Electrical computers and digital data processing systems: input/ – Input/output data processing – Input/output data buffering
Reexamination Certificate
2000-05-11
2004-08-10
Gaffin, Jeffrey (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Input/output data buffering
C710S004000, C710S020000, C710S021000, C710S033000, C710S048000, C710S052000, C710S053000, C710S260000
Reexamination Certificate
active
06775721
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to optical media, and more particularly to the reading of data from an optical media.
BACKGROUND OF THE INVENTION
Data retrieved from an optical media, such as a Compact Disc-Writable (CD-W) or a Compact Disc-Rewritable (CD-RW), need to be decoded by a controller of the optical drive before the data may be used. In the CD decoding process, every 2352 bytes of the data stream is defined as a sector.
FIG. 1A
illustrates a conventional structure of the sectors from a data stream. The sectors include data sectors
102
which contain the actual data. Preceding the data sectors
102
are four Read In (RI) sectors
104
. Following the data sectors
102
are two Read Out (RO) sectors
106
and a link block
108
. The RI and RO sectors
104
-
106
are formed by the power up and power down time, respectively, required by the laser in writing the data sectors
102
. The link block
108
is a gap between RO
2
of the last data sector
102
and RI
1
of the next data sector. Thus, separating each group of data sectors
104
are seven link sectors, comprising the RO sectors
106
, the link block
108
, and the RI sectors
104
.
FIG. 1B
illustrates the conventional structure of each sector in a data stream. Each sector contains a sync field
110
, a header field
112
, and a data field
114
. The sync field
110
is a fixed twelve byte pattern used to separate the sectors and which can be detected by a Sector Sync Detector of the decoder to maintain synchronization with the beginning of the each sector. The header field
112
specifies the sector address
116
and the sector mode
118
. The sector mode
118
has a 3-bit sub-field which indicates the block type. There are eight different types of sectors for CD-R or CD-RW media, as set forth in Table 1 below. Only the Data Block sectors are part of the actual data sectors
102
. The rest of the seven types are referred to as link sectors
104
-
108
which indicate the logical gap between the actual data sectors
102
.
TABLE 1
Block Indicator
000
Data Block
001
Fourth Run-in Block (RI4)
010
Third Run-in Block (RI3)
011
Second Run-in Block (RI2)
100
First Run-in Block (RI1)
101
Link Block
110
Second Run-out Block (RO2)
111
First Run-out Block (RO1)
When reading CD-R or CD-RW media, the sector address
116
for a data sector
102
is always incremental from the previous data sector. However, for the link sectors
104
-
108
, the sector address
116
can be in either incremental or freeze mode across the link sectors
104
-
108
.
FIG. 2
illustrates sector addresses for the incremental and freeze modes. The first line
202
indicates the sector type. The second line
204
indicates each sector's address in the incremental mode. The third line
206
indicates each sector's address in the freeze mode. The mode is set at the time the sectors are written onto the media. These addresses are used by the decoder to locate the data sector requested by the system. The decoder has a register in which it maintains the next expected sector address, based upon the mode. If the expected sector address does not match the actual sector address, then the integrity of the data is questionable. Appropriate action may then be taken. The structure of the sectors in the data stream illustrated in
FIGS. 1A
,
1
B, and
2
is standard in the industry.
Conventionally, the decoder buffers the data sectors
102
and the link sectors
104
-
108
and passes them to a host computer without differentiating between the data sectors
102
and the link sectors
104
-
108
. A software on the host computer is then responsible for detecting and handling the link sectors
104
-
108
and obtaining the data from the data sectors
102
. The host has a choice to either discard the link sectors
104
-
108
or extract some information from them. When the software finds the link sector, it must stop buffering and reread the media to look for and confirm the location of the next data sector. This rereading is very costly in time. Thus, the conventional software approach is inefficient.
Accordingly, there exists a need for an improved method and system for link sector detection and handling for optical media. The method and system should be more efficient than the conventional software approach. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention provides an improved method and system for link detection and handling. The method includes detecting one of the plurality of link sectors; generating an interrupt signal; determining a buffer method selection; buffering the plurality of data sectors only, if a link skip buffer method is selected; and buffering the plurality of data sectors and the plurality of link sectors, except for a link block, and allocating a sector in a buffer for the link block, if a link buffer method is selected. The present invention provides a hardware approach to link sector detection and handling. Instead of passing the data to a system software prior to link sector detection, the method and system in accordance with the present invention performs the link sector detection in the controller hardware. When the controller detects the link sectors, it automatically either skips or buffers the link sectors depending upon the configuration of the controller. By performing the link sector detection in hardware, significant processing time is saved.
REFERENCES:
patent: 5528570 (1996-06-01), Kondo
patent: 5946447 (1999-08-01), Nakagawa et al.
patent: 5960452 (1999-09-01), Chi
patent: 6141772 (2000-10-01), Hashimoto
Farooq Mohammad O.
Gaffin Jeffrey
Promos Technologies Inc.
Sawyer Law Group LLP
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