Method of managing defect areas on an erasable optical disc...

Details Method of managing defect areas on an erasable optical disc... Method of managing defect areas on an erasable optical disc...

1999-11-04

2002-07-02

Tu, Christine T. (Department: 2133)

Error detection/correction and fault detection/recovery

Pulse or data error handling

Memory testing

C714S710000

Reexamination Certificate

active

06415400

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 88113559, filed Aug. 9, 1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to optical disc technology, and more particularly, to a method of managing defect areas on an erasable optical disc in a dynamic manner.
2. Description of Related Art
An erasable optical disc is a type of data storage medium where data can be repeatedly written and erased. On an erasable optical disc, however, some part of the storage space can be damaged due to various reasons, which is no longer usable for data storage. Conventionally, defect areas can be mended by using spare areas in the other part of the same optical disc. Methods for this purpose are customarily referred to as defect management.
There are two common causes for defect areas on an optical disc: surface defect, which is customarily referred to as the first-class defect; and excessive read/write defect, which is referred to as the second-class defect. The second-class defect is customarily defined in terms of logical block; i.e., for a logical block of 16 sectors, if any one of the 16 sectors is bad, the entire logical block is marked as a bad logical block and will not be thereafter used for data storage even though the other 15 sectors are still good.
FIG. 1
is a schematic diagram used to depict a conventional method for managing defect areas on an erasable optical disc
30
. As shown, this defect management method is performed by a file system
10
and an optical drive
20
. The file system
10
is a software driver running on a computer system (not shown) on which the optical drive
20
is installed. The optical drive
20
includes an optical head
22
, a microprocessor
24
, and an interface
26
. The optical drive
20
is coupled to the file system
10
via the interface
26
so that the optical drive
20
can be controlled by the file system
10
to perform read/write operations on the optical disc
30
. Data and commands from the file system
10
are processed by the microprocessor
24
for controlling the optical head
22
to perform specified read/write operations on the erasable optical disc
30
.
The storage space of the erasable optical disc
30
is organized into a system-dedicated read/write area
32
, a formatted area
34
, and a spare area
36
. During normal read/write operations, data are written into the formatted area
34
. However, when the formatted area
34
give rise to bad logical blocks
35
, good logical blocks in the spare area
36
are used to substitute these bad logical blocks
35
(these good logical block are hereinafter referred to as substitution logic blocks), and the addresses of the substitution logic block
37
are registered in the system-dedicated read/write area
32
. Both the system-dedicated read/write area
32
and the spare area
36
are reserved areas where the user is not allowed to change the data stored therein.
The procedure performed by the file system
10
and the optical drive
20
for managing the bad logical blocks on the erasable optical disc
30
includes the following steps.
(Step 1)
After the erasable optical disc
30
is inserted in position in the optical drive
20
, the microprocessor
24
first commands the optical head
22
to move to the system-dedicated read/write area
32
to read the addresses of the bad logical blocks
35
in the formatted area
34
and the addresses of their substitution logic blocks
37
in the spare area
36
. The micro-processor
24
then stores these address data in the internal registers thereof.
(Step 2)
During read/write operation, when the optical head
22
encounters a bad logical block in the formatted area
34
, it promptly informs the microprocessor
24
of this condition.
(Step 3)
In response, the microprocessor
24
checks whether the currently-encountered bad logical block is an old one or not, i.e., whether it was previously found and is already registered in the system-dedicated read/write area
32
, by checking whether it matches to any of the address data currently held in the internal register of the microprocessor
24
. If YES, the procedure jumps to the step (6); otherwise, if NOT, it indicates that this bad logical block is a newly produced one, and the microprocessor
24
sends a request signal via the interface
26
to the file system
10
.
(Step 4)
In response to this request, the file system
10
proposes a mending method for this newly-produced bad logical block, and then sends the mending method back via the interface
26
to the microprocessor
24
.
(Step 5)
In response, the microprocessor
24
first checks that if the spare area
36
still have sufficient storage space to substitute for this newly-produced bad logical block; and if YES, the microprocessor
24
selects a good logical block to serve as the substitution logic block
37
for the bad logical block, and then fetches the address of this substitution logic block
37
. The microprocessor
24
then commands the optical head
22
to write the address of the substitution logic block into the system-dedicated read/write area
32
. And then, the system
10
goes to Step 7.
(Step 6)
As the address of the substitution logic block
37
is set, the microprocessor
24
drives the optical head
22
to move from the currently-encountered defect area to the substitution logic block
37
in the spare area
36
, an d then write d at a into the substitution logic block.
(Step 7)
After the write operation is completed, the microprocessor
24
sends an OK signal via the interface
26
to th e file system
10
.
(Step 8)
In response, the file system
10
display a message to the user, telling that the write operation is completed. The user can then remove the optical disc
30
from the optical drive
20
. After the optical disc
30
is removed, the microprocessor
24
clears its internal register for those address of the substitution logic block
37
.
In the foregoing procedure, the communication between the file system
10
and the optical drive
20
requires a comprehensive set of commands and data signals for effective management of the defect areas on the optical disc
30
. The prior art, however, is considered insufficient in this respect.
Moreover, the spare area
36
in the optical disc
30
is fixed in size when being formatted. During read/write operation, when the optical drive
20
encounters a bad logical block, it will move to the spare area
36
and find a good logical block there to serve as a substitution for the currently-encountered bad logical block. This action is customarily referred to as linear replacement. In the prior art, the starting and ending addresses of the spare area
36
are all fixed and cannot be dynamically varied.
The fixed-size scheme for the spare area
36
, however, has the following draw-backs.
First, it would make the substitution logic block in the repair areas
37
separated far away from the corresponding bad logic block in the formatted area
34
, which would cause the optical head
22
to move a long distance from the bad logical block to the substitution logic block. As a result, the access time is increased.
Second, it is possible that the spare area
36
would give rise to bad logical blocks after the optical disc
30
has been repeatedly accessed for many times. Should this be the case, there would be no substitution logical blocks available to serve as substitutions for these newly-produced bad logical blocks in the spare area
36
; and therefore, the spare area
36
may eventually become insufficient to serve its purpose. When this happens, the optical disc
30
would be no longer capable of mending any bad logical blocks in the formatted area
34
. The prior art thus can only provide a limited period of service for the management of defect areas on the optical disc
30
.
SUMMARY OF THE INVENTION
It is at least an objective of this invention to provide a method of managing defect areas on an erasable optical disc. The method can dynamically assign and find out a supplementary sp

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