Is there a FRAM compatibility list for substituting FRAM for common battery backed chips?

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    • Is there a FRAM compatibility list for substituting FRAM for common battery backed chips?

      I want to mod some of my M2 hardware to use a non-volatile FRAM chip for the timekeeper, mostly to just have it done but also to document the procedure for other collectors of M2 hardware. Considering a lot of the battery backed RTC chips are NOS and probably have diminished battery capacities as is, seems like a valuable procedure. Plus this avoids having to start Dremel'ing the epoxy off the batteries and installing battery holders (annoying, hard to show a tutorial for, batteries run the risk of leaking, etc etc etc all the reasons batteries suck)

      Maybe my google skills are lacking lately, but I cannot find the appropriate FRAM substitute for the following two chips

      ST M48T58Y-70PC1 NonVolatile TimeKeeping RAM

      AND

      Dallas DS1643 NonVolatile TimeKeeping RAM

      Basically just want to convert the boards to run off a FRAM chip. I know its A) possible and B) I've seen it done once on a Japanese YAJ auction for Battle Tryst. Unfortunately the photos weren't high enough res for me to see the chip markings on the FRAM chip. Honestly I don't even think it was silked

      I do know the person who bought the board and should be able to get photos eventually, but if its not silked that won't help much.

      It did use a custom board that interfaced between the FRAM chip and the socket itself, as the FRAM chip was about 1/2 the size of the battery backed chips listed above, and it was surface mount vs through hole.

      If anyone has any thoughts, info, just lmk! I'd appreciate it :)
    • I admittedly don’t know my fram from my sram but I see a lot of threads that suggest sram instead. Looks like there are non-volatile sram 8k x 8 that people use to replace the Konami timekeeper on other pcbs. Konami used timekeepers in other hardware so I’m guessing it’s the same in the m2.

      those may be direct replacements though.

      Is that kind of sram not going to work if you remove the battery?

      And I can take some photos and probe the chip when I get the m2, I don’t see why we can’t identify it even if there’s no silkscreen. The custom board I can map also ;)
      multis: cps* ttx2 gnet f3 mvs sega st-v/16b/24/c2/naomi(netboot) sys2x6 m72
      cabs: sega blast city x2 | taito vewlix c + egret ii
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      projects: some conversions, some repairs
    • the game may refuse to run without the clock.and you will not be able to just plug in fram - it needs some extra logic to get around shortcuts the games use when accessing ram.

      i'm not saying it cant be done, i started designing a module to do this on konami viper boards but never finished it.
      my design kept the clock chip and switched between the clock and fram based on the address being acessed.

      you can just open the clock module and run wires to a coincell holder.
    • well in that case,
      you could use fram or "auto-store-ram" which is a ram chip that copys its contents into an onboard eeprom when the power drops.
      i think the second type can usually just plug in.
      and they may have been from cypress if i remember right.


      the thing with fram is you must use the /WE /CE and /OE properly,
      you cant just tie /CE or /OE to ground permanently like you can with sram.