EE101Lecture20

# EE101Lecture20 - Introduction to Digital Logic Lecture 20...

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© Mark Redekopp, All rights reserved Introduction to Digital Logic Lecture 20: State Machines State Machine Analysis

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© Mark Redekopp, All rights reserved State Machines Provide the “brains” or control for electronic and electro - mechanical systems Implement a set of steps (or algorithm) to control or solve a problem Goal is to generate output values at specific times Combine Sequential and Combinational logic elements Sequential Logic to remember what step (state) we’re in Combinational Logic to find what step (state) to go to next Use state diagrams (a.k.a. flowcharts) to specify the operation of the corresponding state machine
© Mark Redekopp, All rights reserved Washing Machine State Diagram Boxes represent states or steps in the algorithm Arrows = transitions w/ conditions telling us when to take that transition Output values can be associated with a state and transition or only with a state Idle N=2 Fill WV = 1 Agitate Motor = 1 Drain DV = 1 N = N - 1 N > 0 N = 0 COINS + DOOR COINS • DOOR FULL FULL 5 MIN 5 MIN / Reset_Timer=1 EMPTY EMPTY Outputs Generated Transition Conditions /RESET

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© Mark Redekopp, All rights reserved Washing Machine State Diagram We move through the states based on the conditions. Outputs get asserted when the machine is in that state and the transition is true. Idle N=2 Fill WV = 1 Agitate Motor = 1 Drain DV = 1 N = N - 1 N > 0 N = 0 COINS + DOOR COINS • DOOR FULL FULL 5 MIN 5 MIN / Reset_Timer=1 EMPTY EMPTY /RESET Stay in the initial state until there is enough money (coins) and the door is closed
© Mark Redekopp, All rights reserved Washing Machine State Diagram Idle N=2 Fill WV = 1 Agitate Motor = 1 Drain DV = 1 N = N - 1 N > 0 N = 0 COINS + DOOR COINS • DOOR FULL FULL 5 MIN 5 MIN / Reset_Timer=1 EMPTY EMPTY /RESET Move to the Fill state when there is enough money (coins) and the door is closed

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© Mark Redekopp, All rights reserved Washing Machine State Diagram Stay in the Fill state until it is full…also set the Water Valve Open output to be true Idle N=2 Fill WV = 1 Agitate Motor = 1 Drain DV = 1 N = N - 1 N > 0 N = 0 COINS + DOOR COINS • DOOR FULL FULL 5 MIN 5 MIN / Reset_Timer=1 EMPTY EMPTY /RESET
© Mark Redekopp, All rights reserved Washing Machine State Diagram Move to the Agitate state after it is full Idle N=2 Fill WV = 1 Agitate Motor = 1 Drain DV = 1 N = N - 1 N > 0 N = 0 COINS + DOOR COINS • DOOR FULL FULL 5 MIN 5 MIN / Reset_Timer=1 EMPTY EMPTY /RESET

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© Mark Redekopp, All rights reserved State Machines Use sequential and combinational logic to implement a set of steps (i.e. an algorithm) Goal is to produce outputs at specific points of time Combinational logic alone cannot do that because the outputs will change as soon as the inputs change (no notion of time)
© Mark Redekopp, All rights reserved State Diagrams Used to show operation or function of a state machine Like a flowchart but called a state diagram 3 parts States Transitions Outputs State Diagram for a Washing Machine Idle N=2 Fill WV = 1 Agitate Motor = 1 Drain DV = 1 N = N - 1 N > 0 N = 0 COINS + DOOR COINS • DOOR FULL FULL 5 MIN 5 MIN / Reset_Timer=1 EMPTY EMPTY /RESET

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