CSE 220 Lecture 14: ALUs
9 Mar 2017
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Document Summary
In this unit we will look at the design and implementation of a basic alu. The arithmetic part will do addition and subtraction of two n-bit numbers, but we"ll start with 1-bit operations. Logical part will calculate bitwise and and or of two values. When we add two bits (a+b) together to generate a sum (s), we have four possibilities: With 1+1 we will have a carry-out value (cout) These formulas will translate into a simple circuit called a half adder. When we have two more bits, there is a possibility that the carry-out of one column is the carry-in of another column (the column to the left) We need to add a third input bit, cin, to accept extra carry-in values from the previous column (half adder). A carry-out is generated when a+b+cin equals 2 or 3. (this is actual addition of the values like 0+1+1 and not just.
