[Coco] 6809 FPGA

[Dave Philipsen]

On 9/11/2015 12:17 AM, Bill Nobel wrote:
>>>> Personally I would recommend the AS6C4008-55PCN <https://www.mouser.com/Search/ProductDetail.aspx?R=AS6C4008-55PCNvirtualkey56240000virtualkey913-AS6C4008-55PCN> SRAM. It's 512K, 3.3v - 5v tolerant, and only costs around $4.50.
>>>>
>>>> Dave Philipsen
>>>>
> Well, I just ordered some of these,  I have dealt with Mouser lot’s. I should have them in a week or so.
>
> You know I appreciate this help greatly.  I am still a newbie at FPGA’s
>
> Bill Nobel
Well I know the AS6C4008-55PCN will work because I've got it running on 
two different FPGA projects right now.  Maximum speed that I can run the 
CPU core is 16.67 MHz with those.  But, when I used the internal memory 
I could go the full 25 MHz no problem.  While you're waiting on the 
Mouser shipment you should give the internal memory a try even if you 
only try 4K at first.  Grant's code enables it with this:

internalRam1DataOut when n_internalRam1CS= '0' else

and:

internalRam1DataOut when n_internalRam1CS= '0' else

Just comment out these:

sramData when n_externalRamCS= '0' else

and:

n_externalRamCS <= '0' when cpuAddress(15 downto 13) = "001" or 
cpuAddress(15 downto 13) = "010" or cpuAddress(15 downto 13) = "011" or 
cpuAddress(15 downto 13) = "100" else '1';




Dave




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