A state machine requires memory and the ability to make decisions. The actual hardware used to implement a state machine consists of state registers (flip-flops) and combinatorial logic (gates). State registers store the current state until the next state is calculated, and a logic network performs functions that calculate the next state on the basis of the present state and the state machine inputs. The following figure shows the logic transitioning through the state registers to the output decoder logic.
Figure 7.2 Parts of a State Machine |  |
The amount of logic used to calculate the next state varies according to the type of state machine you are implementing. You must choose the most efficient design approach, depending on the hardware in which the design will be implemented.
