Results in a different product term covering the two minterm. The hazard exists because the change in input The change in x2 from 1 to 0 moves the circuitįrom minterm 111 to minterm 101. The first case is referred to as static 1-hazard and the second case as static 0-hazard.Ī third type of hazard, known as dynamic hazard,Ĭauses the output to change three or more times when it should change from 1 to If however, the circuit is implemented instead in product-of-sums form namely, This type of implementation may cause the output to go to 0 when it should remain a 1.
The two circuits shown in Fig implement the Boolean function in sum-of-products form: In the inverter may cause the output of gate 1 to change to 0 before the output Propagation delay through the inverter is taken into consideration. However, the output may momentarily go to 0 if the Then the output of gate 1 changes to 0 and that of gate 2 changes to 1,
This causes the output of gate 1 10 be 1, that of gate 2 Single variable produces a momentary change in output when no change in output When they occur inĪsynchronous sequential circuits hazards may result in a transition to a wrongĪ hazard is a condition in which a change in a Where they may cause a temporary false output value. That may appear at the output of a circuit because different pathsĮxhibit different propagation delays. Hazards are unwanted switching transients InĪddition, there is one more phenomenon called a hazard that may cause the
#Examples of combinational and sequential circuits free
With only one input changing at any time and must be free of critical races. The circuit must be operated in fundamental mode Taken to conform to certain restrictions and precautions to ensure that theĬircuits operate properly. In designing asynchronous sequential circuits, care must be
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