1. ECEN 248 Lab 7: Carry Look Ahead and Carry Save Adders Dept. of Electrical and Computer Engineering

2. Lab 4 in Brief Design a 2 operand 16-bit Carry-Look-Ahead Adder Design a 2 operand 16-bit Carry-Look-Ahead Adder Design 3 operand 16-bit Carry-Save Adder Design 3 operand 16-bit Carry-Save Adder How do they Differ? How do they Differ? They differ in the way carry is computed. Carry takes the maximum time to be computed so if we can do it faster then we get faster adders.

3. Carry Look-Ahead Adder Design Carry-Look Ahead Adder Block Carry Save Adder Block

4. Carry Look-Ahead Adder Design 4-bit Carry-Look Ahead Adder C i+1 = G i + P i.C i G i = A i.B i P i = (A i  B i )

5. Carry Look-Ahead Adder Design 16-bit Carry-Look Ahead Adder using 4-bit Carry-Look-Ahead Adders P G = P 3.P 2.P 1.P 0 ; G G = G 3 + P 3 G 2 + P 3.P 2.G 1. + P 3.P 2.P 1.G 0

6. Carry Save Adder Design Example of Carry Save Addition

7. Carry Save Adder Design Single Bit Carry Save Adder Block The Full adder Block from Lab#5 can be reused as the carry-save adder unit

8. Carry Save Adder Design 3 Operand Carry-Save Addition Carry-Look Ahead Adder is used in final stage for the final addition

9. Specifics and Design Hints LCD Display for Design 1 LCD Display for Design 1 LCD Display for Design 2 LCD Display for Design 2

10. Today Today Work on Lab 7 Work on Lab 7 Next Week Next Week Lab 7 Post-Lab due Lab 7 Post-Lab due Lab 8 Pre-Lab due at the beginning of class Lab 8 Pre-Lab due at the beginning of class Deadlines