74HCT166 8-Bit Parallel-inSerial-out Shift Register IC

The 74HC166 are Si-gate CMOS high-speed devices that are pin compatible with low-power Schottky TTL (LSTTL). They’re designed in accordance with JEDEC standard 7A. The 74HCT166 is an 8-bit shift register with an active LOW parallel enable (PE) input that selects between serial and parallel data entering. Parallel data is stored into the register when PE remains LOW for one set-up time before the LOW-to-HIGH clock transition. When PE is HIGH, data from serial data input is placed into the Q0 inner bit location (Ds). With each positive-going clock transition, the remaining bits shifted one place to the proper (Q0, Q1, Q2, etc.).

This feature allows parallel-to-serial converter expansion by tying the Q7 output to the Ds input of the succeeding stage. One input can be utilized as a lively LOW clock enable (CE) input if the clock input is a gated-OR structure. The CP and CE input pin assignments are random and reversed for layout convenience. For predictable operation, the input CE transitions from LOW to HIGH while CP is HIGH. All other inputs are overridden if the master reset (MR) input is low. And asynchronously clears the register, driving all bit locations to a coffee state. Clamp diodes are included in the inputs, allowing current limiting resistors to be used to link inputs to voltages other than VCC.

In Parallel In Serial Out (PISO) shift registers, the data loaded onto register in parallel format. Rather, it was obtained in a sequential manner. A control-line and a combinational circuit are included in the PISO register (AND and OR gates). In addition to the necessary register components (flip-flops), clock and clear pins are used.