Adder

摘要

An adder that can detect the generation of overflow at a high speed. Carry signal c 14 from the 15^th digit to the 16^th digit in the result of addition from the 1^st digit to the 16^th digit of the input data is generated on the basis of bit signals (a 0 -a 15 , b 0 -b 15 ) for the portion from the 1^st digit to the 15^th digit of the input data, and of carry signal CIN input to the 1^st digit, and it is output from CLA 204 . Then, carry signal c 15 from the 16^th digit to the 17^th digit is generated based on said generated carry signal c 14 and bit signals (a 15 , b 15 ) of the 16^th digit of the input data, and this is output from CIA 205 . Exclusive-NOR circuit 206 then operates on said carry signals c 14 and c 15 , and overflow detection signal OVF 16 is generated.