quan.asm

微机原理——接口应用编程源码

       stack  segment stack
       dw 64 dup(?)
       stack ends
       data segment     
       data ends
code   segment
       assume cs:code,ds:data
start: mov ax,data
       mov ds,ax
       mov dx,63h         ;8255 PB:in PA:out 0
       mov al,10000010B   
       out dx,al
       mov dx,43h         ;8253 counter 2,way 3
       mov al,10110110B
       out dx,al    
wav:   mov dx,61h   ;PB in
       in  al,dx
       mov dx,60h   ;pA out
       out dx,al
       cmp al,00b
       jz  wav1
       cmp al,01b
       jz  wav2 
       cmp al,10b
       jz  wav3       
       jmp wav
wav1:  mov ax,2d69h   ;100hz
       mov dx,42h
       out dx,al
       mov al,ah
       out dx,al
       jmp wav
wav2:  mov ax,048ah    ;1khz
       mov dx,42h
       out dx,al
       mov al,ah
       out dx,al
       jmp wav
wav3:  mov ax,0074h  ;10khz
       mov dx,42h
       out dx,al
       mov al,ah
       out dx,al
       jmp wav
code ends
end start