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 Post subject: VRC-VI multicart
PostPosted: Wed Jul 13, 2011 7:27 am 
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Location: Brasilia, Brazil
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The final board layout has three more chips for the game select circuit. The SRAM chip is large enough to keep saves for the 4 game slots. The pictured chip behind the workram is a 74LS32 used to OR the write and output enable pins for the 62256 chip (to make it behave same as an 6264 chip) so I can have 4 8KB banks. Akumajou Densetsu does not care if WRAM is present or not so it just works...) SRAM banks swap along with ROM banks so each game saves on it's own slot. At the time the picture was made I was using an 3 position pole switch to select the game but I thought it would be a SHAME to drill the beautiful Madara cartridge and that made me put more chips in for the game select circuit.


The three existing VRC-VI games cycle in the following order when reset is pressed:

Moryou Senki Madara (original game for that board)
Esper Dream 2
Akumajou Densetsu
(an 512KB unused bank is left empty unfortunately and the counter is programmed to skip this bank)

The games are translated to english, Akumajou Densetsu had it's progam rom modified to become compatible with the mapper 26 (VRC6 V). Not a single copper track of the original board was cut or scratched, therefore the mod can be undone if I deem necessary. But honestly I doubt I'll ever do that. I am keeping the original mask roms in a safe place though. ;)

And sorry about the AWFUL pictures from a cheap cell phone...


Last edited by l_oliveira on Wed Dec 18, 2013 10:10 am, edited 1 time in total.

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PostPosted: Wed Jul 13, 2011 8:08 am 
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Wow, that's really cool :D I look forward to seeing more of your work!


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PostPosted: Wed Jul 13, 2011 8:14 am 
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Location: Estonia, Rapla city (50 and 60Hz compatible :P)
Its really nice to see you here ^^

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 Post subject: Re: VRC-VI multicart
PostPosted: Sat Mar 09, 2013 4:52 pm 
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I am necro-posting this thread to ask a couple of questions on parts... :mrgreen: what are the 3 non-pictured ones?

Is the HM62256BLP-7 a good SRAM chip for the cart? datasheet
Also would a SMT 74F32 work the same as the 74LS32? datasheet I can see the F is faster and smaller :lol:

TIA!


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 Post subject: Re: VRC-VI multicart
PostPosted: Sat Mar 09, 2013 5:14 pm 
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keropi wrote:
I am necro-posting this thread to ask a couple of questions on parts... :mrgreen: what are the 3 non-pictured ones?

Is the HM62256BLP-7 a good SRAM chip for the cart? datasheet
Also would a SMT 74F32 work the same as the 74LS32? datasheet I can see the F is faster and smaller :lol:

TIA!


The SRAM looks fine, the 74F32 should work fine too as it will be used on the standard 5V supply from the Famicom, not draining any current from the SRAM power circuit. The only reason you're changing from the original 6264 chip is so you can have four 8KB pages for the four games you're going to put into the cart. :)

I used a 74LS393 as counter on my cart. (I had it laying around. I tend to make things with random stuff I grab from my parts drawer ... lol)


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 Post subject: Re: VRC-VI multicart
PostPosted: Sat Mar 09, 2013 5:28 pm 
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Thanks for the info l_oliveira :mrgreen:
I hope I succeed in making a similar cart :roll:


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 Post subject: Re: VRC-VI multicart
PostPosted: Sat Mar 09, 2013 5:40 pm 
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keropi wrote:
Thanks for the info l_oliveira :mrgreen:
I hope I succeed in making a similar cart :roll:


You will ! I am sure !


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 Post subject: Re: VRC-VI multicart
PostPosted: Sat Mar 09, 2013 6:51 pm 
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^ yes, I'll have awesome help :mrgreen:


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 Post subject: Re: VRC-VI multicart
PostPosted: Sat Mar 09, 2013 10:05 pm 
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Be careful about the F series logic; it is substantially higher input current (and also simply consumes more power in general) and may not play with CMOS parts.


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 Post subject: Re: VRC-VI multicart
PostPosted: Sun Mar 10, 2013 9:44 am 
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lidnariq wrote:
Be careful about the F series logic; it is substantially higher input current (and also simply consumes more power in general) and may not play with CMOS parts.


hmmm better play it safe then and just get the LS part.
Is the ls32 the only one suitable or can another model work? (probably with more non-used pins?)


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 Post subject: Re: VRC-VI multicart
PostPosted: Sun Mar 10, 2013 1:20 pm 
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In recent times, they started packaging reduced numbers of gates, usually in surface-mount: e.g. 74AHC1G32, 74AHC2G32. Otherwise, all through-hole variants of the 74'32 always came with 4 gates. After that, anything except 74(no letter), 74F, and 74S (1, 0.6, and 1mA inlet current respectively) should be feasible. (74AS is 0.1mA, and everything else is lower). Avoid 3V-and-lower logic. ( http://en.wikipedia.org/wiki/7400_series )

It looks like he's using two OR gates, so I don't think there's a great alternative here. Dead-bugging SMT isn't that bad, though.


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 Post subject: Re: VRC-VI multicart
PostPosted: Sun Mar 10, 2013 3:19 pm 
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"dead bug" LOL , did not knew the term... been using it in projects where you need to add ics :lol:
Reading more on this and I decided to use the LS series as they are tested and period correct... no need to experiment for cheap things that only take long to arrive :roll:


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 Post subject: Re: VRC-VI multicart
PostPosted: Tue Mar 12, 2013 2:31 pm 
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I wasn't aware there's more than one version of the vrc6 unless I'm reading something wrong.


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 Post subject: Re: VRC-VI multicart
PostPosted: Tue Mar 12, 2013 2:44 pm 
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Not so much "version" as "wiring variant". (http://wiki.nesdev.com/w/index.php/INES_Mapper_024 , http://wiki.nesdev.com/w/index.php/INES_Mapper_026 )


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 Post subject: Re: VRC-VI multicart
PostPosted: Tue Mar 22, 2016 8:52 pm 
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Sorry to bump an old thread but I am doing almost exactly the same thing with a Madara cart.

l_oliveira, are you still out there? I have made a few homebrew multicarts with switches and stuff on them, and just recently I picked up Madara so that I could get it running with English translation and also have Akumajou Densetsu. I have already modified my NES and Famicom adapter and the extra sound channels are amazing. I have a couple of questions:

How does the reset circuit work? Do you have a diagram or can you recall a detailed description? I have a large selection of 74xx chips including flip flops, gates, etc. I would like to know how you did this.

Also, do you still have a copy of your Akumajou Densetsu ROM modified to run on VRC6b? I also prefer not to swap these pins in hardware if possible. an IPS file would be just fine if we're not allowed to share ROMs here. Or else if you recall how you did it, I could try to reproduce it.

Here is a page where I have put pictures of my modified NES cartridges:
http://www.d.umn.edu/~bold0070/projects/nes_carts/


Attachments:
File comment: Here is how I am going to leave the original Mask ROMs in place, and select with /CE. I removed the solder from the pin and inserted a small teflon tube.
thru hole.jpg
thru hole.jpg [ 27.31 KiB | Viewed 4181 times ]
File comment: The PLCC-32 flash ROMs will be accessible from the outside of the case. This glue is still drying in this picture.
cart.jpg
cart.jpg [ 69.46 KiB | Viewed 4181 times ]
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