The ’HC165 devices are 8-bit parallel-load shift registers that, when clocked, shift the data toward a serial (QH) output. Parallel-in access to each stage is provided by eight individual direct data (A−H) inputs that are enabled by a low level at the shift/load (SH/LD\) input. The ’HC165 devices also feature a clock-inhibit (CLK INH) function and a complementary serial (Q\H) output.
Clocking is accomplished by a low-to-high transition of the clock (CLK) input while SH/LD is held high and CLK INH is held low. The functions of CLK and CLK INH are interchangeable. Since a low CLK and a low-to-high transition of CLK INH also accomplish clocking, CLK INH should be changed to the high level only while CLK is high. Parallel loading is inhibited when SH/LD\ is held high. While SH/LD\ is low, the parallel inputs to the register are enabled independently of the levels of the CLK, CLK INH, or serial (SER) inputs.