Biography
Enrollment Date: 2005
Graduation Date：2008
Degree：M.S.
Defense Date：2008.05.31
Advisors：Hongyi Chen Hong Chen
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Study on an Asynchronous ALU and its Implementation
Abstract:
The integrated circuit can be classified into two categories, one is synchronous circuit, and the other is asynchronous circuit. During the development of integrated circuit, because the synchronous circuit has mature theory, it takes up the mainstream station in the integrated circuit field. After the integrated circuit developed into the deep sub-micrometer era, with the scaling down of the feature dimension, synchronous circuit is confronted with many problems, such as power, clock skew, etc. Because in asynchronous circuit, handshake protocols instead of clock signal is adopted between function components to implement necessary synchronization and communication of operations. With this method, the problems caused by the clock signal are overcomed. The advantages of high performance, low power and no clock skew problem make asynchronous circuit attractive for an increasing number of researchers. This paper mainly studied the asynchronous circuit implementation of an Arithmetic-Logic Unit. In the paper, following tasks are accomplished. The design method of the asynchronous circuit is studied. The asynchronous controller’s design method and datapath’s design method are studied principally. The technology of development of the asynchronous standard cell library is studied in the paper. Asynchronous circuit has many advantages, but it is also confronted with many challenges. One of the challenges is the lack of the support of the commercial EDA tools, so the design method is very complex. In order to resolve this problem, the technology of the development of asynchronous standard cell library is studied, and after detailedly research into the development flow, the script suitable for automatic development of standard cell library is achieved. The aim of the work is to make the asynchronous circuit design be able to be carried out with the synchronous EDA tools. A 16-bit asynchronous ALU for the asynchronous microprocessor is studied and implemented. During the design course, firstly the ALU’s function is defined according to the 6502’s instruction set, and then the implementation style is chosen according to the characteristics of various implementation styles. Finally the architecture design, function simulation, layout design, and test method design are fulfilled. The ALU is compatible with the 6502’s instruction set, and the 4-phase bundled-data protocol is adopted in the design. The design of the ALU’s adder, subtracter, comparator, shifter, overflow detection circuit, delay elements and logic elements are studied in detail. In the design of the adder of the ALU, four design schemes are compared with each other. After comparison, two schemes are chosen to implement the ALU, and finally one of the two schemes is chosen to carry out the layout design. The simulation result shows that, the ALU we designed achieves a high performance compared with other synchronous and asynchronous designs. The average delay is 1.32ns, the power dissipation is 3.380mW, and the area of the core of the chip is 0.04 . The design is implemented with the UMC 0.18µm CMOS technology.