The SN74HCS165 is a parallel-input shift register, which can be used to reduce the number of required inputs on a system controller very significantly in some applications. Parallel data is loaded into the shift register, then the stored data can be loaded into a serial input of the system controller by clocking the shift register.

Multiple shift registers can be cascaded to provide more data inputs while still only using a single serial input to the system controller. This process is primarily limited by the required data input rate and timing characteristics of the selected shift register, as defined in the Timing Charactestics and Switching Charactestics tables.

An example block diagram is shown for using a single shift register in the Typical application block diagram below.