JPS6284472A - Reference signal generation circuit - Google Patents

Abstract

PURPOSE:To attain the early stabilization by controlling the generation of a reference clock through frequency comparison with the frequency of a servo pulse at the time of the leading of a servo motor and switching an operation so as to control the generation of a reference clock through phase comparison after the stable rotational speed is obtained. CONSTITUTION:A switching control part 51 controls a frequency comparison part 52 so as to activate in a FAST mode, and transmits the shift amount of the frequency as an increment signal 2' and a decrement signal 3' to a charge pump 2. In such a NORMAL mode where the servo pulse 1' comes to stably input continuously, the switching control part 51 switches the operation so as to activate a phase comparison part 53, thence onward generates and outputs the reference clock 5' from a phase shift amount due to the phase comparison. Thus the operation can follow the servo pulse which tends to be intermittent and can be stabilized in an earlier time.

Description

[Detailed Description of the Invention] [Summary] Head positioning is performed by a reference signal generation circuit that generates a reference clock, and the start-up timing of the servo motor (first mode period) is determined by frequency comparison with the frequency of servo pulses. After the reference clock generation is controlled and a stable rotational speed is obtained (normal mode period), the reference clock generation is controlled by phase comparison with the servo pulse. Early stabilization is possible.

[Industrial application field]

The present invention relates to a reference signal generating circuit that quickly stabilizes and generates a reference clock for head positioning.

For example, in a magnetic disk device used as an external storage device of an information processing system, there is an operation of positioning a head at a target position on a recording medium.

When performing this head positioning operation, a reference clock is created internally that serves as a reference signal for accurately positioning the target position. Attachment is necessary to perform operations quickly and accurately.

[Prior art and problems to be solved by the invention] FIG. 3 shows a block diagram illustrating a conventional example.

This block diagram forms part of a control section (not shown) of a magnetic disk drive, and constitutes a circuit that generates an arbitrary frequency in response to an external signal (in this case, a servo pulse (2)).

This block diagram shows a phase comparator 1 that compares the phase with the servo pulse ■ and sends out the phase difference as an increment signal ■ and a decrement signal ■, and an increment signal ■ and a decrement signal from the phase comparator 1. A charge pump 2 that converts the amount of phase shift due to Phase comparator 1
and a 1/N frequency divider 4 that feeds back the signal.

In a magnetic disk drive, a servo motor (not shown) that drives the rotation of a recording medium etc. starts rotating at a stable rotational speed (for example, the rotation period of the motor is 1.67m5).
) up to the first mode (HF A S T
mode), and after a stable rotational speed can be obtained, the normal mode (N.

RM A 1. (referred to as modes) to control various operations.

Normally, the servo pulses (2) obtained in the FAST mode are unstable, the pulse intervals are wide (that is, the frequency is low), and the intervals also change sequentially. Also, NORMAL
The mode has a constant pulse interval and is stable at a higher frequency than in FAST mode.

On the other hand, since the frequency band handled by the charge pump 2 is limited, it is necessary to shift the pullable band between FAST mode and NORMAL mode, and this is controlled by inputting the FAST mode/NORMAI and mode signals ■. ing.

In addition, when performing phase comparison, when comparing at a stable phase,
Although it is possible to obtain a stable output, the phase is unstable and it is difficult to obtain a stable output when compared with a phase that shifts.

That is, in the case of phase comparison using the servo pulse (2), which tends to be intermittent, it may not be possible to follow the servo pulse (2) and the comparison result may not be output.

As mentioned above, in order to obtain a stable reference clock ■ from the phase comparison results of the servo pulse ■ using the conventional method,
The problem is that it takes a considerable amount of time.

[Means for solving problems]

FIG. 1 shows a block diagram of the principle of the present invention.

This principle block diagram is the charge pump 2 explained in Fig. 3.
．． It is composed of a VCO 3, a 1/N frequency divider 4, and a phase/frequency comparison section 5 having a frequency comparison function 1 for input servo pulses, a phase comparison function, and a switching function for switching both functions.

It is assumed that the control of the charge pump 2 is always performed using the NORMAL mode signal (2).

[Effect]

The charge pump is always controlled in NORM^L mode, and the phase/frequency comparison section performs a comparison function with the servo pulse at the start-up time of the servo motor, that is, at the FAST mode, by comparing the frequency with the servo pulse frequency to ensure stability. When it reaches the NORMAL mode, the FAST mode/NORMA mode is activated by phase comparison with the servo pulse.
! , by configuring it to switch using a mode signal.
In frequency comparison in the FAST mode, even servo pulses that tend to be intermittent can be tracked, making it possible to stabilize the reference signal generation circuit at an early stage.

〔Example〕

The gist of the present invention will be specifically explained below with reference to an embodiment shown in FIG.

FIG. 2 shows a block diagram illustrating the invention in detail. Note that the same reference numerals indicate the same objects throughout the figures.

The phase/frequency comparison unit 5 of this embodiment includes a switching control unit 51 that switches the function of the phase/frequency comparison unit 5 to frequency comparison or phase comparison using the FAST mode/NORMAL mode signal ■, and a switching control unit 51 that switches the function of the phase/frequency comparison unit 5 to frequency comparison or phase comparison using the FAST mode/NORMAL mode signal A frequency comparison section 52 that compares the frequency with the frequency of the feedback signal ■ and sends out the amount of deviation, and a phase comparison section 52 that compares the phase of the servo pulse ■ with the phase of the feedback signal ■ and sends out the amount of deviation. It is comprised of a comparison section 53 and a signal output section 54 that outputs the amount of deviation sent from the frequency comparison section 52 and the phase comparison section 53 as an increment signal (2) and a decrement signal (2).

For example, the switching control section 51 controls the frequency comparison section 52 to be activated in the FAST mode, taking advantage of the fact that it is possible to follow the frequency comparison even if the servo pulse is intermittent and unsuitable. Then, the amount of frequency deviation is sent to the charge pump 2 as an increment signal (2) and a decrement signal (2).

Note that the charge pump 2 is set to the NORM^I mode frequency band (set by the NORMAL mode signal ■) from the beginning.

Next, in the NORMAL mode when the servo pulses ■ are inputted continuously and stably, the switching control section 51 switches to activate the phase comparison section 53, and from then on, the phase shift amount by phase comparison is used as a reference. Create and output clock ■.

〔Effect of the invention〕

According to the present invention as described above, even servo pulses that tend to be intermittent can be tracked, and the reference signal generation circuit can be stabilized at an early stage.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the principle of the present invention, FIG. 2 is a block diagram explaining the present invention in detail, and FIG. 3 is a block diagram explaining a conventional example. In the figure, 1.53 is a phase comparison section, 2 is a charge pump, 3 is a VCOl, 4 is a 1/N frequency divider, 5 is a phase/frequency comparison section, 51 is a switching control section, 52 is a frequency comparison section, 54 is a frequency comparison section Signal output section, favorite υ Tsuki Michi is Kofu "mouth・n 2 Kuniyoshi ζ 1 prisoner

Claims (1)

[Claims] A reference clock ([5]) necessary for positioning the head to a predetermined target position on the recording medium is converted to a servo pulse ([1]
), wherein the servo pulse ([1]) is input into the reference signal generation circuit.
The reference clock ([5
)) and the function of controlling the generation of the servo pulse ([1
phase/frequency comparison means ([
5]), and during a movement speed ramp-up period (first mode period) during which the head starts moving to the target position on the recording medium and reaches a predetermined area, the servo pulse (
[1]) is controlled by a frequency comparison with the frequency of the servo pulse ([1]), and in a stable period (normal mode period) after reaching the predetermined movement speed, the control is performed by a phase comparison with the servo pulse ([1]). A reference signal generation circuit characterized in that the reference clock ([5]) is created by switching the phase/frequency comparison means (5).