1.1.1.2 Class 1 – Delay Machines

Class 1 delay machines build on Class 0 state machines by adding a state time delay through memory elements.. The portion of the general state machine relevant in Class 1 is shown with solid lines in Figure 1-3. It consists of one memory and two transform elements. Because the machine has no internal feedback, the output expression can be represented by the inputs and outputs alone as follows:

Equation 1-4. Class 1 Output Expression

X \leftarrow f g [Q]

As illustrated above, the equation does not involve the internal state, $X$ . Hence, the Class 1 machine can be thought of as a combinatorial function, $f g$ , which produces an output delayed by one state time $(k + 1) T$ , as compared to a Class 0 machine which produces an output in the present state time, $k T$ .

An example of Class 1 delay machines is the implementation of a simple register, where the output is the same as the input delayed by one state time.

Important: The delay and all higher-class state machines (Class 1 through Class 4) are characterized by the ability to hold the information for the entire state time duration.

Figure 1-3. General Class 1 State Machine – Delay Machine