ENEE 408C Lab Capstone Project: Digital System Design Spring 2006 Class Web Site:

TA’s Information Alessandro Geist Office Hours: TBD

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

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

0 A A 0 0 A 0 0 A P B A Step 1: Combinational Addition Outcome Carry Bits Sum Bits

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

1 A A 0 1 A 0 0 A P B A Step 2: Combinational Addition 010 Carry Bits Sum Bits

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

0 A A 0 1 A 0 1 A P B A Step 3: Combinational Addition Carry Bits Sum Bits

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

1 A 0 1 A 0 0 A 1 1 A P B A Step 4: Combinational Addition 1100 Carry Bits Sum Bits

0 A A 0 0 A 1 0 A P B A Step 5: Sequential Shift Carry Bits Sum Bits

0 A A 0 0 A 1 0 A P B A Add these together Final Step Carry Bits Sum Bits

Final Step Add the Sum and Carry of P using a CPA- type Adder Sum: Carry: 0010 Carry: Concatenate with A Product =