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 | Set | DataOut |
* | * | * | U | U |
* | * | U | ~1 | U |
* | * | * | 1 | 1 |
* | * | 1 | 0 | 0 |
* | * | 1 | X | X |
* | U | ~1 | ~1 | U |
* | ~U | X | X | X or U |
* | ~U | 0 | X | X or U or 1 or NC |
* | ~U | X | 0 | X or U or 0 or NC |
* | X | 0 | 0 | X or U or NC |
* | 1 | 0 | 0 | DataIn |
* | 0 | 0 | 0 | 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