1. A method for hardening circuits against single event upsets, comprising in combination: providing a decision block that includes a storage element that stores data as long as a first input and a second input to the decision block remain constant; providing an output from the decision block having a same logic level as the first input if the first input and the second input are at expected logic levels; and providing a previous output of the decision block if the first input and the second input are not at the expected logic levels.