Adding Battery to TSROM board? How?

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Tormenter
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Adding Battery to TSROM board? How?

Post by Tormenter » Tue Nov 21, 2006 6:17 pm

I cant seem to find any information about how to add a battery to a TSROM cart (for games such as Final Fantasy 3 for example). Are there any docs anywhere on how to do this? Im trying to make a Final Fantasy 3 but do not know how to battery save it =( Thanks!

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Quietust
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Post by Quietust » Tue Nov 21, 2006 6:37 pm

Why start with TSROM? TKROM has pretty much the same setup, with the added bonus that it's designed to take a battery. TKROM is probably also slightly more likely to have the CHR /WR line intact on the cart edge.
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Tormenter
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Post by Tormenter » Wed Nov 22, 2006 9:24 am

Well with the TKROM I would have to use 2 games just to make the one game, which I do not want to do really. Plus I would like to learn how to do the batteries as well. Thank You!

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Bregalad
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Post by Bregalad » Wed Nov 22, 2006 10:35 am

Well with the TKROM I would have to use 2 games just to make the one game, which I do not want to do really.
Where did that nonsense come from ?
Plus I would like to learn how to do the batteries as well. Thank You!
Well, *do* a battery is a bit tricky. You need lithium and do some chimical thing on it. You cannot just add a battery to a board that haven't any slot for one. Well, you could, but that would be tricky to do. You'd want to had 2 diodes, 2 resistors, one capacity and one battery on a board that have no room for that. I don't think you'd learn much from it.
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sevast
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Post by sevast » Wed Nov 22, 2006 11:30 am

I don't know if I'm stupid or done something wrong, but I've added a 2032 battery to a tsrom board a few months ago and it still works fine. What does all the extra stuff do? Does it just make sure the power is stable and clean? Does it help prevent reset erase?

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Bregalad
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Post by Bregalad » Wed Nov 22, 2006 11:58 am

Well, you cannot just connect the battery to the VCC/GND pins of the chip, else I'd be surprised if your battery don't leak when you turn on your NES.
Why ? Because your NES uses a 5V power voltage, and lithium batteries are 3V (or 3.6 V). You need 2 diodes and 2 resistors between each power supply to avoid current drop from one power source to the others. A capacity is to be added to ensure proper transisions when the chip's powering source changes (so when you turn on and off your NES, the voltage on the SRAM chip will just slide smoothly instead of having bad pulses). Early SNROM boards doesn't have that capacity, but to personal experience saves are VERY OFTEN lost whathever on what you're doing on such boards, so be aware.
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Tormenter
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Post by Tormenter » Wed Nov 22, 2006 6:45 pm

I know one of the guys that sells reproductions makes adds his own batteries onto the final fantasy 3 carts inside of a holder. Thats what I want to do

sevast
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Post by sevast » Wed Nov 22, 2006 10:36 pm

So the diodes keep the power from kinda mixing and leaking back. The capacator keeps the power stable as it switches between the two voltages. what do the resistors do?

If there were a 5 volt coin battery, would it only need the capacitor?

So, why can't I cut the VCC and the Ground and then just attach the battery?


Tormenter: I have been looking for a battery holder that will fit myself, so if I find one, I'll let you know.

Personally, I've been using the Famicom Final Fantasy III cart for a donor and then using a famicom to nes adaptor from a Stack-up to make it a nes cart. It really costs about the same and then you only have to replace the prg rom with an eprom.

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Bregalad
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Post by Bregalad » Thu Nov 23, 2006 10:36 am

It really costs about the same and then you only have to replace the prg rom with an eprom.
You'll still have to rewire it to have the desired pinout.
So the diodes keep the power from kinda mixing and leaking back. The capacator keeps the power stable as it switches between the two voltages. what do the resistors do?
I'm myself not too sure about that, but a diode in fowrard polarity drops a 0.7V voltage. So you cannot connect just both diodes together, you'll need at least one resistor to drawn the voltage between both source, I think NES carts uses two resistors, but I cannot give the exact shematics, I've just noted that on carts I have. This isn't the ultimate shematic. It's also possible to use circuits with transistors to do battery backup, and there is even integred circuits that does the work. I'm not an expert, it's just the NES games uses two diodes and two resistors. You can go with the shematic you want, actually.
Life is complex: it has both real and imaginary components.

sevast
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Post by sevast » Thu Nov 23, 2006 12:51 pm

Bregalad, I really appreciate the info you've shared. Thanks.

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