主机串行口多机通信.asm

这个是大学的计算机接口实验课上经常用到的原程序

          ORG    0000H
MAIN:     MOV    TMOD, #20H
          MOV    TH1 , #0F3H
          MOV    TL1,  #0F3H
          MOV    SCON, #0D8H
          MOV    PCON, #80H
          MOV    R0,   #30H
          MOV    R1,   #40H
          MOV    R2,   #0AH
          SETB   TR1
S1:       MOV    A,    50H
          MOV    SBUF, A
S2:       JBC    TI,   S3
          AJMP   S2
S3:       CLR    TI
S4:       JBC    RI,  S5
          AJMP   S4
S5:       MOV    A,   SBUF
          CLR    RI
          CJNE   A,    50H,CHB1
          SJMP   COM
CHB1:     MOV    A,    #0FFH
          SETB   TB8
          MOV    SBUF, A
S6:       JBC    TI,   LOOP
          SJMP   S6
LOOP:     CLR    TI
          AJMP   S1
COM:      CLR    TB8
          MOV    A, R3
          MOV    51H,R3
          MOV    SBUF, A
S7:       JBC    TI,S8
          SJMP   S7
S8:       CLR    TI
S9:       JBC    RI,S10
          SJMP   S9
S10:      MOV    A,  SBUF
          CLR    RI
          CJNE   A,  51H,CHB1
          CJNE   R3,#01H,REA
          MOV    A, R2
          MOV    SBUF,A
S11:      JBC    TI,TDATA
          SJMP   S11
TDATA:    CLR    TI
          MOV    A,@R0
          MOV    SBUF,A
S12:      JBC    TI,TDX
          SJMP   S12
TDX:      CLR    TI
          INC    R0
          DJNZ   R2,TDATA
          SJMP   MAIN
REA:      JBC    RI,RXX
          SJMP   REA
RXX:      CLR    RI
          MOV    A,SBUF
          MOV    R4,A
RDATA:    JBC    RI,RDX
          SJMP   RDATA
RDX:      CLR    RI
          MOV    A, SBUF
          MOV    @R1,A
          INC    R1
          DJNZ   R4,RDATA
          LJMP   main
          END