2600 Flash cart tech help

[Paul Slocum]

You don't need to change the ROM image for it to work. Except that you need to double 2k ROMs into 4k. You can do it easily in DOS:

 

copy kaboom.bin kaboom4k.bin

type kaboom.bin >> kaboom4k.bin

 

-Paul

[Goblin]

Thanks, but I doubt that is it. From my programmer I already filled in the remaining 2k with a copy by cutting and pasting. The problem occurs with both 2k and 4k images, and actually the 4k images are what I've been playing around with mostly.

 

When I have some 4k banks empty and some with images, the blank banks cause the system to act like no cart is present (as expected), but banks with images (as described earlier) cause the system to do "something", just not what I expect.

[Paul Slocum]

I built quite a few multicarts, and when I had problems I would try using a 2732 with a 4k ROM just to verify the data/address/CE/etc. lines were all correct. It should fit in your socket and work by just moving the +5V wire. There are a lot less things that can go wrong with just a 2732.

 

Why are you using an EEPROM? Are you going to make it so it can be reprogrammed without removing the chip? That would be pretty neat.

 

-Paul

[Goblin]

I’ve been working on flash (eeprom) multicart for the 2600. I’m using a 256k eeprom, the higher order address leads A12-A14 go to a dip switch and the overall design is very similar to the one on Bob Colbert’s page. I’ve inverted the ~CE through an ’04, tied the ~OE low. I’ve made necessary changes to the design to account for a few different pin allocations and have tied the WE enable high so when in the socket it’s permanently in read mode.

 

I’m sure the HW is correct, in fact I’ve made two different carts: one is a lot cleaner than the other. I think my problem is lies in the actual programming of the eeprom. I’ve tried programming both 2k and 4k roms. I place a different copy of the rom image into each address starting at $0000, and then continuing to $1000, $2000, …. Do I need to pad or massage the .bin image any to get it working on actual HW. Depending upon the rom image I sometimes get a black screen, sometimes I get an image what appears to be a smashed playfield, that is otherwise un-playable and un-recognizable.

 

Anyone have experience with this, or else have a suggestion? Right now I’m stumped.

[Goblin]

Thanks for the tip, I'm going to try and get some clean 2732's this weekend and try it out. I may try replacing the original masked ROM in the meantime.

 

My main motivation for moving to EEPROMs was availability. I was able to order samples from various companies and had them sent to work. Plus I do own an eprom burner, but I don't have a U/V eraser so I didn't want to deal with erasing the ICs. EEPROMs seemed to be the easiest way around this. Eventually I do plan to make a version of the cart that can be upgraded on the fly, however I need to walk before I can run.

[Goblin]

No matter how careful I thought I was it turned out I had a wiring problem. That's now behind me and this thing works great. I can't wait to use it to start showing friends my own graphics hacks. Next week I'm going to begin coding of my first original game. I can't wait.

[Paul Slocum]

Glad you got it working! I made a ton of wiring mistakes too. It's easy to do.

 

-Paul