org 0000h
        ljmp program_start ;bypass interupt table       
org 0030h                
program_start:
        mov port3,#0ffh
        mov port1,#0ffh
        mov r0,#7fh
fill_zeros:
      mov @r0,#00h
      djnz r0,fill_zeros 
system:
      jb port3.2,system
      mov port1,#00h
here:
       sjmp here
end