Reading the data of a 93C46 eeprom

Discussion in 'General Electronics Chat' started by Liviu123, Mar 16, 2013.

  1. Liviu123

    Thread Starter New Member

    Mar 16, 2013
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    Hello everyone,

    New to the Forum.
    I am looking for a link or a simple application to be used in reading the data of a eeprom type 93C46 circuit used for counting the number and duration of activations of a 12V DC power source. Any sugestion would be very helpful. Thanks.
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    The 93C46 is a memory element. It needs some sort of controller to use it as it works over a serial interface.

    Look up SPI for those details.
     
  3. Liviu123

    Thread Starter New Member

    Mar 16, 2013
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    Thank you for the reply. I will try to reformulate the case. If I have a 93c46 in a circuit how can be read the memory content without being altered. The circuit has a 8 pin IDC connector to the external installation (which probably contains that controller) and which provides a +/- 3V supply to it as well. And this one I'd like to adapt to a 12Vdc installation.
    I think it would be helpful for me to find a simple application using a SPI. Also at using an Arduino circuit as well might be a possibility to test but I'll need more directions for that. Thanks.
     
  4. ErnieM

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    Apr 24, 2011
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  5. Liviu123

    Thread Starter New Member

    Mar 16, 2013
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    Thanks for the help. I have an Arduino Eleven bought some time ago, I know which pins are for MOSI, MISO, SCR, SS. I need to identify each of the 8 pins of the other circuit and see what connections need to be done. Do you think should be another approach? Thanks.
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    Either the existing board was designed to allow the contents to be read or it wasn't. If it was, hooking up an external reader/programmer is easy. If not then more drastic measures will be required including a "vampire" connector that taps into the existing circuitry or desoldering and isolating the chip so that you can get to the signal lines without interference.
     
  7. Liviu123

    Thread Starter New Member

    Mar 16, 2013
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    There is one 100% positive answer: yes. It was allowed for the content to be read but within a special application. I will get the pins layout soon.
     
  8. Liviu123

    Thread Starter New Member

    Mar 16, 2013
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    I have the circuit board with a 93c46 eeprom which through an 8 pin connector is linked to the main board. From the main board it receives the +5V and ground and also the 3 wire interface: DI and DO connected together, CS and CLK. (The rest of connections not related to this circuit).
    I have also an Arduino Eleven (or Uno equivalent) with 4 related terminals: MOSI, MISO, SCK and SS.
    The question here is as follows: how can I connect the EEPROM circuit with the Arduino one to read the data from the EEPROM without altering this data. I am thinking at an interface where I can connect the EEPROM containing circuit board and Arduino circuit, take the reading and returning the EEPROM board back to the main board. Any help? Thank you. Thank so far to the Long Island guy.
     
  9. RamaD

    Active Member

    Dec 4, 2009
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    DI & DO connected together puts a lot of limitations, makes things difficult. There is an Application Note from ST Micro on this.
     
  10. Liviu123

    Thread Starter New Member

    Mar 16, 2013
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    Thanks Rama but this is what I get it: DI and DO together. No alteration to this circuit. I was wondering if there is not an applcation similar to my case or maybe we'll declare as new descovery. I'm still waiting for some more suggestions.
     
  11. RamaD

    Active Member

    Dec 4, 2009
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    The application note describes how to use these with DI & DO connected together. Basically, this helps in saving one IO Pin.
    If you have to use this you need to use the resistors as in the AN, you need to write a bit bang SPI taking care of timing requirements!
    The link for the Application Note -
    MICROWIRE EEPROM COMMON I/O OPERATION
     
  12. Liviu123

    Thread Starter New Member

    Mar 16, 2013
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    I know nothing about the SPI in the original motherboard circuit. I suppose that that SPI in there was meant to write and read in the 93c46. The 93c46 on the circuit board has the pin 5 and 6 connected through a 13,7 KOhm, and other connections: from pin 6 through 2.2KOhm to the I/O terminal, pin 7 through 2.2KOhm to clock terminal, pin 8 through a 2.2 KOhm to chip select terminal, pin 1 to +5V terminal, pin 4 to ground terminal, and between pins 1 and 4 is connected a capacitor 110 nF and that's all. The problem is still in the interface from 3 control pins to 4 control pins of Arduino Eleven.
     
  13. RamaD

    Active Member

    Dec 4, 2009
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    It appears that you are reading mirror pins.
    I have given the actual pins (translated from your pin nos.)
    Pin 8 should be +5, and Pin 5 should be ground. And the 110nF is the decoupling cap.
    Pin 1 - Select
    Pin 2 - Clock
    Pin 3 - Data Input D
    Pin 4 - Data Output Q
    There is a resistor of 13.7K between D & Q.
    Is it possible to split these Pin 3 & Pin 4? Then you could use standard SPI.
    For the command streams sent to 93C46 (all start, cmd or opcode, addr), when they are not multiples of 8 bits, then you can pad it up with 0 at the beginning. SPI sends it from MSB first!
     
  14. Liviu123

    Thread Starter New Member

    Mar 16, 2013
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    Thank you for the corrections. Pin 4 of the IC goes through 13.7 K in series with a 2.2 K to Data input of the mother circuit. Pin 3 of the IC is connected to the junction between 13.7 K and 2.2 K resistors. I can not split the pins 3 and 4. The circuit containing the IC should be re-usable as is. (IC = 93c46)
     
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