Design Of Embedded8-bit CPU Based On FPGA

With the advent of the Internet age, network communications, information security and information appliances becomes more and more popular, in which CPUs are the essential components in all of these information products. The CPUs with independent intellectual property rights are very important for the applications in military, economic and security. For this reason, after deeply understanding of the CPU structure, working principle and design method, a CPU design CPU based on FPGA, has been investigated,which is started from a basic logic circuit to an embedded CPU by using the QuartusⅡ software. The main contents of this thesis are listed as follow.(1) In order to design a high performance embedded CPU, a practical set of instructions is selected or developed on the basis of deeply understanding and analysis of the classic CPU basic structure and the classic CPU instruction set. By setting ARM, MIPS instruction sets, which belong to the RISC instruction set, as references, a RISC instruction set is developed. In constrast to the conventional CISC (complex instruction set), the RISC instruction set is the future developing direction of a high performance CPU because it has united format, relatively small variety, less addressing mode.(2) On the basis of drawning up a CPU instruction set, the method of logic diagram input of the Quartus(?)II software is used to design the logic circuits of the CPU, and the instructions. CPU is a complex digital circuit, which consisits of controller, operator, and various internal registers. Its design is completed from each functional part to the overall CPU structure based on the modular design ideas. When all under-controlled modules are designed, the timing of the CPU is arranged by the controller. The circuits need detailed designs including arithmetic logic unit (ALU), shift module, special register, instruction decoder, the program counter (pc), program status word RAM(PSW),10module, the clock signal generator module and so on.(3) In order to verify the correctness of the various logic circuits, the Quartus(?)II software is used in simulations, including the basic logic circuit simulation, small module simulation, large module simulation, and finally the entire CPU circuit simulation. Step simulation method is used to achieve the functional simulation of the design of the CPU to ensure the correctness of the CPU functions.(4) In order to demonstrate the functions of the CPU, an extra RAM and a debugger are builded in the FPGA, in which the extra RAM is used to replace the original external ROM storing instructions, and build a debugger. This debugger is designed for instruction code conveniently writing, and the results verification of each instruction implementation.(5) This article aims to give a the FPGA-based embedded CPU design, including software platform, the design process, each functional module, test waveform diagrams, the method of design CPU based on FPGA. Since the CPU is a complex digital circuit, in order to complete it in a short time and give the detailed design process, the design of an8-bit CPU with the hardware scheduling fuction is presented.