Glitch-free clock multiplexer that provides an output clock signal based on edge detection

Abstract

Clock multiplexing techniques generate an output clock signal by detecting edges of a selected input clock signal and toggling the output clock signal based on detected edges of the selected input clock signal. Toggle signals are generated based on detected edges of the selected input clock signal. Toggle signals are used to control when the output clock signal is to toggle high or low. A latch holds the state of the output clock signal in its current state until changed by receipt of a toggle signal. Switching from use of a first clock signal to use of a second clock signal occurs regardless of whether the first input clock is operating. A delay is introduced that prevents glitches in the output clock signal that are less than one half clock period of the next selected input clock signal in duration.