1. Viterbi Decoder: Presentation #4 Omar Ahmad Prateek Goenka Saim Qidwai Lingyan Sun M1 Overall Project Objective: Design of a high speed Viterbi Decoder Stage 4: 9 th Feb. 2004 Gate Level Design Design Manager: Yaping Zhan

2. Status Design Proposal (finalized) Architecture Proposal (done) Final Algorithm Description Mapping of Algorithm into hardware High level simulation/emulation in Matlab Behavioral Verilog simulation and test bench Gate level Design Floor Plan To be done: Component Layout (10% done) Chip Layout Spice Simulation of Entire Chip 18-525, Integrated Circuits Design Project

3. Architecture/Floor Plan Revisions Small change in our architecture. Instead of using subtractors, comparators are being used. Floor Plan also to remain unchanged (until we have a better estimate using our component layouts) 18-525, Integrated Circuits Design Project

4. Is an 8 bit ripple carry adder really a better choice than an 8 bit carry look ahead adder ? Concerns from last week… 18-525, Integrated Circuits Design Project

5. 216 transistors 18-525, Integrated Circuits Design Project Eight bit ripple carry adder

6. Critical Time Analysis of Ripple Carry propagation for 8-bit ripple carry = 1.15 ns 18-525, Integrated Circuits Design Project

7. 4 bit schematic of carry look ahead (8-bit has 480 transistors) 18-525, Integrated Circuits Design Project 4 bit ripple carry look ahead

8. propagation 8-bit carry look ahead = 1.12 ns 18-525, Integrated Circuits Design Project Critical Time Analysis of Carry Look ahead

9. The choice is obvious… 8 bit Ripple Carry Adder 8 bit Carry Look Ahead Adder Speed (ns.)1.151.12 Transistors216480 18-525, Integrated Circuits Design Project

10. Original Floorplan ML Search ACS Unit BCU Unit TB Unit 650 350 All units in microns Buffering/Routing We thought about alternatives to improve ratio

11. Floor Plan (alternative ideas) L shaped ML Search ACS Unit BCU Unit TB Unit Buffering/Routing BCU Unit ACS Unit 425 310 18-525, Integrated Circuits Design Project

12. Floor Plan (alternative ideas) Break up 450 ML Search ACS Unit BCU Unit TB Unit Buffering/Routing BCU Unit ACS Unit 325 18-525, Integrated Circuits Design Project

13. Schematic: top level 18-525, Integrated Circuits Design Project

14. Yes, but we need to go under the hood!!

15. 18-525, Integrated Circuits Design Project Schematic: Top level BCU

16. Schematic: BCU cell 18-525, Integrated Circuits Design Project

17. Schematic: ACS unit

18. 18-525, Integrated Circuits Design Project Schematic: ML search

19. 18-525, Integrated Circuits Design Project Schematic: Trace Back Unit

20. 18-525, Integrated Circuits Design Project Verilog Simulation: Top Level

21. 18-525, Integrated Circuits Design Project Critical Path The critical path lies within the ACS_unit. Adder Comparator Mux The delay would be dominated by the adder and the comparator, therefore in worst case the critical path would be the delay of 2 8- bit adders Approx clock speed = ½*delay = (1/1.15*2) = approx 400 Mhz

22. 1-bit adder Layout 18-525, Integrated Circuits Design Project

23. Questions?