Int 15 Fn 0F  C - System - Format Unit Periodic Interrupt (ps Esdi Drives  [d]

   AH = 0Fh
   AL = phase code
       00h reserved
       01h surface analysis
       02h formatting

Return: CF clear if formatting should continue, set if it should terminate

Note:  called during ESDI drive formatting after each cylinder is completed

See Also: INT 13/AH=1Ah