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Unformatted text preview: Clark Guest 2009 ECE 25 Logic and Computer Design Adder-Subtracter Full Adder B A S C Full Adder B 1 A 1 S 1 C 1 Full Adder B 2 A 2 S 2 C 2 Full Adder B N A N S N C N C 3 Overfow Sub Clark Guest 2009 ECE 25 Logic and Computer Design Overfow In a computer, a xed number o bits is used to represent numbers When you add numbers, the result may require more bits than what is available. That is overfow 10 Unsigned Signed Addition Subtraction C=1 V=1 C=0 V=1 n-bit adder C n C n+1 C V Overfow Detection Clark Guest 2009 ECE 25 Logic and Computer Design More Arithmetic Adding zeros to the right o a binary number multiplies by a power o two 5 10 = 101 2 20 10 = 10100 2 number o zeros = power o 2 Dropping digits o the right end o a binary number divides by a power o two, dropped digits are the remainder 23 10 = 10111 2 5 10 = 101 2 remainder 11 2 is the remainder For twos complement numbers, bits extended to the let should be the same as the let-most digit...
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- Fall '09
- bill lin