Static Hazard 1 and One Circuit Problems?

Question

I read about Static Hazard. We know Static 1-hazard is: Input change causes output to go from 1 to 0 to 1.

My note covers a Circuit as follows:

My notes says: When B=C=D=1, for any changes in A values, it's probable to have Static Hazard 1.

But I think:

for 1 to 0 transition of A static hazard 1 can be observed. for 0 to

1 transition of A no hazard can be observed.

anyone could describe my sentence is correct or my note say the correct sentence. which of them is correct ? why? Thanks.

Answer 1

If you reduce your circuit with the static values of B, C and D equal 1. You get a circuit that is symmetric for A and negated A.

F = not (A and not A)

So there is a probability of having a static 1 hazard for any change of A.

Edit: Answer to comment: If you write up your circuit as a function it will be:

F = not (not (A and B and D) and not (not A and not B) and not(not A and C))

If you insert you statically assigned values you get:

F = not (not (A and 1 and 1) and not (not A and not 1) and not(not A and 1))

Given that X and 1 = X and X and 0 = 0 we can reduce to:

F = not (not A and not (0) and not (not A))
F = not (not A and 1 and A)
F = not (not A and A)