+---+--+---+ +---+---+---+---*---+ ____ 1A |1 +--+ 14| VCC | A | B | C | D |/Y | /Y = ABCD 1B |2 13| 2D +===+===+===+===*===+ |3 12| 2C | 0 | X | X | X | 1 | 1C |4 7440 11| | 1 | 0 | X | X | 1 | 1D |5 10| 2B | 1 | 1 | 0 | X | 1 | /1Y |6 9| 2A | 1 | 1 | 1 | 0 | 1 | GND |7 8| /2Y | 1 | 1 | 1 | 1 | 0 | +----------+