The 74HC164; 74HCT164 are high-speed Si-gate CMOS devices and are pin compatible with Low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A.The 74HC164; 74HCT164 are 8-bit edge-triggered shift registers with serial data entry and an output from each of the eight stages. Data is entered serially through one of two inputs (DSA or DSB); either input can be used as an active HIGH enable for data entry through the other input. Both inputs must be connected together or an unused input must be tied HIGH.Data shifts one place to the right on each LOW-to-HIGH transition of the clock (CP) input and enters into Q0, which is the logical AND of the two data inputs (DSA and DSB) that existed one set-up time prior to the rising clock edge.A LOW level on the master reset (MR) input overrides all other inputs and clears the register asynchronously, forcing all outputs LOW.