It is currently Sat Apr 29, 2017 10:15 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  [ 23 posts ]  Go to page Previous  1, 2
Author Message
PostPosted: Sun Apr 16, 2017 10:33 pm 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 5586
Location: Seattle
genepensive wrote:
53361-2: pin Q0 (Eprom 13) -> cart pins 34 (CIC toPak) & 30 (PPU D0)
[...]
53361-2: CIC pin 2 -> cart pins 34 (CIC toPak) & 30 (PPU D0)
There's no way that's right: that has to have been shorted together when it shouldn't,


Top
 Profile  
 
PostPosted: Wed Apr 19, 2017 10:48 pm 
Offline

Joined: Tue Feb 16, 2016 8:22 pm
Posts: 10
lidnariq wrote:
There's no way that's right: that has to have been shorted together when it shouldn't,


You were right. I checked against one of the other boards I have and it looks like I shorted a trace under the socket (the solder wandered).

After fixing that, I'm still seeing the following from the CHR rom using Megaman 3 (the EPROMs work right on a 51555-2 board):

http://imgur.com/a/ULfdN

Are MC-ACC pin-compatible with EPROMs?

I have a few of these carts and there's no way to really tell the difference from the label - they all look the same. Some are 51555-2 (MMC3B) and others are MC-ACC boards.

Thanks again for your help.


Top
 Profile  
 
PostPosted: Wed Apr 19, 2017 11:13 pm 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 5586
Location: Seattle
I am reasonably confident that all the resist-lacking Acclaim PCBs just used standard JEDEC pinouts, and that that is the same as UVEPROM pinout for 1 and 2 Mibit ROMs...

But then I don't know what GameMachineJames's comment was about. Where in which Mega Man is that? It shouldn't be too hard to figure out what bank is being displayed vs which one was requested, and after we have that information it'll hopefully shed light on what's wrong.

On some level, given the picture, it has to be "the upper address lines are wrong" but that's so vague as to be useless.


Top
 Profile  
 
PostPosted: Thu Apr 20, 2017 11:33 pm 
Offline

Joined: Tue Feb 16, 2016 8:22 pm
Posts: 10
lidnariq wrote:
Where in which Mega Man is that? It shouldn't be too hard to figure out what bank is being displayed vs which one was requested, and after we have that information it'll hopefully shed light on what's wrong.


This is Mega Man 3 (NA) using the Akklaim (Acclaim) MC-ACC MMC3 clone [53361-2 board] from a Roger Clemens MVP donor. The two other screen shots are from Shadow Man's intro and from the first part of the level.

The EPROMs are 27c020 UV EPROMs. The CHR ROM is doubled up to fit onto the EPROM (Mega Man 3's CHR is 128Kb). PRG is 256Kb. They work perfectly fine on another Roger Clemens board with a proper MMC3B on it.

http://imgur.com/a/trzm6 (works properly, I have this board with sockets installed for testing)

http://imgur.com/a/4bs9h (errors in CHR) <-- this is the board I'm working with. Same donor (in name only), same EPROMs.

Video of the CHR errors: http://sendvid.com/r67me113 - as you can see, it seems like it can read the first portion of the ROMs (notice how everything in the level select looks right), but maybe it can't switch banks properly? I'm not sure. There's not a lot of info on how to rewire MC-ACC boards.

Thanks for your help.

edit: Just a thought.. perhaps CHR only needs to fill half of the EPROM, and the other half needs to be zero-filled? (Something about it being pulled "high" or "low"?)


Top
 Profile  
 
PostPosted: Fri Apr 21, 2017 12:56 am 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 5586
Location: Seattle
genepensive wrote:
Video of the CHR errors: http://sendvid.com/r67me113 - as you can see, it seems like it can read the first portion of the ROMs (notice how everything in the level select looks right), but maybe it can't switch banks properly? I'm not sure. There's not a lot of info on how to rewire MC-ACC boards.
So somehow it's selecting the wrong bank.
On the first screen:
* The boss selector is tiles in banks $7C-$7F, all tiles. Additionally sprites from bank $34 are used to fill in white-person-skin-tone bits. All display correctly.
* When Shadow Man is supposed to be striking a pose, his sprite tiles are supposed to be bank $2F, and the sprites are tile indices $F8 through $FB. Instead we see the smirk portion of a face, which comes from bank ... $3F.

On the next screen:
* All the background tiles are supposed to be from banks $5C-$5E, indices $0C-$0F at the top line; $1C-$1F and $2C-$2F in the middle; $3C-$3F above the platform, and instead we see the letters that are in bank ... $7C-$7E.
* Mega Man's sprites are in bank $00, and they display correctly.

In the first case, the A14 line is high when it shouldn't be; in the second case, the A15 line is high when it shouldn't be. And ... that's all I can tell. I don't know whether it's a wiring problem (although GameMachineJames implied it is) or a logic problem or whether the wiring problem is between the ROM and PPU, PPU and mapper, or CPU and mapper. But if I had to take a guess, I'd look closely for a short between CHR A14 and A15.

Quote:
edit: Just a thought.. perhaps CHR only needs to fill half of the EPROM, and the other half needs to be zero-filled? (Something about it being pulled "high" or "low"?)
I'm confident it's not that...


Top
 Profile  
 
PostPosted: Fri Apr 21, 2017 7:28 pm 
Offline

Joined: Tue Feb 16, 2016 8:22 pm
Posts: 10
lidnariq wrote:
But if I had to take a guess, I'd look closely for a short between CHR A14 and A15.


Wow. I'm blown away. Good call.

There was a tiny solder blob under A15 that was shorting to A14.

THANK YOU! It works perfectly now.


Top
 Profile  
 
PostPosted: Fri Apr 21, 2017 10:17 pm 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 5586
Location: Seattle
By the way, we have an old kinda-dubious pinout of the MC-ACC here ... but
genepensive wrote:
The other thing I noticed is that anything using the ACCLAIM-MC-ACC maxes out at 384Kb combined
There is the possibility, if the pinout is correct, that pin #39 on the MC-ACC might be PRG A18. At least, in terms of spacing it's right.

No idea what the disconnected pins 6-8 are. They might be an enable for RAM, though.

If you feel up to it, you could consider this a request for verifying the pinout that old post...


Top
 Profile  
 
PostPosted: Sat Apr 22, 2017 10:08 pm 
Offline

Joined: Tue Feb 16, 2016 8:22 pm
Posts: 10
lidnariq wrote:
If you feel up to it, you could consider this a request for verifying the pinout that old post...


I have one more MC-ACC board left, I'll give it a shot.

I was able to get Mega Man 3 running on my dev/test (socketed) board, I'll run the MMC test suite on it this weekend.

Thanks again for your help!


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 23 posts ]  Go to page Previous  1, 2

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 2 guests


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