Post-layout verification of the WE DSP32 digital signal processor

Abstract

The authors describe the successful post-layout verification of the WE DSP32 digital signal processor and the application of advanced CAD tools. The development work, which went on for 10 months, culminated in the smooth transfer of the DSP32 design into high-volume production. During this period, they were able to diagnose and repair hundreds of design errors. They also caught errors in the test-vector software and fixed them before first silicon. The authors estimate that their verification work saved the DSP32 project a year of silicon debugging. In addition, they were able to enhance the CAD tools themselves and better define their future application.'Now with Picturetel. 56o produce a marketable IC with high performance and advanced design features requires a full-custom circuit design. Unfortunately, this type of design, which can in-T volve complex features such as full-hardware floatingpoint arithmetic, is very difficult to verify because it greatly taxes the capabilities of existing CAD tools. The task is even more difficult if these tools have not been successfully demonstrated beyond a certain size and level of complexity. We faced exactly this challenge in verifylng the design of the WE DSP32 digital signal processor. Although the CAD tools we were to use had been applied successfully to other ICs, none approached the size or complexity of our circuit. The DSP32 is a programmable, general-purpose digital signal processor with 32-bit floating-point arithmetic and a 32-bit data path. The chip implements an extensive 32-bit instruction set, 1.2 contains 152,000 transistors and operates at a 16-MHz clock frequency. It has been fabricated in 1.5-1.1 Leff (effective channel length) NMOS technology and measures 12.70 mm x 6.35 mm. The device has been used effectively in complex applications of digital signal processing such a s speech recognition, high-speed modems, and speech CODECs (coder/decoders) with a very low bit rate, and multichannel signaling systems. We realized early on that the DSP32 would be a n acid test of how well the CAD tools would work. *