Re: Homebrew STG card

[Karl Klemm <kklemm-at-WPI.EDU>]

With regards to the Xilinx FPGA chips, I have access to computers that
can program them if people want.  I would need a bit of help though.  I
also have Xilinx on my personal computer, but don't have the hardware.

				Karl 

On Thu, 24 Feb 2000, Jon Elson wrote:

> 
> 
> stratton-at-mdc.net wrote:
> 
> > > Another possibility is to encode all the logic, both ISA interface,
> > > digital I/O, and the encoder counters into a programmable gate
> > > array device.  Then, the entire board would consist of one big
> > > chip, like the Xilinx XC95160 and one or two A/D and D/A
> > > chips.
> >
> > He's right about that... plus with canned PCI interface libraries
> > (using these chips is like writing C code) interfacing to that more
> > popular bus would no longer be unrealistic.
> 
> I'm still looking for a cheap PCI library.  One that I know of is $9000.
> 
> > Even with ISA, some programmable logic saves all the address decoders
> > and the like.  It would be wonderful to fold in those pricey encoder
> > chips.  The only thing I wonder about leaving discrete is an 8255 I/O
> > - they are cheap enough that it might be less expensive to keep that
> > external and generate a chip select for it and thus save 24 pins on
> > the gate array.  Of course toss more than one or two chips on the
> > board and it becomes necessary to buffer the bus - but maybe we
> > already have to essentially do that for the DAC's.
> 
> Well, these XC95xx devices are SO cheap, and have SO MANY pins,
> that it is no biggie.  The slower devices are under $10.00 each in small
> quantity, and many have well over 100 pins!
> 
> > One big decision to make is if the LS7266 (encoder chip) register
> > structure should be copied, or replaced with something new.  I found
> > it a rather complicated programming model, but it worked fine once I
> > made sense of it.
> 
> Well, much of this craziness is to save I/O pins.  It is much less of a
> problem if a bunch of encoder counters share the same chip.
> If combined with a PCI interface, then all the craziness to read
> a 24-bit value without any possibility of the value changing before
> you have read all the bytes goes away.
> 
> Jon
> 
> 
>