Saturn FRAM mod

Discussion in 'Modding and Hacking - Consoles and Electronics' started by Nully, Jul 9, 2018.

  1. Nully

    Nully Enthusiastic Member

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    I'm getting ready to do this install and I noticed he said you'd have to set the RTC on every boot. He says "You could leave the CR2032 in the Saturn and remove the Battery power from the FM1808 (it doesn’t need it anyway).", so are we just going to lift the VDD pin and connect it directly to 5v? I'm not sure how battery backed RAM works, but I'm guessing once the system is turned off it's going to monitor for that change if that pad is connected? I don't see anything in the datasheet about a pin being for battery power explicitly.

    Pin Description Pin Name Type Description

    A0-A14 Input Address: The 15 address lines select one of 32,768 bytes in the FRAM array. The address value is latched on the falling edge of /CE.

    DQ0-7 I/O Data: 8-bit bi-directional data bus for accessing the FRAM array.

    /CE Input Chip Enable: /CE selects the device when low. Asserting /CE low causes the address to be latched internally. Address changes that occur after /CE goes low will be ignored until the next falling edge occurs.

    /OE Input Output Enable: Asserting /OE low causes the FM1808 to drive the data bus when valid data is available. Deasserting /OE high causes the DQ pins to be tri-stated.

    /WE Input Write Enable: Asserting /WE low causes the FM1808 to write the contents of the data bus to the address location latched by the falling edge of /CE.

    VDD Supply Supply Voltage: 5V

    VSS Supply Ground

    [​IMG]

    http://db-electronics.ca/2017/02/10/sega-saturn-internal-memory-mod-with-fram-no-battery-required/
     
    Last edited: Jul 9, 2018
  2. APE

    APE Site Supporter 2015

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    I've pulled the SRAM and just dropped the FRAM in directly without changing anything. Worked fine.

    But it does mean the FRAM is being fed power. I suppose you could cut the trace going to the battery and maybe save a little juice. Alternatively, wiring a 120v->5v circuit in there to feed the RTC while plugged in would save the battery.
     
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  3. Nully

    Nully Enthusiastic Member

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    But are you having to set the clock on every single boot using it as a direct replacement? Seems pretty annoying.

    When you say cut the trace, is this on IC9 or do you know which is going to the FRAM to ground it? If you do that at the battery holder, then how is the Saturn going to communicate with it to store the clock info?

    Saw your last line, "in there" is I guess the issue, where am I connecting this to?
     
    Last edited: Jul 9, 2018
  4. abveost

    abveost Robust Member

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    He said a lot of shit. I wouldn't worry too much about it. Just use some common sense. A drop in replacement for a part will do whatever job the old part did. Probably better. Unless it dun gone an splodes yer console.
     
  5. Marteicos

    Marteicos Member

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    The console already have circuitry to feed the chips with 5 volts when powered, both rtc and internal ram. Without this circuitry the console wouldn't work correctly without a battery, an internal ram without power makes the console boot with 0 blocks, for example.
     
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  6. Nully

    Nully Enthusiastic Member

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    I guess I'm just not understanding why this direct replacement would have anything to do with the CR2032 keeping the time unless he doesn't speak english natively and is trying to say he didn't bother putting a battery back in. Or is it going to override the Saturn's saving ability to be stuck in the FRAM instead of to the battery so the battery has to be removed? I'll go ahead and install it soon and report back with findings.
     
  7. Bad_Ad84

    Bad_Ad84 The Tick

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    He's saying without the battery you need to set the rtc on every boot (obviously). As you don't need the battery for keeping the memory powered, he's probably leaving the battery out.

    Or you can leave the battery in and not need to keep setting the clock, disconnecting the battery from the ram circuit would increase battery life. If you Dont care about that, just replace with fram so no risk of losing saves and just replace battery when clock doesn't hold its time anymore.
     
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  8. Nully

    Nully Enthusiastic Member

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    It’s funny because I found several forum posts asking this same question, so I wasn’t the only one confused. He made it seem like a technical reason as to why it couldn’t be done or this “battery power” or I just thought into it too much. Thanks for the responses.

    APE’s response of “save a little juice” finally clicked as well with that last reply.

    I have.an extra chip if someone wants to try this mod out.
     
  9. Bad_Ad84

    Bad_Ad84 The Tick

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    The obviously was that the RTC would die without the battery, not that what he was saying was obvious :)
     
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  10. Getta Robo

    Getta Robo Spirited Member

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    Just wanted to ask, is there a way to combine the best of two worlds? Meaning replacing the SRAM with a FRAM, and also somehow have the RTC? I thought by replacing the stock battery with a rechargeable one, and also having to change some wiring I guess, but I haven't seen any schematics nor having a deep understanding whether that would feasible or not. Could you @Bad_Ad84 shed some light here please?
     
  11. Bad_Ad84

    Bad_Ad84 The Tick

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    Just install the fram and leave the battery installed?

    No risk of losing saves, change battery when you are prompted for date again.

    Basically works the same as the Saturn always has, but don't lose saves if it dies.
     
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  12. Getta Robo

    Getta Robo Spirited Member

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    I wasn't sure if there was another option, thanks for clearing things up.
     
  13. Bearking

    Bearking Konsolkongen

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    Was there a problem with using FRAM with the region free BIOS? I remember someone posting about that a few years ago.
     

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