SME
Digital Logic Design
State machines
Use this for “Trace the 101 detector on the input 110101.”
Explore
The machine starts in S0, having seen nothing of 101 yet, so its output is 0.
Assumptions
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Each state remembers just enough of the input to decide what comes next.
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A Moore machine writes its output in the state: S3/1 means S3 outputs 1.
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The machine reads one bit at each clock edge and follows the arrow labelled with that bit.
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Overlapping: the last 1 of one 101 may start the next.
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More problem types
Flip-flops for a state machine
Use this for “A controller has 5 states. How many flip-flops does binary encoding need, and how many codes go unused?”
The steps of a state machine design
Use this for “Design a clocked circuit that outputs 1 each time it has read 101.”
Moore or Mealy?
Use this for “Is a machine whose output is written on its arrows a Moore or a Mealy machine?”