- Joined Apr 15, 2011
A logical truth table shows the expected output value for each combination of input values.
https://en.wikipedia.org/wiki/Don't-care_term#X_value"Don't care" may also refer to an unknown value in a multi-valued logic system, in which case it may also be called an X value or don't know. In the Verilog hardware description language such values are denoted by the letter "X". In the VHDL hardware description language such values are denoted (in the standard logic package) by the letter "X" (forced unknown) or the letter "W" (weak unknown).
"x" as an input means that that value is "Don't Care". The output does not change whether that "x" is 0 or 1.
Unknown, usually called "Don't Care" and unconnected are ***not*** the same thing. All inputs to logic gates must be terminated to a high or low state. They just must. We can go through another 18 posts, but the answer will not change.But doesn't it also say that an 'x' value could be an unknown.
Yes. but it is traditionally interpreted as a "don't care" state when resolving the output state.I'm sorry but I don't follow you. I've always thought that an "x" means either 0 or 1. I'm sure I've read the same at many places.
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