Re: programmable logic

>I was just getting ready to spam vectorlist in search of interesting logic
>arrays. I have a very nice vector generator design that's fully digital
>that uses 3 10 bit latches, an adder, a 10 bit 2 channel mux, and 2 ten bit
>counters connected to the DACs. It very simple, but unfortunately I can't
>find any commonly available micros the run fast enough to do this in
>software. You need to update the DAC counters on a digital vector
>generator at a 3.33mhz (avg) to generate the vectors.

Ahhh. We're looking at the same thing. You ran into the same "gotcha"
that I did-- need speed for digital vector generator. Plus it seems silly
(not to mention tedious to prototype) a small army of TTL logic... :-/

>A 20mhz PIC internally divides the clock by four, so it runs at a 5mhz
>speed. Too slow.

Right, this is why I went to an Analog Vector Generator like Atari did.
Another way (that Atari also did, but never made it out the door) is to
use a DSP with a couple serial DACs. The Analog Devices 2105 is cheap and
friendly to program...

>The new SX 50mhz part that runs at 50mhz (no internal
>divide by 4) could do it (well the counters would still have to be external
>because of the number of I/O lines available, *and* it's still not fast
>enough to handle the counters), but are they available yet? And can it be
>programmed using a standard PIC programmer?

Supposedly they're sampling now (October) and full production in Q4.
Programming doesn't look to be by a "standard" PIC programmer (like a
PICMaster or something). Parallax however is offering a programmer/ICE for
$249. That's pretty cool assuming it's a full speed ICE for that price.

You *can* get away with overclocking PICs quite a lot. I've heard that
32MHz on the 20MHz parts is pretty solid, but that 40MHz is a little
twitchy.

>WSI makes a *very* fast processor that runs at 100mhz - at one clock per
>instruction, and can do multiple things on each clock, but of coarse no-one
>sells the processor but WSI (they're only interested in quantity orders),
>and you have to buy their custom hardware to program it.

Word has it that Western Design Center (the guys that own the IP for the
6502) have a fully synthesizable 6502 core in VHDL and Verilog. Depending
on the process it's been run at up to 173MHz... :-)

>How is the GAL6001 programmed? Must you buy a custom programmer from
>Lattice? (I've never had need to play with PALs, GALs, just an FPLA many
>years ago, and then just as an address decoder)

I'm trying to figure that out. :-/ Lattice is big on their ISP (in circuit
programmable) stuff, which is just a cable going from a few pins on a PC
parallel port to a header on your board. You can program all their GALs,
Generic Digital Switches, and FPGA's from the same 5-wire bus. Pretty
slick. I'm not so sure about the 6001 and 6002 though. Might take a
stand-alone programmer. :-/ I suppose you could always just use a 2032 or
something with the ISP cable, but I've never seen them available in singles
for cheap. (like JDR)

-Clay

Clayton N. Cowgill Engineering Manager
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Received on Fri Oct 3 17:14:55 1997