5-5.asm

TCP_USB试验平台下的几个常见的实验的相应要求与代码

DATA  SEGMENT
DAP  EQU  2A0H
T0  EQU   290H
T1  EQU   291H
T2  EQU   292H
CTL  EQU  293H

PA  EQU   280HPB  EQU   281H
PC  EQU   282H
CTL1  EQU 283H
DATA  ENDS

CODE  SEGMENT
MAIN  PROC FAR
ASSUME    CS:CODE,DS:DATA
START:
      XOR  AX,AX
      MOV  AX,DATA
      MOV  DS,AX
  ;--8253---------------------
      MOV  DX,CTL
      MOV  AL,27H ;写控制字
      OUT  DX,AL

      MOV  AL,10H
      MOV  DX,T0  ;写时间常数
      OUT  DX,AL


      MOV  DX,CTL
      OUT  DX,AL

      MOV  AL,10H
      MOV  DX,T1  ;写时间常数
      OUT  DX,AL
    ;---------8255-----------
      MOV  DX,CTL1
      MOV  AL,81H ;写控制字
      OUT  DX,AL

   ;---------------------------
      MOV  DX,DAP
 L0:  MOV  AL,00H
 F1:  OUT  DX,AL
   ;------------延时-----------
CALL DELAY
   
      ADD AL,8
      CMP AL,80H
      JZ  S1
      JMP F1

 S1:  MOV  SI,16 S2:  DEC  SI
      OUT  DX,AL
    ;------------延时-----------
CALL  DELAY
    
      CMP  SI,0H
      JZ   P1
      JMP  S2

 P1:  OUT  DX,AL
     ;------------延时-----------
CALL  DELAY
      
      SUB  AL,8
      CMP  AL,0H
      JZ   L0
      JMP  P1
      RET
MAIN  ENDP
DELAY  PROC NEAR

  D1:  MOV  DX,PC ;从PC0读一个负脉冲
       IN   AL,DX
       TEST AL,01H；下降沿
       JNZ  D1
  D2:  IN  AL,DX  ;上降沿
       TEST AL,01H
       JZ  D2
       RET
DELAY  ENDP
CODE  ENDS
END   START