RECORDED DATA REPRODUCING APPARATUS

Abstract: A recorded data reproducing apparatus according to this invention comprises a data pulse generation section (l0 to l5), a peak detection section (l7 to l9) and a control section (20 to 22). The data pulse generation section (l0 to l5) reads out data written on the cylinder of a recording medium on which a magnetic head is currently positioned. According to received gain data, the data pulse generation section (l0 to l5) amplifies a signal corresponding to the readout data, and selectively generates data pulse sequence based on the amplified signal. When the amplified signal corresponds to servo data, the peak detection section (l7 to l9) detects the peak value of the amplified signal. The control section (20 to 22) determines whether or not the magnitude of the detected peak value is nearly equal to a predetermined value. If the determination is nega­ tive, the control section (20 to 22) refers to a gain data table to determine a change amount of the gain data, and supplies the gain data updated based on the change amount to the data pulse generation section (l0 to l5).

Description: This invention relates to a recorded data reproducing apparatus, which can accurately read data from any track or cylinder of a recording medium, based on servo data recorded on the medium as defined in the preamble of claim 1, and to a corresponding method. Because of the necessity for accurately positioning a read head on a target track, a recorded data reproducing apparatus needs to ensure that a signal corresponding to servo data is at a constant level. Conventional recorded data reproducing apparatuses have an AGC amplifier which amplifies a signal read by the read head and has a gain data input terminal. The gain of the AGC amplifier is varied in accordance with gain data supplied to the gain data input terminal. This gain data is generated by an AGC generator based on the output of a differential circuit provided at the succeeding stage of the AGC amplifier. The AGC generator is constituted by complex circuits, such as a rectifier/smoothing circuit for averaging the output of the differential circuit, an amplifier and a level shifter. Therefore, complicated adjustment of the AGC generator is required in the manufacturing process. This increases the manufacturing cost of a recorded data reproducing apparatus. EP-A-0097208 discloses an apparatus and method as defined in the preamble of claims 1 and 9. It discloses a head positioning system using servosectors comprising a gain reference field and position reference fields. A store is used for storing predictive gain correction values depending on selected cylinder and selected head. US-A-3691543 discloses the use of peak detectors for gain control. Accordingly, it is the object of this invention to provide a recorded data reproducing apparatus which has a simple configuration and can obtain data pulse sequence with a desired accuracy and at high speed. The recorded data reproducing apparatus according to this invention as defined in appended claim 1 comprises: data pulse generator means (10 to 15) for sequentially reading out data written on a cylinder of a recording medium on which a head is currently positioned, for amplifying a signal corresponding to the readout data in accordance with gain data supplied thereto, and for selectively generating the data pulse sequence in accordance with the amplified signal; peak detection means (17 to 19) for selectively detecting peak values of the amplified signal; and control means (20, 22), wherein: a cylinder-dependent gain table (21-2) stores cylinder-dependent gain data with respect to a cylinder position on which a head currently positions; and said control means (20, 22) refers to said cylinder-dependent gain table (21-2) to determine the cylinder-dependent gain data and supplies the cylinder-dependent gain data as gain data currently designated to said data pulse generator means (10 to 15), characterized in that: a to-be-changed amount table (21-1) stores a change amount of the gain data with respect to a sum of the peak values; and said control means (20, 22) comprises a data processing unit for controlling operation of the apparatus including data read/write operation, and refers to said to-be-changed amount table (21-1) in accordance with the sum of the peak values detected by said peak detection means (17 to 19) to determine the change amount of the gain data, only when the sum of the peak values does not fall within a predetermined error range with respect to a predetermined value, and designates the gain updated by the determined change amount. The corresponding method according to this invention as defined in claim 9 comprises: referring to a cylinder-dependent gain table (21-2) to designate gain data with respect to a cylinder position of a recording medium on which a head is currently positioned; sequentially reading out data written on the cylinder position on which the head is currently positioned; amplifying a signal corresponding to the readout data in accordance with the gain data currently designated; selectively generating a data pulse sequence in accordance with the amplified signal; selectively detecting peak values of the amplified signal; referring to a to-be-changed amount table (21-1) in accordance with a sum of the detected peak values to determine a change amount of the gain data, only when the sum of the peak values does not fall within a predetermined error range with respect to a predetermined value; and designating the gain data updated by the determined change amount. As explained above, according to this invention, the gain of the AGC amplifier can be adjusted to a proper value necessary for positioning a magnetic head, without using a complicated AGC generator. With this gain adjustment, the AGC amplifier can have a simple configuration and accurate head positioning can always be ensured. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. l is a block diagram of a recorded data reproducing apparatus according to an embodiment of this invention; Fig. 2 is a diagram for explaining the relationship between a magnetic head and servo data; Figs. 3A through 3M are diagrams showing the waveforms of amplified signals corresponding to the servo data located at the positions shown in Fig. 2; and Fig. 4 is a flowchart for explaining the operation of the recorded data reproducing apparatus of this invention. A recorded data reproducing apparatus according to an embodiment of this invention will now be explained in detail with reference to the accompanying drawings. Servo data is recorded in advance on a recording medium, e.g., a disk. As shown in Fig. 2, different servo data patterns indicated by "A" and "B" in Fig. 2 extend on the opposite sides from the center of a track or a cylinder. When a magnetic head l0 relatively moves on the cylinder (actually, the disk rotates with magnetic head l0 fixed), patterns A and B are alternately read by magnetic head l0. Consequently, signals corresponding to those patterns A and B alternately appear. As the disk rotates, the speed of the servo data with respect to the magnetic head varies between an inner cylinder and an outer cylinder. Even if the same servo data is recorded on the inner and outer cylinders, therefore, there would be a difference in a peak intensity of signals picked up from these cylinders by magnetic head l0. This would cause various inconveniences; mainly, it is difficult to provide accurate head positioning. Therefore, it is necessary to attain approximately constant peak output, irrespective of the position of a target cylinder on the disk. Magnetic head l0 reads out data, which has been recorded in advance on the disk so as to sequentially appear as the disk rotates. A signal corresponding to the read data is supplied to an amplifier ll for amplification. The signal amplified by amplifier ll is supplied to a low-pass filter (LPF) l2, which filters out its low-frequency noise. The filtered signal is then supplied to an AGC amplifier l3, which is also supplied with gain data from a CPU 20 through D/A converter 22, in accordance with the position of a presently designated cylinder. AGC amplifier l3 changes its gain in accordance with the received gain data, amplifies the signal from low-pass filter l2, and supplies the amplified signal to differential circuit (DIF) l4 as well as to peak hold circuit (P/H) l8. When the data readout by magnetic head l0 is not servo data but recorded data, differential circuit l4 differentiates the signal from AGC amplifier l3 to detect the zero crossing point of the received signal. The output of differential circuit l4 is supplied to a pulser l5 where a data pulse is created based on the detected zero crossing point. Amplifier ll, low-pass filter l2, AGC amplifier l3, differential circuit l4 and pulser l5 constitute a data pulse generation section. Peak hold circuit l8 receives a timing pulse from timing pulse generator l7 in addition to the output of AGC amplifier l3. Peak hold circuit l8 holds the peak value of the amplified signal from AGC amplifier l3 in response to the timing pulse. At this time, when the data readout by magnetic head l0 is servo data, a timing pulse for holding the peak value of the amplified signal corresponding to the servo data is supplied to peak hold circuit l8 from timing pulse generator l7. An A/D converter l9 converts the peak value held by peak hold circuit l8 into digital data and outputs it to CPU 20. As mentioned earlier, the digital data corresponding to patterns A and B are sequentially supplied to CPU 20. Timing pulse generator l7, peak hold circuit l8 and A/D converter l9 constitute a servo data peak hold section. CPU 20 determines cylinder-dependent gain data for the position of the presently designated cylinder and outputs the gain data to AGC amplifier l3 through D/A converter 22. In addition, CPU 20 receives and holds digital data from A/D converter l9, e.g., a peak value A′ corresponding to pattern A. CPU 20 then receives and holds a peak value B′ that corresponds to pattern B following pattern A, and adds those peak values A′ and B′ Based on the added result A′+B′, CPU 20 refers to a to-be-changed amount table 2l-l of a gain data table 2l to attain the amount of a change that should be made to the gain data. In addition to the to-be-changed amount table 2l-l, in which the amount of change in gain data for head-positioning with respect to the summed result from CPU 20 is registered in advance, gain data table 2l includes cylinder-dependent table 2l-2, which stores cylinder-dependent gain data for the cylinder position presently stored in a cylinder data storage region (not shown). The optimal gain data for the cylinder on which magnetic head l0 presently lies is attained from the amount of change in gain data change and the cylinder-dependent gain data. Thus attained gain data is supplied to D/A converter 22 for analog conversion and is then supplied to AGC amplifier l3. The sum of the peak values of digital data corresponding to servo data patterns A and B is maintained approximately at a predetermined value by repeating the aforementioned operational sequence through the closed loop which is formed by the aforementioned peak hold circuit l8, A/D converter l9, CPU 20, D/A converter 22 and AGC amplifier l3. When the sum A′+B′ of the peak values is nearly constant, CPU 20 calculates the difference A′-B′ between the peak values and outputs data corresponding to this difference to D/A converter 23. D/A converter 23 converts the received difference data into analog data and outputs it to driver 24. Based on the received analog data, driver 24 drives magnetic head l0 to position it at the proper cylinder location. Referring now to Fig. 4, the operation of this embodiment will be explained. At a starting step (Sl2), a disk drive is powered on and the initializing procedures, such as detection of the position of the zero cylinder, are carried out. In subsequent step Sl4, the recorded data reproducing apparatus is ready for receiving any command. The type of an input command is determined in steps Sl6 and Sl8. In step Sl6, it is determined whether or not the input command is a seek command, and if YES, the flow advances to step S30 where cylinder data specified by the seek command is stored in the cylinder data storage region. If NO in step Sl6, the flow advances to step Sl8 where this time, it is determined whether or not the input command is a write command. If the decision is affirmative in step Sl8, the flow advances to step S34, and if it is negative, the input command is determined to be a read command and the flow advances to step S20. Figs. 3A-3M illustrate the waveforms of the outputs from AGC amplifier l3 respectively for the positions Hl to Hl3 (see Fig. 2) of magnetic head l0. For example, the input command is a seek command to move magnetic head l0 to cylinder or track 2 from cylinder or track l as shown in Fig. 2, the cylinder position specified by the seek command is stored in the cylinder data storage region in step S30. In the subsequent step S32, magnetic head l0 is moved to the designated cylinder position. When the input command is a write command, other processings are carried out in step S34. When it is a read command that has been input, the cylinder position at which magnetic head l0 is presently located is read out from the cylinder data storage region in step S20. Based on the readout cylinder position, cylinder-dependent table 2l-2 is referred to, thus providing cylinder-dependent gain data. This cylinder-dependent gain data is supplied through D/A converter 22 to AGC amplifier l3. In the subsequent step S22, it is determined whether or not the sum of two peak values A′ and B′ supplied through A/D converter l9 from peak hold circuit l8 is within a predetermined allowable error range ε from a predetermined value C. If the decision is negative in step S22, step S24 is executed so that gain data to be output to AGC amplifier l3 is changed. More specifically, based on the sum of peak values A′ and B′, gain data table 2l is referred to for determination of the to-be-changed amount of gain data, and this to-be-changed amount of gain data is coupled to the cylinder gain data. The resultant gain data is then supplied again to AGC amplifier l3 to optimize the gain thereof. Thereafter, step S22 is repeated, and if the decision is affirmative in this step, the subsequent step S26 is executed. In step S26, it is checked if two peak values A′ and B′ are nearly equal to each other. If the determination in step S26 is negative, the flow advances to step S27. For instance, when magnetic head l0 is positioned at Hl2 in Fig. 2, peak value A′ does not equal to peak value B′ as shown in Fig. 3B. This is a natural consequence because the major portion of the detection region of magnetic head l0 with respect to the recording medium is on the side of pattern A. To cope with this peak imbalance, magnetic head l0 needs to be moved to the rightward in Fig. 2. For this purpose, CPU 20 calculates the difference between peak values A′ and B′, or A′-B′, and outputs the calculation result to D/A converter 23. D/A converter 23 converts the received digital value into an analog value and then supplies it to driver 24. Based on the analog value (representing the calculation result from CPU 20), driver 24 moves magnetic head l0 to the proper position Hl3 in Fig. 2. The waveform of the resultant signal would have a nearly equal peak value for patterns A and B as shown in Fig. 3A. Thereafter, step S26 is executed again. In the subsequent step S28, recorded data following the servo data is read out from the cylinder on which magnetic head l0 is presently positioned. The output of AGC amplifier l3 is supplied to differential circuit l4 and then to pulser l5 where a data pulse is produced. As has been described in detail, according to this invention, accurate head positioning can be carried out with a simple circuit arrangement, which is very effective in increasing the cylinder density. In the aforementioned embodiment, the cylinder-dependent gain data is output first, when a read command is entered after magnetic head l0 is shifted by a seek command. This operation may be modified such that the gain data determined by the previous read command is stored and this stored gain data is output first when the next read command is entered. This modification can eliminate the need to use the cylinder-dependent table.

Claims: A recorded data reproducing apparatus having a simple configuration and being capable of obtaining data pulse sequence with a desired accuracy and at high speed, said recorded data reproducing apparatus comprising: data pulse generator means (10 to 15) for sequentially reading out data written on a cylinder of a recording medium on which a head is currently positioned, for amplifying a signal corresponding to the readout data in accordance with gain data supplied thereto, and for selectively generating the data pulse sequence in accordance with the amplified signal; peak detection means (17 to 19) for selectively detecting peak values of the amplified signal; and control means (20, 22), wherein: a cylinder-dependent gain table (21-2) stores cylinder-dependent gain data with respect to a cylinder position on which a head currently positions; and said control means (20, 22) refers to said cylinder-dependent gain table (21-2) to determine the cylinder-dependent gain data and supplies the cylinder-dependent gain data as gain data currently designated to said data pulse generator means (10 to 15), characterized in that: a to-be-changed amount table (21-1) stores a change amount of the gain data with respect to a sum of the peak values; and said control means (20, 22) comprises a data processing unit for controlling operation of the apparatus including data read/write operation, and refers to said to-be-changed amount table (21-1) in accordance with the sum of the peak values detected by said peak detection means (17 to 19) to determine the change amount of the gain data, only when the sum of the peak values does not fall within a predetermined error range with respect to a predetermined value, and designates the gain updated by the determined change amount. The apparatus according to claim 1, characterized in that said data pulse generator means (10 to 15) generates the data pulse sequence when the readout data corresponds to recorded data, and said peak detection means (17 to 19) detects the peak values when the readout data corresponds to servo data. The apparatus according to claim 2, characterized in that the servo data has two patterns that are arranged to be alternately read out by said head. The apparatus according to claim 1, characterized in that said control means (20, 22) further includes means (20) for holding the gain data currently designated, until the change amount of the gain data is input, when a cylinder position of said head is changed in accordance with an input seek command. The apparatus according to claim 1, characterized in that said control means (20, 22) refers to said cylinder-dependent gain data table in accordance with the cylinder position specified by a seek command to designate the gain data for the specified cylinder position. The apparatus according to claim 1, characterized in that said apparatus further comprises drive means (24) for adjusting a head position in accordance with difference data input thereto to center said head on the cylinder, and said control means (20 to 22) further includes means (20, 23) for calculating the difference data corresponding to a difference between the peak values when the sum of the peak values falls within the predetermined error range with respect to the predetermined value, and for outputting the difference data to said drive means (24). The apparatus according to claim 3, characterized in that the servo data is written on respective disks. The apparatus according to claim 3, characterized in that the servo data is written on a specific disk. A method of being capable of obtaining data pulse sequence with a desired accuracy and at high speed, comprising: referring to a cylinder-dependent gain table (21-2) to designate gain data with respect to a cylinder position of a recording medium on which a head is currently positioned; sequentially reading out data written on the cylinder position on which the head is currently positioned; amplifying a signal corresponding to the readout data in accordance with the gain data currently designated; selectively generating a data pulse sequence in accordance with the amplified signal; selectively detecting peak values of the amplified signal; referring to a to-be-changed amount table (21-1) in accordance with a sum of the detected peak values to determine a change amount of the gain data, only when the sum of the peak values does not fall within a predetermined error range with respect to a predetermined value; and designating the gain data updated by the determined change amount. The method according to claim 9, further comprising holding the gain data, until the determined change amount of the gain data is input, when a cylinder position of the head is changed in accordance with an input seek command. The method according to claim 9, further comprising referring to the cylinder-dependent gain table in accordance with the cylinder position specified by a seek command to designate the gain data for the specified cylinder position when a seek command is input. The method according to claim 9, further comprising: calculating difference data corresponding to a difference between the peak values when the sum of the peak values falls within the predetermined error range with respect to the predetermined value; and adjusting a head position in accordance with the calculated difference data to center the head on the specified cylinder.

Inventors: ASAI, KENJI, KAIDA, KATSUHIKO C/O PATENT DIVISION
Applicants: KABUSHIKI KAISHA TOSHIBA, TOSHIBA COMPUTER ENGINEERING CORPORATION
Application year: 1987
Main classification: G11B20
IPC codes: G11B20, G11B5, G11B21