Practice question · Match the pairs
In a synchronous sequential circuit, sort each item by which part of the circuit supplies it.
- Combinational logic
- From the clock
- In the state register
- Which of the machine's states it is sitting in right now
- The exact instant at which the state is allowed to change
- Where the machine should go next, given where it is and what its inputs say
Hints
- Ask of each item whether it is stored, calculated, or a matter of timing.
- The next state is calculated long before it is stored, those are two different parts of the circuit.
Show the answer
- Combinational logic → Where the machine should go next, given where it is and what its inputs say
- From the clock → The exact instant at which the state is allowed to change
- In the state register → Which of the machine's states it is sitting in right now
Why
The register stores where the machine is and keeps it steady between edges; the combinational logic calculates the next state and the outputs; the clock decides when the calculated value replaces the stored one. Collapsing the next-state logic into the register is the usual muddle, the register does no computing at all, it only remembers.
Practise Sequential Logic and State
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