Still need a "little" help on bankswitching with E

[Cassidy Nolen]

Hi all,

 

I have tried to do this without bugging the group any more. I do however have proof that I have been trying

 

 

As you can see, I have made quite a mess...

 

My questions are a little more focused this time. I am sure that the program is on the eprom. I have matched the pins to the 2732 that will match up, and have a few questions about the others...

 

I have wired in the 74133, 7474 and the 2 7404's (one on the board, like a 4K game, and one into the bankswitch circuit like the diagram that is floating around), but there is no mention of what to do with pins 1, 2, 27, and 28? Currently, I have them bent up just hanging around. I know that pin 2 is A12, but everything keeps saying "there is a difference between A12 and /A12 on the eprom (I may have that backwards)". Can someone point me toward the difference?

 

I am trying to make a Tempest cartridge; beginning to be more work that its worth.

 

Thanks, I really do appreciate you all and your advice. Special thanks to those of you who emailed me.

 

Cassidy

 

BTW, how do you have your setup rigged for checking things out? This seems like a very difficult process to repeat over and over.

[Thelen]

you have to connect a12 (pin 2 of eprom) to the 7474 ic pin 5 (this is Q0) and pin 28 and 27 of the eprom connected to the +5V. and make sure the CE from the atari(a12) is going uninverted to the 74133 and inverted to CE (pin 20) of the eprom. pin 22 of the eprom (/oe) must go to gnd.

but i see you use a regular cart pcb, did you just solder the 2764 on the board? you will have to modify the pcb so the pinout of the rom (which was on the board) is the same as the 2764. the rom which was on the board is pin compatible with an 2532, but a 2764 not. so you have to modify the pcb (if you didn't)

 

thelen

[jsoper]

Hi Cassidy.

Thelen gave some good advice. I'm confused that you're having trouble understanding the A12 issue. If you built a 4k cart before, it should be clear to you. Also a 7404 has 6 inverters on it, you don't need a second one. http://www.falstaff.demon.co.uk/GIICM.html

is real handy for IC pinouts.

 

I built this circuit onto a protoboard first (you just plug IC's into it). After it worked, I attached a chuck of perfboard to the cartridge board by soldering stiff wires onto the ground contacts. The bankswitch circuit was wired up on the perfboard using sockets, even my eprom was socketed. The problem with soldering an IC is that it might go bad because of heat , then it's hard to debug and replace.

 

You might want to try burning an 8k eprom with a 4k game repeated twice. The game should come up whether it bankswitches or not. Good way to check the setup.

 

You're right that this is work. I only did it once, was trying to make a 500 game multicart. It's mostly working, one of the three eproms has problems and the RAM option is flaky. It has about 400 playable games right now and I spent weeks on it.

 

Don't get discouraged, you're getting there

John