+---+--+---+ +---+---+---+---*---+ ____ /1Y |1 +--+ 14| VCC | A | B | C | D |/Y | /Y = ABCD 1A |2 13| /2Y +===+===+===+===*===+ 1B |3 12| 2D | 0 | X | X | X | 1 | 1C |4 4012 11| 2C | 1 | 0 | X | X | 1 | 1D |5 10| 2B | 1 | 1 | 0 | X | 1 | |6 9| 2A | 1 | 1 | 1 | 0 | 1 | GND |7 8| | 1 | 1 | 1 | 1 | 0 | +----------+ +---+---+---+---*---+