FPGA VAX update

[Peter C. Wallace]

On Fri, 4 Nov 2005, Scott Stevens wrote:

> 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)


Interesting, and you also get the power planes and bypassing done for you.

Another thing I have have seen is people getting large de-balled BGA FPGAs 
cheap from EBay and soldering bypasses and wires to the pads where the balls 
used to be (upside down BGA breadboard)


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

Peter Wallace
Mesa Electronics