Editing Digital electronics (section)

===Synchronous systems===
[[File:JohnsonCounter2.png|thumb|A 4-bit ring counter using D-type flip flops is an example of synchronous logic. Each device is connected to the clock signal, and update together.]]
{{main|synchronous logic}}
The usual way to implement a synchronous sequential state machine is to divide it into a piece of combinational logic and a set of flip flops called a ''state register''. The state register represents the state as a binary number. The combinational logic produces the binary representation for the next state. On each clock cycle, the state register captures the feedback generated from the previous state of the combinational logic and feeds it back as an unchanging input to the combinational part of the state machine. The clock rate is limited by the most time-consuming logic calculation in the combinational logic.