RECORDED DATA REPRODUCING APPARATUS

Abstract: A recorded data reproducing apparatus according to the invention includes a memory section (4) having a gain data table (28) for storing gain data determined in accordance with a cylinder position above a recording medium. Using the data representing the current cylinder position, the optimum gain data is determined from the gain data table (28), and supplied to a read pulse generator section (2) under control by a control section (4). With this arrangement, the gain adjusting circuit simplified, and the gain adjustment process is also simplified.

Description: This invention relates to a recorded data reproducing apparatus for use with hard disk devices, and more particularly to a recorded data reproducing apparatus having simple circuitry, and which is easy to assemble and adjust. In hard disk devices, the level of the signal read out from a magnetic head changes according to the track or cylinder position on the magnetic recording medium. Specifically, when the magnetic head is positioned above an inner track on the magnetic recording medium, the signal level is low. When it is positioned above an outer track, the signal level is high. In order to use such signals output from the magnetic head, for subsequent data processing, the varying signal level must be adjusted to an appropriate level. To cope with this problem, the conventional recorded data reproducing apparatus for use with a hard disk device performs gain adjustments, using an auto-gain control (AGC) generator. To adjust the gain, the signal, amplified by an amplifier, is rectified and smoothed, and is then supplied to the AGC generator. The AGC generator outputs an AGC signal to the amplifier, in accordance with the input; thus, the amplified signal is fed back to the amplifier. The AGC generator, however, requires complicated circuitry. To perform gain adjustment of the amplifier of the AGC generator, manual operation by means of a variable resistor is required. There are many problems in which the number of assembly steps of the apparatus is increased, and the assembly is thus complicated. Prior art document US-A-4 544 964 discloses a magnetic recording system similar to the recording data reproducing apparatus as described in the precharacterizing part of claim 1. This system includes an improved read/write arrangement operating according to given parameters and is adapted to produce digital data signals in terms of a prescribed normalized "data cell" length. Pulse stretching means are adapted to adjust the length/duration of the data cells in response to prescribed changes in the system parameters, and timing-sampling means are adapted to accomodate such variable-length "data cells". Further, adjustable gain means are adapted to automatically adjust read-out gain according to bit location radially on a magnetic record. Further, prior art document EP-A-0 097 208 describes a head positioning system with automatic gain control. In this system a transducing head for detecting position reference information is one of a plurality of heads whose sensitive widths in a direction transverse to tracks may vary from head to head. The system further includes a store responsive to head address information to provide a first output signal whose value is related to the width of the selected head. Further, correction means are responsive to the first output signal to vary the correction signal by a predetermined amount. The first output signal from the store is also applied directly to a gain control loop. Finally, prior art document US-A-4 31 987 discloses a self-compensating device for a magnetic disc apparatus. This system uses gain data tables in a velocity loop of a carriage. It is an object of this invention to provide a recorded data reproducing apparatus wherein the circuit arrangement can be simplified, as can any adjustments necessary, during the manufacturing stage, and wherein an AGC amplifier can be operated at an appropriate gain. To solve this object the present invention provides a recorded data reproducing apparatus as stated in claim 1. With such an arrangement, the gain of the AGC amplifier can be adjusted to an appropriate value by preparing the gain data, which is dependent on a position of the magnetic head and a variation of ambient temperature. Therefore, the AGC amplifier can be operated at an appropriate gain, dependent on the position of the magnetic head and temperature variation, without complicated circuitry or adjustments. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a block diagram showing an embodiment of a recorded data reproducing circuit according to the present invention; Fig. 2 shows a view illustrating the contents of a gain data table used in the embodiment of Fig. l; and Fig. 3 shows a flowchart used to explain the operation of the embodiment of Fig. l. A detailed description of an embodiment of a recorded data reproducing apparatus according to this invention will be given with reference to the accompanying drawings. The configuration of the embodiment will first be described with reference to Fig. l. This recorded data reproducing apparatus includes read pulse generator section 2, control section 4, memory section 6, timer 34, and temperature detector section 8. Read pulse generator section 2 comprises magnetic head l2 for reading out the data from the magnetic recording medium, head amplifier l4 for amplifying the signal read out by head l2, and low pass filter (LPF) l6 for removing the noise from the signal amplified by amplifier l4. Generator section 2 further includes automatic gain control amplifier (AGC amplifier) l8 for amplifying the output from LPF l6 according to input gain data, differential circuit 20 for detecting peaks of the read-out signal, and pulse generator 22 for outputting the read pulse on the basis of the detected peaks of the read-out signal. Control section 4 is composed of CPU 26, which performs a variety of control functions, and D/A converter 24, which converts digital data output from CPU 26 to analog data. Memory section 6 contains gain data table 28. This gain data table 28 is configured as shown in Fig. 2. Gain data table 28 will be explained later. Memory section 6 includes, in addition to gain data table 28, register CY (not shown) used to store data representing the current cylinder position of head l2, and register TE (not shown) for storing detected temperature data. Temperature detector section 8 is made up of temperature detector 32, which detects the ambient temperature, and A/D converter 30, which converts analog temperature data detected by detector 32 into digital data. Timer 34 is used to determine the time interval of detecting the temperature by means of temperature detector 32. After a predetermined time has elapsed, timer 34 generates an elapsed-time interrupt for CPU 26. Referring to Fig. 2, GAl to GA5 are gain data dependent on the cylinder data, which is referred to according to the cylinder data stored in register CY. GTl to GT3 are gain data dependent on the temperature data stored in register TE. In this example, the gain data dependent on the cylinder positions are classified into 5 steps. The temperature-dependent gain data is classified into 3 steps. However, the number of steps is not limited to those above, but may be any desired number, if necessary. Next, the operation of this embodiment will be explained, with reference to Fig. 3. The power supply of the hard disk device is turned on, and initial settings and processings, such as detection of the zero track position, are made (step Sl2). At this time, if a RAM is used for gain data table 28, the gain data is written into gain data table 28. If gain data table 28 is configured by a ROM, such a write operation is not necessary. After that, in steps l4, the apparatus will wait for an input command. In steps Sl6 and Sl8, the input commands are checked. In step Sl6, it is checked if the input command is a seek command or not. If N (NO) in steps l6, step Sl8 is executed. In step Sl8, it is checked if the input command is a write command or not. If N in step Sl8, the command is determined to be a read command. In step Sl9, it is determined if an interrupt has been generated from timer 34 or not. If it has been generated, step S20 is executed. If not, step S22 is executed, so that the temperature data up to the present time can be used. In step S20, the ambient temperature is detected by temperature detector 32. After the detected temperature data is converted into digital data by A/D converter 30, it is fed through CPU 26, and stored in the register TE of memory section 63. In step S22, gain data table 28 is referred to according to the contents of registers CY and TE, and appropriate data is read out. In step S24, the cylinder position-dependent gain data and temperature-dependent gain data, read out from gain data table 28, are combined in accordance with a predetermined procedure, and the combined data is output to AGC amplifier l8. After that, the flow returns to step Sl4. Through the above sequence of operations, head l2 reads out the data at its current position. A signal corresponding to read-out data is amplified by head amplifier l4, and then it is supplied to AGC amplifier l8. Since the gain data is already supplied to AGC amplifier l8 from control section 26 in step S24, the AGC amplifier 18 amplifies the input signal in accordance with the input gain data, and outputs the amplified signal to differential circuit 20. In differential circuit 20, the signal from AGC amplifier l8 is differentiated to detect the peak position and is then output to pulse generator 22. Generator 22 outputs a pulse signal which changes when the signal corresponding to the peak signal detected by differential circuit 20 crosses the zero level. This pulse signal is used as a read pulse. If the answer in step Sl8 is Y (YES), that is, if the command is determined to be a write command, step S28 is executed and processing is performed in accordance with the command. Then, the flow returns to step Sl4. If the answer in step Sl6 is Y (if the command is seek command), step S30 is executed. In step S30, data representing the cylinder position assigned by the seek command is stored in register CY. After that, in step S32, head l2 is driven to the destination cylinder. When head l2 reaches the destination cylinder, the ambient temperature is measured by temperature detector 32. After the measured temperature data is converted to digital data by A/D converter 30, CPU 26 stores this data in register TE. After that, the flow returns to step Sl4 gain. The recorded data reproducing apparatus according to this invention operates as described above. In this case, since the gain of AGC amplifier l8 can be set according to the gain data in a gain data table, a gain adjustment operation is not needed after the circuit has been manufactured. Also, since most of the circuits necessary for the gain adjustment operation can be configured by digital circuits, circuit construction is comparatively easy. Furthermore, by storing the predetermined fixed gain data into the gain data table, the measurement of the electromagnetic characteristics of magnetic head l2 can be performed easily. In other words, the electromagnetic characteristics of the magnetic head can be measured based on the read-out signal of the magnetic head, which is amplified by the AGC amplifier with a gain in accordance with the fixed gain data. In this embodiment, when a read command is input, if there is no interrupt from the timer, the operation of a temperature measurement is not executed. If necessary, the operation can be set so that temperature measurements will not be performed each time the read command is input. In such case, there would be no need for the timer. To update the temperature data, when an interrupt is generated from the timer, a seek operation request can be output to an external unit to measure the temperature. The measurement of temperature may only be accomplished by generation of an interrupt.

Claims: A recorded data reproducing apparatus capable of simplifying a gain adjustment, comprising: read pulse generating means (2) for reading out data from a recording medium, for amplifying a signal corresponding to the read-out data in accordance with input gain data, for differentiating the amplified signal to detect the peak value, and for generating a read pulse on the basis of the detected peak value; means (6) for programming a gain adjust operation which adjusts read-out gain; and control means (4) for referring cylinder-dependent to said programming means (6) in accordance with an input read command to determine an optimum gain data, and for outputting the determined gain data to said read pulse generating means (2), characterized in that: said programming means (6) is constituted by memory means which stores a gain data table tabulating the gain data, dependent on a cylinder position of a head, wherein said control means (4) refers to said gain data table, temperature detecting means (8) detect ambient temperature, and said memory means (6) further includes means for storing the temperature data detected by said temperature detecting means (8), said gain data table (28) storing the gain data dependent on temperature data. The apparatus according to claim 1, characterized in that said memory means (6) further includes means for storing data indicating the current cylinder position, and said control means (4) comprises: determination means (4) for checking whether an input command is either a seek command or a write command, and for determining the input command to be a read command when the input command is neither a seek command nor a write command; cylinder position data output means (4) for outputting the cylinder position data designated by the seek command to said memory means (6) when the input command is determined to be the seek command; cylinder-dependent gain data output means (4) for reading out the cylinder position data stored in said memory means (6), and for referring to said gain data table (28) to generate the cylinder position-dependent gain data in accordance with the cylinder position data read-out, when the input command is the read command; and AGC gain output means (4) for outputting the generated gain data to said read pulse generating means (2). The apparatus according to claim 2, characterized in that said control means (4) further includes: means for outputting temperature data detected by said temperature detecting means (8) to said memory means (6); temperature-dependent gain data output means for reading out the temperature data from said memory means (6), and for referring to said gain data table (28) in accordance with the temperature data read-out to generate the temperature-dependent gain data when the input command is determined to be the read command; and means for determining the gain data to be output to AGC gain output means (4), on the basis of the cylinder position-dependent gain data output from said cylinder position-dependent gain data output means (4) and temperature-dependent gain data output from said temperature-dependent gain data output means (4), and for outputting the determined gain data to said AGC gain output means. The apparatus according to claim 3, characterized in that said control means (4) further comprises means (4) for controlling said temperature detecting means (8) to detect temperature when the input command is the read command. The apparatus according to claim 3, further comprising timer means (34) for generating an interrupt to said control means (4) after a predetermined time elapses, said control means (4) further comprises means (4) for resetting the measuring time of said timer means (34) after temperature data is detected. The apparatus according to claim 5, characterized in that said control means (4) further includes means (4) for controlling said temperature detecting means (8) to detect temperature data in accordance with the interrupt input. The apparatus according to claim 6, characterized in that said control means (4) further includes means (4) for inhibiting said temperature detecting means (8) from detecting temperature when the read command is input after the temperature is detected in accordance with the interrupt and before the next interrupt is generated.

Inventors: KAIDA, KATSUHIKO PATENT DIVISION
Applicants: KABUSHIKI KAISHA TOSHIBA
Application year: 1986
Main classification: G11B5
IPC codes: G11B5