mov   @r0,#0  ;moves 0 into address 02, which is R2 in bank 0
   djnz  r0,Loop   ;r0 gets decremented, so it contains 01, 
                   ;   which is nonzero, so it loops back
   mov   @r0,#0    ;moves 0 into address 01, which is R1 in bank 0
   djnz  r0,Loop   ;r0 gets decremented, so it contains 00, 
                   ;   which is zero, so it does not loop back 
                   ;   but it continues - loop exits