A first first-in first-out (FIFO) circuit includes a storage circuit, a second first-in first-out (FIFO) circuit, and a third first-in first-out (FIFO) circuit. The storage circuit stores write data at a write address in response to a write clock signal. The storage circuit outputs read data from a read address in response to a read clock signal. A write pointer indicating the write address is synchronized with the write clock signal. A read pointer indicating the read address is synchronized with the read clock signal. The second first-in first-out (FIFO) circuit synchronizes the write pointer with the read clock signal. The third first-in first-out (FIFO) circuit synchronizes the read pointer with the write clock signal.