RSEG AT 30H
 FLAG EQU 31H
 CSEG AT 200CH
 DCW SP_INT ;串行口通信中斷
 CSEG AT 2080H
 LD SP,#0E0H
 LD IOC1,#00100000B;選通TXD引腳功能
 LDB BAUD_RATE,#13H
 LDB BAUD_RATE,#80H
 LDB SP_CON,#00011010B;串行口模式2，允許接收
 STB SBUF,BL;清SBUF(rx)
 LD DX,#4000H
 LD CX,#4010H
 LD EX,#4020H
 LDB BL,#10H
 LDB BH,#08H
 LDB INT_MASK,#01000000B;開串行口中斷
 CLRB FLAG
 EI
 LDB SBUF,[DX]+
 WAIT:SJMP WAIT
 SP_INT: PUSHF
          
         LDB AH,SP_STAT
         JBS AH,5,TX
         JBS AH,6,RX
 RETURN: CLRB AH
         
         POPF
         RET
                   
 TX:   DECB BL
      
      
       JE RETURN
       LDB SP_CON,#00011010B
       LDB SBUF,[DX]+
      
       SJMP RETURN
 RX:  JBC FLAG,0,AA
      JBC FLAG,1,BB
      SJMP RETURN
 AA:  
      LDB AL,SBUF
      STB AL,[CX]+   ;接收AL寫入緩沖區(qū)
      DJNZ BH,RETURN
      LDB FLAG,#1H
      ldb BH,#8H    
      SJMP RETURN
 BB:  
      LDB AL,SBUF
      STB AL,[EX]+   ;接收AL寫入緩沖區(qū)
      DJNZ BH,RETURN
      SJMP RETURN
      END