Introduction In this article we will discuss the design of the arithmetic adder and subtracter circuits. These circuits will take input bits and produce two outputs sum and carry or difference and borrow. Half adder A half adder is a logic circuit that adds two bits at a time. These two bits may be the bits of two binary numbers or a bit of one number and a carry from previous stage. This circuit take two inputs and produces two outputs a Sum and a Carry. Truth table of a half adder The Sum output has two minterms and the carry output has one minterm. So the output equation in SOP form is Boolean equation are: Sum = A’B + AB’ Carry = AB The above equations do

# Tag: half adder

# Arithmetic Micro-operations

Arithmetic Micro-operation RTL notation description Addition R3 <-- R1 + R2 Content of R1 and R2 added, result in R3 Subtraction R3 <-- R1 - R2 Content of R2 subtracted from content of R1 added, result in R3 1’s complement R2 <-- R2’ Content of R2 complemented 2’s complement R2 <-- R2’ +1 2’s complement on the Content of R2 Subtraction using 2’s complement R3 <-- R1 + R2’ + 1 Subtraction using 2’s complement Increment R1 <-- R1+1 An increment micro-operation Decrement R1 <-- R1 - 1 A decrement micro-operation We now describe the arithmetic circuits for performing the above arithmetic micro-operations. A Half adder and full adders are the basic building blocks used in above operation. Half Adder: A half adder is an arithmetic circuit used to add two binary bits. These bits are carry-in and a bit of the number. The symbolic notation