code: @Override
      public void setSectorsPerFat(long v) {
          if (v == getSectorsPerFat()) return;
          if (v > 0x7FFF) throw new IllegalArgumentException(
                  "too many sectors for a FAT12/16");
          
          set16(SECTORS_PER_FAT_OFFSET, (int)v);
      }
docs: Sets the number of sectors/fat
  
  @param v  the new number of sectors per fat