Choosing Flip-Flops
See Flip-Flops.
DFFs are the most intuitive choice for a flip-flop, since they follow their input as their state, meaning the input equations of the flip-flop are also the next state equations. However, other types of flip-flops can be les expensive.
Example
Consider the following state assigned table for a sequential circuit:
excitation table using DFFs:
Note that we can write
We can also write:
Excitation table using TFFs:
Note that we can write
We can also write
Excitation table using JKFF:
Recall that if
We can write our flip-flop inputs as
The JK flip-flop implementation has less cost than the T and D flip-flops.