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CS 3503 - Chapter 3 (3A and 10.2.2)

CS 3503 - Chapter 3 (3A and 10.2.2). Dr. Clincy Professor of CS. Finish Ch 3. Dr. Clincy. Lecture. Slide 1. Recall Previous Covered Flip Flops. SR Flip Flop D Flip Flop T Flip Flop JK Flip Flop. Dr. Clincy. Lecture. Slide 2.

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CS 3503 - Chapter 3 (3A and 10.2.2)

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  1. CS 3503 - Chapter 3 (3A and 10.2.2) Dr. Clincy Professor of CS • Finish Ch 3 Dr. Clincy Lecture Slide 1

  2. Recall Previous Covered Flip Flops SR Flip Flop D Flip Flop T Flip Flop JK Flip Flop Dr. Clincy Lecture Slide 2

  3. NOTEYour book doesn’t do a good job in showing you how to derive or design sequential circuits (using state and state assignment tables) – the lecture will do so – please pay close attention to the lecture in understanding how to derive sequential circuits. Dr. Clincy Lecture Slide 3

  4. Sequential Logic Current State or output of the device is affected by the previous states Previous State or Output Previous State or Output Circuit Flip Flops Current State or Output New Input Combinatorial or Combinational Logic Current State or output of the device is only affected by the current inputs Circuit New Input Current State or Output Recall Examples: Decoders Multiplexers Examples: Shift Registers Counters Lecture

  5. x = 0 ¤ z = 0 S0 S1 x = 1 ¤ z = 0 x = 1 ¤ z = 0 x = 0 ¤ z = 0 x = 0 ¤ z = 0 x = 1 ¤ z = 1 x = 1 ¤ z = 0 S3 S2 x = 0 ¤ z = 1 State diagram of a mod-4 up/down counter that detects the count of 2. Sequential Circuit – State Diagram If x=0, count up, If x=1, count down Interested when 2 is realized – z=1 when reach 2, else z=0 If at 0 and x=0, count up to 1 (and z=0) If at 0 and x=1, count down to 3 (and z=0) State diagram describes the functional behavior without any reference to implementation Lecture

  6. x = 0 ¤ z = 0 S0 S1 x = 1 ¤ z = 0 x = 1 ¤ z = 0 x = 0 ¤ z = 0 x = 0 ¤ z = 0 x = 1 ¤ z = 1 x = 1 ¤ z = 0 S3 S2 x = 0 ¤ z = 1 State diagram of a mod-4 up/down counter that detects the count of 2. Sequential Circuit – State Table Can represent the info in the state diagram in a state table Lecture

  7. Sequential Circuit – Equation Inputs – y2,y1,x Outputs –Y2, Y1 Lecture

  8. Sequential Circuit – Circuit Design D Flip Flops used to store values of the two state variables between clock pulses Output from Flip Flops is the present-state of the variables Input, D, of the Flip Flops is the next-state of the variables Lecture

  9. Finite State Machine Model The example we just implemented is an example of a “Finite State Machine” - is a model or abstraction of behavior composed of a finite number of states, transitions between those states, and actions Lecture

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