These devices have four modes (HOLD, SHIFT LEFT, SHIFT RIGHT and LOAD DATA). Each mode is chosen by two function select inputs (S0, S1) as shown in the Truth Table. When one or both enable inputs, (G1, G2) are high, the eight input/output terminals are in the high-impedance state; however sequential operation or clearing of the register is not affected. Clear function is asynchronous to clock. All inputs and outputs are equipped with protection circuits against static discharge, giving them 2KV ESD immunity and transient excess voltage.