User`s guide

Critical Hazard 16

-7

This output (0-R-0) should be interpreted as a possible single

pulse, no longer than the duration of the R level. The actual

device’s output may or may not change, depending on the

transition times of the inputs.

Note that other types of primitives, such as flip-flops, may

produce an X instead of an R-0 or F-1 in response to a

convergence hazard.

Critical Hazard

It is important to note that the glitch so predicted could

propagate through the circuit and may cause incorrect operation.

If the glitch from a timing hazard becomes latched-up in an

internal state (such as flip-flop or ram), or if it causes an

incorrect state to be latched-up, it is called a critical hazard since

it definitely causes incorrect operation.

Otherwise, the hazard may pose no problem. Figure 16-7 shows

the same case as above, driving the data input to a latch.

ure 16-7

Critical Hazard Example

As long as the glitch always occurs well before the leading edge

of the clock input, it will not cause a problem.