1 Reply Latest reply on Apr 21, 2013 1:21 PM by anand.srinivasan.asokan

    Sync Slave FIFO 2 bit Read Issue

    tim.stanka

      This posting is for info only . . . hoping it might help someone

         

      PROBLEM:

         

      We implemented a 2 bit synchronous slave FIFO with auto DMA. We had an issue where I would send a packet from the host and the FPGA master would read 233 words(32 bit) and then the flag would get deasserted and would assert every 60 cycles for a duration of 1 read. Also, every other word (32b) would be missing.

         

      SOLUTION:

         

      FPGA designer was always assrting RD# and just uning the flag to tell him when we had valid data. I asked him to start deasserting RD# on empty and that fixed the problem. The FX3 slave FIFO timing diagrams do not really show you what to do with the control signlal when the flag toggles from asserted-unasserted-asserted. He basically repeated the sequnse he does when the flag is first asserted (see flag, assert RD#, wait 2 PCLKs for data).

         

      Hope this helps someone. I did not see this anywhere in the forum so you guys must be all smarter than us!!!!!!!!!!!!