SN54LS165A

The ’165 and ’LS165A are 8-bit serial shift registers that shift the data in the direction of Q_A toward Q_H when clocked. Parallel-in access to each stage is made available by eight individual, direct data inputs that are enabled by a low level at the shift/load (SH/LD\) input. These registers also feature gated clock (CLK) inputs and complementary outputs from the eighth bit. All inputs are diode-clamped to minimize transmission-line effects, thereby simplifying system design.

Clocking is accomplished through a two-input positive-NOR gate, permitting one input to be used as a clock-inhibit function. Holding either of the clock inputs high inhibits clocking, and holding either clock input low with SH/LD\ high enables the other clock input. Clock inhibit (CLK INH) should be changed to the high level only while CLK is high. Parallel loading is inhibited as long as SH/LD\ is high. Data at the parallel inputs are loaded directly into the register while SH/LD\ is low, independently of the levels of CLK, CLK INH, or serial (SER) inputs.