Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1997-08-06
2001-04-10
Yoo, Do Hyun (Department: 2759)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S209000, C710S056000
Reexamination Certificate
active
06216201
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a data processing apparatus of a compact digital disk drive in which digital data is read from or written to a compact digital disk on a sector-unit basis, the digital data being temporarily stored in a buffer memory. The data processing apparatus of the present invention is applicable to various types of compact digital disk drives such as CD-ROM (compact disk-read only memory) disk drive, CD-R (compact disk-recordable) disk drive and CD-RW (compact disk-rewritable) disk drive.
(2) Description of the Related Art
FIG. 1
shows a compact disk drive in which a data processing apparatus is included. In the compact disk drive of
FIG. 1
, not only a decoding process which reads data from a compact disk (CD)
10
and produces a sequence of serial digital data from the read data, but also an encoding process which performs an encoding of data output from a host computer and produces a sequence of serial digital data to be written to the CD
10
is performed.
As shown in
FIG. 1
, the compact disk drive includes a reading unit
11
which reads out data from the CD
10
and outputs an analog signal indicating the read data. A CD decoding unit
13
performs the EFM (eight-to-fourteen modulation) demodulation of the signal from the reading unit
11
so that a sequence of serial digital data is produced from the read data. A data processing unit
15
performs the data processing of the sequence of serial digital data from the CD decoding unit
13
and outputs the processed data. The processed data from the data processing unit
15
is transferred to a host computer
19
via an external interface such as a SCSI interface or an ATAPI interface. The processed data from the data processing unit
15
is temporarily stored in a buffer memory
17
such as a RAM (random access memory).
Further, in the compact disk drive of
FIG. 1
, the data processing unit
15
performs the data processing of data output from the host computer
19
via the external interface. For example, the data processing is performed to carry out an encoding of the data from the host computer
19
. The data to be processed by the data processing unit
15
is temporarily stored in the buffer memory
17
. A CD encoding unit
14
performs the encoding of the data output by the host computer
19
through the data processing unit
15
, performs the EFM modulation of the coded data, and outputs a sequence of the modulated signal. A writing unit
12
writes the modulated signal at the output of the CD encoding unit
14
to the CD
10
.
FIG. 2
shows a flow of data processing which is performed by the compact disk drive during the decoding process.
In
FIG. 2
, a decimal number in parentheses attached to a name of each field denotes the number of bytes indicating the length of data included in the field.
The compact disk drive performs the reading of data from the CD
10
on a frame-unit basis. In
FIG. 2
, (a) shows a format of one frame of record data obtained after the EFM demodulation of the read data from the CD
10
. As shown, the frame
21
contains a subcode (1 byte), a first main data (12 bytes) followed by parity bits (4 bytes), and a second main data (12 bytes) followed by parity bits (4 bytes). The main data includes digital stereophonic musical signals. The subcode includes time signal bits and pause signal bits. The parity bits are used for an error correction decoding.
In
FIG. 2
, (b) shows a subcode
22
(1 byte) and a main data
23
(24 bytes) which are included within one frame (or the frame
21
). The main data
23
is obtained after the error correction decoding is performed with the parity bits and the first main data and the second main data are combined.
The subcodes which are collected from 98 frames and have 96 bytes of data form a part of one subcode frame. The sequence of the main data which are collected from 98 frames and include 98 main data items, each having 2352 bytes of data, constitute one main data block. In
FIG. 2
, (c) shows a format of one block of the record data including a subcode block
24
and a main data block
25
. As shown, the subcode block
24
includes a sync pattern (2 bytes) and a subcode (96 bytes). The sync pattern is used for detecting the starting point of the subcode block in the record data. The main data block
25
includes 2353 bytes of the main data
23
from the 98 frames.
There are two major formats of record data obtained by reading of the compact digital disks: the CD-DA format and the CD-ROM format. The CD-DA format is used for the reproducing and recording of musical signals. The CD-ROM format is used for the reproducing and recording of digital data signals. A determination as to whether the read data is in the CD-DA format or in the CD-ROM format is made by referencing a specific control bit included in the subcode.
In a case in which the read data is in the CD-DA format (or the musical signals), the CD decoding unit
13
produces the sequence of digital data in the format indicated by (c) in FIG.
2
. On the other hand, in a case in which the read data is in the CD-ROM format (or the digital data signals), a higher level of reliability of the reproduced data is required. In the latter case, the data processing unit
15
performs error correction decoding of the digital data at the output of the CD decoding unit
13
for this purpose. In the case of the CD-ROM format, one block of the record data is treated as one sector.
In
FIG. 2
, (d) shows a mode-1 CD-ROM format of one sector (or one block) of the record data produced by the data processing unit
15
. As shown, the main data block
27
of the CD-ROM format contains a sync pattern (12 bytes), a header (4 bytes), a user data (2048 bytes), an error detection code (EDC) (4 bytes), a set of zero bits (8 bytes), and an error correction code (ECC) (276 bytes).
In
FIG. 2
, (e) shows a user data
29
which is obtained from the main data block
27
at the output of the data processing unit
15
and sent to the host computer
19
. As described above, the read data at the output of the reading unit
11
is supplied to the CD decoding unit
13
. The CD decoding unit
13
performs the data processing in accordance with the flow indicated by (a) through (c) in FIG.
2
. After this, the data processing unit
15
performs the data processing in accordance with the format indicated by (d) in FIG.
2
. The user data at the output of the data processing unit
15
is sent to the host computer
19
via the external interface as indicated by (e) in FIG.
2
. In the data processing unit
15
, the correlation between the memory areas of the buffer memory
17
and the various fields of the record data including the user data, the subcodes and the error codes is defined, and management of the record data using the correlation is carried out.
FIG. 3
shows a method of management of record data in buffer memory areas used by a conventional data processing apparatus. As shown in
FIG. 3
, in the conventional data processing apparatus, the memory areas of the buffer memory are divided into a user data area, an error code area and a subcode area. In the user data area, “n” data items including the user data#1 through the user data#n are sequentially arranged. In the error code area, “n” data items including the error code#1 through the error code#n are sequentially arranged. In the subcode area, “n” data items including the subcode#1 through the subcode#n are sequentially arranged.
In the method of data management of
FIG. 3
, the address (or the memory location) of the buffer memory
17
for the data item to be processed by the conventional data processing apparatus must be computed from the base address (or the starting address) of the related memory area and the offset of the data item in the related memory area in the respective steps of the data processing during the reading of data from the disk or during the writing of data to the disk. That is, it is necessary that both the starting address and the offset be set in a r
Ado Keitaro
Moriwaki Isamu
Cooper & Dunham LLP
Portka Gary J.
Ricoh & Company, Ltd.
Yoo Do Hyun
LandOfFree
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