The SN54 / 74LS173A is a high-speed 4-Bit Register featuring 3-state outputs for use in bus-organized systems. The clock is fully edge-triggered allowing either a load from the D inputs or a hold (retain register contents) depending on the state of the Input Enable Lines (IE1, IE2). A HIGH on either Output Enable line (OE1, OE2) brings the output to a high impedance state without affecting the actual register contents. A HIGH on the Master Reset (MR) input resets the Register regardless of the state of the Clock (CP), the Output Enable (OE1, OE2) or the Input Enable (IE1, IE2) lines. Fully Edge-Triggered