UNROM to UOROM - NESdev BBS

UNROM to UOROM
by NESHomebrew on 2010-07-27 (#64970)

I've been looking around for a definitive rewiring guide to get this working with an EPROM.

I found one post further down in this thread but he seemed a little bit unsure why he did what he did etc.

I've scoured around NESdev, and can't seem to find what I'm looking for. Does anyone have this documented somewhere? I know the knowledge must exist, as I've seen Tokumarus vertically aligned one on a konami board (which I assume is slightly different than a Nintendo board?).

Any help would be appreciated! Thanks in advance.

by Tormenter on 2010-07-27 (#64990)

What game are you trying to make?

by NESHomebrew on 2010-07-27 (#64991)

Tormenter wrote:
What game are you trying to make?

It is a modified rom of Frantik's PCM demo.

by NESHomebrew on 2010-07-30 (#65151)

I guess my wife won't be getting her present on time .

Well, here is an update. I followed the instructions to a tee, and my results turned out negative. Not a bleep, not a bloop, nothing! I checked all the connections for continuity, as well as the proper voltages with the system running. I'll repost the steps I took here if someone wouldn't mind taking a quick glance for any glaring errors I would appreciate it greatly.

Desolder cap and resolder on the other side of the board.
Cut the trace to pin 22 of 28 pin mask ROM (this will become pin 24 of the 32 pin EPROM socket)
Cut the 5V+ connection around pin 28 of the mask ROM (this will become pin 30 of the EPROM socket).
Cut the ground connections to pins 4 & 5 of the 7432 and pin 6 of the 74161.
Pin 1 of EPROM Vpp goes to 5V+
EPROM pin 2 A16 conects to 7432 pin 8
EPROM pin 31 PGM goes to 5V+ (I do this and it works.)
EPROM pin 24 to pin 22 (see note above)
EPROM 17 D3 to 74161 pin 6
74161 pin 11 to 7432 pin 5
7432 pin 1 to 7432 pin 4
7432 pin 6 to EPROM pin 30 A17

by sleepy9090 on 2010-08-02 (#65315)

http://nesdev.com/bbs/viewtopi ... 915073c065

maybe that can help?

by NESHomebrew on 2010-08-02 (#65316)

sleepy9090 wrote:
http://nesdev.com/bbs/viewtopic.php?p=20873&sid=5b72eb5c027aea23d696ca915073c065

maybe that can help?

Well, the only problem is that apparently Konami switched things up on those boards. I had intended my donor to be a regular Nintendo brand UNROM board.

http://nesdev.com/bbs/viewtopic.php?t=4 ... 993063497b

Maybe if I understood why things need to be rewired I could figure it out myself. In the meantime, I ordered a retropak from retrousb, so that should make things a lot easier. Better late than never right? She still loved the rom when I showed her on my PowerPak, so not all is lost.

by tepples on 2010-08-02 (#65317)

The rewiring is needed because the pinouts differ. Nintendo and some other cart makers rearranged the pinouts on their mask ROMs compared to the standard pinouts for UVEPROMs and flash chips because removing the write enable and the programming voltage can sometimes shrink a 32-pin package to 28.

by sleepy9090 on 2010-08-05 (#65475)

The pinout for the unrom board is here
http://nesdev.com/rom.txt
You should be able to match that up with the data sheet for the rom chips you are using.