《微机原理》习题参考答案.doc

微机原理习题参考答案第一章 绪论1.2 +6510=01000001B +65补=+65原=01000001B +11510=01110011B +115补=+115原=01110011B -6510=11000001B -65补=10111111B-11510=11110011B -115补=10001101B方法：正数的原码、反码、补码相同负数的补码在原码的基础上除过符号外，先取反，再加1。1.3+12010=0000000001111000B +120补=+120原=000000001111000B -12010=1000000001111000B -120补=1111111110001000B+23010=0000000011100110B +230补=+230原=0000000011100110B-23010=1000000011100110B -230补=1111111100011010B方法：与上题相同，只是扩展了位数，用16位表示1.455 （00110111） 89 （01011001） -115 （11110011） -7总结：知道补码，求原码(或数值)的方法：如果是正数，直接转换。如果是负数用以下三种方法： 根据X补补=X 求得例如10001101 各位取反 11110010 加一 11110011转换 -115 求补的逆运算例如：11111001 先减一 11111000 各位取反 10000111 转换 -7-(模+补码转换结果)例如：10001101转换 -13模+补码转换结果 128-13=115 加负号 1151.9本题问题不太明确例如：如果手边有手册或是知道产品的型号，就可从手册中查到微处理器的处理位数。也可以根据系统总线得知。因为系统总线是公共的数据通道，表现为数据传输位数和总线工作时钟频率。第二章 intel 8086 微处理器2.2 75422H 字节单元：9CH 字单元：249CH 75424H 字节单元：5DH 字单元：0E65Dh2.3根据物理地址=段地址*10H+偏移地址得到：段地址偏移地址物理地址1000H117AH1117AH1025H0F2AH1117AH1109H00EAH1117AH 我们可以看到不同段的段地址，在不同的偏移地址下，可以对应相同的物理地址,也就相同的存储空间。说明在分配段时是重叠的.2.4 每个段区最大可占用64KB的地址范围，因为寄存器都是16位的，216B=64KB。不允许重叠，则最多可分16个段区，因为8086CPU有20条地址线，寻址范围1MB，1MB/64KB=16个。2.6指令目的操作数寻址方式源操作数寻址方式 MOV ARRAY, BX直接寻址寄存器寻址ADC CX, ALPHABXSI寄存器寻址带位移的基址变址寻址AND GAMMADI,11011000B带位移的变址寻址立即数寻址INC BL寄存器寻址隐含寻址TEST ES:SI, DX寄存器间接寻址寄存器寻址SBB SI, BP寄存器寻址寄存器间接寻址2.7 源操作数是立即数寻址,AX=1200H 源操作数是寄存器寻址,AX=BX=0100H 源操作数是直接寻址,将2000H10H+1200H=21200H和21201H的内容取出,赋给AX=4C2AH 源操作数是寄存器间接寻址,将2000H10H+0100H=20100H和20101H的内容取出,赋给AX=3412H 源操作数是寄存器相对寻址,将2000H10H+0100H+1100H=21200H和21201H的内容取出,赋给AX=4C2AH 源操作数是基址变址寻址,将2000H10H+0100H+0002H=201002和201003H的内容取出,赋给AX=7856H 源操作数是基址变址相对寻址, 将2000H10H+0100H+0002H+1100H=21202H和21203H的的内容取出,赋给AX=65B7H2.8指令源操作数寻址方式物理地址MOV AX, 00ABH立即数寻址跟随在指令后,有cs:ip决定MOV AX,BX寄存器寻址在寄存器中MOV AX,100H直接寻址2000H10H+100H=20100HMOV AX,BX寄存器间接寻址2000H10H+0100H=20100HMOV AX,BP寄存器间接寻址1500H10H+0010H=15010HMOV AX,BX+10注意是十进制 带位移的基址寻址2000H10H+0100H+0AH=2010AHMOV AX,BXSI基址变址寻址2000H10H+0100H+00A0H=201A0HMOV AX,VAL直接寻址2000H10H+0050H=20050HMOV AX,ES:BX寄存器间接寻址2100H10H+0100H=21100HMOV AX,SI寄存器间接寻址2000H10H+00A0=200A0HMOV AX,VALBX带位移的基址寻址2000H10H+0100H+0050H=20150HMOV AX,VALBXSI带位移的基址变址寻址2000H10H+0100H+00A0H+0050H=201F0H2.9指令 Sp 值PUSH CX1FFAH66H1FFBH55HPUSH BX1FFCH44H1FFDH33HPUSH AX1FFEH22H1FFFH11H指令sp值 POP AX1FFCHAX=5566HBX=3344HPOP CX1FFEHCX=3344HSP=1FFEH2.10指令AX 的值MOV AX,0AX=0000HDEC AXAX=0FFFFHADD AX,7FFFHAX=7FFEHADD AX,2AX=8000HNOT AXAX=7FFFHSUB AX,0FFFFHAX=8000HADD AX,8000HAX=0000HOR AX,0BFDFHAX=0BFDFHAND AX,0EBEDHAX=0ABCDHXCHG AH,ALAX=0CDABHSAL AX,1AX=9B56H (CF=1)RCL AX,1AX=36ADH (AF=1)2.110110 0010 1010 0000B+ 1001 1101 0110 0000B1 0000 0000 0000 0000B (0000H) AF=0,SF=0,ZF=1,CF=1,OF=0,PF=1 0110 0010 1010 0000B+ 0100 0011 0010 0001B 1010 0101 1100 0001B (0A5C1H) AF=0,SF=1,ZF=0,CF=0,OF=1,PF=02.12 0001 0010 0011 0100B 0100 1010 1110 0000B 1011 0101 0010 0000B补码形式 1100 0111 0101 0100B（0C754H） AF=0 SF=1 ZF=0 CF=1 OF=0 PF=0 1001 0000 1001 0000B 0100 1010 1110 0000B 1011 0101 0010 0000B补码形式 0100 0101 1011 0000B (45B0H) AF=0 SF=0 ZF=0 CF=0 OF=1 PF=1 2.13 BX=009AH BX=0061H BX=00FBH BX=001CH BX=0000H BX=00E3H (本条语句只对标志位有影响,不存贮结果)2.14BX=0110 1101 0001 0110=6D16HBX=0000 0000 1101 1010=00DAH2.15 DX=0000 0000 1011 1001 DX= 0000 0000 0101 1100=005CH DX=0000 0000 1011 1001 DX= 0000 0000 0001 0111=0017H DX=0000 0000 1011 1001 DX= 0000 0101 1100 1000=05C8H DL= 1011 1001 DX=0000 0000 0111 0010=0072H DX=0000 0000 1011 1001 DX=0010 0000 0001 0111=2017H DL= 1011 1001 DX= 0000 0000 1100 1101=00CDH DH=0000 0000 DX=0000 0000 1011 1001=00B9H DX=0000 0000 1011 1001 DX=0000 0101 1100 1100=05CCH CF=0 DL= 1011 1001 DL=0000 0000 1101 1100=00DCH CF=12.16方法一: 循环移位 方法二:逻辑右移MOV CL,04H MOV CL,04HROL AL,CL SHR AL,CL第三章 宏汇编语言程序设计3.1 1）AX=0001H；2）AX=0002H3）CX=0014H4）DX=0028H5）CX=0001H3.21） ARRAY DB 56H，78，0B3H，1002） DATA DW 2965H，45H，2965，0A6H3） ALPHA DW 0C656H，1278H4） BETA DB 2 DUP（23），5 DUP（A），10 DUP（1，2），20 DUP（？）5）STRING DB THIS IS A EXAMPE6）COUNT EQU 1003.300H00H01H00H00H00H00H01H00H00H00H01H00H00H00H01H00H00H00H01H？42H41H44H43H1DH1FH (1) (2) BYTE_VARR41H42H43H44H4CH（76）57H？01H03H01H03H3.4DATA_SEG SEGMENTDATA1 DB DATA SEG,MENTDATA2 DB 72,65,-10DATA3 DB 109,98,21,40DATA4 DB 10 DUP(0)DATA5 DB 12345DATA6 DW 7,9,298,1967DATA7 DW 785,13475DATA8 DW DB ($-DATA6)-(DATA6-DATA1)DATA_SEG ENDS3.51）MOV BX, OFFSET BUF12) MOV CL BYTE PTR BUF2+23)MOV BUF3+9, A6H4)COUNT EQU BUF3-BUF13.8DATA_SEG SEGMENTAPPAY DB 10 DUP (29H)ALPHA DB -25,4,10,76,3BUFFER DB 100 DUP(?)DATA_SEG ENDS3.9DATA_SEG SEGMENTBCD1 DB ?,?BCD2 DB ?DATA_SEG ENDSCODE SEGMENT ASSUME CS:CODE, DS:DATA_SEG,ES:DATA_SEGSTART: MOV AX,DATA_SEGMOV DS,AXMOV DS, AXMOV CL, 04HMOV SI, OFFSET BCD1MOV AL, SISAL AL,CLMOV BL,SI+1AND BL,0FHADD AL,BLMOV BCD2,ALMOV AH,4CHINT 21HCODE ENDSEND START3.11 1) MOV CH, 32H CH=32H2)ADD CH, 2AHCH=5CH3)SHL CH, 1 CH=0B8H4)MOV BXNUM+9,CHCH=0B8H3.12DATA_SEG SEGMENTX DB ?Y DB ?W DB ?Z DB ?R DB ?DATA_SEG ENDSCODE SEGMENT ASSUME CS:CODE, DS:DATA_SEG,ES:DATA_SEGSTART: MOV AX, DATA_SEGMOV DS, AXMOV DS, AXMOV AL, WSUB AL, XCBW IDIV 0AHMOV R, AHIMUL YIMUL AXMOV AH, 4CHINT 21HCODE ENDSEND START3.14DATA_SEG SEGMENTSTR1 DB THIS IS A DOGSTR2 DB THIS IS A COCK COUNT DB $-STR2NUM DB ?DATA_SEG ENDSCODE SEGMENT ASSUME CS: CODE, DS:DATA_SEG,ES:DATA_SEGSTART: MOV AX, DATA_SEGMOV DS, AXMOV DS, AXMOV ES, AXMOV CH,0MOV CL, COUNTCLDMOV SI,OFFSET STR1MOV DI,OFFSET STR2REPZ CMPSBAND SI,000FHMOV AX,SIMOV NUM, ALCODE ENDSEND START3.16 DATA SEGMENT SRCBUF DB 80 DUP（？） DSTBUF DB 80 DUP（？） DATA ENDS CODE SEGMENT ASSUME CS： CODE， DS：DATA START： MOV AX，DATAMOV DS, AX MOV SI， OFFSET SRCBUF MOV DI， OFFSET DSTBUF MOV CX， 80 LOP1： MOV AL，SI INC SI CMP AL，ODH JE NEXT MOV DI，AL INC DI NEXT：LOOP LOP1 MOV AH，4CH INT 21H CODE ENDS END START3.17 DATA SEGMENT BUF DB n DUP (?) SUM DB O DATA ENDS CODE SEGMENT ASSUME CS:CODE, DS:DATA START: MOV AX, DATA MOV DS, AX MOV CX, n MOV SI, OFFSET BUF LOP1: MOV AL, SI INC SI CMP AL,O JGE NEXT INC SUM NEXT: LOOP LOP1 MOV AH, 4CH INT 21H CODE ENDS END START3.18 DATA SEGMENT BUF DW n DUP(?) BUF1 DW n DUP(?) BUF2 DW n DUP(?)DATA ENDS CODE SEGMENT ASSUME CS:CODE, DS:DATA START: MOV AX, DATA MOV DS, AX MOV CX, n MOV SI, OFFSET BUF MOV DI, OFFSET BUF1 MOV BX, OFFSET BUF2 LOP1: MOV AX, SI INC SI INC SI CMP AX, 0000H JGE NEXT1 MOV BX, AX ADD BX, 02H JMP LOP2 NEXT1: MOV DI, AX ADD DI, 2 LOP2: LOOP LOP1 MOV AH, 4CH INT 21H CODE ENDS END START3.19STACK SEGMENT STACK DB 256 DUP（?）STACK ENDS DATA SEGMENT BUF DB This is a string,$DATA ENDSCODE SEGMENT ASSUME CS:CODE.DS:DATA;SS:STACKSTART: MOV AX, DATA MOV DS, AXMOV SI,OFFSET BUF TACKCHAR: MOV DL,SI CMP DL,$ JZ DONECMP DL,a JB NEXTSUB DL,20HNEXT: MOV AH,02H INT 21H INC SI MP TAKECHAR DONE: MOV AH,4CHINT 21HCODE ENDSEND START320 DATA_SEG SEGMENT DATX DB ? DATY DB ? DATZ DB ?DATA_SEG ENDSCODE SEGMENT ASSUME CS:CODE, DS:DATA_SEGSTART: MOV AX,DATA_SEG MOV DS,AXMOV AL,DATXMOV BL,DATY CMP AL,BL JS NEXT MOV DATZ,AL JMP DONENEXT: MOV DATZ,BLDONE: MOV AH,4CH INT 21HCODE ENDSEND START3.21DATA_SEG SEGMENT DATA DB ? DATB DB ? DATC DB ? DATD DB ?DATA_SEG ENDSCODE SEGMENT ASSUME CS:CODE, DS:DATA_SEGSTART: MOV AX,DATA_SEG MOV DS,AX CMP DATA,0 JZ NEXT CMP DATB,0 JZ NEXT CMP DATC,0 JZ NEXT MOV AL,DATA ADD AL,DATB ADC AL,DATC MOV DATD,AL JMP DONENEXT: MOV DATA,0MOV DATB,0 MOV DATC,0DONE: MOV AH,4CHINT 21HCODE ENDSEND START3.22 程序段是将十六进制数的ASSII码转化为十六进制数.本例是将大写字母A的ASCII变为十六进制数,将结果存入字符变量HEXNUM中。HEXNUM变量中原来的内容未知，程序段执行后的内容是字符A的十六进制数0A3.24DATA_SEG SEGMENT N=10DATA1 DB N DUP(?) DATA2 DB N DUP(?) ADR1 DW ? ADR2 DW ? DATA_SEG ENDSCODE SEGMENT ASSUME CS:CODE, DS:DATA_SEGSTART: MOV AX, DATA_SEGMOV DS, AXLEA SI, DATA1LEA DI,DATA2MOV CX, NLOP1: MOV AH,SICMP AH,DI JNZ NOTEQUINC SIINC DILOOP LOP1MOV AH,0FFHSAHFJMP DONENOTEQU: MOV AH,0SAHFMOV ADR1,SIMOV ADR2,DIDONE:MOV AH,4CHINT 21HCODE ENDSEND START3.26DATA_SEG SEGMENTCOUNT=100BUF DB COUNT NUP(?) MAX DB ?DATA_SEG ENDSCODE SEGMENT ASSUME CS:CODE, DS:DATA_SEGSTART: MOV AX, DATA_SEG MOV DS, AXMOV SI, OFFSET BUFMOV CX,COUNTLOP1: MOV AH,1INT 21HMOV SI, ALINC SILOOP LOP1MOV SI,OFFSET BUFMOV CX,COUNTMOV AL, SILOP2:CMP AL, SI+1JA NEXT2XCHG AL,SI+1INC SINEXT2:LOOP LOP2MOV MAX,ALMOV AH, 4CHINT 21HCODE ENDSEND START3.27DATA_SEG SEGMENT BUF DB 10 DUP(?)STR1 DB Do you want input number(y/n)?,0DH,0AH,$STR2 DB Please input the numbers ,0DH,0AH,$ MAX DB ? MIN DB ?DATA_SEG ENDSCODE SEGMENT ASSUME CS:CODE, DS:DATA_SEGSTART: MOV AX, DATA_SEGMOV DS, AXMOV DX,OFFSET STR1MOV AH,09HINT 21HMOV DX,OFFSET STR2MOV AH,09HINT 21HMOV SI, OFFSET BUFMOV CX,10LOP1:MOV AH,1INT 21HMOV SI, ALINC SILOOP LOP1MOV SI,OFFSET BUFMOV CX,9MOV AL, SILOP2:CMP AL, SI+1JA NEXT2XCHG AL,SI+1INC SINEXT2:LOOP LOP2MOV MAX,ALMOV SI,OFFSET BUFMOV CX,9MOV AL, SILOP3: CMP AL, SI+1JB NEXT3XCHG AL,SI+1INC SINEXT3:LOOP LOP3MOV MIN,ALMOV AH,4CHINT 21HCODE ENDSEND START3.28DATA SEGMENTBUFF DB 10 DUP(?)DATA ENDSCODE SEGMENT ASSUME CS:CODE, DS:DATASTART: MOV AX,DATAMOV DS,AXMOV SI , OFFSET BUFFMOV CX,0AHLOP1: MOV AH,7INT 21HCMP AL,$JZ DONENEXT1 :CMP AL,aJGE NEXT2CMP AL,zJGE DONEJMP SHOWNEXT2:SUB AL,20HSHOW:MOV DL,ALMOV AH,2INT 21HLOOP LOP1DONE:MOV AH,4CHINT 21HCODE ENDSEND START3.29DATA SEGMENTSTRBUF DB ABCDEFGIJKLMN$OPQRSTUVWSXYZCOUNT DB $-STRBUFADRBUF DB ?DATA ENDSCODE SEGMENTASSUME CS:CODE, DS:DATASTART: MOV AX, DATAMOV DS, AXLEA SI, STRBUFMOV CH,0MOV CL, COUNTLOP1: MOV AL, SICMP AL,$JZ DONEINC SILOOP LOP1DONE: MOV ADRBUF,AL MOV AH,4CHINT 21HCODE ENDS END START3.30STACK SEGMENT STACKDW 256 DUP(?)TOP LABEL WORDSTACK ENDSDATA SEGMENTBUFF DB 1,2,3,4,5,6,7,8SUM DW 0000HDATA ENDSCODE SEGMENT ASSUME CS:CODE, DS:DATA,SS:STACKSTART: MOV AX,DATAMOV DS,AXMOV AX,STACKMOV SS,AXMOV SP,OFFSET TOPMOV CH,0MOV CL,8LOP1: MOV SI,OFFSET BUFFMOV AX,OFFSET SUMPUSH AXMOV AH,0MOV AL, SIPUSH AXCALL FAR PTR FACTMOV DX,SUMADD SUM,DXINC SILOOP LOP1MOV AH,4CHINT 21HCODE ENDSCODES SEGMENT ASSUME CS:CODESFACT PROC FARPUSH BPMOV BP,SPPUSH BXPUSH AXMOV BX,BP+8MOV AX,BP+6CMP AX,0JE DONEPUSH BXDEC AXPUSH AXCALL FACTMOV BX,BP+8MOV AX,BXMUL WORD PTR BP+6JMP RETURNDONE: MOV AX,01HRETURN:MOV BX,AX POP AX POP BXPOP BPRET 4FACT ENDPCODES ENDSEND START第五章 半导体存储器5.1 1) Intel 1024(1K1位) ： =1024（片）2） Intel 2114（1K4位）：=256（片）3） Intel 2128（2K8位）：=64（片）4） Intel 2167（16K1位）：=16（片）5.2 1）=128(片)2）1K=210 有十条用作片内寻址3）16K=214 14-10=4，有四条用作片间寻址5.15项目片选端地址线A19A16,A15-A14,A13A11,A10A0起始和结束地址Eprom 1#Y0任意, 10, 000, 变化*8000H*87FFFHEprom 2#Y1任意, 10, 001, 变化 *8800H*8FFFFHEprom 3#Y2任意, 10, 010, 变化*9000H*97FFFH项目片选端地址线A19A16,A15-A14,A13A11,A10,A 9A0起始和结束地址Ram 1#Y4,A10任意, 10, 100, 1, 变化*A400H*A7FFHRam 2#Y4,A10任意, 10, 100, 0, 变化*A000H*A3FFHRam 3#Y5,A10任意, 10, 101, 1, 变化*AC00H*AFFFHRam 4#Y5,A10任意, 10, 101, 0, 变化*A800H*ABFFH第六章 I/O接口技术6.5答：1）程序控制方式2）中断控制方式3）直接存储访问（DMA）方式区别：程序控制方式和中断控制方式都是采用软件形式，实现CPU与外设的数据传送，都要占用CPU的宝贵时间。DMA方式则是一种由硬件实现的数据传送方式，无需占用CPU的时间就可实现数据高速传送。6.86.11INPUT PROC NEARMOV CX，80HLEA DI，BUFFPOLL：IN AL，29HTEST AL，01HJNZ POLLIN AL ，28HSTOSBMOV DL，ALMOV AH，2INT 21HRET第七章 中断系统7.5 中断向量表 堆栈00H40H00H01H40H02HIp 40H00H00H01HCSIpFLAGSCS(SP)=00FAH(SS)=0300H(IP)=0040H(CS)=0100H(FLAGS)=0040H7.6 方法一:直接置入法PUSH DSMOV AX,0MOV DS,AXMOV BX,36LEA AX,INT_POUTMOV BX,AXMOV AX,SEG INT_POUTMOVBX+2,AXPOP DS方法二:dos功能调用PUSH DSMOV AX,SEG INT_OUTMOV DS,AXLEA DX,INT_OUTMOV AX,2509HINT 21HPOP DS7.9主程序段: PUSH DSMOV AX, SEG TRANINTMOV DS,AXLEA DX, TRANINTMOV AX,2579HINT 21HPOP DS MOV SI,OFFSET ASCNUM MOV CX,NUMB MOV DI,OFFSET BCDMMTRANINT: MOV AL,SIAND AL,0FHMOV DI,ALINC DIINC SIIRET7.10MOV DX, 02C0HMOV AL,1BHOUT DX,AL ;ICW1MOV DX, 02C1H MOV AL,10HOUT DX,AL ;ICW2MOV DX, 02C1HMOV AL,0DHOUT DX,AL ;ICW47.11 此题根据OCW3的设置来决定. 以上包括初始化8259的部分IN AL,51H MOV REG-ARR,AL ;读IMR的内容并存储IN AL,50HMOV AL,00001010B ;读取OCW3的内容,并进行设置OUT 50H,ALIN AL,50HMOV REG-ARR+1 ,AL ;读取IRR的内容并存储IN AL,50H ;读取OCW3的内容,并进行设置MOV AL,00001011BOUT 50H,ALIN AL,50HMOV REG-ARR+2,AL ;读取ISR的内容并存储.7.12设置中断向量表：PUSH DSMOV AX,0 ;中断向量表段地址送入DSMOV DS,AXMOV BX,3500H ；中断向量地址送入BXMOV AX,OFFSET IRQ0 ；中断向量填入中断向量表MOV BX,AXMOV AX,SEG IRQ0MOV BX+2,AXPOP DS(其他四个中断向量地址分别设为4080H、4505H、5540H、6000H，向量名改为相应的即可，在此省略)初始化8259A：MOV AL,13H ；ICW1OUT 20H,ALMOV AL,4BH ；ICW2（IRQ0的中断类型码为4BH）OUT 21H,ALMOV AL,01H ；ICW4OUT 21H,AL7.16DATA SEGMENTBUF DB 256 DUP(?)DATA ENDSCODE SEGMENTASSUME CS:CODE,DS:DATASTART:,MOV DX,DATA MOV DS,AX PUSH DSMOV AX,SEG INTPRMOV DS,AXLEA DX,INTPRMOV AX,250AHINT 21HPOP DS ;用dos功能调用,设置中断向量MOV DX,21HIN AL,DXAND AL,0FBH ;开放IRQ2中断OUT DX,ALSTIHLTMOV DX,21HIN AL,DX0R AL,04H OUT DX,AL ;关闭IRQ2中断MOV AH,4CHINT 21H;中断服务程序INTPR: PUSH CXMOV CX,8MOV DL,0MOV DX,200HIN AL,DXMOV BL,AL LOP: RCL BL,1 JCZ NEXT LOOP LOP ;计算1的个数NEXT: INC DLCMP DL MOD 2,0 ;判断1的个数是奇数还是偶数JNZ DISPMOV DX,201H OUT DX,ALDISP:MOV DL,NMOV AH,02HINT 21HMOV AL,20HOUT 20H,AL ;中断结束IRET第八章 常用接口芯片81 MOV AL，10011001MOV DX，0063HOUT DX，AL MOV AL，11000000MOV DX，0063HOUT DX，AL MOV AL，10110110MOV DX，0063HOUT DX，AL82 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 0 0 0 1 1 0 0 A口地址 060H0 0 0 1 1 0 1 B口地址 061H0 0 0 1 1 1 0 C口地址 062H0 0 0 1 1 1 1 控制字地址 063H 83注意：下面是课件P95页题目和图形，其中的口地址可通过一个138译码器获得主程序段：MOV CX，100；MOVSI，OFFSET BUFF；MOVAL，10000001B；控制字，A组方式0，OUT0EFH，AL；PA口输出，PC口高4位输出，低4位输入MOVAL，00001100B；置PC6为1OUT0EFH，AL；LOP：INAL，0EEH；读打印机状态