@data = read_data($infile);            # @data is global
   $data[0x6FFE] = 0;                     # zero CRC
   $data[0x6FFF = 0;                      # locations

   $crc = crc16(0x0000, 0x6FFF,  0);          # works

   $crc = 0;
   for ($a = 0x0000; $a < 0x6fff; $a += 32) { # final value
      next if (unusedBlock($a, 32);           # off by one
      $crc = crc16($a,     $a + 32, $crc);
   }


   $data[0x6FFE] = $crc >> 8;                 # save
   $data[0x6FFF] = $crc & 0xFF;               # CRC
   write_data($outfile); # or write_data_blocks($outfile);