JP2002150728A - Servo information reading circuit and magnetic disk device using the circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of servo information misdetection and a servo information detection error at the time of switching heads in a magnetic disk device. SOLUTION: A state expanding a search window is held until a fixed pattern is detected so as to detect the fixed pattern by expanding the search window immediately after switching the heads, and after detecting the fixed pattern, the search window is returned to normal width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive, and more particularly to a technique for detecting servo information of a magnetic disk drive of a data surface servo system.

[0002]

2. Description of the Related Art In a servo information detecting circuit of a magnetic disk drive, servo information is arranged at equal time intervals on all circumferential tracks of a disk on which a magnetic medium rotates steadily. Write a fixed pattern which is a mark indicating the head of the servo. In the search for servo information, first, the fixed pattern is searched, and a servo signal subsequent to the fixed pattern is read. First, in a state where the fixed pattern has never been found, the fixed pattern is always searched for and the fixed pattern is searched. When the fixed pattern is detected, a search window is opened for a fixed time before and after a timing at which the next fixed pattern is detected based on the timing at which the fixed pattern is detected, and only the fixed pattern detected during the search window is used as a servo control. Judge as the fixed pattern indicating the head. By providing the search window, it is possible to prevent the fixed pattern from being erroneously found at a different position.

Here, the state in which the first head continuously detects servo information within the search window is changed to the second state.
It is ideally possible to switch to the head and find the fixed pattern in the search window, and to continue the state in which servo information is continuously detected in the search window even after switching the head. However, the following problems actually occur. The magnetic disk drive
Usually, a plurality of disks are fixed to a spindle motor in a state of being overlapped at intervals, and are constantly rotating. A head is provided on each disk surface, and the head is supported by a carriage and has a structure in which the head can be positioned at any position in the diameter direction of the disk. Servo information is written on each disk at the same position in the circumferential direction as viewed from each head.

However, the read timing of the servo information by each head is shifted due to the fall of the carriage or the fall of the spindle motor. For this reason, the state where the servo information is continuously detected in the search window by the first head is switched to the second head, the fixed pattern is found in the search window, and the servo information is maintained even after the head switching. If it is attempted to continue the state of continuous detection within the search window, the servo information cannot be detected since servo information is located outside the search window immediately after head switching. Therefore, a method has been adopted in which the servo information is always searched immediately after the head switching, and a fixed pattern at the head of the servo can be detected. Alternatively, the fixed pattern can be detected by expanding the search window only once immediately after the head switching.

[0005]

If the servo information is always searched immediately after the head switching, a fixed pattern indicating the head of the servo information may be erroneously detected. Also, if the search window is expanded only once immediately after the head switching, if the servo information immediately after the head switching is a disk bat, and if it is a servo bat, a servo information detection error after the head switching will always occur. I will.

[0006]

In order to detect the fixed pattern, the search window is widened immediately after the head is switched, and the state where the search window is widened until the fixed pattern is found is detected to detect the fixed pattern. Then, return the search window to the normal width.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. The head switching circuit 6 outputs a head switching signal 1 when performing head switching. When the search window switching circuit 10 receives the head switching signal 1, it outputs a wide search window 3. The wide search window 3 and the search window creation circuit 9 switch the search window signal 4 to the wide window.

The servo head detection circuit 7 searches for a servo head pattern from the servo reproduction signal 11 only while the search window signal 4 is ON, and outputs a servo head detection signal 2 when the servo head pattern is detected. The servo head detection signal 2 is input to the search window switching circuit 10.

The search window switching circuit 10 turns off the wide search window 3 when receiving the servo head detection signal 2 for the wide search window 3. The servo head detection signal 2 is input to the search window creation circuit 9. The search window creation circuit 9 adjusts the timing of the next search window signal 4 based on the servo head detection signal 2. The servo head detection signal 2 is input to the servo information reading circuit 8.

[0010] The servo information reading circuit 8 reads the servo information following the servo head according to the servo head detection signal 2 and outputs the servo information 5.

[0011]

According to the present invention, in a magnetic disk drive, erroneous servo information detection and servo information detection error which occur at the time of head switching can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention.

[Explanation of symbols]

1 ... head switching signal, 2 ... servo head detection signal, 3
... wide search window, 4 ... search window signal, 5 ... servo information, 6 ... head switching circuit, 7 ... servo head detection circuit, 8 ... servo information reading circuit, 9 ...
Search window creation circuit, 10: Search window switching circuit, 11: Servo reproduction signal.

Claims (1)

[Claims] 1. A magnetic medium rotatably supported and capable of discretely reproducing servo information, a plurality of magnetic heads for reading and writing information from and to the magnetic medium, A magnetic disk drive having an actuator positioned on the recording medium, a controller for transmitting a signal for selecting the magnetic head, and a servo information reading circuit for reading the servo information, wherein the servo information reading circuit comprises a servo It has a function of detecting the head, and has a function of generating a search time window for detecting the head of the second servo from the detection of the head of the first servo. And perform head switching,
When moving to a new magnetic medium and detecting the head of the servo, expand the search time window width, hold the state where the search time window width is widened until the head of the servo is detected, and detect the head of the servo. A servo information reading circuit for returning a time window width to a normal search time window width, and a magnetic disk drive using the circuit.