The ’HC166 and ’HCT166 8-bit shift register is fabricated with silicon gate CMOS technology. It possesses the low power consumption of standard CMOS integrated circuits, and can operate at speeds comparable to the equivalent low power Schottky device.

The ’HCT166 is functionally and pin compatible with the standard ’LS166.

The 166 is an 8-bit shift register that has fully synchronous serial or parallel data entry selected by an active LOW Parallel Enable (PE) input. When the PE is LOW one setup time before the LOW-to-HIGH clock transition, parallel data is entered into the register. When PE is HIGH, data is entered into the internal bit position Q0 from Serial Data Input (DS), and the remaining bits are shifted one place to the right (Q0 → Q1 → Q2, etc.) with each positive-going clock transition. For expansion of the register in parallel to serial converters, the Q7 output is connected to the DS input of the succeeding stage.

The clock input is a gated OR structure which allows one input to be used as an active LOW Clock Enable (CE) input. The pin assignment for the CP and CE inputs is arbitrary and can be reversed for layout convenience. The LOW-to-HIGH transition of CE input should only take place while the CP is HIGH for predictable operation.

A LOW on the Controller Reset (MR) input overrides all other inputs and clears the register asynchronously, forcing all bit positions to a LOW state.