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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,2015/1/12,#,Lesson,Microprocessor Instructions Decoding,6,What is clock cycle,2.What does the instruction decoder needs,Warm-up Exercises,decoder 解码器,opcode 操作码,instruction decoder 指令解码器,ADD 加法,ALU 算术逻辑单元,C register C 存放器,incremen t 递增,overlap 重叠,manipulate 操纵,clock cycle 时钟周期,Words Preparation,The instruction decoder needs to turn each of the opcodes into a set of signals that drive the different components inside the microprocessor.,Lets take the ADD instruction as an example and look at what it needs to do.,1.During the first clock cycle,we need to actually load the instruction.Therefore the instruction decoder needs to:,activate the tri-state buffer for the program counter,activate the RD line,activate the data-in tri-state buffer,latch the instruction into the instruction register,Text,指令解码器要将每个算子变成一组信号，驱动微处理器中的不同组件。,2.During the second clock cycle,the ADD instruction is decoded.It needs to do very little:,set the operation of the ALU to addition,latch the output of the ALU into the C register,3.During the third clock cycle,the program counter is incremented(in theory this could be overlapped into the second clock cycle).,Every instruction can be broken down as a set of sequenced operations like these that manipulate the components of the microprocessor in the proper order.,Some instructions,like this ADD instruction,might take two or three clock cycles.Others might take five or six clock cycles.,Text,每个指令可以分解为这样一组顺序操作，按正确顺序操纵微处理器的组件。,ADD,In computer science,the set of machine instructions that a microprocessor recognizes and can execute.An instruction set includes low-level,step-at-a-time instructions,such as add,subtract,multiply,and divide.Each microprocessor has its own instruction set.In some instances,an instruction set is defined more broadly to include instructions in programming languages as well.,Branch of mathematics that arises from counting,the most basic mathematical operation.,Key Terms,Instruction decoder,Special memory locations for storing temporary information much as a scratch pad does,C register,Clock cycle,The cell nucleus contains a collection of interacting proteins that control cell division.Sometimes called the cell cycle clock,Key Terms,ALU,Arithmetic and Logic Unit,，,the part of the central processing unit which performs operations such as addition,subtraction and multiplication of integers and bit-wise AND,OR,NOT,XOR and other Boolean operations.The CPUs instruction decode logic determines which particular operation the ALU should perform,the source of the operands and the destination of the result.,The width in bits of the words which the ALU handles is usually the same as that quoted for the processor as a whole whereas its external busses may be narrower.Floating-point operations are usually done by a separate floating-point unit.Some processors use the ALU for address calculations(e.g.incrementing the program counter),others have separate logic for this.,Questions,What does the instruction decoder needs,Please explain what does the ADD instruction need to do,In the first clock cycle,what does the instruction do,In the second clock cycle,what does the instruction do,Why do some instructions need to take five or six clock cycles,Exercise,Translate the text into Chinese,Exercise,Simple writing,Please describe the function of each clock cycle.,Exercise,THANK YOU,！,
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