600 Memory board modification

TF530 - 63030 + RAM Board

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Homer79
Posts: 44
Joined: Wed Dec 05, 2018 8:03 pm

600 Memory board modification

Post by Homer79 »

http://nedopc.com/lvd/Projects/

This A600 memory board has two variants. The 2008 version can do three modes. 8mb,4mb, 4mb+1.5mb slow fast ram.
The 2007 version can either do 4mb or 8mb depending on the firmware installed.
I figured it should be possible do a firmware fix to impliment the 4mb+1.5mb version without the need of config pins
as that was the reason for the bigger cpld in the 2008 edition.

So far ive managed to recompile the 4mb source with quartus 8.1 with a lot of help from lvd - this works fine

I then modified code to allow for the non autoconfig memory from $C00000 - $C7FFFF It was easier to just allow
an extra 1mb of memory as it was a simple binary adjustment.

All I get at the moment is a bright pink screen, but this was tried on a A500+

original code

// chip selector decoder
always @*
begin
casex( high_addr )
8'b001xxxxx: // $200000-$3fffff
begin
{which_ras[0],which_ras[1],which_ras[2],which_ras[3]} <= 4'b1000; // /RAS0
mem_selected <= 1'b1;
end

8'b010xxxxx: // $400000-$5fffff
begin
{which_ras[0],which_ras[1],which_ras[2],which_ras[3]} <= 4'b0100; // /RAS1
mem_selected <= 1'b1;
end

default:
begin
{which_ras[0],which_ras[1],which_ras[2],which_ras[3]} <= 4'b0000; // nothing
mem_selected <= 1'b0;
end

endcase
end


Modified code

// chip selector decoder
always @*
begin
casex( high_addr )
8'b001xxxxx: // $200000-$3fffff
begin
{which_ras[0],which_ras[1],which_ras[2],which_ras[3]} <= 4'b1000; // /RAS0
mem_selected <= 1'b1;
end

8'b010xxxxx: // $400000-$5fffff
begin
{which_ras[0],which_ras[1],which_ras[2],which_ras[3]} <= 4'b0100; // /RAS1
mem_selected <= 1'b1;
end
//modified section
8'b11000xxx: // c00000-c7ffff - slow memory mapping
begin
{which_ras[0],which_ras[1],which_ras[2],which_ras[3]} <= 4'b0001; // /RAS3
mem_selected <= 1'b1;
end
//
default:
begin
{which_ras[0],which_ras[1],which_ras[2],which_ras[3]} <= 4'b0000; // nothing
mem_selected <= 1'b0;
end

endcase
end

If anyone can help I would be extremely greatful
Homer79
Posts: 44
Joined: Wed Dec 05, 2018 8:03 pm

Re: 600 Memory board modification

Post by Homer79 »

I will post the quartis project files once I've cleaned up them up slightly, as some of the original project files are no longer available.
dalek
Posts: 224
Joined: Thu Nov 08, 2018 11:03 am
Location: NSW Australia

Re: 600 Memory board modification

Post by dalek »

Just checking you've seen the versions from mkl?:

http://www.mkl211015.altervista.org/ram ... dcode.html
Homer79
Posts: 44
Joined: Wed Dec 05, 2018 8:03 pm

Re: 600 Memory board modification

Post by Homer79 »

I have, but the memory chips are extremely difficult to get. I have found one seller, but they want $7 a chip
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