nesdev.org

I have an NES with a CopyNES installed I've been using to dump roms, mostly for use in emulators. Recently, I decided it would be fun to get into the development scene and I started programing some simple programs in my emulator using NBASIC. I would like to try running these on a real NES, with something more permanent than a powerpak lite. My programs are simple and I have a whole bunch of Original Mario Bros donor carts laying around (3 total). Is there anyway I could convert these to makeshift dev carts? I'm totally new to this, but I know a guy who can do the soldering if I just had a simple guide for this cart. I know the hardware on it is limited, but I honestly don't really care. Is it possible?

Thanks in advance for your patience, I am totally new to the hardware side of things.

Sure if you have a copynes it's real easy. I could give you detailed instructions......but you could just download the copynes program + files from kevtris's site (he originally made it)......a txt file describes how to make an nrom dev cart (his site is www.kevtris.org )

Thanks a bundle my friend, just what I needed!

I found a guide to get a ram cart built, but I want something more permanent, perhaps EPROM based. Would these parts serve fine for that purpose if I just substituted them in in the RAm cart guide, or am I oversimplfing things? Some of thing pins don't seem to match up so I'd like to check first.

http://www.futurlec.com/Memory/27C128-120.shtml

256kbit RAM and EPROMs pinouts are almost the same, only the WR pin doesn't exists on ROMs, and the P pin doesn't exist on RAM (both should be put to VCC anyways).

My concern was the guide I read seemed to refer to pin 27 as the VCC connector, and the schematic I linked refers to the VCC as pin 28. Also, there seem to be a few other things that just don't sound right to me. If anyone could kindly confirm/deny that the above chip could be made to work, I'd be most thankful. Otherwise, advice on where to obtain an appropriate chip is also welcome.

Thanks again guys.

It could be made to work. Pin 28 is VCC, but pin 27 is P (or /WE for RAM) which is only used by the EPROM programmer so it should be put to VCC on the cart too.

Yes. I hope I'm not sounding redundant, but I'm going to clarify one last thing.

This sentence in the NROM ram cart guide concerns me:

You will now have to solder a small piece of wire on the bottom of the board across pins 26 and 27 of the 8K RAM chip. This will connect +CE to VCC.

If you look at the scematic, pin 26 is A13, not the Chip Enable (it's pin 20 according to the schematic). Pin 27 is P, not the VCC. Why are we soldering them together? Am I just missing something huge here? Probably, but I don't want to order these parts and just ruin a cart either.

On 8kb (64kbit) SRAMs (6264 compatible) pin 26 is positive CE. Since the RAM is 8kb the higher Adress is A12. The shematic you linked is a 16kb (128kbit) EPROM, which does have an A13 at pin 26 instead. You don't want to tie it to VCC unless you want to restrict yourself to 8kb.

For NROM carts normally no rewiring is needed. It's only needed if you rewire a NROM-128 to a NROM-256 or the other way arround. It looks like you're looking for NROM-128 because of the 16kb (128 kbit) EPROM.

Bregalad wrote:On 8kb (64kbit) SRAMs (6264 compatible) pin 26 is positive CE. Since the RAM is 8kb the higher Adress is A12. The shematic you linked is a 16kb (128kbit) EPROM, which does have an A13 at pin 26 instead. You don't want to tie it to VCC unless you want to restrict yourself to 8kb.

For NROM carts normally no rewiring is needed. It's only needed if you rewire a NROM-128 to a NROM-256 or the other way arround. It looks like you're looking for NROM-128 because of the 16kb (128 kbit) EPROM.

Thanks for all your help, I think I am starting to understand. I need to get an 8KB EPROM chip for the CHR memory, and then a 16KB EPROM chip for the PRG memory, just like the original board. That should make no rewiring neccesary. However, the guide calls for a "32KB SRAM chip." Should I sub in a 32KB EPROM Chip, or is that unnecasary and a 16KB EPROM chip like the one above will do just fine? I want the pinouts to remain the same as in the guide so when I give it to my buddy to solder, he can follow it easily. I understand the electronics pretty well, just can't wield the soldering iron worth anything.

EDIT: Here's the other 8KB chip I was looking at. It lists pin 26 as "NC" or "Not Connected." Is it just me or is that not right?

http://www.futurlec.com/Memory/27C64-200.shtml

It's right NC means the pin is unused.
You can get both 16kb and 32kb EPROM and solder them without ANY rewiting to get a 16kb PRG cart, just if you get 32kb remember to programm your data in the SECOND half of the ROM (since A13 will be put to VCC by the board).

If you want to transform your board into NROM-256 to use all 32kb of PRG, you'll have to bend up pin 27 and wire it to actual A14 on the cart connector so you can use all of 32kb.

I think I understand most everything now, but just one thing is still bothering me.

Shouldn't pin 26 be CE thought rather than "not connected"?

It's a positive CE for RAM and unused for 8kb ROMs.

So there is no positive chip enable on an 8kb rom? Or is pin 20 on that schematic the positive chip enable?

(I'm pretty sure this is my last question, thanks for your patience)

One note....are you using eproms? Cause you cant program those using copynes (iirc) since they need a special voltage to be programmed.