3504notes_p2 - initial and final values respectively. Check...

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Race: any instance where more than one bit of state changes as the result of some transition. Only one of the two races is a… Critical Race: a race in which at least one of the ways in which the race is resolved results in an erroneous (incorrect) state. Critical Transition: transition that goes to a state with more than one stable state These are the only transition prone to critical races We need to make sure that none of the critical transitions become races Critical Transition Diagram, non-directed graph (from page 110 in notes, first table): 1 2 4 3 1 = 00 2 = 11 3 = 01 4 = 10 Now create a new state assignment using these state codes Isomorphism Glitch: momentary output change when no output change is desirable If there is only one step between 2 different output values then the step can be a don’t care. However, if there are more than one, outputs to the left and right of the don’t care must match the
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Unformatted text preview: initial and final values respectively. Check table for all transitions and make sure no outputs will produce a glitch Hazard-proofing: redundant logic gates independent of a variable that will be changing during a transition. Make sure EVERY 2 adjacent 1’s are in the same group after minimizing table You don’t always have to chose EVERY prime implicant to ensure no static hazards Only required for every pair of adjacent 1s, not don’t care or 1s and don’t cares Y+=S+R’y Y1+=y1y2’+xy2’+x’y1 =xy2’+y1(y2’+x’) S1 R1’ Y2+=x’y1+xy2+y1y2 = x’y1+y2(x+y1) S2 R2’ S1 = xy2’ R1 = xy2 S2 = x’y1 R2 = x’y1’ Prone to essential hazards if for input x if 3 changes in x results in a different final state than 1 change in x...
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This note was uploaded on 05/23/2008 for the course ECE 3504 taught by Professor Jsthweatt during the Summer '06 term at Virginia Tech.

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