Difference between Static and Dynamic Hazard

Hazard: In digital circuits, specially in combinational circuits, they give rise to behavior's, glitches and/or wrong output signals. While designing electronics circuits, one must be in a position to distinguish between the static hazards and dynamic hazards. Interference or interruption occurs when due to race condition the signal passes through several paths this leads to a temporary and unwanted alteration of the output. Stating and analyzing the type of hazard and solving it at the conceptual design stage gives the circuit design a chance of escaping problems that may be encountered later on.

What is a Static Hazard?

Static hazards are caused when an output is supposed to be constant but momentarily changes because of variation in the time of initialization of an actual output and the possibility of an actual output in a different path within a circuit. There are two types of static hazards

Types of Static Hazard

• Static-0 Hazard: This occur when there is a sudden transition from 0 to 1 and then back to 0.
• Static-1 Hazard: This takes place wen the out put vasa switches momentarily from 1 to 0 and go back to 1.

What is a Dynamic Hazard?

When the output changes several times then it should change from 1 to 0 or 0 to 1 only once, it is called dynamic hazard. Dynamic hazard occur when the output changes for two adjacent input combinations while changing, the output should change only once. But it may change three or more times in short intervals because of different delays in several paths. Dynamic hazards occur only in multilevel circuit.

How Dynamic Hazards Occur

Static hazards are simpler than dynamic and most time they are produced in circuits with multiple transitions so it is difficult to avoid them. These hazards can only be avoided by proper circuit designing and layout adjustments where necessary.

Difference between Static and Dynamic Hazard

Conclusion

Therefore, there should be a distinction between a static hazard and a dynamic one in an effort to design the most efficient digital circuits. Static hazards include a situation where a part of the system does not switch properly while dynamic hazards occur where there are many oscillations during the transition. The correction of these problems involves getting the correct design and the use of the techniques of the use of redundant logic for static hazards and a timing analysis approach to dynamic hazards. By managing of these risks from the circuit designers, can be assured that the digital systems put in place will function as expected.