This block will sniff the current value of 'x_length', but it will not modify it in any way. Hence, it assumes that the SW running in the PS has requested 8 extra bytes to accommodate the (64-bit) timestamp (i.e., 'x_length' is N+7 bytes, instead of the N-1 value described in the original ADI's 'axi_dmac' documentation).
Generics
Generic name
Type
Value
Description
DMA_LENGTH_WIDTH
integer
24
defines the width of transfer length control register in bits; limits the maximum length of the transfers to 2^DMA_LENGTH_WIDTH (e.g., 2^24 = 16M)
Ports
Port name
Direction
Type
Description
DMA_x_length
out
std_logic_vector(DMA_LENGTH_WIDTH-1 downto 0)
Signal indicating the number of samples comprising the current DMA transfer