电子信息工程-微处理器[外文翻译].doc

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1、如有侵权，请联系网站删除，仅供学习与交流电子信息工程-微处理器外文翻译【精品文档】第 8 页外文资料所译外文资料：1.作者 G.Bouwhuis, J.Braat, A.Huijser2.书名：Principles of Optical Disk Systems3.出版时间：1991年9月4.所译章节：Session 2/Chapter9, Session 2/Chapter 11原文：MicroprocessorOne of the key inventions in the history of electronics, and in fact one of the most import

2、ant inventions ever period, was the transistor. As time progressed after the invention of LSI integrated circuits, the technology improved and chips became smaller, faster and cheaper. The functions performed by a processor were implemented using several different logic chips. Intel was the first co

3、mpany to incorporate all of these logic components into a single chip, this was the first microprocessor. A microprocessor is a complete computation engine that is fabricated on a single chip. A microprocessor executes a collection of machine instructions that tell the processor what to do. Based on

4、 the instructions, a microprocessor does three basic things: 1.Using the ALU (Arithmetic/Logic Unit), a microprocessor can perform mathematical operations like addition, subtraction, multiplication and division; 2.A microprocessor can move data from one memory location to another; 3.A microprocessor

5、 can make decisions and jump to a new set of instructions based on those decisions.There may be very sophisticated things that a microprocessor does, but those are its three basic activities. Microprocessor has an address bus that sends an address to memory, a data bus that can send data to memory o

6、r receive data from memory, an RD(read) and WR(write) line that lets a clock pulse sequence the processor and a reset line that resets the program counter to zero(or whatever) and restarts execution. And lets assume that both the address and data buses are 8 bits wide here.Here are the components of

7、 this simple microprocessor:1. Registers A, B and C are simply latches made out of flip-flops.2. The address latch is just like registers A, B and C.3. The program counter is a latch with the extra ability to increment by 1 when told to do so, and also to reset to zero when told to do so.4. The ALU

8、could be as simple as an 8-bit adder, or it might be able to add, subtract, multiply and divide 8-bit values. Lets assume the latter here.5. The test register is a special latch that can hold values from comparisons performed in the ALU. An ALU can normally compare two numbers send determine if they

9、 are equal, if one is greater than the other, etc. The test register can also normally hold a carry bit from the last stage of the adder. It stores these values in flip-flops and then the instruction decoder can use the values to make decisions.6. There are six boxes marked “3-State”.These are tri-s

10、tate buffers. A tri-state buffer can pass a 1, a 0 or it can essentially disconnect its output. A tri-state buffer allows multiple outputs to connect to a wire, but only one of then to actually drive a 1or a 0 onto the line.7. The instruction register and instruction decoder are responsible for cont

11、rolling all of the other components.Although they are not shown in this diagram, there would be control lines from the instruction decoder that would:1. Tell the A register to latch the value currently on the data bus 2. Tell the B register to latch the value currently on the data bus 3. Tell the C

12、register to latch the value currently on the data bus4. Tell the program counter register to latch the value currently on the data bus5. Tell the address register to latch the value currently on the data bus6. Tell the instruction register to latch the value currently on the data bus 7. Tell the pro

13、gram counter to increment 8. Tell the program counter to reset to zero9. Activate any of the six tri-state buffers (six separate lines)10. Tell the ALU what operation to perform11. Tell the test register to latch the ALUs test bits12. Activate the RD line13. Activate the WR lineComing into the instr

14、uction decoder are the bits from the best register and clock line, as well as the bits from the instruction register.RAM and ROM The address and data buses, as well as the RD and WR lines connect either to RAM or ROMgenerally both. In our sample microprocessor, we have an address bus 8 bits wide and

15、 a data bus 8 bits wide. That means that the microprocessor an address (2n) 256 bytes of the memory and it can read or write 8 bits of the memory at a time. Lets assume that this simple microprocessor has 128 bytes of ROM starting at address 0 and 128 bytes of RAM starting at address 128.ROM stands

16、for read-only memory. A ROM chip is programmed with a permanent collection of pre-set bytes. The address bus tells the ROM chip which byte to get and place on the data bus. When the RD line changes state, the ROM chip presents the selected byte onto the data bus.RAM stands for random-access memory.

17、RAM contains bytes of information, and the microprocessor can read or write to those bytes depending on whether the RD or WR line is signaled. One problem with todays RAM chips is that they forget everything once the power goes off. That is why the computer needs ROM.By the way, nearly all computers

18、 contain some amount of ROM (it is possible to create a simple computer that contains no RAMmany microcontrollers do this by placing a handful of RAM bytes on the processor chip itselfbut generally impossible to create one that contains no ROM).On a PC, the ROM is called the BIOS (Basic Input/Output

19、 System). When the microprocessor starts, it begins executing instructions it finds in the BIOS. The BIOS instructions do things like test the hardware in the machine, and then it goes to the hard disk to fetch the boot sector. This boot sector is another small program, and the BIOS store it in RAM

20、after reading it off the disk. The microprocessor then begins executing the boot sectors instructions from RAM. The boot sector program will tell the microprocessor to fetch something else from the hard disk into RAM, which the microprocessor then executes, and so on. This is how the microprocessor

21、loads and executes entire operating system.Microprocessor Instructions Even the incredibly simple microprocessor shown here will have a fairly large set of instructions that it can perform. The collection of instructions is implemented as bit patterns, each one of which has a different meaning when

22、loaded into the instruction register. Humans are not particularly good at remembering bit patterns, so a set of short words are defined to represent the different bit patterns. This collection of words is called the assembly languages of the processor. An assembler can translate the words into their

23、 bit patterns very easily, and then the output of assembler is placed in memory for the microprocessor to execute. If you use C language programming, a C compiler will translate the C code into assembly language.So now the question is, “How do all of these instructions look in ROM?” Each of these as

24、sembly language instructions must be represented by a binary number. These numbers all know as recodes. The instruction decoder needs to turn each of recodes into a set of signals that drive the different components inside the microprocessor. Lets take the ADD instruction as an example and look at w

25、hat it needs to do.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 regist

26、er.During the second clock cycle, the ADD instruction is decoded. It needs to do very little: set the operation of ALU to addition; latch the output of the ALU into the C register.During the third clock cycle, the program counter is incremented (in theory this could be overlapped into the second clo

27、ck cycle).Every instruction can be broken down as a set of sequenced operations like these that manipulate the components of 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.Microprocess

28、or Performance The number of transistors available has a huge effect on the performance of a processor. As seen earlier, a typical instruction in a processor like an 8088 took 15 clock cycles to execute. Because of the design of the multiplier, it took approximately 80 cycles just to do one 16-bit m

29、ultiplication on the 8088. With more transistors, much more powerful multipliers capable of single-cycle speeds become possible.More transistors also allow for a technology called pipelining. In a pipelined architecture, instruction execution overlaps. So even though it might take five clock cycles

30、to execute each instruction, there can be five instructions in various stages of execution simultaneously. That way it looks like one instruction completes every clock cycle.Many modern processors have multiple instruction decoders, each with own pipeline. This allows for multiple instruction stream

31、s, which means that more than one instruction can complete during each clock cycle. This technique can be quite complex to implement, so it can be lots of transistors.The trend in processor design has been toward full 32-bit ALU with fast floating point processors built in and pipelined execution wi

32、th multiple instruction streams. There has also been a tendency toward special instructions that make certain operations particularly efficient. There has also been the addition of hardware virtual memory support and L1 caching on the processor chip. All of these trends push up the transistor count,

33、 leading to the multi-million transistor powerhouses available today. These processors can execute about one billion instructions per second!The Operational Amplifier will continue to be a vital component of analog design because it is a fundamental component. Each generation of electronic equipment

34、 integrates more functions on silicon and takes more of the analog circuitry inside the IC. As digital applications increase, analog applications also increase because the predominant supply of data and interface applications are in the real world, and the real world is an analog world.The LM386 is

35、a power amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.The inputs are ground referenced w

36、hile the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 mill watts when operating from a 6 volt supply, making the LM386 ideal for battery operation.A Crystal is a basic piezoelectric quartz crystal. On its own, it cannot generate electrical clocks.

37、It has to be connected to a clock oscillator to get a clock waveform. There are two kinds of crystals: Series Resonant, which can be modeled as a high Q series LC circuit, and Parallel Resonant, which can be modeled as a high Q parallel LC circuit. A Crystal Oscillator is an oscillator with the crys

38、tal as the feedback element. There are other kinds of oscillators with active or passive feedback components, but the crystal oscillator provides the most accurate and stable output frequency. Crystal oscillators are the preferred clock source in most high-speed digital systems requiring clocks. A c

39、hip is a small piece of conducting material on which an integrated circuit is embedded. A microprocessor is a silicon chip that contains a CPU. In operation, a computer is both hardware and software. One is useless without another. The hardware design specifies the commands it can follow, and the in

40、structions tell it what to do. With the infiltration in the social field of the computer in recent years, the application of the one-chip computer is moving towards deepening constantly, drive tradition is it measure crescent benefit to upgrade day to control at the same time. In measuring in real t

41、ime and automatically controlled one-chip computer application system, the one-chip computer often uses as a key part, only one-chip computer respect knowledge is not enough, should also follow the structure of the concrete hardware , and direct against and use the software of targets characteristic

42、 to combine concretely, in order to do perfectly.译文：微处理器晶体管是电子学发展史上的关键发明之一，它实际上也是人类历史上最重要的发明之一。集成技术随着时间的推移而提高，芯片也更小，更快，更便宜。处理器完成的功能最早是由几个不同的逻辑芯片实现的，英特尔公司率先将所有这些部件集成到单个芯片中，这就是最早的微处理器，它是在单芯片上制造的完整的运算引擎。微处理器执行一组机器指令，这些指令告诉微处理器去做什么，根据这些指令，微处理器能够完成如下三项基本任务。1.微处理器使用其ALU（算术/逻辑单元）可以完成加、减、乘、除等数学运算。2.微处理器可将数据

43、从存储器的一个位置搬移到另一个位置。3.微处理器可做出判断，并根据这些判断跳转到一组新的指令。一个微处理器可以做非常复杂的工作，但上述三项是最基本的。微处理器有一套地址总线（向存储器发送地址），一套数据总线（向存储器发送数据或者接收存储器数据），一条读信号线RD和一条写信号线WR（用于通知存储器是从寻址地址读取数据还是写入数据），一条时钟信号线（为处理器安排时序的时钟脉冲）和一条复位信号线（将程序计数器置零和重新开始执行）。这里假定数据总线和地址总线的宽度都是位。构成这个简易处理器的组件如下:寄存器A,寄存器B和寄存器C：它们是由触发器构成的简易锁存器。地址锁存器：和寄存器A，一样。程序计数器

44、：一种具备“加一”功能和“置零”功能的锁存器。算术逻辑单元：可以简单到只是一个位加法器，也可以是能够完成位加、减、乘、除的单元（此处我们假定为后者）。测试寄存器：一种保存ALU比较结果的专用锁存器。通常，ALU能够将两个数进行比较，并判断出二者是否相等或者一个比另一个更大。测试寄存器也可以保存加法运算最后一步的进位。这些数值保存在触发器当中，指令译码器利用这些数值做出判决。“State”是三态缓冲器。它可以传送逻辑，逻辑，或者和输出断开。三态缓冲器允许在一条信号线上连接多个输出信号，但只有一个信号输出。指令寄存器和指令译码器负责控制所有其他组件。从指令译码器引出完成如下功能的控制信号线：通知寄

45、存器锁定当下出现在数据总线上的数值通知寄存器锁定当下出现在数据总线上的数值。通知寄存器锁定当下出现在数据总线上的数值通知程序计数器锁定当下出现在数据总线上的数值通知地址寄存器锁定当下出现在数据总线上的数值通知指令寄存器锁定当下出现在数据总线上的数值通知程序计数器增加通知程序计数器复位置零激活任何一个三态缓冲器通知ALU需要完成的操作通知测试寄存器锁定ALU的测试位激活RD信号线激活WR信号线指令译码器的数据位不仅来自指令寄存器，而且来自测试寄存器和时钟信号线。只读存储器和随机存取存储器数据总线、地址总线、读写信号线都连接到ROM上或者连接到RAM上（通常两者都有）。在这个微处理器例子中，有一套

46、位地址总线和一套位数据总线。这意味着微处理器可寻址256字节的存储器，一次可以读写位数据。假定该微处理器有128字节（地址从开始）的RAM和128字节（地址从128开始）的RAM。ROM是只读存储器。ROM芯片是用一组永久的预设字节进行编程得到的。地址总线告知ROM芯片要将哪个字节取出并置于数据总线上。当RD信号线改变状态时，ROM芯片将选中的字节输出到数据总线上。ROM是随机存取存储器。ROM中包含着以字节为单位的信息，微处理器能够依据RD/WR信号哪个有效来决定字节的读写。当前RAM芯片的一个问题是：掉电后，所有保存在RAM上的内容全部丢失。这就是计算机需要ROM的原因。顺便提一下，几乎所

47、有计算机都有一定数量的ROM（可以建造一种简单的不含RAM的计算机许多微控制器在片内集成了一定数量的RAM但是一般不可能建造出一种不含ROM的计算机）。在PC机中，ROM被称作BIOS基本输入输出系统）。当计算机启动时，它就执行在BIOS中找到的指令。这些 BIOS指令完成对机内硬件的测试，然后从硬盘中读取引导扇区。引导扇区也是一个小程序，BIOS将其从硬盘中读出来之后，这个小程序就存储在RAM中。然后，微处理器开始从RAM执行引导扇区的指令。这个程序将告知微处理器从硬盘其他位置读取信息到RAM中，然后微处理器执行相应的指令等。这就是微处理器装载和执行整个操作系统的过程。微处理器指令 甚至这里

48、给出的简单得难以置信的微处理器也拥有一套相当大的指令集。指令的集合是以比特组合的方式实现的；每一条指令在装载到指令寄存器的时候，都有不同的涵义。人类不善于记忆比特组合，因此定义了一组短字来代表不同的比特组合。这些短字的集合就称为处理器汇编语言。汇编器可以很容易地将这些短字翻译成与其对应的比特组合，汇编器的输出被放置到存储器中以便微处理器执行。假如使用C语言进行编程，那么编译器会将C代码翻译为汇编语言。微处理器性能 可用晶体管数量对于微处理器性能有很大的影响。正如先前看到的那样，像8088这样的处理器执行一条典型指令需要个时钟周期。由于要设计乘法器，在8088上完成一次16位乘法需要约80个时钟

49、周期。晶体管越多，具备单周期乘法能力的乘法器就会越多。更多的晶体管允许使用流水线技术。在流水线结构中，指令的执行是重叠的。这样的话，尽管执行每条指令可能需要个周期，却可以在不同阶段同时执行条指令。这样看上去好像每个周期都能完成一条指令。许多现代处理器有多个指令译码器，而每个指令译码器都有各自的流水线。这样，就可以实现多指令流即在一个周期内可以完成多条指令。该技术实现起来相当复杂，所以使用大量的晶体管。处理器设计的趋势已经是全32位ALU、内置快速浮点处理器 和 多指令流水线。还有一个趋势是采用能使特定操作高效执行的特殊指令。此外，还有一种趋势是在处理器芯片附加上硬件虚拟存储器和L1高速缓存。所有这些趋势都需要增加晶体管，这导致了今天集