JPH0973730A - Cd-rom decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the increase of the scale of the peripheral circuit of a CD-ROM decoder. SOLUTION: A CD-ROM decoder 16 is composed of a DSP interface circuit 16a, an error correction circuit 16b, a host interface circuit 16c and a reproducing circuit 16d and a control microcomputer 18 and a buffer RAM 17 are connected to the CD-ROM decoder 16. A DSP interface 13 fetches CD-ROM data or audio data and writes this data in the buffer RAM 17. When the CD-ROM data is fetched, after correction processing is performed for a code error in the error correction circuit 16b, this data is outputted from the host interface circuit 16c to a host computer and when the audio data is fetched, the data is continuously outputted from the reproducing circuit 16c to a reproducing device at a constant cycle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CD-ROM decoder which converts digital data read from a disk medium into a predetermined format and supplies it to a computer device or the like.

[0002]

2. Description of the Related Art In a CD player for reproducing a compact disc (CD), rotation control of the disc and control of a pickup position with respect to the disc are performed so that data recorded on the disc can be read at a constant speed. Be seen. Since these controls are performed mechanically and precisely, they are easily affected by vibrations, and even slight vibrations may shift the pickup position. When such a positional deviation occurs, the continuity of the data read from the disc is lost, and sound skipping occurs in the audio signal generated based on the data. Therefore, a CD player for a specific purpose, which is often subject to vibration, needs a so-called shock proof function that enables continuous data extraction even if the pickup position is displaced due to vibration.

FIG. 3 is a block diagram showing the structure of an audio CD player having a shockproof function. The CD pickup unit 1 receives the reflected light of the light applied to the disc 2, and extracts the intensity of the light as a change in voltage value. The pickup control unit 3 is the pickup unit 1.
Controls the pickup position of the CD pickup unit 1 with respect to the disc 2 so that the data stored in the disc 2 can be read in the correct order. The analog signal processing unit 4 reads the change in the voltage value taken out by the CD pickup unit 1, shapes the waveform, and performs EFM (Eight to Eight to
Fourteen Modulation) signal is generated. The digital signal processing unit 5 receives the EFM signal generated by the analog signal processing unit 4, and receives the EFM demodulation and CIRC (Cross-Interleave Recoding).
The audio data is generated by performing signal processing based on a predetermined CD format such as ed-Solomon code) decoding.
The shock proof control unit 6 receives the audio data generated by the digital signal processing unit 5, temporarily writes the audio data in the buffer RAM 7, then continuously reads out the audio data at a constant cycle, and outputs it to the circuit of the next stage. Supply. The audio data output from the shock proof control unit 6 is converted into an audio signal by a D / A conversion circuit and reproduced, for example. The control microcomputer 8 is composed of a one-chip microcomputer having a built-in memory, and controls the operation of each section according to the control program stored in the memory. At the same time, when it is detected that the pickup position of the CD pickup unit 1 is displaced, the pickup control unit 3 is instructed to return the pickup position to the position before the shift. As a result, the operations of the respective parts are synchronized with each other so that the shock proof function operates properly.

FIG. 4 is a block diagram showing the structure of the shock proof control unit 6. Shockproof control unit 6
Is composed of a DSP interface circuit 6a, a reproduction circuit 6b, and an address management circuit 6c. The DSP interface circuit 6a forms an interface with the digital signal processing unit 6 and sequentially takes in the audio data output from the digital signal processing unit 6 to form a buffer RAM.
Write to 7. The reproduction circuit 6b reads out and outputs the audio data stored in the buffer RAM 7 at a constant cycle. Then, the address management circuit 6c uses the buffer R
The amount of audio data stored in the buffer RAM 7 is maintained within a certain range by managing the write address and read address of the AM 7. That is, the buffer RA
When the M7 is full, the control microcomputer 8 is instructed to stop reading the data from the disk 2, and when the audio data stored in the buffer RAM 7 is less than a predetermined amount, the data is read. Is configured to give instructions to resume.

The speed at which the CD pickup unit 1 reads the data from the disc 2 depends on the reproduction circuit 6c being a buffer RAM.
It is set to several times the speed of reading audio data from 6. As a result, the data read from the disc 2 to the CD pickup unit 1 precedes the audio data output from the reproduction circuit 6c by the amount of data stored in the buffer RAM 6. Therefore, when the data read from the disc 2 becomes discontinuous due to the displacement of the CD pickup unit 1,
The reading operation of the CD pickup unit 1 is stopped, and the CD
Control is performed so that the pickup unit 1 is returned to the correct position. Meanwhile, the reproduction circuit 6c allows the buffer RAM
Since the audio data is continuously read from 7, the shock proof control unit 6 can output the audio data without interruption.

[0006]

By the way, in a CD-ROM system utilizing a CD as a read-only memory (ROM) for a computer, a C for audio is used.
There is an increasing demand for D to be reproducible. Also,
It has been considered to store digital data for a CD-ROM system and digital data for an audio in the same disc and read them while switching these data. Commonality with other players has become an issue.

In the case of a normal CD-ROM system, the compatibility of the CD player for audio from the reading of data to the processing of EFM demodulation and CIRC decoding is maintained in the CD-ROM system. Can be easily realized by adding a D / A conversion circuit or the like. However, when it is necessary to additionally provide the shock proof function as described above, it is necessary to significantly increase the circuit scale. Particularly, in the memory portion, several Mbits are required for the error correction portion and the shockproof function portion of the CD-ROM system, which is a factor of cost increase.

Therefore, an object of the present invention is to enable reproduction of an audio disc in a CD-ROM system without skipping sound while preventing an increase in circuit scale.

[0009]

The present invention has been made in order to solve the above-mentioned problems, and is characterized in that a code error included in digital data read from a disk medium is included in the data. In a CD-ROM decoder which performs the correction processing of the above and transfers it to the computer device side, an input interface circuit that takes in digital data read from a disk medium and sequentially writes the digital data in an attached memory circuit, and the digital written in the memory circuit. An error correction circuit that performs code error correction processing on data, an output interface circuit that reads the digital data from the memory circuit and transfers the digital data to the computer device in response to an instruction from the computer device side, and the memory circuit to the above Audio data by reading digital data at a fixed cycle When the digital data read from the disc medium is associated with audio information, the digital data written in the memory circuit from the input interface circuit is directly output to the audio. It is to read to the reproduction circuit.

According to the invention, audio data and a CD
-The ROM data and the ROM data are commonly taken into the input interface circuit and written in the memory circuit, and C is read from this memory circuit.
Since the D-ROM data is read by the output interface and the audio data is read by the reproducing circuit, the memory for storing the CD-ROM data for error correction and the memory for storing the audio data for shock proof control are commonly used. Will be available. Therefore, it is possible to prevent the circuit scale from increasing.

[0011]

FIG. 1 is a block diagram showing the configuration of a CD-ROM system employing a CD-ROM decoder according to the present invention. The CD pickup unit 11 controls the pickup position with respect to the disc 12 by the pickup control unit 13, receives reflected light from the disc 12, and extracts the intensity of the light as a change in voltage value. The analog signal processing unit 14 reads the change in the voltage value taken out from the CD pickup unit 11, and sets 1 to 588 bits.
An EFM signal to be a frame is generated. In this EFM signal, as shown in FIG. 2, 24 bits at the beginning of each frame are assigned to a synchronization signal, and then 14 bits are repeatedly assigned to data bits with a connection bit of 3 bits interposed therebetween. The digital signal processing unit 15 takes in the EFM signal generated by the analog signal processing unit 14 and outputs the EF.
M demodulation is performed to convert 14 bits into 8 bits as shown in FIG. During this EFM demodulation, 8-bit subcode data is extracted from the first data bit following the sync signal, and 3 bits are extracted from the remaining data bits.
2-byte symbol data is generated. In addition, 32
CIRC decoding is performed on the byte symbol data to generate CD-ROM data of 24 bytes per frame or audio data of 12 words per frame. Here, in the case of CD-ROM data (mode 1), as shown in FIG. 3, a total of 2352 bytes of 24 bytes × 98 frames are treated as one block, and a synchronization signal (12 bytes), a header (4 bytes), User data (2048 bytes), error detection code EDC (4 bits), and error correction code ECC (276 bytes) are assigned. Regarding this CD-ROM data, 2340 bytes excluding 12 bytes of the sync signal in one block of data are scrambled, and are descrambled at the time of reproduction to be returned to the original state.

The CD-ROM decoder 16 comprises a DSP interface circuit 16a, an error correction circuit 16b, a host interface circuit 16c and a reproduction circuit 16d. The DSP interface circuit 16a forms an interface with the digital signal processing section 15 and detects a synchronization signal of the fetched data to create a system clock for determining the operation timing of each section. Further, the data input from the digital signal processing unit 15 is C
In the case of D-ROM data, a descrambling process is performed to restore the original state, and then the CD-ROM decoder 16
Write to the buffer RAM 17 connected to. When the data input from the digital signal processing unit 15 is audio data, the buffer RAM 17 is used as it is.
Write in. The error correction circuit 16b takes in the CD-ROM data written in the buffer RAM 17 from the DSP interface circuit 16a for each block (98 frames), and detects the error detection code EDC and the error correction code EC.
The correction process based on C is performed, and the erroneous data among the data stored in the buffer RAM 17 is rewritten to the corrected correct data. This error correction circuit 1
The operation of 6b is stopped when the audio data is input from the digital signal processing unit 15. Then, the host interface circuit 16c buffers the CD-ROM data subjected to the error correction processing by the error correction circuit 16b in the buffer RA.
The command is read from M17 and output to the host computer, and various commands from the host computer are fetched and given to the control microcomputer 18. The reproduction circuit 16d continuously reads the audio data from the buffer RAM 17 at a constant cycle and outputs the audio data to the reproduction device side including the D / A converter.

The control microcomputer 18 sets the operation timing of each section according to a built-in processing program, and the disk 1
Control is performed so that the data read out from 2 is processed correctly in any case. The control microcomputer 18 has different CD-ROM decoders 16 for handling CD-ROM data and for handling audio data depending on the determination of the flag attached to the subcode data read by the digital signal processing unit 15. Let the process run. That is, from the digital signal processor 15 to the CD-ROM
When data is input, the DSP interface circuit 16a, the error correction circuit 16b, and the host interface circuit 16c are operated to sequentially write the input CD-ROM data in the buffer RAM 17, and to the CD-ROM data. After the code error is corrected, it is output to the host computer side. At this time, the control microcomputer 18 responds to the instruction from the host computer, which is fetched by the host interface circuit 16c,
CD-RO stored at a target position on the disk 12
The pickup controller 13 is instructed to selectively take out the M data. As a result, desired CD-ROM data is read from the disk 12, is subjected to the second code error correction processing by the CD-ROM decoder 16, and is transferred to the host computer. On the other hand, when audio data is input from the digital signal processor 15 to the CD-ROM decoder 16, the DSP interface circuit 16a and the reproduction circuit 16d are operated to sequentially write the audio data in the buffer RAM 17 and buffer the audio data. The data is read from the RAM 17 at a constant cycle and output. Here, the speed at which the CD pickup unit 11 reads data from the disc 12 depends on the reproduction circuit 1
6d is set to several times the speed at which audio data is read from the buffer RAM 17, and audio data written from the DSP interface circuit 16a to the buffer RAM 17 is reproduced from the buffer RAM 17 to the reproduction circuit 16.
The audio data read in d is preceded by the amount stored in the buffer RAM 17. At this time, the control microcomputer 18 uses the buffer RAM 1
By controlling the write address and the read address of 7, the amount of audio data stored in the buffer RAM 7 is maintained within a certain range, and when the data read by the CD pickup unit 11 becomes discontinuous, the read is temporarily performed. The pickup controller 13 so that the CD pickup 11 is returned to the correct position.
Give instructions to. As a result, the CD pickup unit 11
Even when the pickup position is shifted and the data read from the disk 12 becomes discontinuous, a shock proof function for continuously extracting audio data can be achieved.

Further, since the audio data can be expanded on the time axis by utilizing the shock proof function, the CD-ROM system in the double speed compatible CD-ROM system can be used.
It is possible to easily reproduce even a disc in which system digital data and audio digital data are mixed. Make the disc several times faster than standard speed (eg 8 times, 1
In the case of a CD-ROM system that supports double speed such as 8x speed or 12x speed, which is rotated at 2x speed, even if audio data is stored in the same disc, the audio data must be played at 8x speed or 12x speed. I can't. Therefore, it becomes necessary to switch the rotation speed of the disk,
Switching between the rotation speed of 8 times or more and the standard rotation speed increases the load on the spindle motor and the control of the servo system is likely to be unstable, so that it is difficult to actually operate. Therefore, it is necessary to switch the rotation speed between the reading of the digital data for the CD-ROM system and the reading of the digital data for the audio by using the time axis expansion processing achieved by the shock proof function using the buffer RAM 17. Disappear. Therefore, it is possible to continuously read the digital data for the CD-ROM system and the digital data for the audio while keeping the rotation speed of the disk at 8 times speed or 12 times speed.

According to the CD-ROM decoder 16 described above, the buffer R connected to the CD-ROM decoder 16 is
The AM 17 can be shared by the code error correction process and the shock proof control. And this CD-R
Since the OM decoder 16 does not simultaneously perform code error correction processing and shock proof control, it is not necessary to increase the memory capacity. For normal operation,
About 1 to 2 Mbits are required for code error correction processing,
Since the shock proof control requires about 2 to 4 Mbits, it is sufficient for the buffer RAM 17 to have a maximum of 4 Mbits.

[0016]

According to the present invention, the DSP interface circuit is made to correspond to both audio data and CD-ROM data, and the host interface circuit and the reproducing circuit are provided in parallel with the buffer RAM.
The buffer RAM connected to the OM decoder is a CD-RO.
It can be commonly used for the code error correction process for M data and the shock proof process for audio data. Therefore, it is possible to prevent an increase in the circuit scale of the peripheral circuit of the CD-ROM decoder having a shock proof function for reproducing the audio data, and to improve the CD-RO.
The cost increase of the M system can be suppressed.

Further, even when a disc in which digital data for a CD-ROM system and digital data for audio are mixed and stored is reproduced, it is not necessary to switch the rotation speed of the disc for reading both data. The load on the spindle motor that drives the disk to rotate can be reduced. Further, since the servo control of the spindle motor can be simplified, the effect of cost reduction is great.

[Brief description of drawings]

FIG. 1 shows a CD-ROM using the CD-ROM decoder of the present invention.
It is a block diagram showing a configuration of a ROM system.

FIG. 2 is a diagram showing a state of data read from a disk.

FIG. 3 is a diagram showing a format of CD-ROM data.

FIG. 4 is a block diagram showing a configuration of a conventional CD-ROM system.

FIG. 5 is a block diagram showing a configuration of a shock proof control unit.

[Explanation of symbols]

 1, 11 CD pickup unit 2, 12 Disc 3, 13 Pickup control unit 4, 14 Analog signal processing unit 5, 15 Digital signal processing unit 6 Shock proof control unit 7, 17 Buffer RAM 8, 18 Control microcomputer 6a, 16a DSP interface Circuits 6b and 16d Reproduction circuit 6c Address control circuit 16b Error correction circuit 16c Host interface circuit

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Claims (4)

[Claims] 1. A CD-ROM decoder that performs correction processing of code errors contained in data on digital data read from a disk medium and transfers the digital data to a computer device side. An input interface circuit for sequentially writing to the memory circuit, an error correction circuit for correcting code errors in the digital data written in the memory circuit, and the memory circuit from the memory circuit in response to an instruction from a computer device side. An output interface circuit for reading out the digital data and transferring it to a computer device, and an audio reproducing circuit for reading out the digital data from the memory circuit at a constant cycle and outputting it as audio data. Data is voice information A CD-ROM decoder characterized by directly reading the digital data written in the memory circuit from the input interface circuit and supplying the digital data to the audio reproducing circuit when the data is associated with the information. 2. When continuity is interrupted by digital data associated with audio information read from the disk medium and taken into the input interface circuit, the continuous digital data is received until the next reception. 2. The digital data stored in the memory circuit is continuously read to the audio reproduction circuit to maintain continuity of the audio data reproduced by the audio reproduction circuit.
The CD-ROM decoder described in. 3. The method according to claim 1, wherein one of the output interface circuit and the audio reproduction circuit is selectively operated, and the operation of the error correction circuit is stopped when the audio reproduction circuit is operating. CD-ROM decoder. 4. A CD-ROM decoder which performs a correction process of a code error included in data on digital data read from a disk medium and transfers the digital data to a computer device side. An input interface circuit for sequentially writing to the memory circuit, an error correction circuit for correcting code errors in the digital data written in the memory circuit, and the memory circuit from the memory circuit in response to an instruction from a computer device side. An output interface circuit for reading out the digital data and transferring it to a computer device, and an audio reproducing circuit for reading out the digital data from the memory circuit at a constant cycle and outputting it as audio data. Data is voice information The digital data written in the memory circuit from the input interface circuit is read out at a cycle longer than the cycle at the time of writing to extend the time axis and then supplied to the audio reproduction circuit. CD-ROM decoder characterized by: