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N64 EEPROM / SRAM info?
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Author:  getafixx [ Sat Dec 19, 2015 2:42 pm ]
Post subject:  N64 EEPROM / SRAM info?

Is there any chips that are compatible with the N64 Gamepak 4K/16K EEPROMs? They seem to use only 1 data line S_DAT (doesn't specify in or out), a clock, and /reset... but most other serial eeproms have a CS, CLOCK, and a data in and out.

And the same question is posed for the SRAM they used in games like Zelda. I'm assuming that they had some kind of latching built into the SRAM similar to the ROM to work with the multiplexed addresses, but there doesn't appear to be a pinout anywhere for that chip LH52V246A.


EDIT: Just thinking...what if some kind of AND gate was used to combine the D_IN and D_OUT on a serial EEPROM to the S_DAT pin? Would that work for a read/write function? Also, could CS be tied to /RESET on the console with an inverter to control the chip enable? If those worked, then perhaps a replacement could be possible.

Author:  lidnariq [ Sat Dec 19, 2015 4:53 pm ]
Post subject:  Re: N64 EEPROM / SRAM info?

If I had to guess, I'd guess it's shaped like I²C...

Author:  Joe [ Sat Dec 19, 2015 6:59 pm ]
Post subject:  Re: N64 EEPROM / SRAM info?

getafixx wrote:
Is there any chips that are compatible with the N64 Gamepak 4K/16K EEPROMs?
These seem to be custom parts manufactured specifically for Nintendo, so it's unlikely that there are any drop-in replacements. You might be able to get away with some other EEPROM, if you can find any that speak the same protocol, but I can't guarantee that would be enough to fool the games with copy protection.

getafixx wrote:
And the same question is posed for the SRAM they used in games like Zelda.
This is a custom part. It combines a standard SRAM with the bus interface logic to reduce pin count.

Author:  getafixx [ Sat Dec 19, 2015 10:05 pm ]
Post subject:  Re: N64 EEPROM / SRAM info?

Joe wrote:
These seem to be custom parts manufactured specifically for Nintendo, so it's unlikely that there are any drop-in replacements. You might be able to get away with some other EEPROM, if you can find any that speak the same protocol, but I can't guarantee that would be enough to fool the games with copy protection.

Yeah, I know that some games use the CIC as a means of copy protection so that a cart with a different CIC than the game was expecting won't work. I'm not sure that the EEPROMs were used in the same manner, but I figure they'd have to be able to be written and read from the same way... Probably not easy.

Joe wrote:
This is a custom part. It combines a standard SRAM with the bus interface logic to reduce pin count.

That's pretty much it, but does anyone have the pinout for them? There seems to be almost no information, other than it appears to use the same multiplexing technique that the Maskrom used for address and data lines. I'd pop open my Zelda and tone out each line, but i'm afraid that will more than likely erase my saved games (my original record when I bought the game!)

Author:  Joe [ Sun Dec 20, 2015 7:08 am ]
Post subject:  Re: N64 EEPROM / SRAM info?

getafixx wrote:
Yeah, I know that some games use the CIC as a means of copy protection so that a cart with a different CIC than the game was expecting won't work. I'm not sure that the EEPROMs were used in the same manner, but I figure they'd have to be able to be written and read from the same way... Probably not easy.
A handful of games check for different save types, and if they detect the wrong one, activate copy protection. I don't know exactly how this works, so I couldn't tell you if it relies on the EEPROM being an exact match or only checks the capacity of the EEPROM.

getafixx wrote:
That's pretty much it, but does anyone have the pinout for them? There seems to be almost no information, other than it appears to use the same multiplexing technique that the Maskrom used for address and data lines. I'd pop open my Zelda and tone out each line, but i'm afraid that will more than likely erase my saved games (my original record when I bought the game!)
If you aren't trying to replace one, then what good is the pinout? No compatible chips exist.

In any case, the pinout is nearly identical to the mask ROM. The only differences I see are that pins 7 and 22 don't seem to be connected to anything, and pin 8 is used to enable the chip while the console is on (and reduce power consumption while running on the battery).

Code:
N64 mask ROM pinout
       __ __
      |  V  |
AD0 --|     |-- AD15
AD1 --|     |-- AD14
AD2 --|     |-- AD13
AD3 --|     |-- AD12
VCC --|     |-- GND
AL  --|     |-- GND
/R  --|<   >|-- VCC
GND --|<    |-- /W
AH  --|     |-- /R
GND --|     |-- VCC
AD4 --|     |-- AD11
AD5 --|     |-- AD10
AD6 --|     |-- AD9
AD7 --|     |-- AD8
      |_____|
Code:
N64 SRAM pinout
       __ __
      |  V  |
AD0 --|     |-- AD15
AD1 --|     |-- AD14
AD2 --|     |-- AD13
AD3 --|     |-- AD12
VCC --|     |-- GND
AL  --|     |-- GND
N/C --|<   >|-- N/C
EN  --|<    |-- /W
AH  --|     |-- /R
GND --|     |-- VCC
AD4 --|     |-- AD11
AD5 --|     |-- AD10
AD6 --|     |-- AD9
AD7 --|     |-- AD8
      |_____|

Author:  getafixx [ Mon Dec 21, 2015 9:15 am ]
Post subject:  Re: N64 EEPROM / SRAM info?

Thanks for the info!

I was mainly just looking for something to tinker with during my Christmas holidays as I've got some time off of work. Wanted to see if I could increase the size of the EEPROM or the SRAM in a game without it causing issues.

Been looking at NAND memory, and seems to have all the right pins for matching up to a Maskrom pinout. Is that what their Maskroms were using? They seem to have the same address latching function, with an ALE pin to control it (though, the Maskrom has a seperate ALE for high and low access). Something like this: http://www.spansion.com/Support/Datasheets/S34ML01G2_04G2.pdf

Author:  getafixx [ Mon Dec 21, 2015 9:19 am ]
Post subject:  Re: N64 EEPROM / SRAM info?

lidnariq wrote:
If I had to guess, I'd guess it's shaped like I²C...


And you're right, seems to be the closest thing to what they used.

Author:  Joe [ Mon Dec 21, 2015 2:11 pm ]
Post subject:  Re: N64 EEPROM / SRAM info?

getafixx wrote:
Been looking at NAND memory, and seems to have all the right pins for matching up to a Maskrom pinout.

Won't work, though. The protocol those chips use isn't compatible with the N64.

Author:  getafixx [ Mon Dec 21, 2015 7:40 pm ]
Post subject:  Re: N64 EEPROM / SRAM info?

Figures. Well thanks for the help anyways!

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