The 74HC174 are hex positive edge -triggered D-type flip-flops with individual data inputs (Dn) and outputs (Qn). The common clock (CP) and master reset (MR ) inputs load and reset all flip-flops simultaneously.
The D-input that meets the set-up and hold time requirements on the LOW-to-HIGH clock transition is stored in the flip-flop and appears at the Q output.
A LOW on MR causes the flip-flops and outputs to be reset LOW. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.