JP2903335B2 - Error detection circuit of magnetic disk tester - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an error detection circuit for a magnetic disk tester, and more particularly, to a test using a test signal having a frequency exceeding a response frequency of an analog comparator for detecting an error. The error detection circuit.

2. Description of the Related Art A hard magnetic disk (hereinafter simply referred to as a magnetic disk) as an information recording medium is inspected by a magnetic disk tester because an error occurs in data if the medium has a defect.

An error checking method for a magnetic disk will be described with reference to FIGS. In FIG. 1A, a magnetic head 2a and an amplifier 2
A test signal of an appropriate frequency is written / read by b. The read test signal SR includes a missing error in which the waveform disappears due to a defect in the magnetic disk, a modulation error in which the amplitude of the waveform fluctuates, and incomplete reading when the test signal is erased. Signal has an extra error.
In the error check, as shown in (b), the read test signal SR is input to the TAA measuring circuit 3 to calculate an average value (TAA) for one round of the track. The reference voltage TAA is multiplied by a coefficient in percent by the reference voltage generating circuit 4 to obtain a reference voltage SL, which is applied to the + terminal of the analog comparator 5, and the test signal SR is applied to the-terminal to compare the two. You. In (c), the test signal S
Since the peak value of the waveform (a) of R exceeds the reference voltage SL, the detection pulse Pc is output, which is normal. However, since the peak value of the waveform (b) does not reach SL, Pc is not output. In the error determination circuit 6, the presence or absence of Pc is checked at a timing synchronized with the test signal SR, and when Pc is not input at that timing, it is determined that a missing error Em occurs, and under the control of the microprocessor (MPU) 8, Error data is recorded in the memory 7.

As described above, when the peak value of the test signal SR is equal to or slightly exceeds the reference voltage SL as shown in the waveform (c) of the same (c), the comparison between the two by the analog comparator is not always performed reliably. That is, when the time width Δt of the test signal SR cut off by the reference voltage SL is very short, the detection pulse Pc is not output depending on the response characteristics of the analog comparator, so that SR> SL
However, the error determination circuit determines that the error is a missing error Em. (D) shows the case of an extra error. In this case, the test signal is erased and then read out, and the reference voltage is set to SL 'different from the above, and the two are compared by the analog comparator 5, and the erasure error exceeding the reference voltage SL' is detected. Detection pulse for complete signal waveform (d)
Pc 'is detected, and the error determination circuit 6 determines that the extra error Ee has occurred. Also in this case, when the time width Δt cut off by the reference voltage SL ′ is very short, the detection pulse Pc ′ is not output, and therefore, even though the peak value of the waveform exceeds SL ′, extra Error E
e is not detected.

[Problem to be Solved] The following test and analysis were performed by the inventor of the present invention in order to obtain the above problem, that is, the response characteristic time Δt of the analog comparator. FIG. 3 (a) shows a test circuit, in which the + and-terminals of the analog comparator 5 have the same frequency f, the same amplitude, and the opposite sine wave voltages v,
give v ′. Appropriate bias voltages are applied to both terminals to cross the negative peak of the voltage v and the positive peak of the voltage v 'as shown in FIG. Assuming that the time width of the intersecting portion is Δt, Δt changes due to the change of the frequency f, and the converter 5 operates and outputs the detection pulse Pc for the frequency at which Δt becomes a certain value or more. However, at frequencies higher than that, Pt is not output because Δt is short. A value of 2nSec (2 × 10 ⁻⁹ seconds) is obtained as the minimum value of Δt. However, at this stage, the limit of the frequency f has not been specified yet. This is because the value of Δt changes depending on the positional relationship between the two intersecting peaks. It should be noted that, in general, the minimum value of Δt is not specified as a standard of the analog comparator. The analog comparator used in the test had the highest response characteristic at present.

In response, the upper limit of the frequency f was specified by the following analysis. In the above-described error detection of the test signal, the reference voltage SL or SL 'is changed in increments of%. In FIG. 7C, the curve shows the sine wave voltage v in the phase angle range (0 to π / 2). v and its 99% (0.9%)
9) Calculate the phase angle Δθ of the point, and calculate this as Δt / 2, that is,
If 1 nSec is set, the frequency of the sine wave voltage v is immediately obtained. The calculated frequency f is 22.5 MHz, which is the upper limit of the detectable frequency f in 1% steps.

Conventionally, the test signal for error check has 15 to 20
Although a frequency of MHz is used, a frequency of, for example, 40
It is necessary to improve to MHz. On the other hand, since the analog comparator has the above-mentioned upper limit of the frequency, it cannot be applied as it is, and some countermeasure is required.

The present invention has been made in view of the above, and an object of the present invention is to provide an error detection circuit that can improve the frequency of a test signal by adding an appropriate circuit to an analog comparator of a magnetic disk tester. .

Means for Solving the Problems According to the present invention, an average value of a read voltage for one round of a track of a test signal written on a track of a magnetic disk to be inspected is calculated, and a coefficient in% increments is calculated. An error detection circuit in a magnetic disk tester that checks a test signal error by comparing the reference voltage with a read voltage of a test signal by an analog comparator, and detects each rising point of the read voltage. A pulse generating circuit that generates a rectangular pulse having an appropriate time width, a pulse synchronizing circuit that synchronizes the phase of the rectangular pulse with a peak point of a read voltage to obtain a peak hold signal, and a read and control circuit that is controlled by the peak hold signal. Detects each peak value of the voltage and extends this peak value by the time width of the peak hold signal and holds it. Each peak extension signal output from the peak hold circuit is input to an analog comparator and compared with a reference voltage.

[Operation] In the above-described error detection circuit, the pulse generation circuit detects the rising point of the read voltage of the test signal and generates a rectangular pulse having an appropriate time width. The phase of this rectangular pulse is synchronized with the peak point of the read voltage by the pulse synchronization circuit to create a peak hold signal, and the peak hold signal is used to control the peak hold circuit and detect each peak value of the read voltage. At the same time, each peak value is extended and held by the time width of the peak hold signal (equal to the time width of the rectangular pulse). The held peak extension signal is input to the analog comparator and compared with the reference voltage.If the time width of the read voltage exceeding the reference voltage is smaller than the response time width of the analog comparator, the peak value is extended, so it is ensured. Is detected. This makes it possible to improve the frequency of the test signal regardless of the upper limit of the frequency of the analog comparator due to the restriction of the response time width.

Embodiments FIGS. 1A and 1B show a configuration diagram of an embodiment of an error detection circuit of a magnetic disk tester according to the present invention, and a time chart of waveforms for the operation thereof. 4A, a test signal is written / read to / from the track 1a of the magnetic disk 1 by the magnetic head 2a and the amplifier 2b, and the read test signal SR is an average value for one round of the track by the TAA measuring circuit 3. Is calculated, and the average value is multiplied by a coefficient of% in the reference voltage generation circuit 4 to obtain a reference voltage SL for a missing error, a modulation error, or a reference voltage S for an extra error.
L ′ is created and supplied to the + terminal of the analog comparator 5. The above is the same as the conventional method of creating the reference voltage described with reference to FIG. In the present invention, a test signal SR is input to a pulse generation circuit 9 to detect each rising point of the test signal SR, and a rectangular pulse train Ph having an appropriate time width th is described. Occurs. Next, the pulse synchronization circuit 10 synchronizes the phase of the rectangular pulse train Ph with the peak point of the test signal SR to create a peak hold signal SPH, and thereby controls the peak hold circuit 11. The test signal SR is input to the peak hold circuit 11, the peak value of each waveform is detected, and the peak hold signal SPH is controlled to control the peak hold signal SPH to extend the peak value by the time width th as shown in the figure.
Can be obtained. The peak extension signal Sh is input to the negative terminal of the analog comparator 5, and the above-mentioned reference voltage SL or SL '
Is compared to Now, when the voltage va of the test signal SR slightly exceeds the reference voltage SL, the time width Δ
Even when t is shorter than the minimum response time 2 nSec of the analog comparator, the peak value is extended and the crossing time is long in the peak extension signal Sh, so that the comparison operation is performed reliably and the detection pulse Pc is output. Therefore, regardless of the upper limit frequency of the analog comparator, for example, 22.5 MHz, the frequency of the test signal with respect to the reference voltage SL or SL ′ in increments of% is set within the range of the response frequency of the peak hold circuit 11, for example.
It is possible to improve up to 40MHz. Note that the pulse synchronization circuit 10 can be constituted by a phase lock circuit or the like, and the peak hold circuit can be easily constituted by ordinary circuit technology, and therefore the description is omitted.

The detection pulse Pc output as described above is input to the error determination circuit 6 to determine each error as in the related art.
The data is recorded in the memory 7 under the control of the MPU 8.

[Effects of the Invention] As is apparent from the above description, in the error detection circuit of the magnetic disk tester according to the present invention, the peak hold signal synchronized with the peak point of the read voltage by the pulse generation circuit and the pulse synchronization circuit. Is created, the peak hold circuit is controlled by this signal, each peak value of the read voltage is detected, and the peak value is extended by the time width of the peak hold signal and held.
The held peak extension signal is input to an analog comparator and compared with a reference voltage. Even when the time width of the read voltage exceeding the reference voltage is smaller than the response time width of the analog comparator, the peak value is extended, so that the detection is reliably performed. As a result, the frequency of the test signal can be further increased regardless of the upper limit of the frequency of the analog comparator due to the restriction of the response time width.
There is a great effect that the test performance of the tester can be improved with respect to the magnetic disk of high density.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are a block diagram of an embodiment of an error detection circuit of a magnetic disk tester according to the present invention, and time charts of waveforms of respective parts, and FIGS.
(B), (c) and (d) show a conventional magnetic disk tester error checking method and a waveform diagram explaining the problem,
3 (a), 3 (b) and 3 (c) are diagrams for explaining a test and analysis method for the response characteristics of the analog comparator. 1: magnetic disk, 1a: track, 2a: magnetic head, 2b
... Amplifier, 3 ... TAA (average value of one track) measurement circuit, 4 ... Reference voltage generation circuit, 5 ... Analog comparator, 6 ... Error judgment circuit, 7 ... Memory, 8 ... Microprocessor (MPU), 9 ... Pulse Generation circuit, 10: pulse synchronization circuit, 11: peak hold circuit, SR: read test signal, Pc: detection pulse, Ph: rectangular pulse, SL, SL '
… Reference voltage, Sh… Peak extension signal.

Claims (1)

(57) [Claims] An average value of a read voltage of a test signal written on a track of a magnetic disk to be inspected for one round of the track is calculated, and the average value is multiplied by a coefficient in% to obtain a reference voltage. An analog comparator compares the reference voltage with the read voltage, and detects each rising point of the read voltage in a magnetic disk tester for checking an error of the test signal to generate a rectangular pulse having an appropriate time width. A pulse generation circuit, a pulse synchronization circuit that synchronizes the phase of the rectangular pulse with the peak point of the read voltage waveform to make a peak hold signal, and is controlled by the peak hold signal to calculate each peak value of the read voltage. A peak hold circuit that detects and holds each detected peak value by the time width of the peak hold signal. Ri is configured, and comparing with the reference voltage of each peak extension signal outputted from the peak hold circuit is input to the analog comparator, the error detection circuit of a magnetic disk tester.