JP2684172B2 - Magnetic disk inspection method with defective bit length as evaluation condition - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk inspection method for inspecting the quality of a magnetic disk using a defective bit length as an evaluation condition. [Prior Art] A magnetic disk used in a computer system is
When the magnetic medium has a defect such as non-uniformity, the recording of the write data becomes incomplete, and a missing error or a spring error occurs. In order to eliminate such defects and maintain and improve good quality, various inspections are performed by a defect inspection device in a production factory, and among them, an inspection of the recording performance of a magnetic medium is performed. FIG. 4 shows the waveform of the inspection signal in the medium performance inspection of the magnetic disk. When it is read to the track of the magnetic disk, it becomes a sine wave signal having a constant peak value as shown in FIG. Record the test code. The read signal that reads this is due to non-uniformity of the magnetic medium, etc.
The peak value is not constant, but changes for each bit as shown in FIG. However, in the figure, the read signal is rectified and the waveform is a positive value. For one track of this waveform, the average value m of the peak value is calculated, and as an appropriate coefficient
Each bit of the read signal is tested with s ₁ > 1 and s ₂ <1 multiplied by s ₁ m and s ₂ m as the upper and lower limits, and the bits within the limits are judged as good and those outside the limits are judged as bad. To do. Here, in the case of FIG. 2B, the coefficients s ₁ and s ₂ are simply one set, but as shown in FIG. 3C, the coefficients s ₁ and s ₂ are provided with steps to improve the quality of the magnetic disk. The grades are classified. As an example, in the case of FIG.
Then, s ₁ = 1.1 and s ₂ = 0.9 are the strictest standards, and as s ₁ is larger and s ₂ is smaller, the standard is lower. Under these conditions, each bit of the test track is first judged, the number of defective bits is totaled according to the standard, and the quality of the track is judged, and the quality grade of the magnetic disk is determined by the number of defective tracks in all tracks. Is determined. An inspection method in which a plurality of stages are provided for such a coefficient to classify the quality is described in Japanese Patent Application No.
-144272, the title of the invention, "a method of inspecting a magnetic disk by a plurality of detection limit values", has already been filed. Incidentally, in the above-described totaling of defective bits, a method of simply taking the total number of defective bits as a problem has been conventionally adopted regardless of the distribution of defective bits. However,
From the viewpoint of processing the data recorded on the magnetic disk, it is considered that the number of consecutive defective data is related to the quality evaluation. That is, only one isolated defective bit or a very small number of consecutive defective bits can be detected in the soft processing stage and the error can be corrected. On the other hand, when the number of defective bits continues for a certain number or more,
Even if defective bits can be detected, they cannot be corrected and the positions of these bits cannot be used as media. Therefore, the use of the track containing the defective bit is prohibited, and another good track is replaced. Furthermore, when a large number of defective bits are continuous and more than one track has continuous defects, the magnetic disk itself is no longer defective and should be discarded. In this way, the number of consecutive defective bits (hereinafter referred to as the defective bit length) depends on the quality evaluation condition for data processing including the data code configuration method or for use, and the defective bit depends on the consecutive number. Are considered to have different weights. An inspection method for evaluating the quality of the magnetic disk based on such an idea is desired. [Object of the Invention] In view of the above, the present invention counts defective bit lengths and classifies them into length types, and multiplies the defective bit number by a weighting factor for each type to obtain a quality evaluation value. To calculate. It is an object of the present invention to provide a magnetic disk inspection method. [Means for Solving the Problems] A feature of the magnetic disk inspection method of the present invention for achieving such an object is that the number of consecutive defective bits is counted and the number of consecutive defective bits varies. The defective bit length is divided into a plurality of types, and the weighting coefficient is multiplied for each of the divided defective bit length types to calculate the total value of all types for the test track, and the total value is preset to a fixed value. The quality of the magnetic disk is evaluated based on the size of the number of good or bad tracks. Specific examples of the types of defective bit lengths in the above configuration include a defective bit length p in a range that can be corrected by an error correction code, and a range in which use of the track as a defective track is prohibited and another good track can be substituted. The defective bit length q and other good tracks cannot be replaced, or the defective bit length r is in a range where there is no alternative track. Specific examples of the evaluation in the configuration of said number of 1 relative to the defective bit length p, the number k ₁ relative to the defective bit length q (> 1), the number k ₂ with respect to the defective bit length r (> For each test track, k ₁ > 1) is used as a weighting factor, and the calculated value n is calculated by the formula: p + k ₁ q + k ₂ r = n. [Operation] In the magnetic disk inspection method using defective bit length as an evaluation condition according to the present invention, the length of the number of consecutive bits verified as defective is distinguished by the peak value of the read signal,
Considering that the longer the length, the greater the effect on the quality, the product is multiplied by a large weighting coefficient, and the quality is evaluated by the total value, so it is possible to make a rational evaluation considering the usage conditions. . The weighting factors k ₁ and k ₂ and the above reference values are arbitrarily set by the user according to the code system used by the system. [Embodiment] FIG. 1 is a diagram showing a bit sequence of a read signal for explaining the type of the defective bit length in the magnetic disk inspection method using the defective bit length according to the present invention as an evaluation condition. The average value m of the peak values of all bits is taken (m = 1), and the lower limit s ₁ m, s ₂ m are set to 1.1 and 0.9, respectively, after the test. Bits outside these limits are defective bits. The number of defective bits that can be corrected with a decimal number of 1 or 2 and the number that exceeds this number and cannot be corrected, but the number that can be replaced with another good track. The number p, q and r of each is counted as three types that are large and cannot be replaced by another track or have no alternative track.
Note that p, q, and r are not variables, but variables within a certain range. FIG. 2 is a diagram showing an embodiment of a block configuration of a processing apparatus to which a magnetic disk inspection method using a defective bit length as an evaluation condition according to the present invention is applied. Reference numeral 1 is a single-plate inspection apparatus for inspecting magnetic disks one by one. Then, the magnetic disk 2 to be inspected is mounted on this. The inspection device 1 and the write / readout circuit (R / W circuit) 3 operate under the control of the inspection sequence control circuit 7 in accordance with the instruction of the program of the microprocessor (MPU) 6, and first, a sine wave signal is generated when reading out. Such test data is written on the test track of the magnetic disk 2. Then, the test code is read, and the read signal is input to the average value circuit 4 to obtain the average value m of the peak values of the read signal for one round of the test track. In this case, the average value circuit 4 integrates the read signal waveform for one track of the track by the hardware configuration to obtain the average value m, and is a known one that has been conventionally used in inspection devices and the like. The average value m thus obtained is converted into a digital amount in the A / D circuit 5 and taken into the MPU 6. Next, in the MPU6, for the average value m, the coefficients s ₁ and
s ₂ is multiplied and given to the defect detection circuit 8 as the lower limit value after the verification. The test code is read again, the defective bit of the read signal is detected by the defect detection circuit 8, the level thereof is digitized by the A / D circuit 5, and transferred to the MPU 6. The level of the defective bit is
The purpose of A / D conversion by the A / D circuit 5 is to confirm that it is a defective bit. Here, the MPU 6 is divided into the types described in FIG. 1 according to the length of the defective bit length obtained according to the detected defective bit, and the respective numbers are counted and stored in the memory unit 9. For the defective bit lengths p, q, and r that are sequentially transferred with the rotation of the magnetic disk 1, the memory unit 9 serves as a counter (so-called soft counter), and one round of the test track is totaled for each type, and this ends. Then, the total value n is calculated by multiplying the aggregated value for each type by the respective weighting factors 1, k ₁ and k ₂ , and the quality is judged. In the same manner, each test track is similarly determined, and the number of the defective track is stored in the memory section 9. After all the test tracks have been tested, the quality of the magnetic disk is determined. In the above, the range of the number of consecutive defective bits p, q, r for the type of defective bit length, and the weighting factors k ₁ , k _{2 for each type} are predetermined in the memory unit 9 together with the processing program depending on the code system used. It is something to store. FIG. 3 shows a schematic flowchart of the processing program for the configuration of FIG. 2. First, the R / W circuit 3 writes a test code on a test track of the magnetic disk 2 and reads it. The average value m of the peak value of the read signal for one round of the test track is detected by hardware in the average value circuit 4, and the average value m is detected in the MPU 6.
Are multiplied by the coefficients s ₁ and s ₂ to calculate the lower limits s ₁ m and s ₂ m on the test, and these are set in the defect detection circuit 8. Then, in the defect detection circuit 8 in which the test code is read again, a bit out of the lower limit in terms of the test is detected as a defective bit and transferred to the MPU 6. In MPU6, the defective bit length is calculated by counting the number of consecutive defective bits.
The count values are divided into p, q, and r types, and the respective count values are stored in the memory unit 9. With the rotation of the magnetic disk 1,
The sequentially transferred defective bits are processed as described above,
One round of the test track is aggregated and stored in the memory unit 9. In MPU6 This data above _{equation: p + k 1 q + k} 2 r = n is calculated, the value of n is compared to N. . If n is less than N, the routine returns to testing the next test track, but in this case, each test track will have all the test codes recorded and will be shared by each test track by the appropriate test track. On the test,
Assuming that the lower limit value has been obtained, the next test is performed by rereading the test code of. However, it is of course free to carry out from each test track regardless of such a procedure. Next, when n is N or more,
The test track is determined to be defective and its number is stored in the memory unit 9 and the test of the next track is started. When all tracks have been tested, the number m of defective tracks is M
When m is small, the magnetic disk is considered to be good, but when it is large, it is determined to be bad,
A message to that effect is displayed if necessary. The numbers N and M are preset. In the above, the inspection of defective bits is performed only by the upper limit and the lower limit of one set, but Japanese Patent Application No.
In the case of carrying out the method of inspecting a magnetic disk with a plurality of detection limit values according to the invention proposed in No. 5, the method can be combined with the evaluation condition of the defective bit length according to the present invention to comprehensively evaluate the quality. Is something
In that case, according to the classification by the detection limit value of defective bits,
A defective track or a defective magnetic disk is determined. [Effects of the Invention] As is clear from the above description, in the magnetic disk inspection method using the defective bit length as the evaluation condition according to the present invention, the defect evaluation is performed in comparison with the quality evaluation conventionally performed by the mere number of defective bits. Paying attention to the fact that the number of consecutive bits has a great meaning in processing recorded data,
It is possible to make a rational evaluation by distinguishing the defective bit length according to the length of the continuous number, and assuming that the longer the length, the greater the impact, and multiplying the defective bit length by the weight to evaluate at the same level. is there. By combining this with a quality class judgment method that sets steps in the verification limit of defective bits, correct quality evaluation can be performed from the viewpoint of magnetic disk usage, contributing to magnetic disk inspection technology and its use. There are big things to do.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram of a bit string for explaining types of defective bit lengths in a magnetic disk inspection method using defective bit lengths as an evaluation condition according to the present invention, and FIG. 2 is a defect according to the present invention. 4 is a schematic block diagram of an embodiment of an inspection apparatus to which a magnetic disk inspection method using a bit length as an evaluation condition is applied, FIG. 3 is a schematic flowchart of a processing program for the configuration of FIG. 2, and FIGS. 10A and 10C are explanatory diagrams of a signal waveform of a test code used for quality inspection of a magnetic medium and a limit value for inspecting a defective bit in a magnetic disk inspection apparatus. 1 ... Magnetic disk inspection device, 2 ... Magnetic disk, 3 ... Write / read (R / W) circuit, 4 ... Average value circuit, 5 ... A / D circuit, 6 ... Microprocessor (MPU) , 7 ... Inspection sequence control circuit, 8 ... Defect detection circuit, 9 ... Memory section, ... Step number of flow chart.

Claims (1)

(57) [Claims] The test code recorded on the test track of the magnetic disk is read so that the crest value becomes a constant sine wave signal at the time of reading, and the crest value corresponding to each bit of the read signal is set to one or several sets, In a method of inspecting a magnetic disk for detecting a defective bit by comparing with a lower detection limit value and inspecting the magnetic disk, the number of consecutive defective bits is counted, and the number of consecutive defective bits is large or small. The defective bit length is divided into a plurality of types by, and the weighting coefficient is multiplied for each of the divided defective bit length types to calculate the total value of all types for the test track, and the total value is set in advance. The quality of the test track is judged by comparing it with a fixed reference value, and the quality of all the test tracks of the magnetic disk is judged to be good. Others on the magnitude of the number of defective tracks, and evaluating the quality of the magnetic disk, a magnetic disk testing method to evaluate the condition of the defective bit length. 2. The type of the defective bit length has a defective bit length p in a range that can be corrected by an error correction code, and the defective bit length q is a range in which the use of the track as a defective track is prohibited and another good track can be substituted. Of the defective bit length p and the defective bit length r in the range in which no alternative track exists or no alternative track exists. The weighting coefficient is k1 (k1> 1) for q and k2 (k2>k1> 1) for the defective bit length r.
The method for inspecting a magnetic disk using a defective bit length as an evaluation condition according to claim 1, wherein the calculated value n obtained by k1q + k2r = n is the total value.