To exchange contents of two memory location

        

        ORG 000H

        SJMP START

START : MOV R2,#05H /* R2 declared as a pass counter*/

        MOV R0,#30H

        MOV R1,#50H

   UP : MOV A,@R0

        MOV B,@R1

        MOV @R1,A

        MOV @R0,B

        INC R1

        INC R0

        DJNZ R2,UP

STOP  : SJMP STOP