MA 240 2bit ADDER TRUTH TABLE Name: ________________________
Fill out the truth table (meaning the columns for the three sum bits: s_{2}, s_{1}, and s_{0}, where s_{0} is the low order bit, and in general s_{i} is the column for 2^{i}).
(See below for example of 2bit binary addition, with carries.) Just the truth table! (No need to include boolean expressions or circuits.)
a 
b 
a+b = s 
a_{1}a_{0 } + b_{1}b_{0 }  s_{2}s_{1}s_{0 } 

a_{1}  a_{0}  b_{1}  b_{0}  s_{2}  s_{1}  s_{0}  
0  0  0  0  
0  0  0  1  
0  0  1  0  
0  0  1  1  
0  1  0  0  
0  1  0  1  
0  1  1  0  
0  1  1  1  
1  0  0  0  
1  0  0  1  
1  0  1  0  
1  0  1  1  
1  1  0  0  
1  1  0  1  
1  1  1  0  
1  1  1  1 
Example of twobit binary addition, with two carries:
0 1

0^{0} 1 0

^{ 1} 0 1 
0 1 
(superscripted numerals are carry bits from column to the left)