The effect of seriousness of hazards is dependent on the devices or systems which receive the momentary transient signals.
In case of asynchronous sequential networks, the presence of hazards can cause the network to malfunction.
Consider the network shown in Figure below. The Y output is connected as one of the inputs. So feedback is existing in this network.
The excitation table for this circuit has been shown in Figure. The stable states have been circled.
The excitation table indicates that the total input state (A, B, Y) = (11, 1) corresponds to a stable condition . If input B is changed from 1 to 0, then the operating point moves horizontally to another stable total input state (A B Y) = (10, 1) as shown by the arrow in Figure..
But the given circuit in Fig. 2.13.1(a) is same as the one used in Figure (illustration of static 1 hazard). So there is a possibility of static 1 hazard when input B changes.
Due to static 1 hazard, the output Y will go 0 momentarily, which is fed back to gate G2 in Figure.
(a) Given circuit (b) Excitation table
If the delay of NOT gate is appreciably long then, this momentary â€œ0â€ at Y will enter into gate G2 before the NOT gate making a transition from 0 to 1, then the net result is that the network becomes stable with the total input state (A, B, Y) = (10, 0).
Thus the network becomes stable, in an undesired state. So we conclude that the presence of static 1 hazard has made the network to malfunction.
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