MOV  TMOD,#20H ;timer 1, mode 2
          MOV  TH1,#-3   ;9600 baud
          MOV  SCON,#50H ;8-bit, 1 stop bit, REN enabled
          SETB TR1       ;start timer 1
AGAIN:    MOV  A,#"Y"    ;transfer "Y"
          ACALL TRANS    
          MOV  A,#"E"    ;transfer "E"
          ACALL TRANS    
          MOV  A,#"S"    ;transfer "S"
          ACALL TRANS    
          SJMP AGAIN     ;keep doing it
;serial data transfer subroutine
TRANS:    MOV  SBUF,A    ;load SBUF
HERE:     JNB  TI,HERE   ;wait for last bit to transfer
          CLR  TI        ;get ready for next byte
          RET