The MC74AC194/74ACT194 is a high-speed 4-bit bidirectional universal shift register. As a high-speed multifunctional, sequential building block, it is useful in a wide variety of applications. It may be used in serial-serial, shift left, shift right, serial-parallel, parallel-serial, and parallel-parallel data register transfers. The AC/ACT194 is similar in operation to the AS195 universal shift register, with added features of shift left without external connections and hold (do nothing) modes of operation.