Features
• Buffered Inputs
• Fanout (Over Temperature Range)
- Standard Outputs . . . . . . . . . . . . . . . 10 LSTTL Loads
- Bus Driver Outputs . . . . . . . . . . . . . 15 LSTTL Loads
• Wide Operating Temperature Range . . . -55oC to 125oC
• Balanced Propagation Delay and Transition Times
• Significant Power Reduction Compared to LSTTL
Logic ICs
• HC Types
- 2V to 6V Operation
- High Noise Immunity: NIL = 30%, NIH = 30% of VCC
at VCC = 5V
• HCT Types
- 4.5V to 5.5V Operation
- Direct LSTTL Input Logic Compatibility,
VIL= 0.8V (Max), VIH = 2V (Min)

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