2-function output - Decoder to NAND gate

Discussion in 'Homework Help' started by Jason Ramirez, Sep 29, 2014.

  1. Jason Ramirez

    Thread Starter New Member

    Sep 29, 2014
    Hello everyone, new to this forum and looking for some tips to put me in the right direction. Please don't give me a full solution as I like the problem solving aspect, but am a little stuck.

    We are given 2 functions:


    from that, I got:

    From here, I need to:
    "Show input connections necessary to realize the above Boolean expressions using exactly two 3-to-8 Decoders (2 of 74138 chips) and two 4-input NAND gates (7420 chip). No other gates allowed."

    I understand how to combine the 2 decoders to create a 4-to-16 decoder, using A as an input to G2A and/or G2B on one chip and to the G1 with G2A/G2B set to ground/low on the other. What I dodn't understand is the part of only having 2 4-input NAND gates to process the decoder outputs to create the X and Y functions.

    Even using DeMorgan, I get:
    for X, and y has 5 outputs.

    I assume there is a concept I should be applying that maybe I need to research (perhaps I missed it or will be learning it in next class, which I will be missing). So if that is the issue, a concept I need to used, please let me know that so I can look up info on that and learn it.

    Thank you again for all help anyone can provide.