ABSTRACT
Fixed-point subtraction is relatively simple. It also shares much of the same circuitry as addition. Subtraction can be performed in all three number representations: sign magnitude, diminished-radix complement, and radix complement; however, radix complement is the easiest and most widely used method for subtraction in any radix. Like fixed-point addition, subtraction in radix 2 is relatively easy compared to multiplication and division. The adder used in addition can be modified slightly to accommodate subtraction. It was stated previously that subtraction can be accomplished by adding the radix complement of the subtrahend to the minuend, where the radix complement is formed by adding 1 to the diminished-radix complement. The hardware required for fixed-point addition can be easily expanded to accommodate fixed-point subtraction. The chapter presents the structural design of an 8-bit carry lookahead adder/ subtractor comprised of two groups with four adder stages per group.
