Retro Adventures ..was Cart connector OE pin?

[+karri]

I did make a small cart for my simple games. But to my surprise there was no *OE pin available on the cart connector. In the Lynx we had *CART0 and *CART1 to set the data bus to output mode. How is this done on the 7800 carts?

[+batari]

47 minutes ago, karri said:

I did make a small cart for my simple games. But to my surprise there was no *OE pin available on the cart connector. In the Lynx we had *CART0 and *CART1 to set the data bus to output mode. How is this done on the 7800 carts?

Generally, with a logic chip.

 

A 48k cartridge board, for instance, maps to $4000-$FFFF, so it can use a single gate in a quad 2-in NOR chip (7402). A14 and A15 as inputs to one gate, and the EPROM enable on the output.

 

Boards with bankswitching will put this logic on the PLD.

[+bsteux]

Here is an example of a simple 7800 cart : http://atarihq.com/danb/7800cart/C025513.shtml

/CE (Chip enable) is, as Batari stated, generated from a logic (here a simple 74LS138) using A14 and 15.

[DanBoris]

8 hours ago, batari said:

Generally, with a logic chip.

 

A 48k cartridge board, for instance, maps to $4000-$FFFF, so it can use a single gate in a quad 2-in NOR chip (7402). A14 and A15 as inputs to one gate, and the EPROM enable on the output.

 

Boards with bankswitching will put this logic on the PLD.

Bank switching can also easily be done with discrete logic, here is a cartridge that does it with three logic chips...

 

https://atarihq.com/danb/7800cart/C300595.pdf

Edited October 18, 2023 by DanBoris
typo

[+karri]

1 hour ago, DanBoris said:

Bank switching can also easily be done with discrete logic, here is a cartridge that does it with three logic chips...

 

https://atarihq.com/danb/7800cart/C300595.pdf

Thanks! I happen to have about 40 pieces of 512k flash chips. I already made a pcb for them but of course it did not work as I messed up the design. I may stills salvage the design by just soldering a 74LS02 on them. But adding 3 chips - nope. Too much work.

 

The only problem is that my appetite for better carts has increased after playing with the SN cart. So I may just skip the idea of creating my own carts.

 

PS. I did put an order for NOR gates. So I can add a thumb wheel and burn 8 small 48k games on it. Most of my minigames like Pirate Cove, Drunk Witch, Cameltoe... fit well in this cart. Besides, then I don't waste the pcb's I already have.

[+karri]

After a little thinkering I got the cart working in 48K mode. But the next problem is how to program it. The 74ls02 interferes in how the OE to the flash goes. I believe that this circuit should work.

 

Setting 8 means that the 74ls02 logic is disabled and I can program the cart from the Lynx connector.

Settings 0, 1, 2, 3, 4, 5, 6, 7 chooses one of the 48k games on the 512k flash cart.

 

The Lynx connector allows programming the entire chip while the 7800 connector sees just 64K.

[+karri]

And the design works!
Programming the card. Don't pay any attention to the rats nest around the 74LS02 chip.

Here I run the Cameltoe game on the real hw.

[+karri]

I just printed a 3D enclosure for my cart. But there is one thing I am unsure about. There is 2 plastic pins sticking out on both sides of the PCB connector. Obviously they are not needed for anything as the cart works with the 7800 even with no pins. Is there some kind of "cart inserted" detection implemented with these pins? Actually I doubt it as on my PAL unit Asteroids is running even when the cart is inserted if the flash content is 0xff.

[+batari]

There is no pin detection, but instead the PAL BIOS performs some heuristics on some areas of the cart address space to guess whether the cart is 7800, 2600, or if no cart is inserted. I think what you are seeing is a check of the reset vector for $FFFF, which will start Asteroids.

 

[+karri]

36 minutes ago, batari said:

There is no pin detection

Thank you for the info. Then I leave these pins out from my 3D design. It is being printed right now. The slot to the left is for a game selector. There is two buttons that move the dial between 0..9.

The bottom part was too flimsy but the design is ok.

[+karri]

Now I modeled the top as well. And rounded the corners.

Even the first game to put on it is starting to take shape using the new cc7800 compiler.

[+karri]

Happy with the final cart. At least with the mechanics.

[+karri]

Edit. I got help for proofreading already!

 

I started to write a little text adventure for the 7800 and the upcoming 2600+. As I am not a fluent English speaker I wonder if some native English speaker could help in fixing my mistakes with sentences for the games. The plan is to create a few new adventures using the new cc7800 compiler. I am also abandoning the typical North, South, East, West, Up, Down navigation technique. Instead I use the real names for the locations and only show options that are relevant to the current room and situation. So it will be more fluent to play compared to the old text adventures.
 

As you may see from this thread I have real hardware for about 40 carts only. Most of these may be just giveaways at different events. So this is an economical disaster project anyway. Nobody gets paid, but you may get a cart and your name in the credits. I hope to put together some nice interactive fiction. Perhaps even with some minigames.

 

[+saxmeister]

@karri I would be willing to work on the English text that you have. I've done this before on other projects (I also do voiceover, but that doesn't apply here). Let me know if I can help.

[+karri]

21 minutes ago, saxmeister said:

@karri I would be willing to work on the English text that you have. I've done this before on other projects (I also do voiceover, but that doesn't apply here). Let me know if I can help.

Thank you. I already got a lot of help with the language from @MrZarniwoop. So I try to make some fun storylines with him.

[+karri]

I finally got my fixed cart  It works like a dream!

 

Now the only problem is that my games do not work on the 2600+. And the 2600+ does sense whenever I flip the dial to the next game. So this would be a nice collection cart for all my adventure text games