Editing Soft error (section)

== Soft errors in combinational logic ==
The three natural masking effects in [[combinational logic]] that determine whether
a [[single event upset]] (SEU) will propagate to become a soft error are [[electrical masking]], [[logical masking]], and [[temporal (or timing-window) masking]]. An SEU is ''logically masked'' if its
propagation is blocked from reaching an output latch because off-path gate
inputs prevent a logical transition of that gate's output. An SEU is 
''electrically masked'' if the signal is attenuated by the electrical properties of
gates on its propagation path such that the resulting pulse is of insufficient magnitude to be
reliably latched. An SEU is ''temporally masked'' if the erroneous pulse reaches
an output latch, but it does not occur close enough to when the latch is actually triggered to hold.

If all three masking effects fail to occur, the propagated pulse becomes latched and the output of the logic circuit will be an erroneous value. In the context of circuit operation, this erroneous output value may be considered a soft error event. However, from a microarchitectural-level standpoint, the affected result may not change the output of the currently-executing program. For instance, the erroneous data could be overwritten before use, masked in subsequent logic operations, or simply never be used.  If erroneous data does not affect the output of a program, it is considered to be an example of ''microarchitectural masking''.