1. ENEE 408C Lab Capstone Project: Digital System Design Spring 2006 Class Web Site: http://www.ece.umd.edu/class/enee408c

2. TA’s Information Alessandro Geist ageist@umd.edu Office Hours: TBD

3. Carry-Save Multiplier Example Multiply the two 4-bit binary numbers: 1110B x0101A ?

4. 0 A 0 0101 0 A 0 0 A 0 0 A 0 1110 Carry Bits Sum Bits P B A Initialize Carry-Save Multiplier Choose B based on LSB of A

5. 0 A 0 0101 0 A 0 0 A 0 0 A 0 1110 P B A Step 1: Combinational Addition Outcome Carry Bits Sum Bits 10101000

6. 1 A 0 0010 1 A 0 1 A 0 0 A 0 0000 P B A Step 2: Sequential Shift Choose next B based on LSB of A Carry Bits Sum Bits

7. 1 A 0 0 1 A 0 1 A 0 0 A 0 0000 P B A Step 2: Combinational Addition 010 Carry Bits Sum Bits 00101010

8. 0 A 0 1001 1 A 0 1 A 0 1 A 0 1110 P B A Step 3: Sequential Shift Choose next B based on LSB of A Carry Bits Sum Bits

9. 0 A 0 1001 1 A 0 1 A 0 1 A 0 1110 P B A Step 3: Combinational Addition Carry Bits Sum Bits 10100110

10. 1 A 0 1100 1 A 0 0 A 1 1 A 0 0000 P B A Step 4: Sequential Shift Choose next B based on LSB of A Carry Bits Sum Bits

11. 1 A 0 1 A 0 0 A 1 1 A 0 0000 P B A Step 4: Combinational Addition 1100 Carry Bits Sum Bits 00100100

12. 0 A 0 0110 1 A 0 0 A 1 0 A 0 0000 P B A Step 5: Sequential Shift Carry Bits Sum Bits

13. 0 A 0 0110 1 A 0 0 A 1 0 A 0 0000 P B A Add these together Final Step Carry Bits Sum Bits

14. Final Step Add the Sum and Carry of P using a CPA- type Adder Sum: + 010 Carry: 0010 Carry: 0010 0100 Concatenate with A Product = 0100 0110