MMC5 register mirrors?

Discuss technical or other issues relating to programming the Nintendo Entertainment System, Famicom, or compatible systems.

Moderator: Moderators

Post Reply
Bisqwit
Posts: 248
Joined: Fri Oct 14, 2011 1:09 am

MMC5 register mirrors?

Post by Bisqwit »

The page http://wiki.nesdev.com/w/index.php/MMC5 documents the intended registers of MMC5 quite well.
Are any of these registers mirrored? Such as, does writing into $5170, $51B0, $5330, $5530, or $5930, achieve the same as writing into $5130?
User avatar
Bregalad
Posts: 8036
Joined: Fri Nov 12, 2004 2:49 pm
Location: Caen, France

Re: MMC5 register mirrors?

Post by Bregalad »

I guess the answer is "we don't know, and you should test this yourself". As the answer with most advanced MMC5 questions :)
User avatar
rainwarrior
Posts: 8062
Joined: Sun Jan 22, 2012 12:03 pm
Location: Canada
Contact:

Re: MMC5 register mirrors?

Post by rainwarrior »

If you write a hotswap test ROM, I have a few MMC5 carts I could test for you.
User avatar
Quietust
Posts: 1786
Joined: Sun Sep 19, 2004 10:59 pm
Contact:

Re: MMC5 register mirrors?

Post by Quietust »

I'm not sure about writable registers, but I know that none of the readable registers are mirrored - a number of years ago, I wrote a test program that tried to read from all of $5000-$5FFF, and the only locations which returned data were the known documented readable registers ($5010, $5015, $5204, $5205, $5206, and $5C00-$5FFF), with everything else returning open bus.
Quietust, QMT Productions
P.S. If you don't get this note, let me know and I'll write you another.
Bisqwit
Posts: 248
Joined: Fri Oct 14, 2011 1:09 am

Re: MMC5 register mirrors?

Post by Bisqwit »

I'm just wondering whether you can safely read an address like $51E6 and not get side effects.
Post Reply