Hi,

A little problem with the C-One is that the 65816 is sharing the bus
signals with the 128K SRAM. So for enabling the 65816 it would be
easier if the SDRAM slot was used instead of the SRAM. I have tried a
couple of times to get the SDRAM working without success.
There is a picture viewer example on the official C-One website that
uses SDRAM maybe you can try to merge it's memory controller into
FPGA64. Keep in mind though that a lot of software won't run on a 65816.

Other option to increase color ram to 8 bit is moving the color-ram
from internal to external S(D)RAM. Currently it is inside the FPGA.
I'm not sure if this saves any logic, atleast there is more memory
bits free to move logic into (which the Quartus software can do sometimes)

If compatibility is not important you can also save some logic by
removing the 'illegal opcodes' from the 6502 core.

Peter


--- In cone_cores@yahoogroups.com, "sixofdloc" <six@...> wrote:
>
> Moderator, if this is not appropriate for this list, please delete and
> direct me to the proper place for this sort of question.
>
> Now, I'm modding the current FPGA64 core. Having extended the color
> ram to 8 bits (in exactly the manner you would expect), I set about
> trying to add another video mode, using ECM+BMM and making each cell's
> 00 bit color from the upper 4 bits of the current color ram, like so:
>
> elsif (graphicsEnable = '1') and (MCM = '0') and (BMM = '1') and
> (ECM='1') then
> -- Multi-color bitmap mode with cellular background
> case currentPixels(0 to 1) is
> when "00" => pixelColorStore(0) <= currentChar(15 downto 12);
> when "01" => pixelColorStore(0) <= currentChar(7 downto 4);
> when "10" => pixelColorStore(0) <= currentChar(3 downto 0);
> when "11" => pixelColorStore(0) <= currentChar(11 downto 8);
> when others => null;
> end case;
>
> This is where I run out of cells. I tried dumping the lightpen stuff,
> but I'm still at 5040/4992. Obviously this won't do, so I looked
> about for something else to dump. The first thing that comes to mind
> is dropping the 6502 and using the 65816 that's built onto my board.
> This brings me to my question for you core gurus:
>
> How could one go about making the FPGA64 use the onboard 65816 so that
> I could drop the 6502 part of the core?
>
> Thanks for any info on this,
> 006
>