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Altera_Forum's avatar
Altera_Forum
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15 years ago

The problem about setting up the FIFO's deep

Hi guys,

I have a big problem when I use the DCFIFO mega function. I need to store large amounts of data to achieve the data delay function. When I use the small FIFO（deep 1024),it works well. However when I increase the deeps of FIFO, it goes bad(deep 32768).（Writing and reading are not the same ） What happened ? I am confused! Is there anyone who meets the similar prolem? I'm looking forward to your suggestions！ Sincere thanks！

5 Replies

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

    Ive had deep fifos, and never had a problem. You will need to post more details.

    Have you changed any other settings, like the lookahead mode?
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    Thank you for your reply!

    yes, I turn on the show-ahead mode and my FIFO wide is 14bits. Did you set up any Timing Constraints for the FIFO when it gets big?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    not specifically, just make sure you have constraints on both clock domains.

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    I have same problem.

    I use 32bit input and 8bit output FIFO, the fifo deep cannot exceed 1024 words (32768 bits).