197rxtx.asm

Serial Communication Program for 8051

          $MOD51 
          ORG 00H
	      MOV  TMOD,#20H ;timer1, mode 2 (auto reload)
          MOV  TH1,#-6   ;4800 baud, 0F3H for 12 MHz
          MOV  SCON,#50H ;8-bit, 1 stop, REN enabled
          SETB TR1       ;start timer 1 
          ;
AGAIN:    ACALL TRANS
          ACALL RECEIVE
          SJMP AGAIN
TRANS:	  
		  MOV SBUF,A	 ;load SBUF
TX: 	  JNB TI,TX 	 ;wait for the last bit
	      CLR  TI 		 ;clear TI for next char
	      RET 			 ;get ready for next byte

RECEIVE:  
RX:       JNB  RI,RX   ;wait for char to come in
          MOV  A,SBUF    ;save incoming byte in A
          CLR  RI        ;get ready to receive next byte
          RET
          END