2 Replies Latest reply on Jul 25, 2011 8:32 AM by userc_42051

    Multiple TD's for different destination adresses

      Hi All,

      I need assistance with multiple TDs in single DMA chanell.

      I want to use one DMA chanell for sending data to VDAC (TD1 for VDAC1 and TD2 for VDAC2).

      Data is stored in two arrays: 32 bytes wide each.

      Is it posible to send only one byte to VDAC1 and one byte to VDAC2 per rising edge on DMA drq?


       I'm getting only full array send on VDAC1, than on VDAC2.





      Alex Che.

        • 1. Re: Multiple TD's for different destination adresses

          Hi Sndsnake,




          If the requirement is to update VDAC1 and VDAC2 upon rising edge on drq, then it is easier to use two independent DMA Channels with a single TD each.


          Each TD has a fixed source and destination. The drq of two DMA Channels can be connected to a single clock.


          Configure the Request per Burst to 1 and Burst Count to 1. This will transmit 1 byte for every rising edge of the clock to drq.


          The TD can be chained to itself.




          You can refer to Code example available here


          This example demonstrates updating of one VDAC using a single DMA channel. Another similar DMA channel can be used to update the second VDAC.

          • 2. Re: Multiple TD's for different destination adresses

            Thank you for help, i was trying to minimize number of DMA chanels.


            I need 26 of them.




            if some one need a guide how to make 6 ++  DAC`s insted of  2 (3446-AXI) I`ll be glad to help. 





            Alex Che.