Results of using FeRAM instead of Battery+SRAM

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Memblers
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Re: Results of using FeRAM instead of Battery+SRAM

Post by Memblers » Sat Jul 11, 2020 5:31 am

soniccd123 wrote:
Fri Jul 10, 2020 5:21 pm
The games work normally, i've tried SC2000 and DK Country, but are not saving, the memory OE is connected to CART_RD and WR is connected to CART_WR.
For those two games specifically, it's possibly software copy detection. SNES cart copiers would usually have 32kB SRAM, and some games check for that. Later copiers I believe limited RAM size or something to bypass it, but SimCity 2000 was a game I specifically remember cracking the protection in it myself because it didn't work on the Game Doctor SF7 (and ucon64 didn't seem to have a patch for it).

edit: or maybe not, on re-reading it sounds like they play normally, but just don't save?

soniccd123
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Joined: Sat Jun 27, 2020 12:01 pm

Re: Results of using FeRAM instead of Battery+SRAM

Post by soniccd123 » Sat Jul 11, 2020 10:58 am

Memblers wrote:
Sat Jul 11, 2020 5:31 am
soniccd123 wrote:
Fri Jul 10, 2020 5:21 pm
The games work normally, i've tried SC2000 and DK Country, but are not saving, the memory OE is connected to CART_RD and WR is connected to CART_WR.
For those two games specifically, it's possibly software copy detection. SNES cart copiers would usually have 32kB SRAM, and some games check for that. Later copiers I believe limited RAM size or something to bypass it, but SimCity 2000 was a game I specifically remember cracking the protection in it myself because it didn't work on the Game Doctor SF7 (and ucon64 didn't seem to have a patch for it).

edit: or maybe not, on re-reading it sounds like they play normally, but just don't save?
I patched both with ucon64, both just dont save, maybe i can try other games anyway.

soniccd123
Posts: 7
Joined: Sat Jun 27, 2020 12:01 pm

Re: Results of using FeRAM instead of Battery+SRAM

Post by soniccd123 » Mon Jul 13, 2020 11:30 pm

Ok, so i actually found the problem and everything works now, it happens that i'm using a 256K FeRAM chip of which the address lines go from A0 to A14. In the HiRom mode, the SNES maps the save memory at address 6000h-7fffh, these addresses correspond to A13 and A14 in high state (and thats why they're used in the mapping circuitry). In my configuration, A13 and A14 were also connected to the FeRAM A13 and A14. I decided to rewire these two pins and grounded both and voila! It worked! But now i only had 64K of memory available, so i needed to find which lines provided these two bits. I tried BA0 to A13 and BA1 to A14 and it worked perfectly.

So, if anyone have interest in using FeRAM in a custom cart, this schematic should work:

Image

I hope this may help somebody in the future :D

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