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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 two’s complement numbers, bits extended to the le¢t should be the same as the le¢t-most digit...
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This note was uploaded on 11/03/2009 for the course ECE ECE25 taught by Professor Bill lin during the Fall '09 term at UCSD.
- Fall '09
- bill lin