16k rom hardware

[Mortis]

Hi everyone,

 

I apologize in advance if I missed information on this; I couldn't find anything that helps me out (not saying that it could be that I'm just not all that bright).

 

I have "burned" many 8k rom files to cartridges for both the C-64 and the Atari 400/800 machines.

 

I have the PCB that requires a 74ls00 chip which i populated along with the cap and I absolutely can't get a 16 k rom to execute correctly. Any that I test (verified fine btw) starts the Atari directly to memo.

 

My main objective is to get Fort Apocalypse on a physical cartridge (loved that game). I have also tried boulder dash and other's to no avail. They all boot to memo.

 

Anyone want to share what I'm doing wrong?  I know that these may have been two proms and etc, but I thought that the 74ls00 was designed to mitigate that. 

 

Oh, i've been using M27C64A eproms. Also any 8 k roms work perfectly (even with the 74ls00 installed).

 

Thanks for looking ?

[Rybags]

I suspect you have the wrong type of board.  A 74LS00 would be used to perform bankswitching.

 

Both those games you mention run as a standard linear 16K Rom.   Generally when there's 2 IC sockets they will represent Lo/Hi, ie $8000-$9FFF and $A000-$BFFF.

Possibly you could get it going without the logic chip, maybe some jumpering would be required.

Edited May 1, 2021 by Rybags

[Mortis]

Hi Rybags!

 

Thank you for the quick reply.  Much appreciated.

 

I'll try a jumper and see what happens. 

 

I'll reply back if no-go...

 

Thanks again ?

[Rybags]

For reference https://www.atarimax.com/jindroush.atari.org/acarts.html

 

The way carts work - they indicate presence of upper and lower portions on the RD4 and RD5 lines.  On banked carts these can change state, on normal linear carts one or both will be always active (though not RD4 on it's own)

The memory selection works by lines S4 and S5 (active low which suits the CS pin on many Roms) - they select the low or high Rom (both will be inactive or one active at any given time)

CCTL (active low) when a memory access to the $D5xx area occurs.  This is the most common way that bankswitching is performed.

[Mortis]

Rybags, thank you for the awesome link there and all your help.

 

I did verify my programming but for some reason I had missed the part where my ROM ends at 1ff0. Remember what I said out my brightness before... 

 

So I am now using a 27c128...

 

Thank you again 

[ClausB]

1 hour ago, Rybags said:

one or both will be always active (though not RD4 on it's own)

With a right cart in an 800 and no left cart, RD4 will be active on its own. ACE80 is an example of a right cart which can work this way.