【正文】 CALL DELAY CALL SET_E CALL RESET_DI CALL RESET_RW MOV DX,PORTA MOV AL,00000010B OUT DX,AL CALL RESET_E 。LCD游標復(fù)位 CALL DELAY JMP LCD_D DISPLAY1:MOV DX, PORTA MOV BL, DATA_R CALL WR JMP LCD_D 。顯示數(shù)據(jù)。輸入為命令字時，返回前的處理程序 EXIT3: CALL DELAY CALL SET_E CALL RESET_DI CALL RESET_RW MOV DX,PORTA MOV AL,00000001B OUT DX,AL CALL RESET_E 。LCD清屏 CALL DELAY CALL SET_E CALL RESET_DI CALL RESET_RW MOV DX,PORTA MOV AL,00000010B OUT DX,AL CALL RESET_E 。LCD游標復(fù)位 CALL DELAY JMP CONTROL 。清屏返回 。=============================================== 。***********************************************LCD_W: BB4: CMP SW,0 JZ BB4 MOV SW, 0 CMP DATA_R, 0AH 。判斷是否為命令字 JB EXIT4 CMP DATA_R, 0FH JNZ DISPLAY2 。判斷是否為清屏命令。收到清屏命令的清屏處理 CALL SET_E CALL RESET_DI CALL RESET_RW MOV DX,PORTA MOV AL,00000001B OUT DX,AL CALL RESET_E 。此處清屏 CALL DELAY CALL SET_E CALL RESET_DI CALL RESET_RW MOV DX,PORTA MOV AL,00000010B OUT DX,AL CALL RESET_E 。LCD游標復(fù)位 CALL DELAY JMP LCD_D DISPLAY2:MOV DX, PORTA OR DATA_R, 80H MOV BL, DATA_R CALL WRBB5: CMP SW,0 JZ BB5 MOV SW, 0 MOV DX, PORTA OR DATA_R, 80H MOV BL, DATA_R CALL WR JMP LCD_D 。顯示數(shù)據(jù)。輸入為命令字時，返回前的處理程序 EXIT4: CALL DELAY CALL SET_E CALL RESET_DI CALL RESET_RW MOV DX,PORTA MOV AL,00000001B OUT DX,AL CALL RESET_E 。LCD清屏 CALL DELAY CALL SET_E CALL RESET_DI CALL RESET_RW MOV DX,PORTA MOV AL,00000010B OUT DX,AL CALL RESET_E 。LCD游標復(fù)位 CALL DELAY JMP CONTROL 。清屏返回 。=============================================== 。*********************************************** CLIEXIT: MOV AX, INT_SEG MOV DS, AX 。DS指向向量段基址 MOV DX, INT_OFF 。DX指向向量偏移量 MOV AL, 0BH 。中斷號 MOV AH, 25H INT 21H 。恢復(fù)中斷向量 MOV AH, 4CH INT 21H 。========================================================。8251初始化子程序。用到寄存器：DX AX。========================================================INIT_8251 PROC NEAR CALL RESET_8251 。8251復(fù)位操作 CALL DELAY 。延時 PUSH DX PUSH AX MOV AL, 4EH 。8251方式字，一個停止位，無校驗，波特因子16 MOV DX, CON_8251 OUT DX, AL CALL DELAY MOV AX, 35H 。8251控制字 bit2 接收允許 MOV DX, CON_8251 OUT DX, AX CALL DELAY POP AX POP DX RETINIT_8251 ENDP。========================================================。8251初始化子程序。用到寄存器：DX AX。========================================================RESET_8251 PROC NEAR PUSH AX PUSH DX MOV AL, 00H MOV DX, CON_8251 OUT DX, AL 。放入8251的控制寄存器 CALL DELAY OUT DX, AL CALL DELAY OUT DX, AL CALL DELAY MOV DX, DATA_8251 OUT DX, AL 。放入8251的數(shù)據(jù)口 CALL DELAY OUT DX, AL CALL DELAY MOV AL, 40H 。01000000，bit6命令控制字內(nèi)部復(fù)位 MOV DX, CON_8251 OUT DX, AL POP DX POP AX RETRESET_8251 ENDP。========================================================。寫子程序。入口參數(shù)：DATA_T。用到寄存器：DX AX。========================================================SD PROC NEAR PUSH AX MOV AL, 31H 。0011 0001 RTS輸出低電平，三個出錯位復(fù)位 MOV DX, CON_8251 OUT DX, AL 。TxEN為1，允許發(fā)送 POP AX SRDY: MOV DX, CON_8251 IN AL, DX AND AL, 01H 。檢校 TxRED是否為1，是發(fā)送緩沖內(nèi)容 JZ SRDY MOV DX, DATA_8251 MOV AL, DATA_T OUT DX, ALSED: MOV DX, CON_8251 IN AL, DX AND AL, 04H 。檢校 TxE是否為1，等待發(fā)送結(jié)束 JZ SED CALL DELAY RET SD ENDP 。========================================================。讀子程序。出口參數(shù)：DATA_R。用到寄存器：DX AX。========================================================RD PROC NEAR MOV AX, 34H 。8251控制字 bit2 接收允許 MOV DX, CON_8251 OUT DX, AX RD1: NOP NOP MOV