Description in VHDL is given by http://www.cs.sfu.ca/~ggbaker/reference/std_logic/src/std_logic_entities.vhd
Truth Table
| DataIn | Enable | DataOut |
| * | U | U |
| * | X | UW |
| * | 0 | Z |
| * | 1 | DataIn, Strength Reduced |
| * | Z | UW |
| * | W | UW |
| * | L | Z |
| * | H | DataIn, Strength Reduced |
| * | - | UW |
UW: if dataIn == U then U else W Strength Reduced: 0 -> L, 1 -> H, X -> W