Bit of a weird issue with a Pokémon Yellow cart

[Segata Sanshiro]

I had the idea of replacing my perfectly fine CR1616 battery in my Pokémon Yellow with a CR2032 so it's good for another 10 or so years. However, sometimes it saves once - I load the save and then the save is gone or it doesn't save at all.

Now I've only had experience of replacing batteries in Gold and Silver carts and have used the exact battery in another cart, this time a Gold version and it works fine.

The voltage is the same so I can't figure out what's wrong.. :shrug:

I also replaced the CR1616 and it's saving fine again.

:shrug:

[geluda]

Voltage is the same, current is different? My advice, use a CR1616.

[Segata Sanshiro]

Yeah?

I'll order a CR1616 then I guess. Thanks.

[ASSEMbler]

cr2032 is a lot thicker right? Possibly shorting and not supplying power.

[H360]

It will wipe itself if there is no power. So, something is not right in your connection or there is not enough milliamps. But all the coin cell batteries are the same in mAh. I think 25 mAh is all they hold.

Best thing to do is to install FRAM instead of the stupid SRAM Nintendo used.
I have seen it done before and you do not need the battery anymore.

I was going to do it, but I have way to many projects going on at the moment.

[Segata Sanshiro]

I was wondering if something like that could be done. If you could find a tutorial or provide specifics I'd love you forever.

[H360]

OK inside of your Gameboy Cartridge (Color), there is an IC on the bottom left, under the MBC5 IC.

This is volatile SRAM (http://doc.chipfind.ru/pdf/winbond/w24257.pdf), and it is linked to a DC inverter (this gives a steady 200 mAh to the SRAM no matter how powerful or weak the battery is, so it does not loose its memory) IC (http://www.ti.com/lit/ds/slvs141a/slvs141a.pdf) on the top left between the two.

If you de-solder this SRAM IC and replace the SRAM with any 256Kbit FRAM Memory IC with these matched specs, (http://ramtron.com/files/datasheets/FM28V020_ds.pdf) then it should work.

However, since there is no more power going through the DC inverter (no battery), some games MAY have different effects how they were programmed to store the data. I know Pokemon Silver / Gold looses its clock / time in game, but the saves work.


I can make a tutorial and put it on my site (http://haunted360.com), do more testing etc... but I need to order the FRAM IC first :)


Also, GameBoy Color games use CR2032 and GameBoy games use CR1616.

[Segata Sanshiro]

Happy to lose clock times.

If you could do this I'd buy 10 chips off youish.

[H360]

lol.

You would need to send me your cartridge or solder this yourself.

I can not make the chips myself and sell them :P

[Segata Sanshiro]

Ah I see.

Might be easier to send you my carts then. I'd want my Red, Blue, Yellow, Gold, Silver and Crystal carts done. :)

[H360]

Ah I see.

Might be easier to send you my carts then. I'd want my Red, Blue, Yellow, Gold, Silver and Crystal carts done. :)

No problem.

Let me test it first for you on my Pokemon Yellow, then I will let you know :thumbsup:

[Segata Sanshiro]

Thanks! :)

[Segata Sanshiro]

Found this: http://forums.modretro.com/viewtopic.php?f=3&t=4110

[H360]

You're welcome :)



Found this: http://forums.modretro.com/viewtopic.php?f=3&t=4110

Yea, there is one on the Ben Heck Forums posted also. I just replied to it...
I lost some new information I typed, because the system is messed up, but again, I will make a full guide on my site so anyone can easily understand and follow it.

[Segata Sanshiro]

Bump to the top.

Is this chip suitable?

http://uk.futureelectronics.com/en/technologies/semiconductors/memory/fram-mram/Pages/8160012-FM28V020-SG.aspx?IM=0

[H360]

Yes. It should be fine :)

[Bad_Ad84]

Id probably leave the battery in, but disconnect it from the FRAM.

This way you should keep the RTC and keep your times, but never lose saves.

[H360]

Exactly. You can do that and it will work perfectly fine :)

[Segata Sanshiro]

Awesome, thanks. I'll be doing this for a Poke Yellow cart primarily but as I found the chips cheaper than before I'll buy a few I think. Yellow has no internal clock so there's no real reason to keep it in there right?

[Bad_Ad84]

If there is no RTC, the battery is purely there for retaining saves.

So yes, theres no reason to keep it there.

[H360]

This means that the real time clock is in the MBC IC?

[Segata Sanshiro]

The time is kept by the oscillator crystal, I think.

[H360]

No. The crystal does not keep the time, more it helps provide the frequency at which it will run at :D
It would be in an IC that is powered by the battery.

And... I found it. It is in the MBC chip.

"Beside for the ability to access up to 2MB ROM (128 banks), and 32KB RAM (4 banks), the MBC3 also includes a built-in Real Time Clock (RTC). The RTC requires an external 32.768 kHz Quartz Oscillator, and an external battery (if it should continue to tick when the gameboy is turned off)."

Source: http://meatfighter.com/gameboy/TheNintendoGameboy.pdf

[Bad_Ad84]

But you said it DIDNT keep the time, now you are saying it does and is kept by the crystal (which is wrong, but implies you knew it was keeping the time).

If you want the time to save, you need the battery.

[H360]

I said replying to Segata Sanshiro (http://www.assemblergames.com/forums/member.php?47718-Segata-Sanshiro), "No. The crystal does not keep the time, more it helps provide the frequency at which it will run at :D"

[Bad_Ad84]

I was replying to him.

The fact I said, "But you said it DIDNT keep the time, now you are saying it does and is kept by the crystal"

You didnt say any of those things, so clearly it wasnt directed at you =/

[H360]

I was replying to him

Well lets use those quotes then buddy ;)

[Segata Sanshiro]

I don't want the time, just the save. lol

I assume I could remove the crystal in addition to the battery on a gold cart - maybe.

[H360]

No need to remove the crystal. Just the battery if you dont want the clock.

[Segata Sanshiro]

I know, but I could right?

[H360]

Sure. You can remove the crystal if you want :)