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Character rom

Discussion in 'Electronic Design' started by derek, Dec 12, 2004.

  1. derek

    derek Guest

    Hi,

    Recently I have a MCU design problem. I have designed a electronic
    device which can communicate with computer by ethernet to retrieve
    data. And I want to include character ROM so that it can display
    native characters. However, I have calculated the ROM size requirement
    is about 2M bytes.

    So the ROM must transfer data to the MCU serially as there are not so
    many free pins at MCU side. For such a large ROM size with serial
    interface I found only flash memory such as MMC card can do that.
    However, because it is flash memory I need to read a minimum of one
    sector which is 256 bytes for each character. This made the display
    slow.

    Actually I have thought to retrieve the font by the ethernet. However,
    the menu cannot display correctly during offline and this brings a lot
    of other problems.

    Do anyone think another solution for me?

    Thanks!
     
  2. Dave Garnett

    Dave Garnett Guest

    Atmel Dataflash
     
  3. Ziza

    Ziza Guest

    Why don't you try to compress data?
     
  4. Rich Grise

    Rich Grise Guest

    A Two Megabyte character ROM? What language are you using, Chinese?
    I put a whole ASCII character set in a 2716 or so some years ago.
    If you could provide more details of what you have, etc, I'm sure there'd
    be more suggestions forthcoming.

    And I'm _really_ curious what kind of character set takes such a huge ROM!

    Good Luck!
    Rich
     
  5. Investigate the design of Teletext character ROMs. Made in the days when
    2 MB was a dream.
     
  6. Guest

    Sorry, the exact size should be about 700K bytes. The font is Chinese
    which is 16x16.
     
  7. We should have figured that out from the .hk domain.

    My back of envelope tells me that you have about 22K distinct characters
    to encode. Does that sound right?

    Since I don't know Chinese, I couldn't tell you if there are any
    language specific tricks one could use such as defining characters as
    groups of simpler blocks which only need to be stored once.

    If no such tricks are available, a simple compression algorithm could
    save you some memory. Make sure you look for one that supports efficient
    random access into the compressed data so you don't have to unpack the
    whole ROM to look for one character.
     
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