CS355 Sylabus

Circuit Design Example: Add one to a 2 bit binary number

Problem description:
Construct a circuit that has 2 inputs and 3 outputs, the 2 inputs represents a 2-bit binary number and the 3 outputs represents the value that is equal to the input number plus 1.
First, we find the boolean function (in table form) from the description above:

a b z₂ z₁ z₀

- - + - - -

0 0 0 0 1

0 1 0 1 0

1 0 0 1 1

1 1 1 0 0
Now we can apply the circuit construction algorithm on each of the columns to obtain the circuit:
You can experiment the circuit with this demo file: click here
Notice that individually, the logic functions for each of the outputs z₂, z₁ and z₀, is not very meaningful. But joinly, they represent an outcome that is equal to the input + 1.