利用中断方式设计数字时钟

p8259 equ 20h ;端口首地址 p8255 equ 288h ;端口首地址 p8253 equ 280h ;IO Y1

data segment

led db 3fh,06h,5bh,4fh,66h,6dh,7dh,07h,7fh,6fh ;数码管 sec1 db 0 sec2 db 0 min1 db 0 min2 db 0 mes db 42h

Old_0A DW 0 Old_8259 DB 0 data ends

stacks segment db 64 dup (0) stacks ends

code segment

assume cs:code,ds:data,es:data start:

mov ax,data mov ds,ax cli;关闭中断

mov al,00110110b

mov dx,p8253+3 ;计数器0,工作在模式3 out dx,al

mov ax,2710h mov dx,p8253 out dx,al

mov al,ah ;先赋高八位再赋低八位 out dx,al

mov al,01110110b

mov dx,p8253+3 ;计数器1,工作在模式3 out dx,al mov ax,100

mov dx,p8253+1 out dx,al

mov al,ah ;先赋高八位再赋低八位 out dx,al ; 设置中断向量表 PUSH ES PUSH BX

MOV Al,0BH ;保护原中断向量,0B中断类型号 mov ah,35h

INT 21H ;读中断向量表

MOV Old_0A+2,ES;ES为段地址,BX为段偏移地址 MOV Old_0A,BX POP BX POP ES push ds

原中断向量 ; mov al,0bh ; 写新中断向量

mov ah,25h

mov dx,seg INT_0A mov ds,dx

mov dx,offset INT_0A int 21h pop ds

mov al,10000000b ;对8255进行设置,PB/PC输出 mov dx,p8255+3 out dx,al

in al,p8259+1 ;8259奇地址中断向量屏蔽 mov old_8259,al ;字设置保护原屏蔽字 and al,11110111b ;开IRQ3 out p8259,al

sti ;开中断

play: lea bx,led ;led段码 mov dl,sec1 ;秒个位 mov dh,0 mov si,dx

mov al,[bx][si]

mov dx,p8255+1 ;点亮led out dx,al

mov ah,11111110b mov al,ah

mov dx,p8255+2 ;pc输出选通信号 out dx,al PUSH CX

MOV CX,00f00h ;延时 delay1:

LOOP delay1 POP CX

mov ah,11111111b mov al,ah

mov dx,p8255+2 ;pc输出选通信号 out dx,al

mov dl,sec2 ;秒十位 mov dh,0 mov si,dx

mov al,[bx][si]

mov dx,p8255+1 ;点亮led out dx,al

mov ah,11111101b mov al,ah

mov dx,p8255+2 ;pc输出选通信号 out dx,al PUSH CX

MOV CX,00f00h ;延时 delay2:

LOOP delay2 POP CX

mov ah,11111111b mov al,ah

mov dx,p8255+2 ;pc输出选通信号 out dx,al

mov dl,min1 ;分个位 mov dh,0 mov si,dx

mov al,[bx][si]

mov dx,p8255+1 ;点亮led out dx,al

mov ah,11111011b mov al,ah

mov dx,p8255+2 ;pc输出选通信号 out dx,al PUSH CX

MOV CX,00f00h ;延时 delay3:

LOOP delay3 POP CX

mov ah,11111111b mov al,ah

mov dx,p8255+2 ;pc输出选通信号 out dx,al

mov dl,min2 ;分十位 mov dh,0 mov si,dx

mov al,[bx][si]

mov dx,p8255+1 ;点亮led out dx,al

mov ah,11110111b mov al,ah

mov dx,p8255+2 ;pc输出选通信号 out dx,al PUSH CX

MOV CX,00f00h ;延时 delay4:

LOOP delay4 POP CX

mov ah,11111111b mov al,ah

mov dx,p8255+2 ;pc输出选通信号 out dx,al jmp play mov ah,4ch int 21h

INT_0A proc near ;中断服务子程序 cmp sec1,9 jz int1 inc sec1 jmp exit int1:

mov sec1,0

inc sec2 cmp sec2,6 jnz exit mov sec2,0 inc min1 cmp min1,10 jnz exit mov min1,0 inc min2 cmp min2,6 jnz exit mov min2,0 exit:

mov al,20h out 20h,al iret

INT_0A endp code ends end start