[Coco] CocoFlash Updates

[RETRO Innovations]

On 9/12/2016 12:25 PM, RETRO Innovations wrote:
> http://www.go4retro.com/projects/cocoflash/
>
>
> With apologies to Zippster, but in July or so, Barry asked if I could 
> squeeze the Orchestra 90 functionality into the CocoFlash, so folks 
> could assume some additional sound options for games and such.
>
> This Summer was hectic, but I was able to do so, and the conversation 
> in the list around the circuitry was very enlightening.  The Orch90 
> functionality analog section is the top right of the cart, the R2R 
> ladders are most prominent.  I used discrete resistors since I helped 
> with layout and I could get the wattage rating I wanted more easily 
> and more cheaply.
>
> In any event, the (hopefully) finished cart design is shown above.  
> (The wire is due to a trace issue caused by some debugging efforts).  
> I have verified the sound waveform matches the OR90 output, but has a 
> but more Vp-p, since I opted for some newer ABT-family latches, which 
> drive to the rails a bit better.
>
> When I get some time, I'll put some more information on the design on 
> the web page, but feel free to ask questions if desired.
>
> Jim
>

Kudos to Barry, as he found a bug in my CocoFLASH Verilog, (writes to 
ff7a were mirroring to $ff5a, which is where the bank register is 
located, which meant songs were flipping the bank register all the time 
and causing crashes).

Luckily, I had put some code into the unit to "move" the base address of 
the registers, so Barry was able to move it to $ff50, which does not 
conflict (until I can get the new code to him)

Does anyone know of a single address in the $ff40-$7f space that is not 
used by anything?  I assume not, but thought I would check.

Jim