A fifo_depth() constraint specification
above 40 allocates FIFOs from memory, known as DMA FIFOs. The following is an example of
a FIFO allocation for a request of fifo_depth(3000)
bytes which is allocated in memory.
Figure 1. DMA FIFO Allocation
Note: TLAST is dropped when data goes through DMA
FIFO.
Note: Write to DMA FIFO must be continuous or multiple
of 4 words (4 words = 128 bits).
You can also specify the type of FIFO allocated, whether stream switch or DMA, as well as their locations. More information can be found in FIFO Location Constraints.