ERPROM help

Discussion in 'General Electronics Chat' started by Robin Mitchell, Oct 27, 2009.

  1. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    Hi everyone,

    Someone (cant remember the name) suggested for me to use serial eeprom as memory for my 4bit computer. I have been doing some research and I have found one website great:
    http://www.seattlerobotics.org/Encoder/aug99/serialeeprom.html

    I think I understand how to use it but i cant find this type of eeprom on the internet (Write, Read ports only).

    But there are the other chips with A0, A1 and A2. HOW DO THEY WORK?

    Are there any good tutorials on eeproms and programming the without a computer because i just want to store a couple of bytes of info effectivly.

    Thanks!!!
     
  2. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    Here is a schematic on how to connect one Serial EEPROM (24LC64 by Microchip) the A0,A1,A2, bits are for addressing upto 8 different devices, just connect all 3 Ax lines to ground.

    I also included the datasheet link for the device an some sample code links....

    Sample code (it is written in Keil C but I am sure it can be ported over to other compiler pretty easy.) http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en535632

    Datasheet >> http://ww1.microchip.com/downloads/en/DeviceDoc/21189Q.pdf


    I hope this helps.....
     
  3. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
    732
    200
    So the A0, 2 and 3 assign diffrent memory sectors?

    How do you read and write becuase in these eeproms there is only serial data, not pin like write and read...

    Are there any eeproms that just save a one or zero, and can be "played back" like a tape. So i might send 1001010010 in and if i reset and start again it sends this...

    Thanks for the help!!!
     
  4. Papabravo

    Expert

    Feb 24, 2006
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    1,790
    Start by reading the datasheet, that is what it is there for. To answer your question you send it a serial command with parameters and it sends you back a serial data stream with the data. The lines A0, A1, and A2 are hard wired to GND or VCC so you can have multiple devices connected to the same serial bus. The value of A0, A1, and A2 is encoded in the serial command from the processor and is decoded by one and only one of the devices on your bus. The advice for having a system with one device is to connect those lines to GND and encode the "000" for those bits into the appropriate position in the command.
     
  5. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    That sounds complex,

    Is there any other kind of storage for a ....lets just say begginer with memory :D
     
  6. BMorse

    Senior Member

    Sep 26, 2009
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    serial eeproms are about the easiest to implement without too much code overhead.
     
  7. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    200
    So I guess im at a dead end :(
    All i want to do is save bits by sending a single pulse...
    Bang!....one bit saved
    nothing....nothing to save, move on!!!

    Thanks for the help guys (and gals possibly)
     
  8. Papabravo

    Expert

    Feb 24, 2006
    10,144
    1,790
    Sadly, I think you are just plain outta luck with respect to your expectations. Maybe you will change your mind when you learn more about....things. I suppose you could do this with a single magnetic core, but there would be other complications like destructive reads that require write-back and so forth.

    http://en.wikipedia.org/wiki/Magnetic_core_memory
     
  9. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    1,758
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    Why would a beginner build a discreet 4 bit microcontroller? Sounds like the slow & painful way to learn about microcontrollers IMHO.
     
  10. BMorse

    Senior Member

    Sep 26, 2009
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    not necessarily a dead end, but just a small roadblock.... I am sure there is a way for you to implement some bit banging routines for I2C in your app, it might take some time but it is very doable. Once you get the code done, it would also help for other I2C devices not just Serial EEProms.....

    My. 02
     
  11. davebee

    Well-Known Member

    Oct 22, 2008
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    In a way, by using a serial RAM chip, you're trading hardware complexity for software complexity. Serial RAMs use fewer pins than parallel-access RAM which is sometimes important and sometimes just plain easier to work with, but you have more code to deal with in order to access them.

    If you really want the easiest RAM to operate, and you only need a few bytes storage, you could use a static RAM chip. You might have to buy one with much more storage than you need, but what you could do is tie most of the address lines to a fixed logic level so your hardware only has a couple of addresses to set to simplify your memory access.
     
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