KR19980019726A - How to Improve Data Read on Hard Disk Drives - Google Patents

Abstract

end. FIELD OF THE INVENTION The present invention relates to a method of improving data read of a hard disk drive.

I. SUMMARY OF THE INVENTION An object of the present invention is to provide a data read improvement method for improving a data read success rate of a hard disk drive.

All. Summary of the Invention A solution of the present invention is characterized by retrying data reads by selecting at least one of a plurality of control variables used in a read channel when a data read error occurs, and using a neighbor value of a corresponding control variable value optimized in a manufacturing process. .

la. Important use of the invention: Regardless of the lead channel method, it can be widely used for data read algorithms of hard disk drives.

Description

How to Improve Data Read on Hard Disk Drives

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to data read of a hard disk drive, and more particularly, to a method of improving data read that can improve read success rate when rewriting data.

A hard disk drive is widely used as an auxiliary memory device of a computer system that stores data transmitted from a host computer in a magnetic form on a disk, which is a recording medium, and reads the corresponding data when the data read command is received and transmits the data to the host computer. The main functions of the hard disk drive can be roughly divided into the data write operation and the read operation as described above, and the data read operation has a significant meaning in that the user writes out the data written on the disk after a certain period of time. I would say. Hereinafter, the operation of each component during data read / write will be described with reference to FIG. 1 showing the configuration of a hard disk drive.

1 shows a block diagram of a general hard disk drive, which shows an example of a hard disk drive having two disks 2 and four heads 4 corresponding thereto. Referring to FIG. 1, the disks 2 are typically mounted in a stack form and rotated on the drive shaft of the spindle motor 26 and each disk surface corresponds to one head 4. The head 4 is located on the surface of the disk 2 and is mounted to a vertically extending arm 6 of the arm assembly of a rotary voice coil motor (VCM) 20. The preamplifier 8 preamplifies the signal picked up by one of the heads 4 during data read and applies the analog read signal to the read / write channel circuit 10. During data writing, encoded write data applied from the read / write channel circuit 10 is driven to drive one of the heads 4 corresponding to the write data on the disc 2. At this time, the preamplifier 8 selects one of the heads 4 under the control of a disk data controller (DDC) 28. The read / write channel circuit 10 decodes the read signal path applied from the preamplifier 8 to generate read data RDATA, and encodes the write data WDATA applied from the DDC 28 to the preamplifier 8. . The read / write channel circuit 10 also demodulates the head position information which is a part of the servo information written on the disc 2 to generate a position error signal (PES). The PES generated from the read / write channel circuit 10 is applied to the A / D converter 12, and the A / D converter 12 converts the applied PES into a digital step value corresponding to its level so as to provide a microcontroller ( 14) to provide.

The DDC 28 writes data received from the host computer onto the disc 2 via the read / write channel circuit 10 and the preamplifier 8 or transmits data read from the disc 2 to the host computer. . The DDC 28 also interfaces the communication between the host computer and the microcontroller 14. The microcontroller 14, on the other hand, controls the DDC 28 in response to data read / write commands received from the host computer and controls track search and track following. At this time, the micro controller 14 controls the track tracking by using the PES value input from the A / D converter 12 and responds to various servo control signals output from a gate array (not shown). Perform control. The D / A converter 16 converts a control value for position control of the heads 4 generated from the microcontroller 14 into an analog signal and outputs the analog signal. The VCM driver 18 generates a current I (t) for driving the actuator by a signal applied from the D / A converter 16 and applies it to the VCM 20.

The VCM 20 located on the other side of the actuator having the heads 4 attached to one side of the VCM 20 horizontally moves the heads 4 on the disk 2 corresponding to the direction and the level of the current input from the VCM driver 18. Move it. The motor controller 22 controls the spindle motor driver 24 according to a control value for rotation control of the disks 2 generated from the microcontroller 14. The spindle motor driver 24 drives the spindle motor 26 to rotate the disks 2 under the control of the motor controller 22. The buffer memory 30 connected to the DDC 28 temporarily stores data transferred between the disk 2 and the host computer under the control of the DDC 28. Hereinafter, a data read operation of a conventional hard disk drive having the above-described configuration will be described with reference to FIGS. 2 and 3.

2 is a flowchart illustrating a data read process for explaining a data read process of a conventional hard disk drive. Referring to Fig. 2, the microcontroller 14 switches to the data read mode in response to receiving a data read command from the host computer in the standby mode, and moves the head 4 to the target track (track search). And track following). Thereafter, the microcontroller 14 checks whether the track search and track following are completed in step 40. If the inspection results that the head 4 is performing track tracking with a value within the ON-TRACK WINDOW range defined on the target track, the microcontroller 14 proceeds to step 42 where the current head 4 Check if it is located in the target sector. As a result of the inspection, when the head 4 is positioned on the target sector, the microcontroller 14 proceeds to step 44 to read data written on the disk 2. When the data is read, the microcontroller 14 proceeds to step 46 to check whether a read error occurs. If the data read error does not occur until the read completion, the micro controller 14 ends the above-described data read process and returns to the standby mode. However, if a data read error occurs in the test result in step 46, the microcontroller 14 proceeds to step 50 and performs a subroutine for reading data retry, that is, read RSR. A typical hard disk drive includes an RSR for retrying a data read when a data read error occurs. The reason is that due to the characteristics of the hard disk drive, some of the data written on the disk may be damaged by an external shock (due to the collision between the head and the disk) or may not be detected at the first data read due to signal attenuation. Because it can.

Hereinafter, a process of performing data read RSR performed when a data read error occurs will be described with reference to FIG. 3.

FIG. 3 is a flowchart illustrating a data read retry subroutine (RSR) execution performed when a data read error occurs in FIG. 2. Referring to FIG. 3, the microcontroller 14 first performs a normal retry (N_R) method as a first method for retrying data read when a data read error occurs.

The N_R method is the simplest data read retry method applied when a data read error occurs and reads data from a target sector repeatedly by a predetermined number of times. That is, in step 60 of FIG. 3, the microcontroller 14 sets N_R repetition number N to 1 and proceeds to step 62 to perform N_R. When performing N_R, the microcontroller 14 checks whether a read error occurs in step 64. When a read error occurs, the microcontroller 14 sequentially performs steps 66 and 68 to repeatedly perform a data read operation for a predetermined number of times (10 times). If the test result of step 64 does not cause a read error to occur within a predetermined number of times (for example, N = 3), the microcontroller 14 returns to step 48 of FIG. 2 to complete the data read operation. Examine whether or not. If the data read error occurs until the predetermined number of reads is exceeded in step 68, the microcontroller 14 proceeds to step 70. As a second method for retrying the data read, the domain pinning retries (DOMAIN PINNING RETRY): Hereinafter, the DP_R) method is performed.

The DP_R method is a relatively recently developed method applied to a hard disk drive employing a thin film head. In the case of a hard disk drive employing a thin film head, a phenomenon in which a magnetic pole array in a magnetic core material made of semiconductor technology is not aligned in one direction due to the characteristics of the thin film head is caused. do. In this case, since the magnitude of the signal picked up from the magnetic layer of the disk 2 through the head 4 is minute, the normal read operation cannot be performed. In order to solve this problem, the head 4 is moved to a spare sector, a light current is applied to the head 4 core, and the head 4 is moved to the target sector again to retry data read. This is called the DP_R method. That is, the microcontroller 14 performs DP_R in step 70 and proceeds to step 72 when DP_R is performed to check whether a data read error has occurred. If data is normally read as a result of the test, the microcontroller 14 returns to step 48 after terminating the data read RSR. If a data read error occurs in step 72, the microcontroller 14 performs an offtrack retry method (hereinafter referred to as O_R) as a third method for data read retry.

The O_R method assumes that the signal written on the disc 2 is shift written in the inner circumferential direction or the outer circumferential direction on the disc 2 in the on-track state. This is a method of retrying data read while offtracking (4) in multiple steps. That is, the microcontroller 14 sets the O_R repetition number N and the off track amount Off to 1 and 2 in step 74, and then proceeds to step 76 to perform O_R. At this time, the off-track amount is set in a positive direction (assuming the same meaning as the outer circumferential direction) for convenience, but should also be set in a negative (-) direction (assuming the same meaning as the inner circumferential direction). When performing O_R, the microcontroller 14 proceeds to step 78 and checks whether a data read error has occurred, and if data is read normally, terminates the data read RSR and returns to step 48. On the other hand, if the test result data read error occurs in step 78, the microcontroller 14 proceeds to step 80 to increase the number of O_R repetitions and the off track amount (Off), and then proceeds to step 82. At this time, it should be noted that as the number of O_R repetitions increases, the off track amount (Off) must be increased in proportion to it. The off track amount (Off) set at the last number of preset O_R repetitions is set to a value within the on-track window range. Should be done. In step 82, the microcontroller 14 checks whether the O_R repetition count N exceeds a preset repetition count value (for example, the repetition count N = 10), and then performs steps 76 to 82 described above to the preset repetition count value. Repeat If the O_R repetition number exceeds the preset repetition number (N = 10) in step 82, the microcontroller 14 reports the data read error to the host computer and then terminates the above-described data read RSR process.

On the other hand, when the above-described series of data read retry methods are applied to an actual hard disk drive, the data read RSR process may become more complicated. For example, after performing the N_R method for the first 1020 times and the NP_R method once for the 15th time, perform the O_R method up to about 50 times while varying the off track amount in multiple stages, and then perform the N_R method again. The data read RSR can be applied in a manner. However, in the conventional hard disk drive, the N_R method or the O_R method performed at the time of a data read error is excessively repeated more than necessary, resulting in unnecessary waste of time even for signals that will not be read, resulting in a decrease in the performance of the entire drive. .

Accordingly, an object of the present invention is to provide a data read improvement method that can improve the data read success rate of a hard disk drive.

1 is a block diagram of a typical hard disk drive.

2 is a data read flow chart for explaining a data read process of a conventional hard disk drive.

FIG. 3 is a flowchart illustrating a data read retry subroutine performed when a data read error occurs in FIG. 2. FIG.

4A and 4B are flow charts of data read retry subroutines in accordance with one embodiment of the present invention.

Hereinafter, an operation according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Many specific details are set forth in order to provide a more thorough understanding of the present invention, such as data (including servo information), repetition counts, control parameters, and specific processing flows described in the following description and accompanying drawings. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. Meanwhile, the control variables may be variously set according to a read channel method. For example, in case of applying the peak detection method of the lead channel, set the delay of the window when changing the signal waveform, change the detection level (that is, the threshold level) up or down, or set the analog filter. Major parameters such as values (ie, cutoff frequency (hereinafter referred to as Fc) or boost values) can be considered as control variables, and in the case of applying a generalized PRML (Partial Response Maximum Likelihood) method In addition to Fc and boost, a control variable related to timing locking or a gain related control variable and a control coefficient or delay variable of a digital filter can be considered as control variables. In an embodiment of the present invention, assuming a hard disk drive using a PRML-type lead channel, which is currently in generalized trend, Fine_Gain, Filter_Cutoff Frequency, Filter_Boost, and Digital The combination of filter coefficients and VCO fine control are considered as variable control variables during the use of the lead channel, among which filter cutoff frequency (hereinafter referred to as control variable A) and VCO fine control (hereinafter referred to as control variables). An embodiment of the present invention will be described by setting a variable B) and a fine gain (hereinafter referred to as a control variable C) as a control variable.

4A and 4B illustrate a flow diagram of a data read RSR (Retry SubRoutine) execution flow according to an embodiment of the present invention, which is performed as a subroutine when a data read error occurs. First, when the data read command is received from the host computer, the microcontroller 14 switches to the read mode to search and follow the target track, and then reads data from the target sector. If a read error occurs during data read, the microcontroller 14 performs data read RSR as shown in FIGS. 4A and 4B. Referring to FIG. 4A, the microcontroller 14 first repeats the N_R (Normal_Retry) method in steps 90 through 98 as a first method for retrying data read. At this time, the number of repetitions of the N_R method is set to 5 times, and if data is normally read within the set number of repetitions, the process returns to step 48 shown in FIG. 2 to check whether data read is completed. If the data read error continues even after the N_R method is performed for the set number of repetitions, the microcontroller 14 proceeds to step 100 and performs the DP_R (Domain Pinning_Retry) method as the second method for retrying the data read. When the DP_R method is executed, the microcontroller 14 checks whether a data read error occurs in step 102. If the data is not read normally, the microcontroller 14 performs the O_R (Offtrack_Retry) method, which is the third method for data read retry, in steps 104 through 112. To perform. At this time, the number of repetitions (M) of the O_R method is set to 10 times, and if data is normally read within the set number of repetitions, the process returns to step 48 shown in FIG. 2 to check whether data read is completed. If the data read error occurs continuously even after the O_R method is performed for the set number of repetitions, the microcontroller 14 proceeds to step 114 and retries the data read with the neighboring value of the control variable A. FIG. At this time, the control variable A is Filter_Cutoff_Frequency as described above and has an optimized value by an experiment during the manufacturing process, and the neighborhood value means a neighborhood value of the optimized value. For example, if the optimization value of the filter_cutoff_frequency in the manufacturing process is 15 MHz, the neighbor value is 13 MHz or 17 MHz. In addition, the neighboring values of the optimized values can be repeatedly used by recording in a predetermined area of a system cylinder provided on the disk 2. In other words, the microcontroller 14 retries the data read by varying the control variable A to 13 MHz or 17 MHz in step 114. At this time, the microcontroller 14 checks whether data is normally read through step 116. If the data is normally read, the microcontroller 14 returns to step 48 of FIG.

On the other hand, when the test result data read error occurs in step 116, the microcontroller 14 proceeds to step 118 and retries the data read with the neighboring value of the control variable B. The control variable B represents an optimized VCO_fine_control variable and its neighborhood value may be set in the same manner as the above filter_cutoff_frequency neighborhood value. Thereafter, the microcontroller 14 checks whether a data read error occurs in step 120. When a data read error occurs, the microcontroller 14 proceeds to step 122 and retries the data read with a neighbor value of the control variable C. The control variable C represents a fine-gain variable and uses the same method of retrying the data read by setting the neighboring values of the control variables A and B described above. If a data read error occurs despite the retry of the data read with the neighbor value of the control variable C (step 124), the microcontroller 14 performs the N_R method again in step 126. At this time, the number of repetitions may be set to two or more times according to the designer's intention, but in one embodiment of the present invention, the number of repetitions is performed once. That is, the microcontroller 14 repeatedly performs the above-described N_R method, DP_R method and O_R method by the set number of times through steps 126 to 136 and checks whether a data read error occurs during the repeated execution. While returning to step 48, if data read errors continue to occur even if the above three methods are repeatedly performed a set number of times, the data read RSR according to an embodiment of the present invention is reported after the data read error is finally reported to the host computer. End the process.

As described above, the present invention can improve the data read success rate by changing the optimized control variable of the read channel to its neighbor value and retry the data read and secure the lead reliability of the product by shortening the data read retry execution time. There is an advantage to this.

On the other hand, a series of data read retry methods according to an embodiment of the present invention may have a different application order according to the designer's intention of the hard disk drive, and the repetition frequency setting of the application method may also be changed according to product characteristics.

Claims (5)

In the data read enhancement method of a hard disk drive having a read channel, And selecting at least one of a plurality of control variables used in the read channel in the event of a data read error and retrying a data read with the neighboring value of the control variable optimized during the manufacturing process. 2. The method of claim 1, wherein the neighborhood value is recorded and used in a system cylinder area on a record carrier. In the data read enhancement method of a hard disk drive having a read channel, A first step of retrying the data read a predetermined number of times when the data read error occurs and checking whether the data read error occurs repeatedly; If the data read error occurs repeatedly as a result of the inspection, select one of the plurality of control variables used in the read channel, change the neighboring value of the control variable value optimized during the manufacturing process, and then read the data read. And a second process of retrying. 4. The method of claim 3, wherein the read channel is a read channel to which a PRML scheme is applied. 5. The method of claim 4, further comprising a third step of reporting a final data read error to a host computer when a data read error occurs repeatedly a predetermined number of times during the second process.