KR100465967B1 - How to improve the data lead of hard disk drive - Google Patents

Abstract

end. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data lead improvement method for a hard disk drive.

I. Disclosure of Invention Technical Problem [8] The present invention provides a data lead improvement method capable of improving the data lead success rate of a hard disk drive.

All. The present invention is characterized in that at least one of a plurality of control variables used in a lead channel is selected and a data lead is retried to a neighboring value of a corresponding control variable value optimized in a manufacturing process when a data lead error occurs .

la. Important Uses of the Invention: Regardless of the read channel scheme, it can be widely used in data read algorithms of hard disk drives.

Description

How to improve the data lead of hard disk drive

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data lead of a hard disk drive, and more particularly, to a data lead improvement method capable of improving the read success rate during data re-read.

The hard disk drive is widely used as an auxiliary storage device of a computer system that stores data transmitted from a host computer in a form of a magnetic disk on a recording medium, reads data corresponding to the received data, and transmits the read data to the host computer. The main function of the hard disk drive can be broadly divided into a data write operation and a read operation as described above. The data read operation is important in that the user can reproduce and output data written on the disk after a predetermined time elapses I will say. Hereinafter, operations of the respective components in data read / write will be described with reference to FIG. 1 showing the configuration of the hard disk drive.

FIG. 1 is a block diagram of a general hard disk drive. FIG. 1 shows an example of a hard disk drive having two disks 2 and corresponding four heads 4. Referring to FIG. 1, discs 2 are generally in the form of stacks mounted on a drive shaft of a spindle motor 26 and rotate, and each disc surface corresponds to one head 4. The head 4 is located on the surface of the disc 2 and is mounted on a vertically elongated arm 6 of an arm assembly of a VCM 20. The preamplifier 8 pre-amplifies the signal picked up by one of the heads 4 at the data read time and applies the analog read signal to the read / write channel circuit 10 When data is written, encoded read data (Encoded Write Data) applied from the read / write channel circuit 10 is written on the disk 2 by driving a corresponding head of the heads 4. 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 applied from the preamplifier 8 to generate read data RDATA, encodes the write data WDATA applied from the DDC 28, and applies the read data to the preamplifier 8 . The read / write channel circuit 10 also demodulates head position information, which is a part of the servo information written on the disk 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, 14).

The DDC 28 writes the data received from the host computer on the disk 2 via the read / write channel circuit 10 and the preamplifier 8 or transmits the data read from the disk 2 to the host computer . The DDC 28 also interfaces communication between the host computer and the microcontroller 14. On the other hand, the microcontroller 14 controls the DDC 28 in response to a data read / write command received from the host computer, and controls track seeking and track following. At this time, the microcontroller 14 controls the track following by using the PES value inputted from the A / D converter 12 and outputs servo signals corresponding to various servo control related signals outputted from a gate array (not shown) Control is performed. The D / A converter 16 converts a control value for controlling the position 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 the current I (t) to the VCM 20. [

The VCM 20 positioned on the other side of the actuator with the heads 4 on one side is configured to move the heads 4 horizontally on the disk 2 corresponding to the direction and level of the current input from the VCM driver 18. [ . The motor control unit 22 controls the spindle motor driving unit 24 according to a control value for controlling the rotation of the disks 2 generated from the microcontroller 14. [ The spindle motor driving section 24 drives the spindle motor 26 to rotate the disks 2 under the control of the motor control section 22. [ The buffer memory 30 connected to the DDC 28 temporarily stores data transmitted 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 attached hereto.

FIG. 2 is a flowchart illustrating a data read process for explaining a data read process of a conventional hard disk drive. 2, in response to receiving a data read command from the host computer in the standby mode, the microcontroller 14 switches to the data lead mode in response to the data read command, and performs servo control for moving the head 4 to the target track And track following). In step 40, the microcontroller 14 checks whether track search and track following are completed. If the head 4 is tracking the track at a value within the ON-TRACK WINDOW range defined on the target track, the microcontroller 14 proceeds to step 42 to determine whether the current head 4 It is checked whether it is located on the target sector. If the head 4 is found on the target sector, the microcontroller 14 proceeds to step 44 to read the data written on the disk 2. When the data is read, the microcontroller 14 proceeds to step 46 to check whether a read error has occurred. If the data read error does not occur until the read completion, the microcontroller 14 ends the data read process and switches back to the standby mode. However, if a data read error occurs in step 46, the microcontroller 14 proceeds to step 50 and performs a subroutine, i.e., a read RSR, for data read retries. In general hard disk drives, RSR is provided for retrying data read when a data read error occurs. The reason is that, due to the nature of the hard disk drive, a part of the data written on the disk may be damaged by an external impact (due to a collision phenomenon between the head and the disk) or may not be detected at the time of the first data read It is because.

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

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

The N_R method is the simplest data lead retry method that is applied when a data read error occurs, and it repeatedly reads booty data to a target sector by a predetermined number of times. That is, in step 60 of FIG. 3, the microcontroller 14 sets the N_R repetition number N to 1, and then proceeds to step 62 to perform N_R. When the N_R is performed, the microcontroller 14 checks whether a read error occurs in step 64. If a read error occurs, the microcontroller 14 sequentially performs the steps 66 and 68 to repeatedly perform the data read operation for the preset number of times (10 times).

If the read error does not occur in the predetermined number of times (for example, N = 3) within the predetermined number of times as a result of the check in step 64, the microcontroller 14 returns to step 48 in FIG. 2 to complete the data read operation . If a data read error occurs in step 68, the microcontroller 14 proceeds to step 70 and performs a domain pinning retry as a second method for retrying data lead. DP_R) method.

The DP_R method is a method that is applied to a hard disk drive employing a thin film head as a relatively recently developed method. In a hard disk drive employing a thin film head, a magnetic pole array in a core material made of semiconductor technology can not be aligned in one direction at the head gap position due to the characteristics of the thin film head 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, a normal read operation can not be performed. In order to solve this problem, after the head 4 is moved to the spare sector, a write current is applied to the core 4 of the head 4, and the head 4 is moved again to the target sector to present a data lead This is called the DP_R method. In other words, the microcontroller 14 performs the DP_R in step 70 and proceeds to step 72 when performing the DP_R to check whether a data read error has occurred. If the data is normally read as a result of the inspection, the microcontroller 14 terminates the data lead RSR and returns to step 48. [ If a data read error occurs in step 72, the microcontroller 14 performs an off-track retry (O_R) method as a third method for data lead retry.

The O_R method assumes a state in which a signal written on the disc 2 is shifted or written in an inner direction or an outer direction on the disc 2 in an on-track state, (4) are retracted in multiple stages while retrying the data lead. That is, the microcontroller 14 sets O_R repetition number N and 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 to positive (+) direction (assuming that it has the same meaning as the outer circumferential direction) but is set to negative (-) direction (assuming the same meaning as the inner circumferential direction). O_R, the microcontroller 14 proceeds to step 78 to check whether a data read error has occurred. If the data is normally read, the data read RSR is terminated and then the process returns to step 48. [ On the other hand, if a 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. [ Note that the off-track amount (Off) must be increased proportionally as the number of O_R repetitions increases, and the off-track amount (Off) set at the last number of times of the preset O_R repetition is set to a value within the on- . In step 82, the microcontroller 14 checks whether the number N of O_R repetitions exceeds the preset number of repetitions (for example, the number of repetitions N = 10), and repeats steps 76 to 82 . If the number of repetitions of O_R exceeds the preset number of repetitions (N = 10) in step 82, the microcontroller 14 reports a data read error to the host computer and terminates the data read RSR process.

Meanwhile, when the above-described series of data read retry method is applied to an actual hard disk drive, the data lead RSR process can be further complicated. For example, the N_R method is performed for the first 10 to 20 times, the NP_R method is performed once for the 15th time, the O_R method is performed up to about 50 times while the off track amount (Off) The data lead RSR can be applied in the manner that it performs. However, in the conventional hard disk drive, the N_R method or the O_R method performed when a data read error occurs is repeated excessively more than necessary, thereby wasting unnecessary time for a signal that is not to be read, thereby degrading the performance of the entire drive .

Accordingly, it is an object of the present invention to provide a data lead improvement method capable of improving the data lead success rate of a hard disk drive.

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 such as the data described in the following description and accompanying drawings (including servo information), the number of repetitions, each control parameter and the specific process flow are shown to provide a more thorough understanding of the present invention. 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, when applying a lead channel with a peak detection method, you can set a delay for a window when the signal waveform is fixed, change the detection level (ie, Threhold Level) up or down, or set the analog filter The main parameters such as the cutoff frequency (Fc) or the boost value can be regarded as control variables. In the case of applying the read channel of the recently generalized PRML (Partial Response Maximum Likelihood) scheme, In addition to Fc and boost, control variables related to timing locking, control parameters related to gain, and control parameters of digital filter and delay variables can be considered as control variables. In one embodiment of the present invention, it is assumed that a hard disk drive using a PRML-based read channel in the current generalization trend is used, and fine_Gain, Filter_Cutoff Fre-quency, Filter_Boost, Cutoff frequency (hereinafter referred to as a control variable A), VCO_pine_control (hereinafter referred to as " VCO_pin_control "), and the like are considered as variable control variables during use of the read channel. (Hereinafter referred to as control variable B) and a fine gain (hereinafter referred to as control variable C) are set as control variables to describe an embodiment of the present invention.

4A and 4B are flowcharts illustrating a data lead RSR (Retry SubRoutine) according to an embodiment of the present invention, and are performed as a subroutine when a data read error occurs. First, when receiving a data read command from the host computer, the microcontroller 14 switches to the read mode, searches for and tracks the target track, and reads data from the target sector. When a data read lead error occurs, the microcontroller 14 performs the data lead RSR as shown in FIGS. 4A and 4B as an embodiment of the present invention. Referring to FIG. 4A, the microcontroller 14 repeats the N_R (Normal_Retry) method in steps 90 through 98 as a first method for data read retries. At this time, the number of repetition of the N_R method is set to 5, and if the data is normally read within the set number of repetition times, the process returns to step 48 shown in FIG. 2 to check whether the data read is completed. If the data read error continues even if the N_R method is repeated the set number of times, the microcontroller 14 proceeds to step 100 and performs a DP_R (Domain Pinning_Retry) method as a second method for data read retries. When the DP_R method is performed, the microcontroller 14 checks whether a data read error occurs in step 102. If the data is not normally read, the microcontroller 14 performs an O_R (Offtrack_Retry) method, which is a third method for data read retry through steps 104 to 112 . At this time, the number of iterations (M) of the O_R method is set to 10, and if the data is normally read within the set number of repetition times, the process returns to step 48 shown in FIG. If the data read error continues even if the O_R method is performed for the set number of repetitions, the microcontroller 14 proceeds to step 114 and retries the data read to the neighboring value of the control variable A. At this time, the control variable A is a filter_cutoff_frequency as described above, and has a value optimized by experiments in the manufacturing process, and its neighboring value means a value close to ± of the optimized value. For example, if the optimum value of the filter_cutoff_frequency is 15 MHz in the manufacturing process, the nearby value is 13 MHz or 17 MHz. Further, the neighboring values of the optimized values may be repeatedly used by recording the predetermined values in a predetermined area of a system cylinder provided on the disk 2. [ That is, in step 114, the microcontroller 14 changes the control variable A to 13 MHz or 17 MHz to retry the data reading. At this time, the microcontroller 14 checks whether the data is normally read through step 116. If the data is normally read, the microcontroller 14 returns to step 48 of FIG. 2 to check whether or not the data read is completed.

On the other hand, if a data read error occurs in step 116, the microcontroller 14 proceeds to step 118 and retries the data read to the neighboring value of the control variable B. The control variable B represents the optimized VCO_pine_control variable, and its neighboring values can be set in the same manner as the values near the filter_cutoff_frequency mentioned above. In step 120, the microcontroller 14 checks whether a data read error occurs. If a data read error occurs in step 120, the microcontroller 14 proceeds to step 122 and retries the data read to the adjacent value of the control variable C. The control variable C represents a fine-gain variable and uses the same method as that for retrying the data read by setting the neighboring values of the control variables A and B described above. If a data read error occurs in step 124 despite retrying the data lead to the neighboring value of the control variable C, the micro controller 14 re-executes the N_R method in step 126. [ At this time, the number of iterations may be set to two or more times according to the intention of the designer, but it is assumed to be performed once in one embodiment of the present invention. In other words, the microcontroller 14 repeatedly performs the N_R method, the DP_R method, and the O_R method described above repeatedly for a predetermined number of times through steps 126 to 136. If the data is read normally during repetitive execution, If the data read error continues to occur even if the above three methods are repeated a predetermined number of times, the data lead error is finally reported to the host computer. Then, the data lead RSR The process ends.

As described above, the present invention can improve the data lead success rate by changing the optimized control variable of the read channel to its neighbor value, thereby improving the data lead success rate and shortening the data lead retry execution time, There is an advantage to be able to do.

Meanwhile, a series of data lead retry methods according to an embodiment of the present invention may be performed in a different order in accordance with the intention of the designer of the hard disk drive, and the number of repetition times of the application method may be changed according to the product characteristics.

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

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a hard disk drive.

FIG. 3 is a flowchart of a data lead retry subroutine (Retry SubRoutine) performed when a data read error occurs in FIG. 2;

4A and 4B are flowcharts of a data lead retry subroutine execution according to an embodiment of the present invention;

Claims (3)

A data lead improving method for a hard disk drive having a read channel, A first step of checking whether a data read error occurs repeatedly by retrying the data read by a predetermined number of times when a data read error occurs; If a data read error occurs repeatedly a predetermined number of times, one of a plurality of control variables used in the read channel is selected and changed to a neighbor value of a control variable optimized in the manufacturing process, And a second step of re-attempting the data lead. The method of claim 1, wherein the read channel is a read channel to which a PRML scheme is applied. 3. The method of claim 2, further comprising a third step of reporting a final data read error to the host computer when a data read error occurs repeatedly a predetermined number of times during the second process.