These Low-Power Schottky eight-bit universal registers feature multiplexed
inputs/outputs to achieve full eight-bit data handling in a single 20-pin
package. Two function-select inputs and two output-control inputs can be used
to choose the modes of operation listed in the function table. Synchronous
parallel loading is accomplished by taking both function-select lines, S0
and S1, high. This places the three-state outputs in a high-impedance state,
which permits data that is applied on the input/output lines to be clocked
into the register. Reading out of the register can be accomplished while the
outputs are enabled in any mode. The clear function is synchronous, and a
low level at the clear input clears the register on the next low-to-high transition
of the clock.