Re: [stella] Fpga2600 Status Update

Subject: Re: [stella] Fpga2600 Status Update
From: "Kroko" <Nil.Krokodil@xxxxxxx>
Date: Sun, 20 Mar 2005 09:32:34 -0500
Hi Adam !

What a nice piece of VHDL code ! I will better not ask how may hours you 
spent on this :-)

>(This is where you can make me feel good by cheering me on, if nothing 

Are you planning to release a cleaned version of the TIA schematics with 
modern, readable
symbols where all the questions are answered that you had to find out in the 
last few month ?


----- Original Message ----- 
From: <adam@xxxxxxxxxxxxxxxx>
To: <stella@xxxxxxxxxxxxxxxxxx>
Sent: Sunday, March 20, 2005 4:26 AM
Subject: [stella] Fpga2600 Status Update

> Hash: SHA1
> [regarding ]
> It's been a while, so I thought I'd update.
> As you know, the RIOT code is complete and tested.
> I've been pounding away at the TIA code recently, mostly spurred on by
> releases of various commercial projects and another similar open source
> effort.  (The author of that other effort hasn't released any code yet,
> but promises he'll make it open source when he's done).  At this point
> I don't care so much about finishing first as I do about finishing;
> I picked this project up to learn something new, and I'd like to see
> it through.  (This is where you can make me feel good by cheering me on,
> if nothing else).
> Regarding the most recent tia.vhd checked into CVS on sourceforge...
> (that's for those of you
> playing along at home).
> Analog output on the audio pins is a bit problematic for an FPGA.
> I've replaced the analog AUDIO0 and AUDIO1 pins with 4 bits each.
> I'll feed these into a cheap resistor ladder DAC and then into my 2600,
> as well as a pair of RCA jacks.
> Similarly, I've decided NTSC video is a bit of a pain; the current
> code outputs 4 bits of color, instead of the single phase shifted
> colorburst signal.  I plan to feed these plus the three luminance bits
> into a lookup table (basically a ROM) to get 4 bits each red, green,
> and blue, then use these to drive another set of cheap resistor ladder
> DACs which will drive the component colors on a VGA monitor.  I expect
> the picture to be sharp. :)
> As you'd probably guess, this means the DELAY pin is completely ignored.
> I'll leave true NTSC up to someone who's up enough on their analog to
> produce the correct phase shifted colorburst signal from those 4 bits
> of color.  I suspect, however, given the current target audience and
> expected usage of this code, that it will never actually happen, which
> is fine with me.  Now that we live in the 21st century, I think it's ok
> for the relic of NTSC to die.  This project is all about preserving the
> look and feel of the old games using new technology anyway.
> Simulations of the code look good, and I've ordered parts to interface
> my developer board to my 2600, and to a VGA monitor.  I'm hoping that it
> will go as smoothly as my RIOT testing went.  If it does, then I should
> have some good screenshots to share.
> Once that's done, the next step will be to evaluate the 6502 core I dug
> up way back when...
> - -- 
> adam@xxxxxxxxxxxxxxxx
> KG6GZR             
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