Keyword: First Word Fall Through, FIFO16, CORE Generator, pre, fetched, output, zero, latency, first, in, first, out
Is the First Word Fall Through (FWFT) feature available for the FIFO Generator Core?
The FWFT feature is available beginning with the FIFO Generator v2.1 core released with ISE 7.1i IP Update #1. This core supports FWFT for the Independent Clock FIFO that has memory types of Block RAM or distributed RAM, but not for FIFO16 ("Built-in FIFO") implementation.
Due to silicon errata items with the Virtex-4 devices, FWFT support using the Virtex-4 Built-in FIFO16 cannot be supported. Please see (Xilinx Answer 22462) for details on this errata item. If FWFT is required, the alternative is to use the FIFO Generator core with "Block RAM" type.
Note that Virtex-5 FIFO implementations using "Built-in" type do support FWFT.