Static hazard occur in combinational circuits and can be eliminated by using redundant gates. Static hazard is classified as:
1. Static-1 hazard :
If the output is currently at logic state 1 and after the input changes its state, at the same moment the output changes to 0 before settling on 1, then it is a Static-1 hazard.
2. Static-0 hazard :
If the output is currently at logic state 0 and after the input changes its state, at the same moment the output changes to 1 before settling on 0, then it is a Static-0 hazard.
Difference between Static-1 and Static-0 hazard:
|STATIC-1 HAZARD||STATIC-0 HAZARD|
|Output changes from 1 to 0.||Output changes from 0 to 1.|
|It is false ‘0’ level for a short interval.||It is false ‘1’ level for a short interval.|
|AND-OR circuit produces static-1 hazard.||NAND-NOR circuit produces static-0 hazard.|
|The graph goes from high to low then again high.||The graph goes from low to high then again low.|
|Static-1 hazard with contact networks is a tie set hazard.||Static-0 hazard with contact networks is a cut set hazard.|
|SOP is used for removing static-1 hazard.||POS is used for removing static-0 hazard.|
|We deal with 1s in staic-1 hazard.||We deal with 0s in static-0 hazard.|
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