1 Reply Latest reply on May 1, 2016 3:17 PM by Madhu Lakshmipathy

    FX3 Slave FIFO StreamIN PKTEND Issue

    zhang.tian-chao

      HI:

         

      I use AN65974 streamin example firmware to try pktend signal.

         

      Slave FIFO is 32bit.

         

      DMA buffer size is 16*1024, DMA buffer count is 8.

         

      If I fire ptkend at every 8192 bytes (2048 words), I will got the FLAGA issue as picture.

         

      Every 8 FLAGA we will get a long time FLAGA.

         

      Why?

        • 1. Re: FX3 Slave FIFO StreamIN PKTEND Issue
          Madhu Lakshmipathy

          Hi,

             

          Everytime you fire a PKTEND, one buffer is wrapped. (Which means you can no longer fill data in that buffers. At the end of 8 PKTEND you will have 8 buffers none of which can accept any more data. (Though the buffer size is 16K, asserting the PKTEND will wrap each buffer, so the new data will always go to next buffer).

             

          After 8 PKTEND, the 8 buffers are wrapped and no more data can enter into FX3's DMA from FPGA. So flag A will wait as long as the data is consiumed by the PC.

             

          If your PC is receiving large amounts of data rapidly (just like how Fx3 C++ or C# streamer application does), then there will not be such long delay.

             

          Regards,

             

          - Madhu Sudhan