First-in first-out buffer (FIFO)
Texas Instruments Semiconductor

CD40105B is a low-power first-in-first-out (FIFO) "elastic" storage register that can store 16 4-bit words. It is capable of handling input and output data at different shifting rates. This feature makes it particularly useful as a buffer between asynchronous systems.

Each word position in the register is clocked by a control flip-flop, which stores a marker bit. A "1" signifies that the position's data is filed and a "0" denotes a vacancy in that positiion. The control flip-flop detects the state of the preceding flip-flop and communicates its own status to the succeeding flip-flop. When a control flip-flop is in the "0" state and sees a "1" in the preceding flip-flop, it generates a clock pulse that transfers data from the preceding four data latches into its own four data latches and resets the preceding flip-flop to "0".