MOV PSW,#00H     ;no matter for this program
MOV DPH,#0F0H
MOV DPL,#11H     ;there is single mov dptr,#nn command!

MOVX @DPTR,A
MOV DPH,#0F0H
MOV DPL,#00H
MOV A,#55H
MOVX @DPTR,A