;***************************************
;*    無線收發(fā)實驗                     *
;*    D0:CS選擇頻道，0－頻道1，1－頻道2 *
;*     D1:POWR UP  0-待機，1－加電      *
;*     D2:TXEN  0-接受模式， 1－發(fā)送模式 *
;***************************************
data segment
 ioport equ 0e800h-0280h;0e800
 io8253a    equ ioport+280h
 io8253b    equ ioport+281h
 io8253d    equ ioport+283h
 io8251a    equ ioport+288h
 io8251b    equ ioport+289h
 io273        equ ioport+290h
 mes1 db 'you can play a key on the keybord!',0dh,0ah,,24h
 mes2 db 'receive mode!',0dh,0ah,24h
 mes3 db 'please press the  key T or R ,',0dh,0ah
      db 'T is transmit mode,R is receive mode !',0dh,0ah,24h
data ends
stacks segment
 db    100    dup(?)
stacks ends
code    segment
    assume cs:code,ds:data,SS:STACKS,es:data

start:    mov ax,data
    mov ds,ax
    mov es,ax
    mov ax,stacks
    mov ss,ax   
;************************;
;*8251串行通訊           *;
;************************;
      mov dx,io8253d       ;設置8253計數(shù)器0工作方式
      mov al,16h
      out dx,al
      mov dx,io8253a
      mov al,52          ;給8253計數(shù)器0送初值
      out dx,al
;         jmp a1
      mov dx,io8251b       ;初始化8251
      xor al,al
      mov cx,03         ;向8251控制端口送3個0
delay:   call out1
      loop delay
      mov al,40h        ;向8251控制端口送40H,使其復位
      call out1
      mov al,4eh        ;設置為1個停止位,8個數(shù)據(jù)位,波特率因子為16
      call out1
      mov al,27h        ;向8251送控制字允許其發(fā)送和接收
      call out1
      mov  dx,io273
          mov al,01h
      out dx,al          ;nrf401 待機
tishi:      mov dx,offset mes3 ;顯示提示信息
      mov ah,09
      int 21h
         mov ah,01         ;是,從鍵盤上讀一字符
      int 21h
         cmp al,54h
      jz  trins
         cmp al,74h
      jz  trins
      cmp al,52h
      jz  rece
      cmp al,72h
      jz  rece
         jmp tishi 

;以下位發(fā)送程序

trins:   mov dx,io273
         mov al,06h
      out dx,al        ;發(fā)送模式
;      call delay5ms 
         mov dx,offset mes1   ;顯示提示信息
      mov ah,09
      int 21h
trins1:  mov ah,01         ;是,從鍵盤上讀一字符
      int 21h
         mov bl,al
waiti:   mov dx,io8251b
      in al,dx
      test al,01        ;發(fā)送是否準備好
      jz waiti        
wait2:     mov dx,io8251a
         mov al,bl
     out dx,al         ;發(fā)送
     cmp al,1bh        ;若為ESC,結束
     jz exit 
     mov cx,0fF00h
s51:    loop s51          ;延時
        jmp trins1;waiti

;以下為接收程序
rece:   mov dx,io273
         mov al,02h
     out dx,al         ;轉為接收模式
;       call delay5ms 
        mov dx,offset mes2 ;顯示提示信息
     mov ah,09
     int 21h
wait1:  mov ah,01         ;有無鍵按下
     int 16h
        jne exit          ;有鍵按下退出    
next:   mov dx,io8251b
     in al,dx
     test al,02         ;檢查接收是否準備好
     jz  wait1          ;沒有,等待
     mov dx,io8251a
     in al,dx          ;準備好,接收
     mov dl,al
     mov ah,02         ;將接收到的字符顯示在屏幕上
     int 21h    
     jmp wait1          ;接收
exit:   mov ah,4ch        ;退出
     int 21h

out1 proc near            ;向8251送一字節(jié)的子程序
      out  dx,al
      push cx
      mov  cx,5000h
gg:      loop gg           ;延時
      pop  cx
      ret
out1 endp

delay5ms proc near
         mov dx,io8253d       ;設置8253計數(shù)器1工作方式
      mov al,70h
      out dx,al
      mov dx,io8253b
      mov al,0fh        ;給8253計數(shù)器1送初值,低字節(jié)
      out dx,al
      mov al,14h
      out dx,al          ;給8253計數(shù)器1送初值,高字節(jié)，總值5000
suocun:  mov dx,io8253d     ;設置8253計數(shù)器1鎖存
      mov al,40h
      out dx,al
      mov dx,io8253b
      in al,dx
      mov bl,al
      in al,dx
      mov bh,al
      cmp al,00
      jnz suocun 
;         mov al,bl
;      cmp al,00
;      jnz suocun
      ret
delay5ms endp

code ends
end    start