JP3160923B2 - Control circuit for magnetic disk drive - Google Patents

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 control circuit therefor.

[0002]

2. Description of the Related Art Conventionally, a magnetic disk drive has a servo disk medium, and a control circuit generates a signal for positioning a write / read head based on information recorded on the disk medium. That is, the control circuit generates a servo pulse signal by pulsing the signal read from the servo disk medium, and further generates a servo clock signal synchronized with the servo pulse signal by the phase-locked oscillation circuit. And the servo
A pulse signal of a specific pattern included in the servo pulse signal, that is, an index pattern, is detected based on the clock signal, and an index pulse signal is generated when the pulse signal is detected. Since the index pattern appears every one rotation of the magnetic disk, the index pulse signal is output every one rotation of the magnetic disk, and the positioning of the head is determined by the index pattern.
This is performed using a pulse signal.

[0003]

By the way, the signal read from the servo disk medium is weak, and the detection and pulsing may not be performed correctly due to mixing of external noise and the like. In such a case, it becomes difficult to detect the index pattern pulse signal,
Missing or erroneous occurrence of the index pulse signal occurs, causing a failure in the write operation of the magnetic disk device.

In the conventional magnetic disk drive, when writing or reading data to or from a disk medium, if the access area extends over a plurality of cylinders, the head is immediately moved to the beginning due to the movement time of the head when switching cylinders. And a waiting time called a rotation waiting time is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control circuit for a magnetic disk drive which solves such a problem, prevents a failure during a write operation, increases reliability, and can reduce the rotation waiting time. Is to do.

[0006]

Means for Solving the Problems A first aspect of the present invention is a servo system.
A control circuit for a magnetic disk drive that generates an index pulse signal based on a signal read from a disk medium; a servo pulse detection unit that pulsates the signal read from the servo disk medium and outputs a servo pulse signal; A clock generating means for outputting a servo clock signal synchronized with the servo pulse signal; and detecting a pulse signal of a predetermined pattern included in the servo pulse signal using the servo clock signal. An index pattern detecting means for outputting a signal, a counting means for counting the servo clock signal, and an index pulse signal when the count value of the counting means reaches a predetermined count value,
And a pulse generating means for initializing the counting means, a count value setting means for setting the predetermined count value based on a cylinder number, and each time the index / pattern detecting means outputs the detection pulse signal, First error detecting means for checking whether or not the count value of the counting means matches the predetermined count value, and initializing the counting means when the count value does not match continuously a predetermined number of times. Features.

According to a second aspect of the present invention, in a control circuit of a magnetic disk device for generating an index pulse signal based on a signal read from a servo disk medium, a signal read from the servo disk medium is pulsed to generate a servo signal. Servo pulse detecting means for outputting a pulse signal; clock generating means for outputting a servo clock signal synchronized with the servo pulse signal; and a predetermined clock included in the servo pulse signal using the servo clock signal. When detecting a pulse signal of a pattern, an index pattern detecting means for outputting a detected pulse signal, and a counting means for counting the servo clock signal,
When the count value of the counting means becomes a predetermined count value, an index pulse signal is output, and the pulse generating means for initializing the counting means and the predetermined count value are set based on a cylinder number. Each time the count value setting means and the index / pattern detection means output the detection pulse signal, it is checked whether or not the count value of the counting means matches the predetermined count value. First error detecting means for initializing the counting means when the values do not match, and when the index / pattern detecting means outputs the detection pulse signal, the count value of the counting means matches the predetermined count value. A second error detection means for outputting a first error detection signal when not performed, and a count value of the counting means becomes the predetermined count value, and A third error detection unit that outputs a second error detection signal when the turn detection unit does not output the detection pulse signal; and a third error detection unit that outputs the first error detection signal. Alternatively, when the third error detection means outputs the second error detection signal, an error processing means for outputting a signal for prohibiting writing to a disk medium is provided.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a control circuit of the magnetic disk drive according to the first and second inventions. The servo pulse detector 1 receives the signal S1 read from the servo disk medium.
And outputs a servo pulse signal S2. The pulse signal S2 includes a pulse signal of a specific pattern by dropping a pulse, that is, an index pattern. The phase-locked oscillator 2 oscillates in phase with the servo pulse signal S2 and outputs a servo clock signal S3. The clock signal S3 does not include the above-mentioned index pattern, and the period of the clock signal S3 is constant even if the servo pulse signal S2 has a temporary pulse loss or a timing error due to the entry of noise or the like. is there. The index pattern detector 3 uses the timing of the clock signal S3 as a reference,
An index pattern is detected by monitoring a pulse missing pattern of the pulse signal S2. And index
When a pattern is detected, an index pattern detection signal S4 is output.

The loop counter 4 counts the clock signal S3, and when the count value matches a predetermined count value provided by the count value setting unit 8, the index pulse signal S7.
Is output, the count value is initialized, and the count of the clock S3 is continued. Each time the timing error detector 5 receives the detection signal S4, it checks whether or not the count value S5 of the counter 4 matches the predetermined count value. If they do not match, the index timing error signal S
8 and outputs a reset signal S6 to initialize the counter 4 when the mismatch is repeated a predetermined number of times. The count value setting unit 8 sets the cylinder number S1 to be accessed.
3 is received from another control circuit (not shown), a count value is set based on the number, and output to the counter 4.

The control circuit of the magnetic disk drive according to the first invention is constituted by the above components. However, the function of the timing error detector 5 outputting the error signal S8 is for the second invention. The control circuit of the magnetic disk drive according to the second invention further includes an index missing detector 6 and an index error processor 7.

When the count value S5 from the counter 4 reaches the above-mentioned predetermined count value, the index missing detector 6 checks whether or not the detection signal S4 is input, and the detection signal S4 is not input. At this time, an index missing detection signal S9 is output. Index error processor 7
Receives an error signal S8 and a detection signal S9 from the detectors 5 and 6, respectively, and outputs an index / error detection signal S11 to a higher-level circuit (not shown) when at least one of the signals is input. A write control signal S12 that disables switching of a write gate signal S10 for controlling writing to a disk medium to an active state.
To a data writing circuit (not shown).

Next, the operation of the part constituting the control circuit of the magnetic disk drive according to the first invention will be described. The servo·
When receiving the signal S1 read from the servo disk medium, the pulse detector 1 converts the signal S1 into a pulse to generate a servo signal.
The pulse signal S2 is output. The phase-locked oscillator 2 oscillates in phase with the servo pulse signal S2 and outputs a servo clock signal S3.

The count value setting unit 8 sets a count value corresponding to one rotation of the magnetic disk based on the given cylinder number S13, and outputs it to the counter 4. The loop counter 4 counts the clock signal S3 output from the oscillator 2,
When the count value matches the count value provided by the count value setting device 8, the index pulse signal S7 is output, the count value is initialized, and the counting of the clock signal S3 is continued. The clock signal S3 supplied to the counter 4 has a constant period even if there is a temporary pulse loss or a timing error due to noise mixing in the servo pulse signal S2 as described above. Output a stable index pulse signal S7.
Therefore, the reliability of the write operation can be improved by performing the write operation based on the index pulse signal.

When writing or reading data over a plurality of cylinders and switching cylinders, the count value setting unit 8 appropriately sets the count value to be output to the counter 4 according to the cylinder number. As a result, the time required for cueing can be minimized, and as a result, the rotation waiting time can be reduced.

On the other hand, the index / pattern detector 3
Monitors the missing pattern of the pulse of the pulse signal S2 based on the timing of the clock signal S3 to detect the index pattern. When an index pattern is detected, an index pattern detection signal S4 is output. Each time the timing error detector 5 receives the detection signal S4, the count value S
It is checked whether or not 5 matches the count value set by the count value setting device 8. If there is a discrepancy, the number of times the discrepancy is counted is counted. If discrepancies are detected a predetermined number of times, the counter 4 is initialized. In other words, the fact that such a mismatch continues is highly likely that the timing of the index pulse signal S7 has deviated from the correct appearance timing of the index pattern for some reason. S
7 should match the timing of the index pattern appearance. The detector 5 performs the function for that.

Next, the operation of the control circuit of the magnetic disk drive according to the second invention will be described. In addition to initializing the counter 4 as described above, the detector 5 checks whether the count value S5 of the counter 4 matches the count value set by the count value setting device 8 when receiving the detection signal S4. If they do not match, the index timing error signal S8 is output assuming that the timing of index pattern detection is shifted. Also, the index missing detector 6
When the count value S5 from the counter 4 reaches the count value set by the count value setting device 8, it is checked whether or not the detection signal S4 is input. If the detection signal S4 is not input, the index pattern is used. Is missing, an index missing detection signal S9 is output. The index error processor 7 outputs error signals S8 from the detectors 5 and 6, respectively.
And the detection signal S9, and when at least one of the signals is input, the index error detection signal S11
To the host circuit, and sends a write control signal S12 to the data write circuit, which disables switching of the write gate signal S10 for controlling writing to the disk medium to the active state. In other words, data writing in a state where the detector 5 detects a timing error of the index pattern or the detector 6 detects a lack of the index pattern is prohibited. Helps improve reliability.

[0017]

As described above, in the control circuit of the magnetic disk drive of the first invention, the servo clock signal synchronized with the servo pulse signal is counted, and the count value is initialized every time the count value reaches a predetermined value. And the generation of index pulse signals. The servo clock signal is not easily affected by missing or erroneously detected pulses in the servo pulse signal.
A pulse signal is obtained, and the reliability of the writing operation is improved.

Further, since the predetermined count value can be set based on the cylinder number, when switching cylinders, the phase of the index pulse signal is appropriately changed according to the cylinder number to minimize the time required for cueing. Anyway, the rotation waiting time can be reduced.

According to the control circuit of the magnetic disk drive of the second invention, in addition to the effect of the first invention, when the index pattern of the servo pulse signal is lost or a timing error occurs, the write protection is instructed. Since a signal is output, the reliability of the write operation is further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a control circuit of a magnetic disk drive according to first and second inventions.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Servo pulse detector 2 Phase synchronous oscillator 3 Index pattern detector 4 Loop counter 5 Timing error detector 6 Missing index detector 7 Index error processor 8 Count value setting device

Claims (2)

(57) [Claims] In a control circuit of a magnetic disk drive for generating an index pulse signal based on a signal read from a servo disk medium, a signal read from the servo disk medium is pulsed to output a servo pulse signal. Servo pulse detecting means, clock generating means for outputting a servo clock signal synchronized with the servo pulse signal, and a pulse signal of a predetermined pattern included in the servo pulse signal using the servo clock signal Index pattern detecting means for outputting a detection pulse signal when detecting
Counting means for counting clock signals; and when the count value of the counting means reaches a predetermined count value,
A pulse signal output means, a pulse generating means for initializing the counting means, a count value setting means for setting the predetermined count value based on a cylinder number, and the index / pattern detecting means for detecting the detected pulse signal. A first error detecting means for checking whether or not the count value of the counting means matches the predetermined count value each time the count value is output, and initializing the counting means when the count value does not continuously match the predetermined number of times; And a control circuit for a magnetic disk drive. 2. A control circuit for a magnetic disk drive for generating an index pulse signal based on a signal read from a servo disk medium, wherein the signal read from the servo disk medium is pulsed to output a servo pulse signal. Servo pulse detecting means, clock generating means for outputting a servo clock signal synchronized with the servo pulse signal, and a pulse signal of a predetermined pattern included in the servo pulse signal using the servo clock signal Index pattern detecting means for outputting a detection pulse signal when detecting
Counting means for counting clock signals; and when the count value of the counting means reaches a predetermined count value,
A pulse signal output means, a pulse generating means for initializing the counting means, a count value setting means for setting the predetermined count value based on a cylinder number, and the index / pattern detecting means for detecting the detected pulse signal. A first error detecting means for checking whether or not the count value of the counting means matches the predetermined count value each time the count value is output, and initializing the counting means when the count value does not continuously match the predetermined number of times; And second error detecting means for outputting a first error detection signal when the count value of the counting means does not match the predetermined count value when the index pattern detecting means outputs the detection pulse signal. When the count value of the counting means becomes the predetermined count value and the index pattern detecting means does not output the detection pulse signal, a second error A third error detection unit that outputs an output signal, and the second error detection unit outputs the first error detection signal, or the third error detection unit outputs the second error detection signal. An error processing means for outputting a signal for prohibiting writing to a disk medium when output, a control circuit for a magnetic disk device, characterized by comprising: