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Historically, two types of state diagrams have evolved, one for the design of the Mealy FSM the other for the design of the Moore FSM. The two are known as ‘Mealy state diagrams’ and ‘Moore state diagrams’.

These days we use a more general type of state diagram, which can be used to design both the Mealy and Moore type of FSM. This is the type of state diagram we use throughout this book. As you will learn, it allows you to build a lot of ideas into the FSM diagram.

Figure 1.6 shows each state of the FSM and the transitions to and from that state to other states.

The states are usually drawn as circles (but some people like to use a square box).

The transitions between states are shown as an arrowed line connected between the states.

Figure 1.6 Transition between states.

In addition to the transitional line between states, there is an input signal name.

The right‐angled lines _| represent the clock input (in this case a rising edge 0 to 1) (Figure 1.7).

Figure 1.7 Transition with and without outside world inputs.

In Figure 1.7, the transition between states s0 and s1 will occur at the clock pulse in the upper state diagram, while in the lower state diagram it will only occur if the outside world input set to 1 ‘st = 1’ and a ‘0 to 1’ transition occurs on the clock input.

What changes would be needed to Figure 1.7 to make the transition between s0 and s1 occur when input st = 0?

Turn to Frame 1.9 after you have attempted this question.