JP3515446B2 - Digital data buffering method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of buffering digital data, which is temporarily held in a buffer memory when processing digital data in sector units.

[0002]

2. Description of the Related Art In a drive system such as a CD-ROM system in which digital data recorded on a recording medium is loaded into a computer device, a decoding process for correcting a code error contained in the handled digital data is performed. . Since this decoding process is performed for each sector having a predetermined number of bytes, it is configured to perform so-called buffering in which digital data is stored in the memory in units of sectors.

FIG. 5 shows a drive system C, which is one of the drive systems.
It is a block diagram which shows the structure of a D-ROM system.

The disk 1 stores digital data in a predetermined format along a spirally drawn recording track, and is rotationally driven so as to keep a linear velocity or an angular velocity constant. The pickup unit 2 irradiates the disk 1 that is rotationally driven with a laser beam, and reads the digital data stored in the disk 1 based on the change in the state of the reflected light. The analog signal processing unit 3 responds to the output of the pickup unit 2 and generates an EFM signal representing the digital data recorded on the disc 1. This EFM
The signal consists of data that originally consists of 8 bits, but the EFM (E
ig ht to Fourteen Modulation), as shown in Fig. 6, the 24 bits at the beginning of each frame are assigned to the sync signal, and then 14 bits are converted into data bits by sandwiching 3 connection bits. It is repeatedly assigned.

The digital signal processing section 4 subjects the EFM signal input from the analog signal processing section 3 to EFM demodulation to convert 14-bit data into 8-bit data, as shown in FIG. During this EFM demodulation, one byte of subcode data is extracted from the first data bit following the sync signal, and 3 bytes are extracted from the remaining data bits.
2-byte symbol data is generated. Further, the digital signal processing unit 4 performs CIRC decoding on the 32-byte symbol data to generate CD-ROM data in which one frame has 24 bytes.

As shown in FIG. 7, in CD-ROM data, a total of 2352 bytes of 24 bytes × 98 frames are treated as one sector, and a sync signal (12 bytes) and a header (4 bytes) are provided at the start of each sector. Are assigned respectively. The sync signal indicates the head position of the sector, and is attached to the beginning of each sector as a fixed pattern. The 4-byte header is further assigned with absolute time information (minute / second / frame number: 1 byte each) corresponding to the address on the disc and a mode identification code (1 byte) for identifying the format of the data in the sector. Has been. And in 2336 bytes following the header,
User data, error correction code (ECC), error detection code (EDC), etc. are assigned according to the mode and form. For example, as shown in FIG. 8, in the case of mode 1,
User data (2048 bytes), EDC (4 bytes), zero (8 bytes) and ECC (276 bytes) are allocated. Further, in the case of mode 2, in form 1, the subheader (8 bytes) and the user data (2048
Byte), EDC (4 bytes) and ECC (276 bytes) are allocated, and in Form 2, the sub-header (8
Bytes), user data (2324 bytes) and EDC
(4 bytes) is allocated.

The CD-ROM decoder 5 receives the CD-ROM data input from the digital signal processing section 4 from
The code error correction process is performed again, and the CD-ROM data is transferred to the host computer in response to a request from the host computer. The buffer RAM 6 is a CD-ROM
It is connected to the decoder 5, and the digital signal processing circuit 4 to C
The CD-ROM data taken into the D-ROM decoder 5 is stored for a predetermined period. That is, since the ECC and EDC attached to the CD-ROM data are usually set for each sector, the buffer RAM 6 stores at least one sector of CD-ROM data and sequentially stores the CD-RO data.
It is configured to be read by the M decoder 5. Also,
The buffer RAM 6 stores a suitable number of sectors of CD-ROM data which has been subjected to predetermined processing by the CD-ROM decoder 5 in preparation for transfer to the host computer.

The control microcomputer 7 has an analog signal processing section 3 and a digital signal processing section 4 according to a predetermined operation program.
The CD-ROM decoder 5 and the CD-ROM decoder 5 are controlled so that the respective units can execute the respective processes at correct timings. In addition, the control microcomputer 7
CD-R that is configured to control the operation of each part in response to a request from the host computer
Transfer the OM data to the host computer side.

In the above CD-ROM system,
The header information is taken into the control microcomputer 7 for each sector. Then, the control microcomputer 7 is configured to recognize the format of each sector of the CD-ROM data based on the fetched header information and control the operation of the CD-ROM decoder 5 according to the result.

[0010]

When transferring CD-ROM data to the host computer side, it is necessary to recognize the format of the sector to be transferred. That is, C
As shown in FIG. 8, in the D-ROM data, the position of the user data in the sector differs depending on the mode. Therefore, the format of each sector is recognized, the user data is read out accurately and transferred to the host computer side. I am trying to do it.

In addition, it is necessary to recognize the format of the sector in which the code error correction processing and the detection processing for the CD-ROM data are performed. That is, CD-
If the ROM data has both ECC and EDC as in mode 1, and E as in form 2 in mode 2,
It is necessary to switch the processing for the code error between the case where only DC is provided.

The format of each sector is a CD-ROM
The mode identification code included in the header of the data or, in the case of mode 2, the sub-header is read and the contents of each are discriminated and recognized. Such determination operation is usually
Since it is executed under the control of the control microcomputer 7 that controls the operation of the CD-ROM decoder 5, it puts a burden on the control microcomputer 7. In particular, when the operation speed becomes high, it becomes necessary to process all the various control operations at high speed. When the load on the control microcomputer 7 increases, the control operation of the control microcomputer 7 may not be able to follow the processing operation of each part. .

Therefore, an object of the present invention is to reduce the load on the control microcomputer so that it can cope with high-speed operation.

[0014]

The present invention has been made to solve the above-mentioned problems, and is characterized in that digital data forming a sector for every predetermined number of bytes is stored in a buffer memory. In a buffering method for temporarily storing digital data, a first address area corresponding to N (N is an integer of 2 or more) sectors of the digital data is secured at a storage address of a buffer memory, and A second address area for N bytes is secured separately from the first address area, the sequentially input digital data is stored in the first address area in sector units, and the format of each sector of the digital data is also stored. Is to sequentially store sector information, which is represented by 1 byte or less, in the second address area.

According to the present invention, by storing sector information together with digital data in the buffer memory,
The format of digital data for each sector can be easily identified by reading the corresponding sector information. At this time, since it is not necessary to recognize the format of each sector from the header information included in the digital data, the load on the microcomputer is reduced by the amount of the determination operation.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining a digital data buffering method according to the present invention.
It is a schematic diagram which shows the allocation state of the address inside.

The buffer RAM for buffering CD-ROM data as digital data has a capacity capable of storing several sectors of CD-ROM data in preparation for data transfer to the host computer side. C
Since the D-ROM data is usually processed in units of 1 sector (2352 bytes), the first address area for N sectors is secured in units of 2352 bytes in the buffer memory. At the same time, a second address area for N bytes is secured so that sector information for N sectors can be stored. This second address area is
However, it is easier to manage the addresses if they are continuously provided in the first address area as shown in FIG.

In the first address area, the CD-ROM data is stored sector by sector from the first sector to the Nth sector. At the same time, N bytes of sector information from the first sector to the Nth sector are stored in the second address area in a one-to-one correspondence with the CD-ROM data. Normally, as shown in FIG. 2, the sector information is given as 3-bit binary data, and therefore, a fixed value of 5 bits is added to the 3-bit data and written in the second address area in 1-byte units. Note that the 5 bits given as a fixed value can also be used to store information other than sector information.

As described above, since the first address area and the second address area are provided in parallel in the buffer RAM, the CD-R of the specific sector from the first address area is provided.
At the same time as reading the OM data, it becomes possible to read the sector information indicating the format of the sector from the second address area. This sector information is stored in the buffer RA
It is used for address control when reading CD-ROM data from M and transferring it to the host computer side.
It can be used for switching control of correction processing and detection processing of code errors included in ROM data. Further, when the host computer side specifies the format of the CD-ROM data, it is determined whether the specified format matches the format of the CD-ROM data of the sector to be transferred based on the sector information. It is also possible to judge.

FIG. 3 is a flow chart for explaining the sector information determination operation. This sector information is confirmed on the CD
A reading unit for reading the header and sub-header of the ROM data is provided, and the reading is performed based on the contents read by this reading unit.

In step S1, the header of the head position of the CD-ROM data is read, and in the following step S2,
The mode identification code of the header is determined. In this judgment, the 1-byte mode identification code is "00h".
If (h: hexadecimal display), the sector information is "000b".
(B: binary display), and if "01h", sector information is confirmed as "010b". If the sector information is "000b", the mode is 0, and if it is "010b", the mode is 1. If the mode identification code is “02h”, the process proceeds to step 3. If the mode identification code is not "00h", "01h", or "02h", the sector type data is "111b".
Confirm as.

In step 3, the subheader following the header is read. In the following step S4, the read 8-byte sub-header is converted into the first 4 bytes and the second 4
It is divided into bytes and compared with each other, and it is determined whether or not they match. That is, since the same data of 4 bytes is repeated twice in the sub-header, it can be detected as a sub-header by detecting the match between them. If the subheader match is not confirmed in step S4, the sector information is confirmed as "011b". In this case, even mode 2 is formless without a subheader. Then, if the subheaders match, the process proceeds to step S5, and the form is determined. The specific bit of the sub-header is determined. If the specific bit is "0b", the sector information is determined as "100b". If the specific bit is "1b", the sector information is "10b".
1b ”. If the sector information is “100b”, it is form 1 of mode 1, and if it is “101b”, it is form 2 of mode 2.

By the above determination operation, as shown in FIG. 4, sector information given by 3-bit binary data is generated, and in the second address area secured in the buffer memory together with the first address area, It is written at the same time as the CD-ROM data.

FIG. 4 is a block diagram showing the structure of a CD-ROM decoder which realizes the digital data buffering method of the present invention. This CD-ROM decoder
This is equivalent to the CD-ROM decoder 5 shown in FIG. 5, and as shown in FIG. 1, a buffer RAM in which first and second address areas are secured in the storage area is connected.

The descramble circuit 11 descrambles 2340 bytes of the CD-ROM data input every 2352 bytes (1 sector) excluding the 12-byte sync signal, and restores it to a predetermined format. The output data. The write register 12 takes in the CD-ROM data output from the descramble circuit 11, and writes the data in the first address area of the buffer RAM through the first data bus 18 in units of one sector.

The header information register 13 takes in a 4-byte header from the data output from the descramble circuit 11, and stores the header information in the second data bus 19.
To the control microcomputer. Furthermore, the header information register 13 regards the 8-byte data following the header as a subheader and fetches it, and supplies the header and the subheader (including the regarded one) together to the sector information conversion circuit 14. The sector information conversion circuit 14 generates 3-bit sector information according to the flowchart shown in FIG. The sector information write register 15 includes a sector information conversion circuit 14
The sector information input from the buffer RAM is fetched, and the sector information is transferred to the second of the buffer RAM through the first data bus 18.
Write to the address area of.

The write address generation circuit 16 includes a buffer R
An address for sequentially designating an area for one sector (2352 bytes) in the first address area secured in the AM is generated, and a write address of the CD-ROM data held in the write register 12 is designated. Of the write addresses, the address corresponding to the head data of each sector is taken into the address register 21 described later through the first data bus 18. At the same time, the write address generation circuit 16 generates an address designating an area of 1 byte in the second address area secured in the buffer RAM, and the sector information write register 15 holds the sector information. Specify the write address. This write address is also fetched in the address register 21 in the same manner as the head address corresponding to the CD-ROM data.

The error correction detection circuit 17 reads the CD-ROM data written in the buffer RAM from the write register 12 on a sector-by-sector basis, and performs code error correction processing and detection processing based on ECC and EDC. Incidentally, C
If the D-ROM data is form 2 of mode 2,
Since ECC is not set, only code error detection processing based on EDC is performed. This error correction detection circuit 20
The code error correction / detection operation in (1) is switched based on the sector information by reading the sector information together with the CD-ROM data from the buffer RAM. Here, the CD-ROM data which has been subjected to the predetermined processing is held in the buffer RAM again in preparation for the transfer to the host computer.

The read address generating circuit 20 responds to the instructions of the sector information judging circuit 24 and the command judging circuit 26, which will be described later, with addresses for sequentially designating the first address area and the second address area in the buffer RAM. The generated CD-ROM data and sector information stored in the buffer RAM are read. The address register 21 fetches and holds the write address corresponding to the head data of each sector and the write address corresponding to the sector information among the addresses generated by the write address generation circuit 16. That is, in the buffer RAM, as shown in FIG. 1, N-sectors of CD-ROM data are stored in the first address area, and the address at which the head data of each sector is stored is N sectors. Only stored in the address register 21. Then, N pieces of sector information corresponding to the CD-ROM data of N sectors are stored in the second address area, and the storage address of each sector information is stored in the address register 21. Address counter 2
2 repeats the count operation every time the address generation circuit 19 updates the address, and supplies the count value to the command determination circuit 26 described later. The address counter 22 operates while the address generation circuit 19 supplies the read address to the buffer RAM, and counts the number of sectors of the data read from the buffer RAM.

The sector information read register 23 temporarily holds the sector information read from the buffer RAM.
The sector information determination circuit 24 uses the sector information read register 2
The format of the CD-ROM data of the sector corresponding to the sector information is recognized based on the sector information stored in 3. Then, the sector information determination circuit 24 sets the offset of the address generation circuit 19 when transferring data to the host computer according to the format of the CD-ROM data. That is, the CD-ROM data stored in the buffer RAM transfers the user data excluding the header and sub-header to the host computer side. Therefore, the header and sub-header addresses are used as offsets to match the format of each sector. Add to the address of.

The command register 25 temporarily holds a command such as a transfer instruction sent from the host computer. The command determination circuit 26 gives an operation instruction to the address generation circuit 19 and the sector information read register 21 according to the outputs of the address register 21 and the address counter 22 and the command stored in the command register 25. That is, when the host computer requests transfer of a specific sector, the command judgment circuit 26 judges whether or not the requested sector is stored in the buffer RAM. Then, when the target sector is stored in the buffer RAM, first, the sector information corresponding to the target sector is read into the sector information read register 23, and the format of the target sector is determined based on the sector information. Then, according to the format determination result, the address generating circuit 19 is activated so as to add the offset to the start address, and the user data of the target sector is read. For example, when the target sector is in mode 1, the user data of the target sector is read from the position where 12 bytes of the synchronization signal and 4 bytes of the header are added to the start address stored in the address register 21. To be done. When the reading of the user data is started, the address counter 22 starts the counting operation,
The number of bytes of user data read from the buffer RAM is counted. Then, when the number of bytes of the read user data reaches the number of bytes instructed by the host computer, the command determination circuit 26 gives a stop instruction to the address generation circuit 19. As a result, the data stored in the buffer RAM is automatically transferred to the host computer without the control of the control microcomputer.

If the CD-ROM data of the target sector is not stored in the buffer RAM, the command determination circuit 26 reads new CD-ROM data to the control microcomputer through the second data bus 18. Send instructions. As a result, the control microcomputer activates the pickup and operates each unit so as to read the CD-ROM data including the target sector. And the buffer RAM
After the target sector is stored therein, the above-mentioned automatic transfer operation is performed.

The transfer buffer 27 includes the address generation circuit 1
The user data read according to the address generated by 9 is fetched through the first data bus 17 and transferred to the host computer.

The sync signal detection circuit 28 detects a 12-byte sync signal added to the start of each sector of the input data, and a timing signal indicating the start of the sector of the input CD-ROM data will be described later. It is given to the timing generation circuit 29. When the sync signal cannot be detected, the sync signal detection circuit 28 transfers data indicating a detection error from the second data bus 19 to the control microcomputer 7.
The timing generation circuit 28 generates various timing clocks based on the timing signal output from the synchronization signal detection circuit 28. These timing clocks are
It is supplied to each part together with the control microcomputer and determines the operation timing of each part.

In the above CD-ROM decoder,
Sector information indicating the format of the CD-ROM data for each sector is stored in the buffer RA together with the CD-ROM data.
It can be stored in M. And the buffer RAM
The sector information stored in can be used for controlling the operation of the error correction detecting circuit 17 and controlling the transfer of user data to the host computer side.

[0036]

According to the present invention, the area for storing sector information indicating the format of each sector is secured in the buffer RAM, so that the format of each sector can be recognized by referring to the storage content of the buffer RAM. You can At this time, since it is not necessary to determine the sector format based on the header information and the like, the control microcomputer is not burdened and high-speed operation can be supported.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing address assignment of a buffer memory corresponding to a digital data buffering method of the present invention.

FIG. 2 is a diagram showing correspondence between a sector format and sector information.

FIG. 3 is a flowchart illustrating a sector type determination operation.

FIG. 4 is a block diagram showing a configuration of a CD-ROM decoder corresponding to the digital data buffering method of the present invention.

FIG. 5 is a block diagram showing a configuration of a CD-ROM system.

FIG. 6 is a diagram showing a format of CD-ROM data for one frame.

FIG. 7 is a diagram showing a structure of a header of CD-ROM data.

FIG. 8 is a diagram showing a format of CD-ROM data for one sector.

[Explanation of symbols]

1 compact disc 2 Pickup part 3 Analog signal processor 4 Digital signal processor 5 CD-ROM decoder 6 buffer RAM 7 Control microcomputer 11 descramble circuit 12 Write information register 13 Header information register 14 Sector type conversion circuit 15 Sector type register 16 Write address generation circuit 17 Error correction detection circuit 18 First data bus 19 Second data bus 20 Read address generation circuit 21 Address counter 22 Address register 23 Sector information read register 24 Sector information judgment circuit 25 Command register 26 Command decision circuit 27 transfer buffer 28 Sync signal detection circuit 29 Timing generation circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-309106 (JP, A) JP-A-8-161819 (JP, A) JP-A-8-17147 (JP, A) JP-A-10- 55613 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 20/10 G06F 3/06 G11B 20/12

Claims (3)

(57) [Claims] 1. A digital data buffering method for temporarily storing, in a buffer memory, digital data forming a sector for each predetermined number of bytes, wherein N (N is 2) of the digital data is stored in a storage address of the buffer memory. A first address area corresponding to the above (integer) sectors is secured, and N separate from the first address area.
A second address area for bytes is secured, the sequentially input digital data is stored in the first address area in sector units, and the format of each sector of the digital data is represented by 1 byte or less. Are sequentially stored in the second address area, and a digital data buffering method is provided. 2. The method of buffering digital data according to claim 1, wherein the sector information is generated based on specific information included in the digital data when the digital data is input. . 3. The digital data buffering method according to claim 2, wherein the first address area and the second address area are secured at consecutive addresses.