Not to be confused with can't happen.

Don't care or don't care condition is a digital signal state designation often represented by X that indicates the actual signal value or values have no impact on the output of a circuit. Unlike can't happen conditions, don't care terms are still valid inputs however they do not influence the output value.

See also

• incompletely specified function
• HIGH
• LOW
• high impedance
• weak unknown
• strong unknown

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