COMPUTER-AIDED DESIGNING METHOD OF CARRY LOOK-AHEAD ADDER

摘要

PURPOSE: To reduce the complication of the design of a carry look ahead adder. CONSTITUTION: A carry look-ahead adder for adding two binary numbers 40 and 42 and an input carry bit is designed by using a computer support design method. A user inputs the number of lengths and the number of blocks in a group to a computer. The computer designs a first structure 50 having plural logic blocks 10-24 in accordance with the number of the lengths and designs a second structure 51 for designating the number of preceding level logic blocks which are made into groups into next level logic blocks 29-31 by using the number of blocks in the group. The computer designs more than one next level logic blocks. The first structure 50 receives the respective binary numbers 40 and 42 and generates transmission and generation bits. The respective logic blocks 29-31 in the second structure receive the transmission and generation bits from the preceding level logic blocks 10-24, operate the respective bits in parallel and generate the output carry bits of an adder. The computer constitutes the logic circuit based on the number of inputs and generates the output carry and total bits of the adder.