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Altera_Forum's avatar
Altera_Forum
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19 years ago

Flash EPCS access problem

Hi,

I'm trying to write my FPGA configuration file on its EPCS16 flash using Nios processor. The final goal is to use Uart/Usb/Ethernet communication to download the FPGA configuration file on the board.

I have implemented an EPCS_Controller on my Nios CPU using SOPC builder, and I'm using 'alt_flash_dev' drivers to access to it.

I success to read flash datas. But I have some problems concerning write access : I can't write a block entirely (65536 bytes, I don't have enough memory to store such amount of datas), so I would like to write only part of a block, like this way :

my_epcs = alt_flash_open_dev(epcs_controller_name);

if(my_epcs) {

printf ("epcs opened successfully!");

ptr = 0;

while (ptr<3146000) { // fichier 3mo maxi

my_data = .. // store 0x2000 datas

ret_code = alt_write_flash(my_epcs, ptr, my_data, 0x2000);

ptr = ptr + 0x2000;

}

alt_flash_close_dev(my_epcs);

}

The problem is that each access with &#39;alt_write_flash&#39; function seems to erase the entire block/sector of the flash (which represent 0x10000 datas). Is there a solution to my problem ?

Thanks,

Jérôme

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    19 years ago

    Hi Jérôme,

    > I can&#39;t write a block entirely (65536 bytes, I don&#39;t have enough memory to store such amount of

    > datas), so I would like to write only part of a block,

    You can write as little as you like -- but no more than the page size.

    > The problem is that each access with &#39;alt_write_flash&#39; function seems to erase the entire

    > block/sector of the flash

    Correct. You can either erase a single sector, or the entire device. There&#39;s no way to erase

    anything smaller than a sector.

    > Is there a solution to my problem ?

    If you need to preserve some data in the sector, you need to: read--modify--erase sector--write sector.

    If you don&#39;t have enough memory (RAM) to read an entire sector, you&#39;ll need to be creative.

    You could try reserving a sector to hold a copy of the original sector while you perform the update.

    It&#39;s very not pretty -- but it can work.

    Regards,

    --Scott
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    19 years ago

    --- Quote Start ---

    originally posted by jérôme@Apr 28 2006, 04:19 AM

    the problem is that each access with &#39;alt_write_flash&#39;[/b] function seems to erase the entire block/sector of the flash (which represent 0x10000 datas). Is there a solution to my problem ?

    Thanks,

    Jérôme

    <div align='right'><{post_snapback}> (index.php?act=findpost&pid=14815)

    --- Quote End ---

    [/b]

    --- Quote End ---

    This is the nature of using most any flash device.

    For your situation, it makes sense to use the alt_write_flash_block() function. It won&#39;t automatically erase the flash....like alt_write_flash() does. In this way you could write to the flash in whatever data size you want and detect when a sector erase is necessary yourself.

    Something like the following should work if you implement it in a loop passing new "data" in with each pass: 

    if(new_flash_block != current_flash_block)
    {
      printf("\nFlash Block %d", new_flash_block);
      alt_erase_flash_block(fd, (new_flash_block * regions->block_size), 
                                      regions->block_size);
      current_flash_block = new_flash_block;
    }
    alt_write_flash_block(fd, (current_flash_block * regions->block_size), 
                                   target_addr, data, data_len);

    Cheers,

    - slacker