The SN54 / 74LS165 is an 8-bit parallel load or serial-in register with complementary outputs available from the last stage. Parallel inputing occurs asynchronously when the Parallel Load (PL) input is LOW. With PL HIGH, serial shifting occurs on the rising edge of the clock; new data enters via the Serial Data (DS) input. The 2-input OR clock can be used to combine two independent clock sources, or one input can act as an active LOW clock enable.