By synchronizing the clock frequency of a device with the laser pulse, the temporal dependence of single-event upset on clock cycle can be investigated using a pulsed laser. The upper traces in this figure show the laser pulse arriving just prior to the falling edge of the clock signal and no upset observed at the device output; however, whenever the laser pulse arrives slightly after the falling edge of the clock waveform, the next clock cycle is phase shifted, or delayed in time by one-half of the clock period.