公开(公告)号：JPH1145516A

公开(公告)日：1999-02-16

申请号：JP20015897

申请日：1997-07-25

Applicant: IBM

Inventor： HATANO AKIRA ,  KAGAMI NAOYUKI ,  MATSUBARA NOBUYA

IPC: G11B5/09 ,  G06F11/267 ,  G11B20/12 ,  G11B20/18

Abstract: PROBLEM TO BE SOLVED: To drastically reduce unnecessary flags and to reduce defective disks by preventing errors to be generated at random from being flagged. SOLUTION: A cyclic redundant check CRC is performed on read data by a CRC circuit 20, and a data error is detected by an ECC circuit 21. At this time, a surface analyzation test SAT is executed by a calculator 16 in such an algorithm that when error generation positions in the same sector are apart from one another by more than a prescribed distance, no flagging is carried out. In other words, a data is read out of a target data area, and an error position is detected by the ECC circuit 21 to check distances of the previous and present error portions respectively, and if there distances are closer values than the prescribed distance perceptively, checking the distance is performed a prescribed number of times, and if the closer state is more than prescribed criteria, flagging is performed. Consequently, flags on errors caused at random by noise are drastically reduced, and errors required for flags are certainly flagged.