EE101Lecture21

EE101Lecture21 - Introduction to Digital Logic Lecture 21:...

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© Mark Redekopp, All rights reserved Introduction to Digital Logic Lecture 21: State Machine Design
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© Mark Redekopp, All rights reserved State Machine Design State machine design involves taking a problem description and coming up with a state diagram and then designing a circuit to implement that operation Problem Description State Diagram Circuit Implementation
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© Mark Redekopp, All rights reserved State Machine Design Coming up with a state diagram is non- trivial Requires creative solutions Designing the circuit from the state diagram is done according to a simple set of steps
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© Mark Redekopp, All rights reserved Solving Problems w/ State Diagrams To come up w/ a state diagram to solve a problem – Write out an algorithm or series of steps to solve the problem – Each step in your algorithm will usually be one state in your state diagram
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© Mark Redekopp, All rights reserved 6 Steps of State Machine Design 1. State Diagram 2. Transition/Output Table 3. State Assignment Determine the # of FF’s required Assign binary codes to replace symbolic names 4. Choose FF type / Excitation Table 5. K-Maps for NSL and OFL One K-Map for every FF input One K-Map for every output of OFL 6. Draw out the circuit
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© Mark Redekopp, All rights reserved Sensor Broken Tooth Clogged Tooth Tooth Space Fly Wheel Example Determine the functionality (or “health” of a fly wheel Healthy if teeth and spaces alternate Unhealthy if tooth breaks off (i.e. 2 consecutive spaces) or if a space gets clogged (i.e. 2 consecutive teeth) Sensor, S, outputs 1 when it sees a tooth, 0 when it sees a space Healthy Fly Wheel Unhealthy Fly Wheel
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© Mark Redekopp, All rights reserved Fly Wheel Example • Design a state machine to check if sensor produces two 0’s in a row (i.e. 2 consecutive spaces) or two 1’s in a row (i.e. 2 consecutive teeth) •G1 = Got 1 consecutive ‘1’ …healthy •G0 = Got 1 consecutive ‘0’…healthy •G11 = Got 2 “1’s” in a row…unhealthy •G00 = Got 2 “0’s” in a row…unhealthy G0 H=1 G1 H=1 G00 H=0 G11 H=0 S = 1 S = 0 S = 1 S = 0 S = 0 S = 1 S = 0 S = 1 On Reset (power on)
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© Mark Redekopp, All rights reserved Transition Output Table • Convert state diagram to transition/output table 0 G1 G00 G00 1 G11 G0 G1 0 G11 G0 G11 1 G1 G00 G0 H State State State S = 1 S = 0 Output Next State Current State
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© Mark Redekopp, All rights reserved State Assignment • 4 States => 2 Flip-Flops (Q 1 Q 0 ) • Make up binary codes for each state 0 1 1 G1 0 1 G00 0 1 G00 1 1 0 G11 0 0 G0 1 1 G1 0 1 0 G11 0 0 G0 1 0 G11 1 1 1 G1 0 1 G00 0 0 G0 H Q 0 * Q 1 * State Q 0 * Q 1 * State Q 0 Q 1 State S = 1 S = 0 Output Next State Current State
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© Mark Redekopp, All rights reserved Pick Flip-Flop Type • We know we need 2 FF’s • Pick D-, JK-, or SR-FF’s – D-FF’s are the easiest to do design with but can sometimes yield large NSL – JK-FF’s are good choices and usually yield small NSL but make finding the NSL more tedious
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© Mark Redekopp, All rights reserved Excitation Table
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EE101Lecture21 - Introduction to Digital Logic Lecture 21:...

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