JPS607653A - Magnetic disc device - Google Patents

Abstract

PURPOSE:To prevent a record from omission by detecting the difference between the number of clock signal pulses within a prescribed reading time and the number of data signal pulses to recognize the presence of a data signal. CONSTITUTION:Counting circuits 2, 4 input a clock pulse signal and a data pulse signal respectively, and when receiving a read instruction, count the numbers of pulses and send the counted values to a comparator 6 as counted value signals. The comparator 6 inputs the counted value signals, calculates the difference and then sends the calculated result to a storage circuit 8. The storage circuit 8 inputs and stores the compared signal, inputs a sending command from an upper device and then sends the stored calculated result to the host device.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic disk device, and more particularly to a magnetic disk device that performs recording using a formatting method in which the length of a record, which is a recording unit when information is recorded on a magnetic disk, is variable.

There are 20,000 recording formats for recording information on magnetic disks in magnetic disk devices: the sector format, in which the length of a physical recording unit called a record is fixed, and the format format, in which the length is variable. Which of these methods to adopt is determined as one of the design conditions of the magnetic disk device.

Among these, the recording format of the format method is as shown in Figure 1, an example of which is the home address (indicated as HA in Figure 1).
Subsequently, multiple records (几〇~Rn) are recorded with a gap (Gl) between them, and each record (
几0~Rn) is in a format in which an address mark (AM), a gap (G), and an identification code (ID) are recorded first, followed by data.
When reading these, a method is used in which the starting end of each record is determined by detecting both AM and ID, and subsequent data is read based on this determination. For this reason, when AM or ID cannot be detected due to noise or other disturbances, data is not read out, resulting in what is called a record dropout.

In the case of the first or intermediate record, such a record omission is detected by reading the record number recorded in the data of the next record, but in the case of the last record, there is no record following it, so the record is Since the omission cannot be detected and the final record is processed as if it had never been recorded, there is a risk that important data may be lost. (Basic information about the record such as record number, address, data length, etc. is recorded at the beginning of the data of each record in the format method.) Therefore, data is recorded in the final record by some means. If it is possible to grasp the fact that the last record has been recorded, the data of this final record can be read by rereading or other means, and loss of υ data can be prevented, so a highly reliable magnetic disk device can be obtained.

The present invention proposes a means to achieve the above-mentioned object, and is based on data generated from a readout signal of data recorded by modulating the number of clock pulses serving as a reference for data readout. Utilizing the fact that the number of pulses is not equal, the number of pulses of these signals is counted and compared to detect the presence of a record. By providing a means to detect the presence of a record, it is possible to prevent record dropout and create a highly reliable magnetic disk. The purpose is to provide a device.

The magnetic disk drive of the present invention includes a first counting circuit that inputs a clock pulse signal, which is a reference signal for reading data, and counts the number of pulses of the clock pulse signal in response to a read command; a second counting circuit that inputs a data pulse signal that generates pulses and counts the number of pulses of the data pulse signal in response to a read command; and inputs the outputs of the first counting circuit and the second counting circuit. a comparison circuit for detecting the difference between the number of pulses of the clock pulse signal and the number of pulses of the data pulse signal; inputting and storing an output signal of the comparison circuit; inputting a read command from a host device; and a storage circuit that outputs the stored signal.

The present invention will be described in detail below with reference to the drawings.

Figure 2 (aJ and (b) shows the clock signal and MFM method (a type of magnetic recording method, 1" and '0", respectively).
The read waveform of data written using a method in which the direction of the write current is reversed and recorded between
As shown in Figure 0, the pulse waveform of the clock signal is a waveform in which the time interval between pulses is equal to the interval T, whereas the pulse waveform of the data signal is a waveform in which the time interval between pulses is equal to the interval T, 1. For the three combinations of .5T and 2T, the number of pulses of the clock signal and the number of pulses of the data signal within the same time are different values. The same applies to most other recording systems, and generally the pulse signal of the data signal either increases or decreases with respect to the number of pulses of the clock signal, and is not equal to the number of pulses of the clock signal.

The present invention utilizes such a phenomenon to recognize the presence of a data signal by detecting the difference between the number of pulses of the clock signal and the number of pulses of the data signal within a predetermined read time. An embodiment of the present invention is shown in a block diagram in FIG. 3.

In FIG. 3, counting circuits 2 and 4 input a reflex clock pulse signal 102 and a data pulse signal 104, receive a read command 106, count the number of pulses, and transmit the counted value to a counted value signal 108 and a data pulse signal 104, respectively. It is sent to the comparator circuit 6 as 110.

Comparison circuit 6 inputs count value signals 108 and 110, calculates the difference between them, and sends the result to storage circuit 8 as comparison signal 112. The storage port #158 inputs and stores the comparison signal 112, inputs a send command 114 to the host device, and sends the stored calculation result to the host device.

The magnetic disk device configured as described above operates as follows.

When a data read operation is performed in a magnetic disk device, a clock pulse signal 102 and a data pulse signal 104, which are generated from the read waveforms of the clock signal and data signal read from the servo head and the data head, are generated by the counting circuit 2 and the data pulse signal 104, respectively. At the same time, a read command (see FIG. 1) 106 is also input to the counting circuits 2 and 4.

Counting circuits 2 and 4 count the number of pulses included in clock pulse signal 102 and data pulse signal 104 at the time specified by this read command 106 and send the values to comparison circuit 6 as count value signals 108 and 110. , the comparison circuit 6 receives the count value signals 108 and 110.
is received, the difference in the number of pulses is calculated, and the result is sent to the storage circuit 8 as a comparison signal 112.

The storage circuit 8 receives this comparison signal 1 sent from the comparison circuit 6.
12 is received and stored, and when the transmission command 114 is received from the host device, the stored division result is sent to the host device, so the host device receives this and determines whether the comparison results are equal or not. By determining whether or not the record is large, it is possible to recognize whether the record exists or not, and it is therefore possible to determine whether the record is missing.
When a record is missing, it is possible to read the record by re-reading or other means, thereby preventing record omission.

As described above in detail, by using the magnetic disk device of the present invention, there is an effect that a highly reliable magnetic disk device that prevents record omissions can be obtained.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the recording format according to the format method, and Figures 2 (a) and (b) respectively show the read waveforms of the clock signal and the data signal by the MFM, and the waveforms of the signal converted from them into pulse signals. Waveform diagram shown,
FIG. 3 is a block diagram showing one embodiment of the present invention. In the figure, 2.4...counting circuit, 6...
... Comparison circuit, 8... Storage circuit. 31

Claims (1)

[Claims] a first counting circuit that inputs a clock pulse signal that is a reference signal for reading data and counts the number of pulses of the clock pulse signal according to a read command; and a data pulse that generates a pulse corresponding to the peak of a data read waveform. a second counting circuit that inputs a signal and counts the number of pulses of the data pulse signal according to a read command; and a second counting circuit that inputs the outputs of the first counting circuit and the second counting circuit and counts the number of pulses of the clock pulse signal. and a comparison circuit for detecting the difference between the number of pulses of the data pulse signal and the number of pulses of the data pulse signal, and a storage for inputting and storing the output signal of the comparison circuit, inputting a read command from a host device, and outputting the stored signal. A magnetic disk device comprising a circuit.