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HW 3 Due on Tuesday September 10th before class starts.


This homework covers Logic_Gates A_Basic_Computer. Some of these web pages have solved problems in the Questions section that may help.

  • You may use http://logic.ly/demo/ to check your answers. Note that you may use the copy icon and CTRL+V (for some reason there is no paste icon for this program) to copy and paste the 1-bit adder circuit.
  • You may write your answers on a piece of notebook paper.


  1. Logic Gate Combinations I
  2. Logic Gate Combinations II
    1. Logic Circuits
  3. Basic Computer

1. Logic Gate Combinations I

In the image below, four logic gates are connected. What are the values of Z andOutput if B = 1 and A = 0? For reference, the logic table associated with a NAND gate is shown.

  1. Z = 1, Output = 0
  2. Z = 0, Output = 0
  3. Z = 1, Output = 1
  4. Z = 0, Output = 1

Input A Input B Output
0 0 1
0 1 1
1 0 1
1 1 0

2. Logic Gate Combinations II

In the image below, a NAND and an AND gate are connected, with three inputs, A, B, and C. What are the values A, B, and C so that the light goes out?

2.1. Logic Circuits

What are A & B?


3. Basic Computer

In the image below, two bit adders are combined forming a 2-bit adder which is combined with a switch to an LED. Determine the switch combinations of A, B, C, D, E, F, so that the following LED Outputs are obtained. Note the LED reads a 4 bit pattern (4 inputs), so there are 16 combinations ranging from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F that can be displayed by the LED. Note that the letter A in the LED mean the decimal number 10, and the letter E means 14.

  1. What are A, B, C, D, E, and F to give LED = C?
  2. What are A, B, C, D, E, and F to give LED = A?
  3. What are A, B, C, D, E, and F to give LED = 4?

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