The problem about setting up the FIFO's deep

[Altera_Forum]

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！

[Altera_Forum]

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]

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]

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

[Altera_Forum]

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

[Altera_Forum]

I have same problem.  

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