Groups of FlipFlops

A number of FFs can be connected to make a new device. This is called a SHIFT register. If you follow a single bit of data entered at D, you will see why (see page 118 of Carr).

Data can be entered starting at the left D. Note that there are two inputs required - a clock is required to cause the FFs to take notice of the inputs, since it triggers on the positive edge.

Note that you can read the data out in parallel - all 4 FF outputs can be seen.

Shift registers only work if they are edge-triggered - can you see why?