Lab Report #3 - making decisions
             (logic gates / selectors / multiplexer / demultiplexer)

05 February 2002

Christopher Cheng
Michiko Halili
Jose Salita

  • What inputs did your 0110 black box detect?

    • The black box looked for a 0110 input combination. Whenever it detected a 0110 combination, it would send an output of 1 to the 7490 chip. To make sure that it would give an output of 1 only for that particular combination, the black box was constructed using a 7400 and a 7402 and then devised a circuit that would send out a 1 only when the input was 0110.

    1. What output did it give?

      2. Whenever a 0110 input combination was received, an output of 1 was sent. Otherwise, it would send out an output of 0.

    2. How did you connect your black box to the 7490?

      3. The output of the black box was connected to pins 2 and 3 of the 7490.

    3. What did it do to the 7490?

    The 7490 resets whenever pins 2 and 3 receive an input of 1. So, whenever the black box receives a 0110 input, it sends a 1 to the 7490, thereby resetting the chip. Now, only the first six LED’s connected to the 7442 light up because it gets reset by the 7490.