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Altera_Forum
Honored Contributor I
762 Views

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!
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5 Replies
Altera_Forum
Honored Contributor I
43 Views

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
Honored Contributor I
43 Views

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
Honored Contributor I
43 Views

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

Altera_Forum
Honored Contributor I
43 Views

Can you explain it in detail? I am a novice....:oops:

Altera_Forum
Honored Contributor I
43 Views

I have same problem.  

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