US Patent 11971831 First-in, first-out buffer

An apparatus has first-in, first-out buffer circuitry to transfer data from a source domain to a sink domain across a clock domain boundary. The FIFO buffer circuitry has data transfer circuitry; source domain and sink domain data transfer control circuitry to maintain state vectors indicative of a state of the FIFO buffer circuitry in the respective domain; and synchronisation circuitry in each of the source domain and the sink domain to stabilise a signal received from the other of the source domain and the sink domain and to store the received state vector. The synchronisation circuitry is clock-gated by an enable signal and the synchronisation circuitry is responsive to a change in the state of the FIFO buffer circuitry in the respective domain to advance the respective state vector by controlling the enable signal to enable output of elements of the received state vector.