微机原理实验报告 (4).docx

一、实验目的（1）掌握8254的工作原理和编程方法；（2）了解光电开关，掌握用光电传感器测量电机转速的方法。二、实验内容光电测速的基本电路由光电传感器、计数器组成。被测电机主轴上固定一个圆盘，圆盘的边缘上有小孔。传感器的红外发射端和接收端装在圆盘的两侧，电机带动圆盘转到有孔的位置是，红外光通过，接收管导通，输出低电平。红外光被挡住时，接收截止，输出高电平。用计数器/定时器记录在一定时间内传感器发出的脉冲个数，就可以计算出电机的转速。三、线路连接8254计数器/定时器0和2作为定时器，确定测速时间，定时器0的CLK0连1MHZ脉冲频率，OUT作为定时器2的输入，与CLK2相连，输出OUT2与8255的PA0端相连。GATE0和GATE2均接+5V，8254计数器/定时器1作为计数器，输入CLK1与直流电机计数端连接，GATE1与8255的PC0相连。电机DJ端与+5V0V模拟开关SW1相连。四、流程图如图1所示图1直流电机测速程序流程图五、实验数据记录和处理data segmentioport equ 0d880h-0280hio8255k equ ioport+283hio8255a equ ioport+280hio8255c equ ioport+282hio8254k equ ioport+28bhio82542 equ ioport+28ahio82541 equ ioport+289hio82540 equ ioport+288hmess db strike any key,return to dos!,0ah,0dh,$cou db 0cou1 db 0count1 db 0count2 db 0count3 db 0count4 db 0data endscode segmentassume cs:code,ds:datastart: mov ax,data mov ds,ax mov dx,offset mess mov ah,09h int 21h mov dx,io8254k mov al,36h out dx,al mov dx,io82540 mov ax,50000 out dx,al nop nop mov al,ah out dx,al mov dx,io8255k mov al,90h out dx,al mov dx,io8255c mov al,00 out dx,alll: mov ah,01h int 16h jnz quit1 mov dx,io8254k mov al,70h out dx,al mov dx,io82541 mov al,0ffh out dx,al nop nop out dx,al mov dx,io8254k mov al,90h out dx,al mov dx,io82542 mov al,100 out dx,al mov dx,io8255c mov al,01h out dx,al jmp a0quit1: jmp quita0: mov dx,io8255aa1: in al,dx and al,01h jz a1 mov dx,io8255c mov al,00h out dx,al mov dx,io8254k mov al,70h out dx,al mov dx,io82541 in al,dx mov bl,al in al,dx mov bh,al mov ax,0ffffh sub ax,bx call disp mov dl,0dh mov ah,02 int 21h mov dl,0ah mov ah,02 int 21h jmp lldisp proc near mov dx,0000h mov cx,03e8h div cx mov count1,al mov ax,dx mov cl,64h div cl mov count2,al mov al,ah mov ah,00h mov cl,10 div cl mov count3,al mov count4,ah mov al,count1 call disp1 mov al,count2 call disp1 mov al,count3 call disp1 mov al,count4 call disp1 ret disp endp disp1 proc near and al,0fh cmp al,09h jle num add al,07h num: add al,30h mov dl,al mov ah,02 int 21h ret disp1 endp quit: mov ah,4ch int 21h code ends end start六、实验结果与分析七、思考题关闭电机后，为什么8254计数不为0？答：关闭电机后，主机未断电，计数值锁存在锁存器中，所以读数会一直为锁存器的值，8254计数不会显示为