The 'ALVTH16821 devices are 20-bit bus-interface flip-flops with 3-state outputs designed for 2.5-V or 3.3-V V_CC operation, but with the capability to provide a TTL interface to a 5-V system environment.

The devices can be used as two 10-bit flip-flops or one 20-bit flip-flop. The 20-bit flip-flops are edge-triggered D-type flip-flops. On the positive transition of the clock (CLK), the flip-flops store the logic levels set up at the D inputs.

A buffered output-enable (OE\) input can be used to place the ten outputs in either a normal logic state (high or low level) or a high-impedance state. In the high-impedance state, the outputs neither load nor drive the bus lines significantly. The high-impedance state and increased drive provide the capability to drive bus lines without need for interface or pullup components.