The Design And Validation Of Instruction Decoding Controlling System On Microprocessor X

The microprocessor X adopts CISC instructions set,which has varied types and many very-long or length-changeable instructions whose execution needs multi-period. It has been designed and verified in the National University of Defense Technology,and we has own IP on the microprocessor X.How to control the decoding of all instructions with high-speed and high-effectiveness is a difficult problem involved in the design of microprocessor based on CISC.In this paper,a method to control the instructions decoding to detach simple instructions from complex instructions is presented based on the research of the system of microprocessor X' instructions and it' structure,and a decoding controlling system is designed and verified.The decoding of the simple instructions is realized directly in combinational circuits.The decoding of the complex instructions is realized by the microprogram.The decoding method presented in this paper has the advantages of high speed of the combinational circuits and simplicity of the microprogram structure,and can improve the capacity of microprocessor X effectively.The instruction decoding controlling system is consisted of two parts:the direct decoding controlling unit for simple instructions and the microprogram decoding controlling unit for complex instructions.The direct decoding controlling unit realizes instruction decoding classfiedly,detachment of direct data,instruction match and correlation check by means of modularized design.The microprogram decoding controlling unit realizes all functions related to decoding controlling of the complex instructions.This paper proposes a validation scheme,creates a platform as well as validates the decoding controlling system in different levels according to it's structural and functional features.The verification result indicates that the whole system in microprocessor is very efficative and works correctly.