GB2315359A

GB2315359A - Track seeking apparatus

Info

Publication number: GB2315359A
Application number: GB9714915A
Authority: GB
Inventors: Seong-Ro Ko
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1996-07-16
Filing date: 1997-07-16
Publication date: 1998-01-28
Anticipated expiration: 2017-07-16
Also published as: CN1110815C; KR980011330A; CN1175770A; DE19730528C2; GB9714915D0; GB2315359B; DE19730528A1; JPH1069706A; KR100238068B1

Abstract

A real-time track seek apparatus and a method therefor are provided by directly gaining access to tracks without passing through a peripheral microcomputer or an interface apparatus when track information is reproduced. The real-time track seek apparatus includes a track information reader and control unit having a track number register, a comparator, a start mark signal detector 22, an ID register, a counter, a cyclic redundancy check code checker. The track information reader and control unit 27 compares the current track number with the target track number to determine a movement direction and the number of tracks and to accordingly make a pickup device move. Here, if a start mark and an ID mark are recognized from reproduced data, the track information reader and control unit 27 reads a track number following the recognized result and judges whether the read result is accurate. If the track number is accurate, the current track number is compared with the target track number to judge whether both are identical to each other. Accordingly, the pickup device is made to continuously move or stop, which provides an effect of reducing a track seek time and stand-by time.

Description

1 -1 2315359 REAL-TIME TRACK SEEK APPARATUS AND METHOD THEREFOR The

present invention relates to a real-time seek apparatus and a method therefor, which can reduce a seek time taken f or a head to move to a designated track by directly gaining access to tracks without using a peripheral microcomputer or an interface apparatus when track information recorded on a disk is reproduced in a recording and reproducing system.

A general data recording and reproducing system records information on a recording medium such as a disk and reproduces recorded information from a recording medium, in which a track number recorded on a rotating disk is read out to make a pickup apparatus move to a desired track. Thus, a high speed information storage device or a high speed image reproduction system requires a technology of reducing a time needed for movement of a pickup device, reproduction of the track information and a track search.

Figure 1 is a flow-chart diagram showing a method for moving a pickup device to a target track in a general disk recording and reproducing apparatus. When inf ormation recorded on a disk starts being reproduced, a signal detector receives the reproduced data and detects a mark signal necessary for various types of reproduction. The mark signal is demodulated by a data demodulator circuit and then is input to a microcomputer, which identifies a current position using a track number contained in the demodulated mark signal (step S11). Then, the microcomputer checks how many tracks are moved up to a target track on the basis of the current track position and outputs a control command (first seek command) signal to a servo system (step S12).

Then, a servo system performs a focusing servo operation and a tracking servo operation to make a pickup device move to a target track position. A microcomputer analyzes a signal output f rom the data demodulator circuit and judges whether a track where the pickup device is located is a desired target track (step S13). In the result of judgement, if the track is not a target track, the microcomputer outputs a modified seek command signal to the servo system in order to move the pickup device again by a difference between the current track and the target track (step S12). The steps S12 and S13 are repeated until the pickup device reaches the target track. If the seek track is judged as the target track, an information reproduction operation is resumed, to output a second seek command signal for confirming that the pickup device is moved as desired to the servo system (step S14).

Thereafter, the microcomputer reads a track number with respect to the track position detected from the output data of the data demodulator circuit (step S15), and judges whether a current track where the pickup device is located is a desired target track (step S16). In the result of judgement, if the track is not the target track, the microcomputer supplies a modified seek command signal to the servo system in order to move the pickup device again by a difference between the current track and the target track (step S14). A track number is read out again (step S15) in which the steps S14, S15 and S16 will repeat until the pickup device reaches the target track. If the seek track is determined as the target track, the microcomputer stands by a next command (step S17).

As described above, in the conventional prior art, a f irst seek command is supplied to the servo system to make the pickup device move by a distance to be moved, and then a second seek command is given to confirm whether a pickup device is accurately moved. Here, a series of operations for reading track -information are performed by an interface controller connecting a host computer and a disk recording and reproducing apparatus, or a microcomputer.

However, such a conventional prior art should use peripheral control units such as an interface controller and a microcomputer to seek a target track, consequently, an unnecessary long time is required. Also, since the apparatus should operate perfectly in order to reproduce information accurately, the above procedures are repeated several times until the pickup device reaches the target track if the pickup device has not been located in the target track according to the first seek command. That is, a repetition operation is performed as necessary in order to conf irm if the pickup device is moved to the desired track accurately. In the case where a seek operation is performed several times after the primary track seek has failed, it causes a problem that a stand- by time of the pickup device is longer than a moving time thereof.

With a view to reduce or to solve the above problems, it is an aim of embodiments of the present invention to provide a real-time track seek method, which can reduce a track seek time by directly gaining access to tracks without using a peripheral microcomputer or an interface apparatus when track information recorded on a disk is reproduced.

It is another aim of embodiments of the present invention to provide a real-time track seek apparatus adopting the above method.

According to a f ir,st aspect of the present invention, there is provided a real-time track seek method for performing a track seek operation on a disk in real-time using a pick-up device f or use in a disk recording and reproducing apparatus, the real-time track seek method comprising the steps of: (a) comparing a current track number with a target track number and then determining a movement direction and the number of tracks, to accordingly make the pickup device move; (b) reading a following track number if a start mark and an ID mark are recognized from the reproduced data to judge whether the track number is accurate; and (c) comparing the current track number with the target track number if the track number is accurate in order to judge whether the current track matches the target track, and making the pickup device continuously move or stop according to the comparison result.

Preferably, said step (a) comprises the sub-steps of:

(al) setting the input target track number in a register if the target track is designated; (a2) detecting a mark signal from the reproduced signal to confirm the current track number; (a3) comparing the current track number with the target track number to determine a movement direction; (a4) making the pickup device move according to the determined direction while standing by to detect a start mark signal.

Preferably, said step (b) comprises the sub-steps of:

(bl) starting a count operation if the start mark pattern has been recognized while standing by to detect an ID mark signal; (b2) stopping the counting operation if no ID mark signal is recognized within a predetermined time and then continuously making the pickup device move; (b3) reading a track number following the ID mark if an ID mark is recognized within the predetermined time; and (b4) judging whether the read track number is accurate.

Preferably, said step (c) comprises the sub-steps of:

(cl) comparing the current track number with the target track number if the track number is accurate, to judge whether the seek track is the target track; (c2) when the state is 11011 in the result of comparison, judging that the current track number is identical to the target track number to accordingly make the pickup device stop and stand by for a next command; (c3) when the state is 11111 or 11-111 as a result of comparision, judging that the current track passes over the or does not reach the target track, to thereby stop 6 counting and to thereby make the pickup device move continuously according to the determined direction and the difference between the current track and the target track.

There is also provided, according to a second aspect of the present invention, a real-time track seek apparatus for performing a track seek operation of a disk in real time using a pickup device, for use in a disk recording/reproducing apparatus, the real-time track seek apparatus comprising: reproducing means for reproducing a signal read out by the pickup device; a start mark signal detector for detecting a start mark signal indicating a start of a sector or a frame from the reproduced data and outputting the detected result; a mark detection and control unit for detecting ID mark and ID data from the reproduced data and outputting a desired target track number and controlling said start mark signal detector and said reproducing means; a servo system for driving the pickup device; a track information read and control unit for determining a movement direction and the number of tracks to be moved with respect to the pickup device, using the ID data detected by said mark detection and control unit and said desired target track number, and for controlling said servo system according to the movement direction and the number of tracks to be moved.

Preferably, said track information read and control unit comprises:

a track number register for storing a desired target track number output from said mark detection and control unit; a comparator for comparing the current track number contained in ID data detected by said mark detection and 7 control unit with the target track number stored in the track number register to determine a movement direction of the pickup device and the number of tracks to be moved thereof:

a start mark detector for comparing the start mark signal detected by said star mark signal detector with a predetermined start mark pattern in order to recognize a start mark; an ID register f or storing an ID mark detected by said mark detection and control unit; a counter for starting counting at the same time of detection of the start mark by said start mark detector and being reset by an ID mark stored in said ID register; and a cyclic redundancy check code checker for reading ID data following the ID mark from said mark detection and control unit and judging whether the read track number is correct.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:

Figure I is a flow-chart diagram showing a general method for moving a pickup device to a target track in a general disk recording and reproducing apparatus; 8 Figure 2 is a block diagram showing the structure of a real time track seek apparatus according to an embodiment of the present invention; Figure 3 is a flow-chart diagram showing a real-time track seek method according to embodiments of the present invention; and Figure 4 is a flow-chart diagram for explaining a real-time track seek method in more detail according to embodiments of the present invention, which is performed in the track information read and control unit.

A preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings Figures 2 through 4.

Figure 2 shows the structure of a real-time track seek apparatus including a reproduction system and a servo system according to an embodiment of the present invention. In Figure 2, a pickup device (not shown) which reads out a signal recorded on a disk is connected to the input end of an automatic gain control and low-pass filtering (AGC & LPF) unit 21. The AGC & LPF unit 21 maintains a constant output with respect to a variation of level of the read signal and allows only a low-band component of the read signal to pass to enhance the quality of the read signal.

The read signal output from the AGC & LPF unit 21 is input to a start mark signal detector 22 and an analog-to digital converter (ADC) 23, respectively. The start mark signal detector 22 detects a start mark signal indicating a start of a unit of the received signal, that is, a sector or a frame, to output the detected start mark signal to a mark detection and control unit 26. The ADC 23 converts the received signal from AGC & LPF unit 21 into a digital signal to output the digital signal to a phase locked loop circuit (PLL) 24.

The PLL 24 outputs the received digital signal in synchronization with a base clock signal of the Figure 2 apparatus. A demodulator 25 receives the digital signal output from the PLL 24, and converts the received digital signal into an original signal before modulation. The mark detection and control unit 26 connected to the output end of the demodulator 25 detects a mark signal containing identification (ID) marks and ID data from the modulated data, based on the start mark signal output from the start mark signal detector 22. The mark detection and control unit 26 outputs control signals to the AGC & LPF unit 21, the start mark signal detector 22, the ADC 23, the PLL 24, the demodulator 25, to control the operation of each blocks.

A track information read and control unit 27 which is one of main characteristics of the present invention is connected to the output end of the mark detection and control unit 26. The track information read and control unit 27 reads out ID data representing track information such as a track number, a sector number, a cyclic redundancy check code from the mark detection and control unit 26, without passing through a microcomputer. The track information read and control unit 27 is connected to a servo system 28 to thereby exchange information with each other. The track information read and control unit 27 transfers a seek command signal to the servo system 28, while the servo system 28 transfers a servo operation completion signal to the track information read and control unit 27. Also, the servo system 28 drives a focusing servo and a tracking servo according to the determined movement direction and the number of tracks to be moved thereto, to make the pickup device move to a target track.

The track information read and control unit 27 includes a track number register for storing and outputting information with respect to a track to be moved thereto. A comparator connected to the output end of the track number register compares a current track number received from the mark detection and control unit 26 and the target track number output from the track number register to determine a movement direction and the number of tracks of the pickup device to be moved, and judges whether the current track number equals to the target track number. Also, the track information read and control unit 27 includes a start mark detector for detecting a start mark, an ID register for storing an ID mark, and a counter connected to the start mark detector and the ID register. Count operation of the counter is started when detecting a start mark by the start mark detector and is reset by an ID mark received from the ID register. A cyclic redundancy check (CRC) code checker which reads ID data following an ID mark and judges whether the read track number is accurate, is connected to the output end of the ID register.

The operation of the real-time track seek apparatus having the above constitution is described with reference to Figures 3 and 4.

Referring to Figure 3, when a reproduction operation of information recorded on a disk is started, the mark detection and control unit 26 detects a mark signal from the reproduced signal to check a current track position (step S31). Then, the mark detection and control unit 26 supplies a desired target track number to the track information read and control unit 27 to designate a target track (step S32). The track information read and control unit 27 judges whether a current track on which the pickup device is positioned is a target track (step S33). If the current track is not the target track, the track information read and control unit 27 determines a movement direction and the number of tracks to be moved thereto based on the figure 4 flow-chart to be described later (step S34 and S35). Accordingly, the servo system 28 is controlled to make the pickup device move to a seek track position. Thereafter, the track information read and control unit 27 judges again whether a current track on which the pickup device is positioned is the target track (step S33). If the current track is not the target track, the track information read and control unit 27 controls the servo system 28 to move the pickup device again by a difference between the current track and the target track.

As a result, if the seek track is judged as the target track, the track information read and control unit 27 stands by for receiving a next command (step S36).

Figure 4 is a flow-chart diagram for explaining a real-time track seek method in more detail. The track information read and control unit 27 reads a mark signal from the mark detection and control unit 26 when a target track number is input from the mark detection and control unit 26, to confirm a current track number via the cyclic redundancy check code checker (step S42). Thereafter, the track information read and control unit 27 sets a target track number to be scanned in a register (step S43), and compares the current rack number with the target track number in a comparator to determine a movement direction.

If the movement direction is determined, thetrack information read and control unit 27 turns on a tracking loop and a focusing loop of the servo system 28 (step S44), to then make the pickup device move and stand by a start mark signal (step S46). In step S46, if a start mark signal is applied from the start mark signal detector 22, the mark detection and control unit 26 outputs control signals to the start mark signal detector 22, the PLL 24, and the demodulator 25 to control the operation of each block (step S47). If the start mark detector in the track information read and control unit 27 recognizes a start mark by comparision of a predetermined start mark pattern and the start mark signal received via the mark detection and control unit 26 from the start mark signal detector 22, the counter starts counting from the point in time thereof (step S48). In step S49, if a correct ID mark is detected in the ID register at the time when the ID mark is detected, the counter is reset and the comparator reads a track number contained in ID data following the ID mark (step S50). The counter is reset if no ID mark is recognized within a predetermined time (step S51). Then, the track information read and control unit 27 returns to the step S46 to stand by continuously until a start mark signal will be detected.

Meanwhile, the cyclic redundancy check code checker judges whether the current track number is correct. If the track number is correct, the comparator compares the current track number with the target track number contained in the track number register and judges whether the resultant state is 11111, "Off or 11-111 (step S52). In the result of comparision, when the state is 11011, the track information read and control unit 27 determines that the current track number is identical to the target track number to accordingly make the pickup device stop. Also, the track information read and control unit 27 turns on a tracking loop of the servo system 28 at the present position of the pickup device, to thereby maintain the location of the pickup device in the current track via a one-step jump operation of the tracking loop, and stands 5 by a next command (step S53).

In step S52, if the state is 11111 as a result of comparison, it is judged that the current track passes over the target track. If the state is 11-111 as a result of comparison, it is judged that the current track does not reach the target track. on the basis of the comparison result of the comparator, the track information read and control unit 27 determines a movement direction of the pickup device (step S54), resets the counter (step S55), and returns to the step S45, to thereby make the pickup device move continuously according to the determined movement direction. Such procedures are repeated on a one-sector or one-frame basis.

It is possible that when a distance to be moved is far or very near, an additional counter is used so that separate divided operations are applied for a -first seek (coarse movement) and a second seek (fine movement).

As described above, embodiments of the present invention aim to reduce a track seek time by directly gaining access to tracks without passing through a peripheral microcomputer or an interface apparatus when track information recorded on a disk is reproduced, to provide simplification of the system. Also, a processing time is reduced as much as an interfacing time, to shorten a stand-by time inevitably occurring in a high-speed data recording and reproducing system.

- 14 While only certain embodiments of the invention have been specifically described herein, it will be apparent that numerous modifications may be made thereto without departing from the scope of the invention.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstractand drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

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Claims

1. A real-time track seek apparatus for performing a track seek operation of a disk in real-time using a pickup device, for use in a disk recording/ reproducing apparatus, the real-time track seek apparatus comprising:

reproducing means for reproducing a signal read out by the pickup device; a start mark signal detector for detecting a start mark signal indicating a start of a sector or a frame from the reproduced data and outputting the detected result; a mark detection and control unit for detecting ID mark and ID data from the reproduced data and outputting a desired target track number and controlling said start mark signal detector and said reproducing means; servo system for driving the pickup device; and track information read and control unit for determining a movement direction and the number of tracks to be moved with respect to the pickup device using the ID data detected by said mark detection and control unit sand said desired target track number, and for controlling said servo system according to the movement direction and the number of tracks to be moved.

2. The real-time track seek apparatus according to claim 1, wherein said track information read and control unit comprises:

a track number register for storing a desired target track number output from said mark detection and control unit; a comparator for comparing the current track number contained in ID data detected by said mark detection and control unit with the target track number stored in the track number register to determine a movement direction of the pickup device and the number of tracks to be moved thereof; a start mark detector for comparing the start mark signal detected by said start mark signal detector with a predetermined start mark pattern in order to recognize a start mark; an ID register f or storing an ID mark detected by said mark detection and control unit; a counter for starting counting at the same time of detection of the start mark by said start mark detector and being reset by an ID mark stored in said ID register; and a cyclic redundancy check code checker f or reading ID data following the ID mark from said mark detection and control unit and judging whether the read track number is correct.

3. A real-time track seek method for performing a track seek operation on a disk in real-time using a pick-up device, for use in a disk recording and reproducing apparatus, the real-time track seek method comprising the steps of:

(a) comparing a current track number with a target track number and then determining a movement direction and the number of tracks, to accordingly make the pickup device move; 17 - (b) reading a following track number if a start mark and an ID mark are recognized from the reproduced data to judge whether the track number is accurate; and (c) comparing the current track number with the target track number if the track number is accurate in order to judge whether the current track matches the target track, and making the pickup device continuously move or stop according to the comparision result.

4. The real-time track seek method according to claim 3, wherein said step (a) comprises the sub-steps of:

5. The real-time track seek method according to claim 3, or 4, wherein said step (b) comprises the sub-steps of:

(bl) starting a count operation if the start mark pattern has been recognized while standing by to detect an ID mark signal; - 18 (b2) stopping the counting operation if no ID mark signal is recognized within a predetermined time and then continuously making the pickup device move; (b3) reading a track number following the ID mark if an ID mark is recognized within the predetermined time; and (b4) judging whether the read track number is accurate.

6. The real-time track seek method according to claim 3, 4 or 5, wherein said step (c) comprises the sub-steps of:

(cl) comparing the current track number with the target track number if the track number is accurate, to judge whether the seek track is the target track; (c2) when the state is 11011 in the result of comparison, judging that the current track number is identical to the target track number to accordingly make the pickup device stop and stand by for a next command; (c3) when the state is I'll' or 11-111 as a result of comparision, judging that the current track passes over or does not reach the target track, to thereby stop counting and to thereby make the pickup device move continuously according to the determined direction and the difference between the current track and the target track.

7. A real time track seek apparatus substantially as herein described with reference to Figures 2 to 4.

8. A real time track seek method substantially as herein described with reference to Figures 2 to 4.