Sega Genesis Cart PCB & 27C160 Compatibility

Ok, so I got a couple of 27C160's programmed. I just desoldered the mask roms, soldered the eproms to a Sega 171-6278A cartridge PCB made in 1992. This PCB is a single 16bit rom, SRAM, and the logic for the SRAM and a battery.

So, the game fails to do anything. There is no Sega license text or anything. I soldered the chip straight in, no wiring or anything. All the joints look good. The PCB seems to take care of the BYTE line by connecting it to +5v for Word Wide operation.

Am I missing something? Shouldn't I be able to just replace the ROM? I'm going to try putting the maskrom back on and seeing it if works as that would mean the EPROM is at fault, but does anyone have any other ideas what might be wrong?

Edit: The original mask rom I soldered back into place and it works fine. So either my eprom was programmed wrong, or the board doesn't just accept eproms? Don't you just take your BIN image and put it on an eprom? I didn't program the chip myself, but does anyone think it is likely that the byte ordering is backwards or something?

 

Sure the donor's a 16M game/A20 is connected? Probably the byte ordering is wrong.

 

I'm positive it's 16M. The game is World Series Baseball. The EPROM was programmed with the same BIN file you would load in an emulator. In a hex editor you can read all the cart info at the beginning that is ASCII text. Is that incorrect? Did I need to byte swap it before programming?

 

There are a couple of different pinouts for genesis roms. I thought that the one that has +5 at pin 32 also has +5 at pin 42 instead of A19.

 

Well I have traced and pin 32 (the BYTE line) is connected to the +5v line.

If the byte ordering is wrong, should I connect D0 - D7 of ROM to Cartridge D8 - D15, and D8 - D15 of ROM to Cartridge D0 - D7? I have two identical PCBs and identical ROMs so I guess I could bend up the pin on one and wire the data pins.

 

My memory is really bad, but according to this I'm more than sure you need to swap bytes before programming.

 

If it won't work on the first try then burn the EPROM again with bytes swapped... if any address lines are incorrect, you should most likely get a red screen (failed checksum).

When I was massing with the soft for my flash cart(and memory chip) burner/reader, it was the first thing that caused some problems, so I just changed some things in the soft to get things written on cart nicely

 

Well the problem with that TmEE, I don't have a burner. I had to get someone to program the roms for me and mail them back. Surely someone here has taken a .BIN Sega Genesis ROM image and programmed it onto an EPROM before. During programming do you have to select an Edianness or something for byte ordering?

I just spent several hours rewiring D0-D7 to D8-D15 to try to get it to work. Still nothing. I'm pretty well convinced that the EPROMs were not programmed they way they needed to be and that it's a lost cause. So this sucks.

 

Yeah, pretty sure .BIN ROMs are big-endian so you have to program them big-endian.

Well that sucks, you'd think they'd verify the ROMs...

 

I'm pretty sure they were verified, but I'm betting it was just programmed wrong. Was what I described about swapping D0 fot D8, D1 for D9, etc etc something that could compensate for reverse Edian? Just trying to figure out the exact cause of my headache here.

 

Yup, that should work.

 

Well then the ROM chips are at fault, because I rewired as I said and still nothing but a blank screen. But I guess atleast now I have a ton of experience soldering and desoldering chips now... Question, would the ROM being 100ns cause problems?

 

Nope, not sure what the problem is.

 

I guess I might try making a repro again but I think I'll try NES or SNES to eliminate the 16bit word edian issue. I actually have a Star Fox 2 eprom but I just haven't had the time to deal with that one yet. I really need to get some better wire if I'm going to do that one.

 

For my programmer, I first tried burning a byte swapped rom image and it was a total failure.

I then took a .bin file (I believe it's little endian format, intel as one can read any ASCII text fine in a PC/Windows hex editor ) as output by programs like U-Con.

That one worked fine.

I use a cheap chinese TOP2048 programmer.

 

I'll pull out some of my genesis stuff when I get the chance and help you if you want. I know I've got some 27c322's lying around. I'll see if I can find that genesis board in any of the games I have lying around. I just pmed you for some info on what you're burning.

As far as Starfox 2 goes, I just use I 30-32 guage kynar wire wrap wire. You can get it from radio shack. I like using a wire wrap tool to attach the wire to the eprom. Some prefer to use IDE cable because the wires line up, but it's never worked well for me.

 

I'd really appreciate the help. I may have to invest in my own eprom programmer if I can't sort this out with the guy that programmed these chips. I sent you an email with the info.

 

Can you get the chips you asked to "burn" re-dumped ? if you compare the dumps with the original files we might be able to figure out what went wrong...

 

When you burn something on the chip and then dump it with the same device, things would look same as original....

if you have a MCD, and a CD-R and a small MD controller port to LPT port cable, you can dump the cart and see if the system sees right stuff or not...
http://www.retrodev.com/transfer.html

Me loves my home made burner/reader http://www.hot.ee/tmeeco/EEPROM/INACT.JPG http://www.hot.ee/tmeeco/DWNLOADS/MPCPSHIT.RAR

 

Well, one of the two chips which should be the exact same, I cut part of the legs off of in order to fit it into the case with the data legs bent up to rewire D0 - D7 and D8 - D15 to be swapped. But the other chip should be dumpable if I desolder it as it is currently in the cartridge.

I might look into getting a 9 pin dsub and a 25 pin dsub to make that cable to dump the cartridge. It would be easier than sending the chip to someone else to dump. I'll just have to make a trip to radioshack and buy the connectors. I already have a 9pin serial cable that should do the trick.