Description in VHDL is given by http://www.cs.sfu.ca/~ggbaker/reference/std_logic/src/std_logic_entities.vhd
Truth Table
| DataIn | Enable | Reset | DataOut |
| * | * | U | U |
| * | * | 0 | 0 |
| * | 0 | 1 | NC |
| * | 1 | 1 | DataIn |
| * | X | 1 | X or U or NC |
| * | U | ~0 | U |
| * | ~U | X | X or U or 0 or NC |
* = do not care ~ = not equal U = L.'U' 0 = L.'0' or L.'L' 1 = L.'1' or L.'H' X = L.'X' or L.'W' or L.'Z' or L.'-' NC = no change