There are three kinds of shift registers- serial in/ serial out or parallel in/parallel out, serial in/ parallel out and parallel in/ serial out. They are made up of a row of connected flip-flops that data can move down. Data is moved by the shift register clock that must be configured to shift data before data can move through the shift register. The amount of clock pulses depends on how many bits you put through. If you send a byte of data the clock pulses 8 times to move each bit to the right. Changes in the movement of data occur when there is a change in the clock pulse level from high to low or from low to high. When the clock pulse goes from low to high the shift register is initialized to move data, but it is not until the clock pulse goes from high to low that the shift register actually moves the data.
In serial in/serial out serial data enters a Serial Input pin. Each bit shifts one flip-flop to the right with one clock pulse. In parallel in/parallel out an entire binary number is passed in one clock pulse. In serial in/parallel out serial data is passed one bit per clock pulse and it moves out a Serial Out pin in the original binary number it was sent out in. For example if the bx sent out a 10101010 it would move through the shift register one clock pulse at a time, but be passed out the Serial Out pin in its original binary form.
On the shift registers I researched each flip-flop has its own store to which the current number is written by a latch. Each new number that moves through the shift register is written to its store.
I have researched the Fairchild 74F675A and the Allegro Micro UCN5818AF. Below is information specific to these shift registers.
Allegro Micro 5818 shift register
Connection Diagram
Logic Diagram
Truth Table
links
allegro micro 5818 32-bit shift register
allegro micro 5818 data sheet
allegro micro 5818 pdf
other datasheets about the 5818
Fairchild 74F675
Connection Diagram
Shift Register Operations Table
Storage Register Operations Table
Logic Diagram
links
Fairchild 74F675A
Fairchild 74F675A pdf documentation
Bibliography
Golomb, Solomon W., Shift Register Sequences, Holden Day (San Francisco:1967)
Martin, Robert L., Studies in Feedback-Shift-Register Synthesis of Sequential Machines, MIT (Cambridge:1969)