1、OF,DF,IF,SF,ZF,AF,PF,CF (注: 详见P12-13,P15)4、微处理器如何获取指令?Where does the microprocessor get its instructions ? The simple answer is that a microprocessor executes(执行) instructions provided by a computer program . However,a microprocessor cant follow just any instructions . A program that contains an ins
2、truction to “self destruct(自毁)” wont have much effect because a microprocessor can perform only a limited list of instructions “self destruct”isnt one of them . The list of instructions that a microprocessor can perform is called its instruction set. These instructions are hard-wired(硬线连接) into the
3、processors circuitry(电路、电路系统) and include basic arithmetic(算法) and logic operations. Fetching data and clearing registers.A computer can perform very complex tasks,but it does so by performing a combination of simple tasks from its instruction set . How does a microprocessor work? Inside the chip/ca
4、rrier , a microprocessor is a very complex integrated circuit , containing as many as 300 million miniaturized electronic components . The miniaturized circuitry in a microprocessor is grouped into important functional areas ,such as the ALU and the control unit.The ALU(arithmetic logic unit) perfor
5、ms arithmetic operations , such as addition and subtraction . It also performs logic operations,such as comparing two numbers to see if they are the same . The ALU uses registers to hold data that is being processed , just as you use a mixing bowl to hold the ingredients for a batch of brownies . Th
6、e microprocessors control unit fetches each instruction , just as you get each ingredient out of a cupboard or the refrigerator . 偶地址开始存放数据(即:首地址一般为偶数)在计算机内一个字节给一个地址,高地址存放高字节数据,低地址存放低字节数据5、存储器地址的分段(必考题且有可能要求画存储图)实模式下允许的最大寻址空间为1MB.物理地址=段地址*16D+偏移地址(详见P16)6、计算机的性能指标评价计算机性能的几个指标:运算速度,机器字长,内存储器的容量,外存储器的
7、容量 (注:详见P24-25)第4章 指令系统和寻址方式一、共性:Mov AX,BX Mov AX BX (错误的,缺少“,”)Mov AH,ALMov BX(16位),AL(8位)(错误的,不满足数据的一致性)二、汇编语言的特点:1. 面向机器的低级语言,通常是为特定的计算机或计算机系列专门设计的2. 保持了机器语言的优点,具有直接和简捷的特点。3. 可有效地访问、控制计算机的各种硬件设备,如磁盘、存储器CPU等。4. 目标代码简短,占用内存少,执行速度快,是高效的程序设计语言5. 经常与高级语言配合使用,应用十分广泛(P100)三、指令格式及指令字长度1. 指令格式是指令用二进制的代码表示
8、的结构形式,通常由操作码和地址码两部分组成。操作码用来表征该指令的操作特性和功能,即指出进行什么操作;地址码指出参与操作的数据在存储器中的地址。2. 指令格式设计的一般准则:(1)指令字长要短,以得到时间和空间上的优势。(2)指令字长必须有足够的长度(3)指令字长一般应是字节的整数倍以便存储系统的管理。(4)指令格式的设计还与如何选定指令中操作数地址的位数有关。(详见P102) 3.操作码指令系统中指令的个数N与操作码的位数n必须满足关系式:N AX-BX - AXSBB: CX,DX = CX -DX -CXADC:CX+DX+DF -NEG(求补):D-X -XCMP: AX,BX 不送结果,只影响标志位 AX.BX AX-BX -BX 除DEC指令不影响标志位外,其余指令均对条件标志位有影响。(3)乘法指令(P134)(3-1)MUL(无符号数乘法指令)(3-2)IMU(有符号数乘法指令)(4)除法指令(P34-135)(4-1)DIV(无符号数除法指令)(4-2)IDIV(有符号数除法指令)5.逻辑运算指令(1)逻辑运算指令(详见P136-137) MOV AX,0102 AND AX,00FF 求AX=? AX=0002OR AX,00FF求 AX=? AX=01FF(2)移位指令(P137-138)(2-3)循环移位指令6.程序控制类指令(1)无条件转移指令(
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