Abstract: Apparatus for glitch-free switching between multiple asynchronous clock sources on an integrated circuit. Clock gaters provide a clock from a single source that can be turned on and off without causing partial pulses to be created. Control circuitry going to the individual clock gaters is synchronized to the destination clock domain and provides the ability to shut all clocks off for a period of time equal to the longest clock period. By combining the clocks with an OR gate and gating all clocks off before switching from one clock to another, a glitch-free train of clock pulses can be created from individual clock inputs. Since clock glitches can cause erratic behavior in integrated circuits, this invention allows one to switch between different, asynchronous clocks without causing erratic behavior.

Abstract: Apparatus for glitch-free switching between multiple asynchronous clock sources on an integrated circuit. Clock gaters provide a clock from a single source that can be turned on and off without causing partial pulses to be created. Control circuitry going to the individual clock gaters is synchronized to the destination clock domain and provides the ability to shut all clocks off for a period of time equal to the longest clock period. By combining the clocks with an OR gate and gating all clocks off before switching from one clock to another, a glitch-free train of clock pulses can be created from individual clock inputs. Since clock glitches can cause erratic behavior in integrated circuits, this invention allows one to switch —between different, asynchronous clocks without causing erratic behavior.