PCB with only one eprom. exist?

[coderbr]

I would like to know if there is any example of atari card that does not use special chips. That only uses one eprom preferably 27c512. Where I can record the rom to use and do my tests. Thanks if anyone has an example of gerber or photo.

[alex_79]

Eprom typically have active low chip select pins, and in the 2600 the cartridge has to be enabled only when A12 is HIGH, so you need to invert that signal and this is easier to do using a logic chip like a 74LS04 than discrete components.  

 

So the simplest cartridge that you can build contains an eprom and the inverter chip. But you're limited to 4KB in this way, as the Atari only has 12 address lines (A0 to A11) available for the cart, while A12 is used as chip select.

Data pins D0-D7 and addresses A0-A11 are connected directly between the Eprom and the Atari, as well as Power and GND. A12 from the atari is conencted to an input of the inverter, and the corresponding output goes to /OE on the eprom, while /CE is connected to GND (You can swap those last two connections, using /OE to enable the eprom gives shorter access time at the cost of a slightly increased power consumtion, but it doesn't really seem to matter on the 2600).

 

As said you can only access 4kb in this way. If you're using larger eprom you have to set the extra address lines to  a fixed value and the rest of the eprom would be inaccessibile. Alternatively, with some switches and resistors, you can build a multicart.
Here is an example:
http://www.thehopelesshobbyist.com/games/atari-2600-32-in-1-game-cartridge
(e.g. using a 27c512 you can build a multicart using 4 swicthes to select between 16 4KB roms)

 

If you wan to play a game that is larger than 4kB, you must build a cart that supports the bankswitching scheme that particular rom was programmed to use.

Some links:
http://www.grandideastudio.com/pixels-past/

https://hackaday.io/project/12961-atari-2600-bankswitch-cartridge

https://web.archive.org/web/20190609093353/https://www94.pair.com/jsoper/

https://rdemming.home.xs4all.nl/Atari/MultiCart2600/

https://web.archive.org/web/20080305113143/http://www.atarionline.com/ataricart.html

P.S. This topic about eproms and building cartridges really belongs to the "Hardware" forum. The "Programming" subforums are about writing software for the 2600.

 

[coderbr]

Thanks for all the explanations. They are being very useful. Sorry for the post here. But I had clicked on "2600" and ended up on the list:

*2018 Atari Awards!
*Atari 2600 Programming
*2600 High Score Club
*Harmony Cartridge
*2600 Game Descriptions
*AtariBoxed.com Rarity Database

so I thought this was the best place ... now I found the hardware section.
In the future I will post these questions in the hardware section. Thank you.
Just to complement, I also found this on the internet ... used a transistor to do the inversion you said:
https://www.pakequis.com.br/2008/09/multicart-para-atari-2600.html