4 Replies Latest reply on Mar 20, 2017 11:09 PM by nisa

    about FLAG

    931786714_2222966

      I'm using the EX-USB FX3 SDK's SLAVE  FIFO interface to design.

         

      I'm not sure ,if FLAGA and FLAGB can only be  used for the Slave FIFO write operation,or  FLAGA and FLAGB can also be  used for the Slave FIFO read operation. If FLAGA and FLAGB need to be configured as to indicate the availability of read operation or write operation fist?

         

      By the way, there is a mistake in the manual's Table 1. Synchronous Slave FIIFO Interface Signals (An65974 , P3). FLAGC and FLAGD is not in the Figure 4. Synchronous Slave FIFO Write Sequence(An65974 , P7) as you described in Table 1. Synchronous Slave FIIFO Interface Signals.

         

      Thanks.

        • 1. Re: about FLAG
          nisa

          FLAGA and FLAGB are used for the Slave FIFO write operation and FLAGC and FLAGD are used for the Slave FIFO read operation.

             

          For write we have Flag A & B. One tell if there is a empty buffer on the DMA side (ready flag), other says if the buffer is about to be full (watermark flag). These are needed for flow control. Similar is the case for read operation where the FPGA tries to read from the slave with the help of flag C&D.

             

           Figure 4 is  Synchronous Slave FIFO Write. For write we need to check FLAGA and FLAGB only. So, we have not given the diagram of Flag C&d as we do not care about them during the write sequence.

          • 2. Re: about FLAG
            931786714_2222966

            sorry, I've maken a mistake. FLAGC and FLAGD is not in the Figure 3. Synchronous Slave FIFO Read Sequence

               

            (An65974 , P6) as you described in Table 1. Synchronous Slave FIIFO Interface Signals.

            • 3. Re: about FLAG
              931786714_2222966

              Can I only use FLAGA and FLAGB to design? I'll configure FLAGA to thread0 for Slave FIFO write operation,and configure FLAGB to thread3 for Slave FIFO read operation.For we know the deepth of the Slave FIFO,we can count to be sure when the Slave  FIFO is FULL/EMPTY. Is that available?

              • 4. Re: about FLAG
                nisa

                Yes, you can do so. In the AN65074, we have used two flags per thread because master was not counting the data (but observing the flag status). If you want to count, then it is fine.