It is currently Tue Mar 28, 2017 4:31 pm

All times are UTC - 7 hours



Forum rules


1. NO BLATANT PIRACY. This includes reproducing homebrew less than 10 years old, with the exception of free software.
2. No advertising your reproductions, with the exception of free software.
3. Be nice. See RFC 1855 if you aren't sure what this means.



Post new topic Reply to topic  [ 10 posts ] 
Author Message
PostPosted: Fri Sep 16, 2016 9:24 pm 
Offline

Joined: Mon Apr 04, 2016 7:59 am
Posts: 28
I have a rather strange 32-pin 128KB EEPROM that strangely seems to already conform to the pinout of a 28-pin NES MaskROM. It contains an unreleased prototype that I would like to put into a cartridge to make it work. FWIW, it has already been dumped, but I want to get the original chip running in a donor board.

Once again, this particular EEPROM (Toshiba TC571001D-15) is NOT the standard pinout. In fact, the datasheet implies that it was designed for 28-pin MaskROM compatibility even though it's a 32-pin chip:
http://www.datasheets360.com/pdf/1585995656965978174

The final retail game is 28-pin 128KB so I checked the pinout against the 28-pin 128KB PRG chip here:
http://nesdev.com/NES%20ROM%20Pinouts.txt
It matches up except that Vcc is labeled NC on the Toshiba chip. Expecting to find a 28-pin chip in my donor cartridge (same PCB), I found a 32-pin chip instead. Because my chip is already 32-pin, I compared this pinout as well. I see that pins 30, 31, and 32 are all tied to +5v on this donor board, which corresponds to NC, PGM, and VCC on my chip. Good: I won't have to jumper NC to Vcc, but will it cause a problem to have PGM connected to +5v? Also, the second /CE on the PCB will be connected to OE on this chip and the PCB's A17 will be connected to the chip's Vpp.

Being an unreleased prototype, I don't want to solder directly or bend legs so I thought I'd check and see if this pinout might just work anyway. I'm prepared to use 28-pin sockets, cut a hole, and just jumper VCC if I have to.


Top
 Profile  
 
PostPosted: Fri Sep 16, 2016 9:43 pm 
Online

Joined: Sun Apr 13, 2008 11:12 am
Posts: 5429
Location: Seattle
According to that datasheet, the TC571000AD is a traditional UVEPROM, and it has the exact same pinout as most other UVEPROMs (such as the M27C1001).

Note that Nintendo's variant pinout was specifically designed to be upwards compatible with the 28-pin 128 KiB mask ROM, whereas all the JEDEC ROMs were instead upwards compatible with the 28-pin 64 KiB programmable memories.


Top
 Profile  
 
PostPosted: Fri Sep 16, 2016 10:18 pm 
Offline

Joined: Mon Apr 04, 2016 7:59 am
Posts: 28
lidnariq wrote:
According to that datasheet, the TC571000AD is a traditional UVEPROM, and it has the exact same pinout as most other UVEPROMs (such as the M27C1001).

Note that Nintendo's variant pinout was specifically designed to be upwards compatible with the 28-pin 128 KiB mask ROM, whereas all the JEDEC ROMs were instead upwards compatible with the 28-pin 64 KiB programmable memories.

Thanks, but according to the same datasheet TC571001D EPROM, which is what I have, is supposed to have the same pinout as a 28-pin MaskROM. They even have a handy chart showing the kind of MaskROM they are talking about and, surprise surprise: it matches up with the "PRG ROM - 128KBytes (28pin)" from here. ;)

I removed pins 1, 2, 30, and 31 from a socket but have yet to install it (heck, I haven't even tested the just-purchased donor yet ;)). Will this likely cut it?


Top
 Profile  
 
PostPosted: Fri Sep 16, 2016 10:54 pm 
Offline
Site Admin
User avatar

Joined: Mon Sep 20, 2004 6:04 am
Posts: 3375
Location: Indianapolis
VPP and /PGM should be connected to 5V.

How /OE is connected may depend on the mapper.


Top
 Profile  
 
PostPosted: Fri Sep 16, 2016 11:51 pm 
Offline

Joined: Mon Apr 04, 2016 7:59 am
Posts: 28
Memblers wrote:
VPP and /PGM should be connected to 5V.

How /OE is connected may depend on the mapper.

Thanks. I had figured the opposite and assumed that neither are supposed to get anything when not programming. ;) It doesn't look like a 28-pin MaskROM would have even had /OE and I'm connecting it in the 28-pin MaskROM compatibility config (assuming I'm reading everything right). This is for an SNROM board (MMC1+CHR RAM) and those pins aren't even populated on other versions of this game's board so I'm hoping it really is that easy.


Top
 Profile  
 
PostPosted: Mon Sep 19, 2016 6:45 pm 
Offline

Joined: Mon Apr 04, 2016 7:59 am
Posts: 28
Memblers wrote:
VPP and /PGM should be connected to 5V.

How /OE is connected may depend on the mapper.

This is SNROM, mapper 1. I tried VPP and /PGM to +5V while leaving /OE disconnected and I got a gray screen. When I connect /OE to ground I get garbled graphics. When I connect it all straight through I get the same garbled graphics. When I leave 1, 2, 30, and 31 disconnected, I get a gray screen. Not sure what else to try. I probably shouldn't be experimenting with the original EPROM of an unreleased prototype but my programmer doesn't support TC571001D for me to make an equivalent backup.


Top
 Profile  
 
PostPosted: Mon Sep 19, 2016 7:08 pm 
Online

Joined: Sun Apr 13, 2008 11:12 am
Posts: 5429
Location: Seattle
Well, you can still dump the first half of it by reading it as though it were a 27'1001...

Playing around with a socket to rewire things for the programmer, or building your own reader (given a PIC or an arduino/atmega) would also be a reasonable answer.


Top
 Profile  
 
PostPosted: Mon Sep 19, 2016 7:30 pm 
Offline

Joined: Mon Apr 04, 2016 7:59 am
Posts: 28
lidnariq wrote:
Well, you can still dump the first half of it by reading it as though it were a 27'1001...

Playing around with a socket to rewire things for the programmer, or building your own reader (given a PIC or an arduino/atmega) would also be a reasonable answer.

I made an adapter and have the dump and it works in FCEUX so I'm good there. I can easily use the dump to burn a standard 27C020 and make a repro, but my goal is to turn the original prototype chip into the only working cartridge copy known to exist (proto is still unreleased; dump is not public). That's the novelty and the main reason I bought the prototype. :)

I think I figured it out though. Even though the datasheet says pin 30 is NC, I still have to wire it to hole 1. Not sure if I'll have time to do it tonight but I'll try. :) Thanks!


Top
 Profile  
 
PostPosted: Wed Sep 21, 2016 4:18 pm 
Offline

Joined: Mon Apr 04, 2016 7:59 am
Posts: 28
OK, reading the data sheet I see that Memblers is absolutely right: VPP and PGM still need 5v in read mode. Luckily, they both get that when connected straight thru-hole. It also says that /OE and /CE both need to be low for the chip to be read. Thanks to this pinout putting /OE on pin 2, /OE and /CE should already be connected on the board and both should go low together (everything I read says that pin 2 and 22 are connected on the board; I'll test continuity to be sure). Manually forcing this by tying them to ground didn't work and I suspect it's because it creates a conflict between the PRG ROM and the CHR RAM both being enabled together. This is probably why I got corrupt graphics when I could get it to run (PPU was reading PGM data since both were enabled on the same clock). It looks like the ONLY change this needs is VPP to 5v, though I plan to eject pin 30 from the socket just to be sure (probably labeled "NC" because there's literally nothing connected to it in the chip, though I'd expect it to be a duplicate Vcc pin for true 28-pin compatibility).

I hope this works!


Top
 Profile  
 
PostPosted: Thu Sep 22, 2016 2:31 pm 
Offline

Joined: Mon Apr 04, 2016 7:59 am
Posts: 28
Well, holes 2 and 22 are definitely NOT tied together on the board like the NESDEV pinout says they are. There's no continuity there. The last time I tied pin 22 (/CE) to ground it went from corrupt graphics to gray screen (pin 2, /OE, already tied to ground). I know that the board still works with the original chip (Shingen the Ruler). It's probably not a board issue. I'm going to assume that I need to tie /OE to pin 22 myself and leave hole 2 unpopulated.

Any other ideas?


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 10 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group