Method and apparatus for 3-stage 32-bit adder/subtractor

摘要

An apparatus that takes two N-nary operands and selectably performs either addition or subtraction on them to produce an arithmetic result and a carry indicator. Carry-lookahead logic is utilized to create HPG signals for each N-nary dit of the intermediate sum of the two operands and also to create "block" HPG indicators for blocks of dits. In the preferred 1-of-4 embodiment, subtraction may be implemented as four's complement addition. The value of each dit of the intermediate sum is incremented by one before final output if a carry has propagated into the dit.