Combinational vs sequential digital circuits

• A simple digital-system model:

• Combinational means memoryless

  • The outputs depend only on the present inputs

• Sequential systems have memory

  • The outputs depend on the present inputs and on the previous inputs

• This distinction is another abstraction

  • All circuits are sequential? outputs do not change instantaneously
  • The abstraction: We restrict ourselves to steady-state behavior

Inputs

Outputs

System

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