Replacing a simple eprom/eeprom with an SD card

Discussion in 'The Projects Forum' started by programmer6502, Apr 11, 2014.

  1. programmer6502

    Thread Starter Member

    Feb 1, 2014
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    I know threads have been posted about SD cards relating to or replacing eproms/eeproms but most have to do with Microcontrollers. I have lot's of old projects I would like to build, or projects for old hardware and I'm wondering how hard it would be to replace a say, a common vintage 27128 16k eprom with an SD card. I'm assuming you would need some decoder or breakout board and some sort of software in the SD card to divide the space into different address banks the old hardware can recognize. It would be great to do this because SD cards are cheap and convenient and I wouldn't have to buy a couple hundred dollar eprom/eeprom programmer and UV light eraser.

    Thanks!
     
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Not very practical. Eproms have a parallel address and data buses. SD chips are a serial device.

    But it depends on how you are using the eprom. If it is for simple data storage then it could be possible. But you would still probably need RAM.

    If it was for code you certainly would need RAM but would still need some form of ROM to boot load the RAM from the SD.
     
  3. programmer6502

    Thread Starter Member

    Feb 1, 2014
    126
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    Yeah of course, but don't they have stuff like UARTs that can convert between serial and parallel? Okay, with all the RAM and ROM stuff, sounds like a use for a microcontroller after all.
     
  4. programmer6502

    Thread Starter Member

    Feb 1, 2014
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    Well since I have this up I have another question. I have an Atari 2600 that I would like to make a flash cart for. I would like to use an SD card to store the games, then have a selector that let's you select the game, which would then load into a battery backed up parallel ram chip acting as an eeprom. (I want to use ram so I can have unlimited rewrites). And finally the ram chip would load the game into the Atari on boot. Of course the Atari was designed for parallel eprom/eeprom cartridges. I should just be able to use a shift register to convert the serial data from an SD breakout board to the parallel ram chip right?
     
    Last edited: Apr 12, 2014
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    That's a better method for sure. You replace the parallel EPROM with a parallel RAM chip.

    Then your microcontroller loads the RAM chip with the code you want, it can get that code from an SD card.

    Once the RAM is loaded, the antique device can read and execute its code from that RAM exactly the same as if it was the EPROM.
     
    programmer6502 likes this.
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