -0800 (PST)
"Peter C. Wallace" <pcw at mesanet.com> wrote:

> 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...
> 

An interesting development that I have noted is people selling modern FPGA chips on salvaged boards on eBay, i.e. the chip all soldered onto a card and ready for hobbyists to fool with.  I am talking about 'salvage' boards, meaning in at least several instances it looked like the area of the board with the FPGA on it had been cut out with a tinsnips.  The FPGA and board was salvaged from some bigger project.

In many designs, there is a hole-per-pad zone surrounding the whole FPGA for testing purposes, and the chips can be 'recycled' in this fashion pretty easily.  It gives people who want to fool with these chips an easy way to get at them without needing to do any fine-pitch SMD soldering.  Sort of the poor-mans 'development board' (i.e. the more pricey eval boards that Xilinx and Altera sell)


-- 
http://sasteven.multics.org/MacSE30/MacSE30.html