- When both inputs of a SR flip flop are 0, suppose one input goes high (i.e., 1) immediately. Then, the feedback loop in the flip flop is already busy propagating the previous 0 through both the gates until a stable state is reached.
- When the other input also goes to 1 immediately, this change also starts to propagate, before the effect of the first change has settled. The effects of the two changes are literally "racing" for priority and it is absolutely not worth guessing as to which one wins. This is called race condition. Thus a R=0,S=0 input is forbidden in a SR flip flop.
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