8031 & at28c256

Discussion in 'Embedded Systems and Microcontrollers' started by hadeedunhaad, Jun 7, 2011.

  1. hadeedunhaad

    Thread Starter New Member

    Apr 22, 2011
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    0
    Hi all,

    - Is it possible to have both code and data in AT28C256 EEPROM and run an 8031 microcontroller ? I will have to burn the code in the EEPROM through my programer then the data has to be send to the same IC through serial communication with IBM PC.

    - Or is it possible to send both code and data to the chip via IBM PC ?

    Will i have to go for another I2C eeprom for my data ?

    Thank you.
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,163
    1,796
    No. A little bit of external logic will allow your device to contain both CODE and READ ONLY data.

    Use an AND gate with PSEN-bar and RD-bar going to the OE-bar pin

    Instruction fetches will come from the EEPROM and so will data fetches to external memory. If you want to write to the external memory you will need to be more creative.
     
  3. hadeedunhaad

    Thread Starter New Member

    Apr 22, 2011
    24
    0
    thank you for your reply,

    I'm aware of that circuit with the logic gate (i found that in a book).
    Still i've a few questions unanswered. I'm unable to visualize the whole working process. ie is to avoid any error in my PCB design i need to be very sure of it. I've already made a prototype and my project was about finish then this problem came up. I ran out of the ROM memory. My code went outside 4K.

    these are some of my doubts:

    - Initially when my memory(EEPROM) is blank can i send the code to EEPROM via IBM PC serial comm ? But i feel like it is impossible as the micro-controller should be dumb without the code, and how can it communicate with the PC to fetch the code to the memory.

    - how do i allocate code and data in predefined memory addresses ?

    Or is it possible for anyone of you to direct me to some sources where i could find this information.
    i was about to go with two separate memories. One parallel EEPROM(AT28C64) for code and I2C for data(AT24C128). Will I sound like a stupid to use such a combination. Since its a professional job i gotta make it economical design as well.

    Thank you for your patience. Any one could help me in this regards.
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,163
    1,796
    I'm not familiar with your design. If you must program the part without any code on the 8031 then you must use an external programmer and insert the part into a socket on your board after it has been programmed.

    If you have some non-volatile code on the 8031 it should be a "bootloader" that will accept data over the serial port and write it into the external memory device.
     
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