发布时间 : 星期日 文章微机接口自考北大上机题更新完毕开始阅读
code ends
end start
11. 8253通道0方式0,从8255C口读入计数值,手动逐个输入脉冲,从A口输出在数码管显示其值。
code segment
assume cs:code
start: mov dx,28bh
mov al,88h
out dx,al
mov dx,28ah
in al,dx
mov cl,4
shr al,cl
and al,0fh
mov bl,al
mov dx,283h
mov al,10h
out dx,al
mov al,bl
mov dx,280h
out dx,al
l1: mov dx,280h
in al,dx
mov dx,288h
out dx,al
mov ah,1
int 16h jz l1
mov ah,4ch
int 21h
code ends
end start
12. 8253通道1方式1(硬件可重触发),计数值0Fh,用8255A口输出在数码管显示值,有键按下返回DOS,无键按下继续执行。
data segment
led db 3fh,06h,5bh,4fh,66h,6dh,7dh,07h,7fh,6fh,77h,7ch,39h,5eh,79h,71h
data ends
code segment
assume cs:code,ds:data
start: mov ax,data
mov ds,ax
lea bx,led
mov dx,28bh
mov al,80h
out dx,al
mov dx,283h
mov al,52h
out dx,al
mov al,0fh
mov dx,281h
out dx,al
l1: mov dx,281h
in al,dx xlat
mov dx,288h
out dx,al
push dx
mov ah,06h
mov dl,0ffh
int 21h
pop dx