FILL START
     LAD GR1,#FFFF
     LAD GR2,#0000 ;; counter
     LAD GR3,#0003 ;; limit
     LAD GR4,#0001 ;; const
LL   ST  GR1,#0050,GR2
     ADDL GR2,GR4
     CPA GR2,GR3
     JMI LL
     RET
     END