I've been doing some research today on modding a GB/GBC cartridge that saves with SRAM. I'm pretty sure that most of us know that SRAM requires constant power to retain its data, which is provided from a coin cell. These coin cells go dead after an amount of time and you loose your saves on LSDJ or basically any game that saves. Well what if we switched out the SRAM in that cartridge for Fe-RAM or just FRAM (not to be confused with the automotive filters) that does not require a constant supply of power to retain its data. I've been doing some research and I believe that I have found a good candidate for a replacement, a Fujitsu MB85R256F FRAM chip. It has the same amount of pins as the original, Sharp LH5164AN-10L, but I am unable to find pin-out sheets for either. I believe that if they have pin-out or at least similar pin-outs than a swap test might be in order. I'm just wondering if anybody has tried this before or what other people think of it.
There was a guy that did that to a pokemon cart.
Yes!
The LH5164AN will most likely have the same pinout as the 5264 found inside of the gameboy itself. You can find it here:
http://gbdev.gg8.se/wiki/images/4/41/Super-gameboy.gif
...
actually, the original pinout came up on my first search;
http://www.sharpsma.com/download/LH5164A-DSpdf
I do want to criticize your reasoning behind why the MB85R256F is a "good candidate" or not. Having the same number of pins means nothing. After looking at the pinouts,. they are nearly identical after all though your FRAM chip is four times larger in capacity. I say nearly because there are two problems, pin 26 and pin 1. The FRAM has A13 on pin 26 whereas the gameboy has CE2 (high enable) on pin 26.
Pin 26 in the gameboy seems to go to the low power reset chip, so I cannot think of the function off the top of my head.
probing around... The pin seems to be low when on battery power and high when the gameboy is supplying power. I guess it just disables the chip when on battery power. With this in mind...it seems like this pin may be connected straight to the board without having to worry. When it is off, the lower bank of ram will be selected and when it is on, the higher bank will be selected.
As for pin 1, you must bring it high or low, it cannot be left hanging since it is an addressing pin. Either high or low will be fine.
Never assume you can just drop a chip in place of another.
all this is making me want a flasher. I wanna tinker with an idea. old c64 games on the gameboy...put sid music player on a cart with a mini sid chip (if it exists) and some fram. or is someone doing that already?
i have a bunch of copper to melt... maybe i will try making some boards out of epoxy and wax. i like the way the nanoloopcart is...
Last edited by bitjacker (Jan 26, 2014 9:00 pm)
all this is making me want a flasher. I wanna tinker with an idea. old c64 games on the gameboy...put sid music player on a cart with a mini sid chip (if it exists) and some fram. or is someone doing that already?
i have a bunch of copper to melt... maybe i will try making some boards out of epoxy and wax. i like the way the nanoloopcart is...
what are you?
a guy with too many hobbies, i guess.