SDRAM refresh doubt

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#1
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I've built a custom AVR32UC3A0256 board based on the EVK110 development kit, but I use an 8MB ISSI SDRAM model instead of the 32MB Micron's model ( the model that comes with the EVK110 ) . ISSI's model is pincompatible with Micron's model. The only diference is that it uses one adress bit less.

I configured all AVR32 registers involved in the SDRAM access and I can read and write the entire memory, but my problem apears when I read sequentially a "big part" of the memory. I mean, if I exectue a large quantity of sequential reads over the memory I start to loose data, but if I insert some SDRAM write instuctions while I'am reading the SDRAM I don't lose any data. It seems like the SDRAM does not refresh properly while is being sequentially read , and the problem disapears if I force some write instruction while I'm reading.

  // fill a part of the SDRAM
  for (i = 0; i <260000;i++){
        sdram[i]=(unsigned long)(i%255);
  }

  float_aux=long_aux;

  // check written values
  for (i = 0; i <260000;i++){

    /* If I uncoment this part of the code, it works
    if ((i%2048)==0){
        sdram[i]=i%255;
    }*/

    if (sdram[i]!=(unsigned long)(i%255)){
        num_errors++;
    }else{
        num_ok++;
    }//if

  }//for

It seems like the SDRAM doesn't refresh properly while is being sequentially read unless I place some write instructions in the middle. Probably I'am not configuring properly any of the registers.

Any idea?

Thanks

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Check the datasheet against your code?

Hans-Christian

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Can you share your initialization code ?

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I think you’re about 11 years too late. 5 years too late for using an AVR32.

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I was going to suggest http://start.atmel.com as a place to potentially get some AVR32UC3 initialisation code but when I got there the cupboard was bare (which may be a hint as to the support status of UC3 as far as Microchip are concerned).

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"Dare to be naïve." - Buckminster Fuller