It is currently Fri Sep 21, 2018 2:07 pm

All times are UTC - 7 hours



Forum rules





Post new topic Reply to topic  [ 4 posts ] 
Author Message
 Post subject: snes multicart game menu
PostPosted: Mon May 07, 2018 5:38 am 
Offline

Joined: Wed Jan 24, 2018 12:04 pm
Posts: 6
Hello guys, I was looking for some help or advice on how to create a multicart menu.
I'm currently working on a 4-in-1 game (Ancient Stone tablets) and instead of using LED to indicate wich chapter I'm in, a boot menu would be nicer.
I know it can be done on a custom board (wich I can definintely make) because I saw some chinese bootleg repro cart that have a similar features.

I was more looking for some info on how to make it
Ie: Rom modification, IC circuits, etc.

I dont have any idea where to start from and I dont want to purchase someone else work just to copy it.

Hope someone here can give me a hint.
Thank you


Top
 Profile  
 
PostPosted: Mon May 07, 2018 6:33 am 
Offline

Joined: Tue Feb 07, 2017 2:03 am
Posts: 579
the easiest way is to probably to make a circuit that latches the upper bank address bits. To break out the ROM address lines, this way you can make game 1 00:8000 = 00000 and then game 200:8000 = 10000 etc which means you don't need to patch the roms. So your menu code sets the bits and then has a way to trigger a reset. You would need to map it in the open bus where you know the games to write to.


Top
 Profile  
 
PostPosted: Mon May 07, 2018 9:36 am 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 7535
Location: Seattle
To add a menu, you need the following:
* A program to run on the SNES and display the things you want in response to the joypad
* A communication protocol from the SNES's CPU to the cartridge
* A device on the cartridge to react to that communication and change the upper address lines (or chip selects) on the ROM (or ROMs) in the cart.

As far as implementation, there's boundless variation in how one could implement each constraint.


Top
 Profile  
 
PostPosted: Mon May 07, 2018 10:16 am 
Offline

Joined: Sun Sep 19, 2004 11:12 pm
Posts: 20563
Location: NE Indiana, USA (NTSC)
The simplest thing that could possibly work would behave similarly to AOROM, BNROM, or GNROM on the NES. In these mappers, a write to a 74LS161 latch controls the ROM's upper address lines, selecting which game runs. A menu would be inserted into the first program on the cartridge, and at the end, it would jump to the start of the selected program. The other three programs would have their reset vectors patched to zero out the latch and jump to the menu.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 5 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