Transcript Phase1
EE 5323 Project 16 Bit Sklansky Adder Phase 1 Report Yuan Xu 4139225 [email protected] Contents • • • • • • Literature review Schematic Netlist Design Optimization Waveforms of test cases Power consumption at the maximum operating frequency Literature Review • Sklansky adder belongs to tree adder family. • The difference between Sklansky adder and other tree adders is prefix network. • Compare to other tree adders, Sklansky adder has minimum logic levels, wiring tracks, but maxinum fanout. Also, it has largest delay at the same condition. Literature review Structure of 16 bit Sklansky Adder (Black square is dot operator Grey square is empty dot operator White triangle is buffer) 15 14 13 12 11 10 15:14 13:12 11:10 15:12 14:12 15:8 14:8 11:8 10:8 13:8 9 9:8 8 7 6 7:6 7:4 5 5:4 6:4 4 3 2 3:2 3:0 1 0 1:0 2:0 12:8 15:0 14:0 13:0 12:0 11:0 10:0 9:0 8:0 7:0 6:0 5:0 4:0 3:0 2:0 1:0 0:0 Reference List • D.Harris, “ A Taxonomy of Parallel Prefix Networks, Signals ”, Systems and Computers, 2003. Conference Record of the Thirty-Seventh Asilomar Conference on, 2, 2213-2217 Vol.2,2003 • J. Sklansky, “Conditional-sum addition logic,” IRE Trans. Electronic Computers, vol. EC-9, pp. 226231, June 1960. • J M. Rabaey, A. Chandrakasan, B. Nikolic, “ Digital Integrated Circuits-A Design Perspective (Second Edition)”, Prentice Hall, 2003 Schematic of adder • Precomputation (Generating Propagate value P and Generate value G). • Gi:i=Ai·Bi • Pi:i=Ai⊕Bi Schematic of adder • Bubble shifted Dot operator Schematic of adder • Empty empty dot operator Schematic of adder • Bubble shifted empty dot operator Schematic of adder • Overall view of adder HSPICE netlist see attached file • • • • Sizing: NMOS: L=50nm, W=90nm PMOS: L=50nm, W=135nm Temperature: 25°C Design Optimization • Sizing the gate to minimum size (90nm) can reduce area and power • By using bubble shifting, we save totally 28 inverters, and 4 inverters on the critical path • Adding the buffer can effectively reduce delay. Setting stage=1, fanout=4 Waveforms of test cases • Worst case: For Sklansky adder, the worst case happens when inputs are 7FFF+0001. Since G will propagate from A_0 to S_15 which is the critical path. Waveforms of test cases • Worst case 7FFF+0001 • A_0-A_15 B_0-B_15 Cout,S_0-S_15, • • • Waveforms of test cases Other cases( FFFF+0001, 7FFF+0001, 3FFF+0001, 1FFF+0001, 0FFF+0001, 07FF+0001, 03FF+0001 A_0-A_15 B_0-B_15 Cout,S_0-S_15 Power consumption at the maxinum operating frequency, V=1.1V • Worst case Delay= 4.11E-10 S • Ptotal=4.50E-05W • Pmax=1.64E-03W