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snes SA-1 repro help

Oct 2, 2013 at 8:50:56 PM
eric.of.troy (83)
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(... Eric?) < Meka Chicken >
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I'm lookin to repro one of the parodius games as a "because I now need the snes trilogy since I made the first one" type of deal.  Its not translated but seriously, who needs a translation for a shmup? **cough** all your base are belong to us **cough**

Only issue is the last one uses the SA-1 chip.

I have PGA golf 96 for a donor.  It has the SA-1 chip and the right amount of sram, only a 16MB maskrom compared to the 32MB i'd need.

I think the eeprom I wanna use is a 29L3211 but before I go destroy a donor cart, I wanna make sure I have everything lined up.

I'm also lookin to see if anyone has any pointers as to how it should be wired up, if someone wouldn't mind being so gracious to do so.

Thanks!

-Eric

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I do custom things!!  -->  Eric's Sales Thread

Oct 2, 2013 at 9:38:55 PM
snucker (42)
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< Eggplant Wizard >
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As long as the pin out of the mask rom is the same as the pin out of your new chip, there's no problem.

Pins 1 (WE instead of A21) & 33 (BYTE instead of 5V) seem to be incompatible. A more experienced person should confirm though. Also the chip needs 3.3V not 5V.


Edited: 10/02/2013 at 09:40 PM by snucker

Oct 3, 2013 at 12:27:39 AM
plc268 (5)

< Little Mac >
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Wiring should be similar to this:
http://www.mmmonkey.co.uk/cheaper...

Basically, you're gonna take those three pins that require 3.3V and feed them through a 3.3V regulator.

Oct 3, 2013 at 12:34:46 PM
eric.of.troy (83)
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(... Eric?) < Meka Chicken >
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Good deal, Thanks!

I've figured it'd be something like that. Good stuff over there on mmmonkey lol.

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I do custom things!!  -->  Eric's Sales Thread

Oct 3, 2013 at 12:54:53 PM
snucker (42)
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< Eggplant Wizard >
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There ya go =)

Like I said pins 1 & 33 don't match and the chip needs 3.3V. By the looks of things the regular 5V pin and pins 1 & 33 just need to be connected to a voltage regulator

Oct 3, 2013 at 6:25:46 PM
Guntz (115)
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< Master Higgins >
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It's worth mentioning that the 29L3211 is designed to work on 3.3v, including all the data and address lines. The SNES uses 5v for all that, so the 29L3211 will slowly die if you don't add some level shifters or something. That mmmonkey article has a link to a nesdev thread in the comments, it's worth reading.

Oct 4, 2013 at 5:55:35 PM
josete2k (7)

(Jose Ruiz) < Eggplant Wizard >
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The 29L3211 works fine in conjunction with an extra chip... like SA-1 or SDD-1. And this is because the adress lines from these chips aren't 5vcc, maybe 4vcc and the 3211 has a BIG tolerance in exits and outputs lines (vccin+1,2v).

If you connect a 3211 directly to the snes bus, it doesn't work in many times.


Oct 4, 2013 at 6:19:43 PM
Guntz (115)
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< Master Higgins >
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Thanks for the input jose. Good information for SNES is hard to come by. I just felt it was worth mentioning the voltage requirements of the chip.

Even if the voltage input is within spec, if it's pretty high the excess voltage will generate more heat and can cause the flash chip to break down faster. It all must be taken into consideration, efficient modding depends on it.


Edited: 10/04/2013 at 06:20 PM by Guntz

Oct 4, 2013 at 8:28:42 PM
eric.of.troy (83)
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(... Eric?) < Meka Chicken >
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Good stuff guys, thanks!

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I do custom things!!  -->  Eric's Sales Thread