www.pudn.com > dianziqin.rar > dianziqin.asm

;*******************************; 
;*         电子琴实验          *; 
;*******************************; 
 
data segment 
io8255a        equ 288h 
io8255b        equ 28bh 
io8253a     equ 280h 
io8253b        equ 283h 
table dw 524,588,660,698,784,880,988,1048;高音的 
;table dw 262,294,330,347,392,440,494,524;低音的 
msg db 'Press 1,2,3,4,5,6,7,8,ESC:',0dh,0ah,'$' 
data ends 
 
code segment 
assume cs:code,ds:data 
start: 
    mov ax,data 
    mov ds,ax 
 
    mov dx,offset msg 
    mov ah,9 
    int 21h              ;显示提示信息 
sing:     
    mov ah,7 
    int 21h              ;从键盘接收字符,不回显 
    cmp al,1bh 
    je finish            ;若为ESC键,则转finish 
    cmp al,'1' 
    jl  sing 
    cmp al,'8' 
    jg sing              ;若不在'1'-'8'之间转sing 
     
    sub al,31h 
    shl al,1             ;转为查表偏移量 
    mov bl,al            ;保存偏移到bx 
    mov bh,0 
     
    mov ax,4240H         ;计数初值 = 1000000 / 频率, 保存到AX 
    mov dx,0FH 
    div word ptr[table+bx] 
    mov bx,ax 
     
    mov dx,io8253b          ;设置8253计时器0方式3, 先读写低字节, 再读写高字节 
    mov al,00110110B 
    out dx,al 
 
    mov dx,io8253a          
    mov ax,bx 
    out dx,al            ;写计数初值低字节 
     
    mov al,ah 
    out dx,al            ;写计数初值高字节 
     
    mov dx,io8255b          ;设置8255 A口输出 
    mov al,10000000B 
    out dx,al 
     
    mov dx,io8255a             
    mov al,03h 
    out dx,al            ;置PA1PA0 = 11(开扬声器) 
    call delay           ;延时 
    mov al,0h 
    out dx,al            ;置PA1PA0 = 00(关扬声器) 
     
    jmp sing 
finish: 
    mov ax,4c00h 
    int 21h 
     
delay proc near          ;延时子程序 
    push cx 
    push ax 
    mov ax,15 
x1: mov cx,0ffffh 
x2: dec cx 
    jnz x2 
    dec ax 
    jnz x1 
    pop ax 
    pop cx 
    ret 
delay endp 
code ends 
end start