What is function of the fifo_wr_sync pin of the axi_dmac ip core? Do i have to connect it to 1 or 0? When i have to use it and how?
If the IP is configured with the "Transfer Start Synchronization Support", after the DMA is configured it will start transferring data only after the fifo_wr_sync is 1 at the same time with fifo_wr_en.
If you don't set that parameter, you can leave it unconnected / connected to ground.
It is used for cases when data is transferred for more channels and the data corresponding to the first active channel is not the first data on the bus for each clock cycle.
A further note that may save some additional head-scratching:
If the DMA is configured to have DMA source type of "Streaming AXI", the function of the fifo_wr_sync pin is transferred to s_axis_user in the AXI-S interface.
This means that both s_axis_user and s_axis_valid must be 1 when s_axis_ready is 1 for data to be transferred.
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