Re: Stellation Mill 6809 card clone / FPGA

[MdntTrain <js@cimmeri.com>]

On Jan 13, 1:28 am, steve.how...@altium.com.au wrote:
> > Ok, question Steve.   If we were to use a real CPU, would we really
> > need
> > an FPGA for such a small amount of glue logic?  Seems like it would be
> > extreme overkill.   Why would we not want to implement the 6809 in the
> > FPGA
> > itself?
>
> Absolutley, putting the whole board including its CPU into the FPGA is
> just touching on how most designs, if not all, will be in the future.
> Which is why the FPGA and the PB04 ASIC adaptor board are in two
> halves.
> One of the most notable issues when implementing this stuff, is how to
> hunt down bugs, and for first the first time, I found myself in awe at
> the fact that Alex's IIe came to a stop when I tried to use Apple's
> 3.5" floppy disk controller, due to a bug in the actual processor code
> itself (we are currently building a known good 65C02 core to fix this
> - the freebies from the net are buggy). So what Im trying to say is,
> by using a real 63C09 in PB04, we can design the support logic first
> and confirm it all works correctly. Then we bring in the soft 63C09 to
> replace the real one, and make sure it works correctly. Once its all
> ok, the PB04 board is removed leaving the final design all inside one
> weeny FPGA, hopefully with all out hair intact.
>
> Is the FPGA we are using overkill for such a small amount of logic we
> have to support? Yes. But with the 50AN costing only $9, and the 250E
> only $18, its definatley worth it. It makes for a cheap and easy 2
> layer board, simple to design in the FPGA space, as well as to
> download, makes a nice simple bill of materials (one chip), and gives
> us lots of logic to experiment with in the future - ie, you could add
> Alex's Z80 soft card in there well. But more importantly, it gives us
> the required logic to put all the soft tools, that once sat on the
> bench, into the FPGA whilst we build the design. Tools such as logic
> probes, logic analyzers, decoders, ROM images, etc.
>
> And the FPGA's just keep getting cheaper.
>
> Steve

Well, I have no idea how to do any of what you're saying, but I'm sold
and willing to try it out.

I probably will also try to make a regular board as well.

 JS