Clocked sequential system
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In digital electronics, a clocked sequential system is a system whose output depends only on the current state, whose state changes only when a global clock signal changes, and whose next-state depends only on the current state and the inputs.
Nearly all digital electronic devices (microprocessors, digital clocks, mobile phones, cordless telephones, electronic calculators, etc.) are designed as clocked sequential systems. Notable exceptions include digital asynchronous logic systems.
In particular, nearly all computers are designed as clocked sequential systems. Notable exceptions include analog computers and clockless CPUs.
Typically each bit of the "state" is contained in its own flip-flop. Combinational logic decodes the state into the output signals. More combinational logic encodes the current state and the inputs into the next-state signals. The next-state signals are latched into the flipflops under the control of the global clock signal (a wire connected to every flip-flop).
A clocked sequential system is a kind of Moore machine.
