1.1.1.6 Summary of State Machine Classes

Table 1-1. Summary of State Machine Classes
Class	Name	Next-State	Output
Class 0	Combinatorial Logic	State does not exist $X \leftarrow 1$	Output depends upon the inputs with no delay (combinatorial) $I \leftarrow f [Q]$
Class 1	Delay	State depends upon the inputs alone to delay the output $X \leftarrow g [Q]$	Output is same as Class 0 but delayed by one state time $I \leftarrow f g [Q]$
Class 2	State output, direct state transition	Next-state depends upon the previous state, hence forming a sequence of states $X \leftarrow g [X]$	Output depends upon the current state. Each state can produce only one output. $I = f [X]$
Class 3	State output, conditional state transition (Moore)	Next-state depends upon both the previous state and the inputs, hence having the ability to have alternate state sequences $X \leftarrow g [X, Q]$	Output depends upon the current state. Each state can produce only one output. $I = f [X]$
Class 4	Conditional state output, conditional state transition (Mealy)	Next-state depends upon both the previous state and the inputs, hence having the ability to have alternate state sequences $X \leftarrow g [X, Q]$	Output depends upon the current state and inputs. Each state may produce multiple outputs. $I = f [X, Q]$
Legend: Q = Inputs/Qualifiers to the state machine I = Outputs/Instructions from the state machine X = State of the machine (Represents “next-state” if followed by $\leftarrow$ ) T = State time g = Next-state function f = Output function