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ECE 301 – Digital Electronics Introduction to Sequential Logic Circuits (aka. Finite State Machines) and FSM Analysis (Lecture #17)

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ECE 301 - Digital Electronics2 Combinational vs. Sequential Combinational Logic Circuit Output is a function of the inputs. Does not have state information. Does not require memory. Sequential Logic Circuit Output is a function of the present state (and of the inputs). Has state information Requires memory. Uses Flip-Flops to implement memory.

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ECE 301 - Digital Electronics3 Synchronous vs. Asynchronous Synchronous Sequential Circuit Clocked All Flip-Flops use the same clock and change state on the same triggering edge. Asynchronous Sequential Circuit No clock Can change state at any instance in time. Faster but more complex than synchronous sequential circuits.

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ECE 301 - Digital Electronics4 Finite State Machine: Models Moore Machine Outputs are a function of the present state. Outputs are independent of the inputs. State diagram includes an output value for each state. Mealy Machine Outputs are a function of the present state and the input. State diagram includes an input and output value for each transition (between states). There is an equivalent Mealy machine for each Moore machine.

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ECE 301 - Digital Electronics5 Finite State Machine: Models

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ECE 301 - Digital Electronics6 FSM: State Diagram (Moore) State Output Input A B C

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ECE 301 - Digital Electronics7 FSM: State Diagram (Mealy) State Output Input

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ECE 301 - Digital Electronics8 Finite State Machine Analysis

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ECE 301 - Digital Electronics9 FSM Analysis: Procedure Determine the Flip-Flop input equations In terms of the present state and input variables Determine the FSM output equation(s) Determine the next state values in the state table Assume binary encoding Use Flip-Flop Characteristic Equation Construct the state table Assign a state to each binary state assignment Draw the corresponding state diagram Determine the behavior of the FSM

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ECE 301 - Digital Electronics10 Example: FSM using D Flip-Flops FSM Analysis

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ECE 301 - Digital Electronics11 FSM Analysis: Example (D FF) input state output What type of FSM is this?

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ECE 301 - Digital Electronics12 FSM Analysis: Example (D FF) Determine the FF input equations and the FSM output equation(s)

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ECE 301 - Digital Electronics13 FSM Analysis: Example (D FF)

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ECE 301 - Digital Electronics14 FSM Analysis: Example (D FF)

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ECE 301 - Digital Electronics15 FSM Analysis: Example (D FF)

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ECE 301 - Digital Electronics16 Example: FSM using JK Flip-Flops FSM Analysis

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ECE 301 - Digital Electronics17 FSM Analysis: Example (JK FF) input state What type of FSM is this?

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ECE 301 - Digital Electronics18 FSM Analysis: Example (JK FF) Determine the FF input equations and the FSM output equation(s)

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ECE 301 - Digital Electronics19 FSM Analysis: Example (JK FF)

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ECE 301 - Digital Electronics20 FSM Analysis: Example (JK FF)

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ECE 301 - Digital Electronics21 Example: FSM using T Flip-Flops FSM Analysis

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ECE 301 - Digital Electronics22 FSM Analysis: Example (T FF) input state output What type of FSM is this?

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ECE 301 - Digital Electronics23 FSM Analysis: Example (T FF) Determine the FF input equations and the FSM output equation(s)

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ECE 301 - Digital Electronics24 FSM Analysis: Example (T FF)

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ECE 301 - Digital Electronics25 FSM Analysis: Example (T FF)

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ECE 301 - Digital Electronics26 Acknowledgments The slides used in this lecture were taken, with permission, from those provided by Pearson Prentice Hall for Digital Design (4 th Edition). They are the property of and are copyrighted by Pearson Education.

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