公开(公告)号：DE2622184A1

公开(公告)日：1976-12-16

申请号：DE2622184

申请日：1976-05-19

Applicant: IBM

Inventor： MARSHALL JOHN WILLIAM

IPC: H03M13/00 ,  G06F3/06 ,  G06F11/10 ,  G11B20/18 ,  G06F11/08

Abstract: Multiple symbol correction employing auxiliary pointers is enhances by unique interaction of the code structures either with ambiguous auxiliary pointers or data structures for precisely locating errors. For example, a code apparatus can correct two symbols in error only with two error location pointers; with three error location pointers, the code cannot correct the errors since error location is ambiguous. Once this has been determined, the features set forth in the present invention are employed in order to delimit the error burst such that the code apparatus may correct two symbols in error, even with ambiguous error location pointers. With no auxiliary pointers, methods and apparatus can create such auxiliary pointers in particular data structures and error patterns.

公开(公告)号：DE2964891D1

公开(公告)日：1983-03-31

申请号：DE2964891

申请日：1979-06-01

Applicant: IBM

Inventor： WOODWARD DONALD RAYMOND ,  MARSHALL JOHN WILLIAM

IPC: G06F11/08 ,  G06F11/27 ,  G06F11/277 ,  G01R31/28 ,  G06F11/00 ,  G06F15/00

公开(公告)号：DE2510445A1

公开(公告)日：1975-10-02

申请号：DE2510445

申请日：1975-03-11

Applicant: IBM

Inventor： MARSHALL JOHN WILLIAM ,  MCDONALD JUN EARL GEORGE ,  ROATH PHILLIP BRUCE

IPC: H04L1/00 ,  G11B5/09 ,  G11B20/14 ,  H03K5/1536 ,  H03M5/14 ,  H04L25/08 ,  H04L25/49 ,  G11B5/02

Abstract: Signals read back from a magnetic record medium have assigned sets of legal wavelengths, i.e., elapsed times between any successive two transitions. During readback, the zero crossover, hence the transition location, can be unintentionally phase shifted (as by base line changes) by the channel. The signal is detected and converted to a string of 1's and 0's, wherein the 1's represent detected transitions. A set of three such wavelengths is analyzed for illegal code values representing illegal wavelengths. The illegal code value is then converted to a legal code in accordance with the two adjacent code values in such set. In one embodiment, the illegal code value represented a wavelength that was too short. One of the transitions defining the illegal wavelength is shifted in time toward the longer of two other wavelengths immediately abutting the short illegal wavelength.

公开(公告)号：DE2427463A1

公开(公告)日：1975-01-23

申请号：DE2427463

申请日：1974-06-07

Applicant: IBM

Inventor： MARSHALL JOHN WILLIAM

IPC: G06F3/06 ,  G11B20/10 ,  G11B20/18 ,  H03M13/00 ,  H04L1/00 ,  H04L7/00 ,  G11B5/02

Abstract: Electrical signals recorded on a magnetic medium as magnetic indicia represent digital data. Digits of data are recorded as encoded pairs of indicia (couples) by corresponding pair of signals. Successive encoded indicia are recorded on the medium serially in sequence; for example, in stripes oriented diagonally across magnetic tape. During reading, defects in the medium, or errors in data transfer, resulting in a loss of synchronization between encoded indicia and the digit represented, are compensated for. Encoded indicia are continuously compared with a resynchronization pattern dispersed throughout recorded data at regular intervals. When an error is detected, the encoded indicia are decoded and stored in two buffers, each storing sets of digits decoded from differently chosen indicia pairs. The contents of one of these buffers is thereafter utilized when a resynchronization pattern identifies the correct set of digits.