EP0127311A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

Method of and controller for handling medium defects in a disc drive system

Assignee: EMC Corp

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Filing: 1984-04-24

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Granted: —

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Expires: 2004-04-24

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Abstract

Abstract A remapping technique for handling medium defects in a disc drive system is disclosed. Each surface on each disc is divided into a number of tracks with the corresponding tracks on all discs defining a cylinder Each surface is further divided into a plurality of sectors. Each sector in each cylinder not having a defect is assigned a logical address in a predetermined order such that, as the discs rotate and as the head address increments within a cylinder, each succeeding defect-free sector within that cylinder has a logical address which is related by a predetermined algorithm to the logical address of the preceding defect-free sector. Defective sectors are labelled with an appropriate unique pattern in their headers so that they can be identified and distinguished from logical address numbers. A predetermined number of sectors at the end of each cylinder are allocated as spares, the number of spares being at least as large as the number of potentially defective sectors in a cylinder and the number of spares to which logical addresses are assigned being equal to the number of non-spare sectors which are defective. In using the technique, each defect-free sector in a cylinder is located and assigned its logical address. In transferring information, the header address of a sector in a cylinder held in a data buffer (29) is compared (33) with the logical address expected at that logical in a register (31). tfthe addresses match the data at that sector is transferred by sequencing logic (35). If the addresses do not match the header address at the next physical sector is compared with the expected address. The procedure is repeated until the address at a physical sector match with the logical expected address. However, if the sequence of mis- matches exceeds a predetermined number, counted in a counter (45), the sequencing operation is terminated and an error signal generated by a detector (47). The technique eliminates moving the heads radially inward or radially outward to spare tracks allocated for data belonging in defective sectors as in most prior art systems.

Inventors

👤 Stephen A. Caldara

Bibliographic Details

Application Number —

Jurisdiction EP

Data Source google_patents

Last Synchronized 2026-10-28 04:09

CPC Classifications

G; G11; G11B; G11B20/00; G11B20/10; G11B20/18; G11B20/1883; G11B2220/00; G11B2220/20

Claims Analysis

Total Claims: 7

Claim 1

Independent Claim 120 words

A method of handling medium defects in a disc drive system of the type wherein data is recorded in sectors arranged in a plurality of cylinders each comprising one or more tracks on one or more disc surfaces, and wherein physically consecutive sectors have logical addresses related in accordance with a predetermined algorithm, characterised in that spare sectors are provided at the end of each cylinder, the logical addresses are assigned to defect-free sectors, skipping defective sectors so that each defect-free sector has its logical address determined in accordance with the said algorithm from the logical address of the immediately preceding defect free sector, and data read and write operations are conducted using only the sectors with the logical addresses.

Claim 2

Independent Claim 120 words

Claim 3

Independent Claim 65 words

A method according to claim I, characterised in that the logical addresses are recorded in the defect-free sectors, the expected next logical address is computed from the current logical address, compared with the logical address read from the next sector until a match occurs, and so on iteratively, and data read and write operations are conducted in accordance with the logical addresses when matches occur.

Claim 4

Dependent Claim 33 words

A method according to claim 2, characterised in that the number of mis-matches is counted for each expected logical address and an error is signalled if the counted number reaches a predetermined value.

Claim 5

Dependent Claim 22 words

A method according to claim 1, 2 or 3, characterised in that the predetermined algorithm consists in incrementing logical addresses by one.

Claim 6

Dependent Claim 126 words

A disc controller for implementing a method according to claim 1 and comprising a buffer (29) for receiving data read from a disc, including a disc sector logical address, characterised by a register (31) for an expected next logical address, a next address generator (39) for generating the new expected next logical address from the current expected next logical address, in accordance with the predetermined algorithm, a comparator (33) for comparing the logical addresses in the buffer (29) and the register (31), and sequencing logic (35) controlling read and write operations in accordance with the logical addresses when the comparator (33) signals a match, the sequencing means allowing the next address generator (39) to operate each time a match occurs but not when a mismatch occurs.

Claim 7

Dependent Claim 36 words

A disc controller according to claim 5, characterised by means (45) for counting mismatches and means (47) which signal an error if the count of mismatches on any expected next logical address reaches a predetermined value.

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