It is currently Fri Oct 20, 2017 10:09 pm

All times are UTC - 7 hours





Post new topic Reply to topic  [ 3 posts ] 
Author Message
 Post subject: MMC1 confusion
PostPosted: Tue Mar 22, 2005 12:21 pm 
Offline
User avatar

Joined: Tue Dec 21, 2004 8:35 pm
Posts: 600
Location: Argentina
i dont know how mmc1 works.
mmc1.txt says that writing a value with a the MSB 1 it reset the mapper.. so what i do is:
Code:
MMC1.Reg0 &= ~0x0C;
MMC1.Reg0 |= 0x0C;


But the new "nes documentation" pdf, says that each register can be reset with a value of 0x80 (or maybe a i missunderstood it).
I have also find in other docs that each bit of the register must be writed bit by bit. But writing bit-by-bit to reg3, so when to do prg-rom swap?

_________________
ANes


Top
 Profile  
 
 Post subject: Re: MMC1 confusion
PostPosted: Tue Mar 22, 2005 1:24 pm 
Offline
User avatar

Joined: Sun Sep 19, 2004 10:59 pm
Posts: 1389
Anes wrote:
i dont know how mmc1 works.
mmc1.txt says that writing a value with a the MSB 1 it reset the mapper.. so what i do is:
Code:
MMC1.Reg0 &= ~0x0C;
MMC1.Reg0 |= 0x0C;


But the new "nes documentation" pdf, says that each register can be reset with a value of 0x80 (or maybe a i missunderstood it).
I have also find in other docs that each bit of the register must be writed bit by bit. But writing bit-by-bit to reg3, so when to do prg-rom swap?


That "nes documentation" is NOT new - most of the information inside it was gathered from ancient documentation (like firebug's mappers.txt). If you want information you can trust, I would advise checking the wiki.
(of course, in said wiki, MMC1 mirroring was backwards until about a week ago)

Resetting the MMC1 can be done through any register, but ALL it does is set bits 2/3 of reg0; all other bits are unaffected (for some reason, you're clearing the other bits in reg0, which is wrong).

All MMC1 documents (should) mention that all mapper registers are updated serially - you write to one address range 5 times in a row, shifting your value right 1 bit each time, and the register itself is updated on the very last write.

_________________
Quietust, QMT Productions
P.S. If you don't get this note, let me know and I'll write you another.


Top
 Profile  
 
 Post subject:
PostPosted: Tue Mar 22, 2005 1:49 pm 
Offline
User avatar

Joined: Tue Dec 21, 2004 8:35 pm
Posts: 600
Location: Argentina
thanks i have it much clear now.

_________________
ANes


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 6 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