FIFOs

Synchronous FIFO

A parameterized single-clock FIFO with full/empty flags, built with the classic extra-MSB-bit pointer trick and fall-through reads.

Asynchronous FIFO (Dual-Clock, Gray-Coded Pointers)

The canonical CDC data-transfer structure: a dual-clock FIFO with Gray-coded read/write pointers synchronized across the boundary through 2-flop synchronizers.

Circular Buffer (Overwrite-on-Full)

A ring buffer that overwrites the oldest entry when full instead of blocking writes — the key behavioral distinction from a FIFO.

FIFO with Almost-Full Flag

A FIFO variant that raises a programmable-threshold almost-full flag several entries before it is actually full, for early backpressure.

FIFO with Almost-Empty Flag

A FIFO variant that raises a programmable-threshold almost-empty flag when occupancy drops to a low-water mark, useful for prefetch/refill decisions.