JPH0738268B2 - Data recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a data recording method for reading and checking recorded data and rewriting when an error occurs in data recording in a magnetic tape device or the like. It is about.

[Conventional technology]

A method is known in which a dual gear head having a recording gear and a reproducing gear is used to record data while reproducing (read after write) to check a data error and rewrite when an error occurs. . This type of writing method can also be performed using a recording / playback head. Conventionally, the above error detection is performed by determining whether or not the analog output obtained from the head is equal to or more than a threshold value (threshold), or by a CRC check or the like.

[Problems to be solved by the invention]

By the way, if the instantaneous velocity fluctuation (ISV) of the tape and the peak shift of the reproduction waveform are sufficiently managed, the time axis error during recording and reproduction will be extremely small, but the cost of the magnetic tape device will inevitably increase. . Further, as the recording density is increased, the fluctuation of the time width becomes a problem. In the conventional recording method, since the time margin between the sampling pulse and the data is not checked, the rewriting is performed assuming that the writing is normally performed even if the time margin is small. Absent. For example, when the read data shown in FIG. 4 (A) is sampled and output by the sampling pulse shown in FIG. 4 (B), in the conventional method, the first data is compared with the sampling pulse shown in FIG. 4 (B). Regardless of whether the read data in FIG. 4 (A) is at the position of the solid line or at the position of the dotted line, it was regarded as normal recording. If the time axis relationship between the sampling pulse and data during read-after-write and those relationships during data reading in the playback mode match, normal reading is possible even with the dotted line. Not necessarily the same. In the playback mode, for example, the instantaneous speed fluctuation of the tape becomes large, and FIG.
If the read data of is moved further to the right of the position of the dotted line, it becomes impossible to read the data.

In order to solve this kind of problem, it is disclosed in Japanese Patent Laid-Open No. 53-70415 that the error is detected by switching the width of the reproduction information pulse or the clock pulse when the reading is performed at the same time as the writing of the data. There is. However, it is necessary to provide means for switching the pulse width, which inevitably increases the cost of the device.

Therefore, an object of the present invention is to provide a data recording method capable of easily performing highly accurate recording capable of preventing the occurrence of an unreproducible state.

[Means for Solving the Problem] The present invention for achieving the above object includes a step of writing data in a recording medium, a step of reading the data, and a sampling of read data obtained in the reading step. The front side time margin consisting of the time interval between the sampling pulse and the leading edge of the pulse indicating the read data is measured, and the rear side time margin consisting of the time interval between the sampling pulse and the trailing edge of the pulse indicating the read data is measured. Comparing the step of measuring and the front side time margin and the rear side time margin and two predetermined values for the front side and the back side, respectively, which indicate a time axis fluctuation range that may occur in the reproduction mode, A step of determining whether the front time margin and the rear time margin are greater than or equal to the predetermined value or less, and the front time margin The present invention relates to a data recording method, which comprises the step of, when it is determined that the margin or the rear side time margin is less than the predetermined value, regard this data as an error and rewrite it in the recording medium.

[Action]

When the data is recorded, the time axis of the recording waveform is deviated due to an instantaneous speed fluctuation or the like. The data read for the check is sampled. If data is generated during the sampling pulse, normal data can be read. According to the present invention, even if the sampling pulse occurs at a time when normal sampling can be performed, the writing is not completed immediately and the time margin between the sampling pulse and the data is determined. If this time margin is less than the predetermined value, even if normal sampling is possible, it is regarded as an error and data is rewritten. If this time allowance is determined to be equal to or larger than the time-axis fluctuation range that may occur in the reproduction mode, it will not happen that the recorded data cannot be read in the reproduction mode.

〔Example〕

Next, a data recording / reproducing method according to the embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a part of a cassette type magnetic recording / reproducing apparatus generally called a cassette tomato reamer. A magnetic tape (1) as a recording medium is in contact with a composite magnetic head (4) in which a recording (write) head (2) and a reproducing (read) head (3) are integrated. A recording (write) circuit (5) is connected to the recording head (2), and a reproducing (read) circuit is connected to the reproducing head (3). The recording circuit (5) is a buffer memory, CRC addition circuit, NRZI (Nonreturn to Zero Inv).
erted) signal forming circuit and the like.

On the reproduction side, the reproduction head (3) is connected to the demodulation circuit (7) via the head amplifier (6). The demodulation circuit (7) is a circuit that includes a peak detection circuit and the like to obtain read data (RD) in a binary format. In this example, since the data is recorded in the NRZI system, the demodulation circuit also outputs read data in this system.

The data sampling circuit (8) connected to the demodulation circuit (7) samples the read data (RD) to obtain sample data (SD).

In the synchronous oscillator circuit (9), a sampling pulse (clock pulse) synchronized with the read data (RD) is created, and this is given to the sampling circuit (8) by the line (10), and the time for measuring the time margin according to the present invention is provided. The signal (clock) is sent to a time margin (time margin) measuring circuit (11).

The time margin measuring circuit (11) is connected to a demodulation circuit (7) and a data sampling circuit (8) in addition to the synchronous oscillation circuit (9), and sampling pulse and data pulse are generated based on signals obtained from these circuits. Of the sampling pulse and the trailing edge of the data pulse.

The time margin determination circuit (14) connected to the time margin measurement circuit (11) by the two lines (12) and (13) has a front side time margin M _E and line (12) obtained on the line (12). 13) Rear side time margin M _L
It is determined whether or not both are equal to or more than a predetermined value or less than a predetermined value, and if less than a predetermined value, a signal indicating a time axis error is output to the line (15).

The read voltage determination circuit (16) connected to the head amplifier (6) is composed of a voltage comparator, compares the threshold voltage (threshold value) with the read voltage, and the read voltage is lower than the threshold voltage. Sometimes it outputs a voltage axis error signal on line (17). The lines (15) and (17) are connected to a control device (19) composed of a CPU or a device on the host side via an OR gate (18). CRC for control device (19)
Since the check circuit (19a) is also connected, a rewrite instruction signal is generated and the recording circuit (5) outputs the same data or data even if any of the time axis error, the voltage axis error and the error due to the CRC check is detected. Rewrite the data group.

FIG. 2 shows the synchronous oscillator circuit (9), the time margin measuring circuit (11), and the time margin judging circuit (14) of FIG. 1 in detail. The synchronization signal oscillator circuit (9) is a 2n + 1-phase pulse generation circuit, and has a front output that generates n pulses before and after with a time difference around the sampling pulse, in addition to the output terminal DSP that generates the sampling pulse. Terminal EP ₁
To EP _n and rear output terminals LP _{1 to} LP _n . The time margin measuring circuit (11) is composed of front side and rear side time margin measuring circuits (20) and (21). The front side time margin measuring circuit (20) includes output terminals EP ₁ to EP _{1 of the} synchronous oscillation circuit (9). E
P _n is connected, and output terminals LP _{1 to} LP _n are connected to the time margin measuring circuit (21) on the rear side. Further, the read data (RD) output line of the demodulation circuit (7) and the sampling circuit (8) are connected to the respective measurement circuits (20) and (21) as shown in FIG.

The time margin determination circuit (14) includes two digital comparators (22) and (23), two timing margin predetermined value generation circuits (24) and (25), and an AND gate (26). One input terminal of the front side time margin comparator (22) is connected to the front side time margin measuring circuit (20), and the other input terminal is connected to the front side time margin predetermined value generating circuit (2
4) is connected to. Rear time margin comparator (2
3) One input terminal is the rear time margin measurement circuit (2
1) and the other input terminal is connected to the rear time margin predetermined value generating circuit (25). The output terminals of the two digital comparators (22) (23) are AND gates (26)
It is connected to the.

(Operation) Next, the measurement and determination of the time margin will be described with reference to FIG. 3 showing the states of the respective parts in FIG. If NRZI format read data indicated by RD in FIG. 3 is generated and a sampling pulse indicated by DSP is generated from the output terminal of the synchronous oscillation circuit (9), this is sent to the sampling circuit (8), The sample data shown in SD in the figure is obtained. The time margin measuring circuits (20) (21) on the front side and the rear side of the sampling pulse compare the read data RD input here with the output pulses EP _{1 to} EP _n , LP of the synchronous oscillation circuit (9).
Sampling is from _{1 to} LP _n . EP _n to DSP and DSP to L
The time width to P _n is determined to be somewhat longer than 1/2 of one bit width. In FIG. 3, EP _n has occurred before the time t ₁ when the read data RD changes from the low level to the high level, so the sampling output by EP _n is “0”. However, the pulses EP ₃ , EP ₂ , which occur after t ₁ ,
Sampling output by EP _1, etc. is "1". These sampling outputs are written into a memory comprised of flip-flops included in the measuring circuit (20). After that, when a sampling pulse indicated by DSP occurs at time t ₂ , sample data SD sampled by this occurs.
From the sampling circuit (8), which is sent to the measuring circuit (20). Sample data for measuring circuit (20)
The same value as SD is measured as time margin data. That is, since t ₁ ~t ₂ in the read data of FIG. 3 (RD) is high level, used as a data having a relationship sampling output "1" to the time margin. For example EP _n
... EP _3, EP _2, in correspondence with the sampled output by EP ₁ outputs a [0 ... 111] as a time margin data.

The time margin is measured at the sampling pulse cycle indicated by DSP. Measurements of the time margin is also performed in accordance connexion t ₂ ~t ₃ sections. EP _{1 to} E during the period from t _{2 to} t ₃
Since all sampling outputs of P _n and LP _{1 to} LP _n are “1”,
Data showing a sufficient time margin is obtained.

t ₃ in ~t ₅ of section, LP ₁ ~LP _n after t ₃ time points DSP
Are sequentially generated, the read data (RD) is sampled by LP _{1 to} LP _n in the time margin measuring circuit (21) on the rear side, and the sampling output obtained thereby is written in the memory composed of flip-flops.
In the rear side time margin measurement circuit (21), LP ₁
~ Read the time margin based on the sample data (SD) by DSP preceding LP _n . That is, at time t ₃
Based on "1" which is sample data (SD) by DSP,
The same "1" sampling output can be obtained, for example
Sampling output for LP ₁ , LP ₂ , LP ₃ “1” “1” “1”
Is output as data indicating the time margin M _L.

In the period from t _{3 to} t ₅ , EP _n to EP ₁ are input to the front side time margin measuring circuit (20). Therefore, the sampling output of the read data (RD) is obtained. In this case, the output of EP _n is “1”, but EP ₃ , EP ₂ , E
An output of "0" is obtained for P _{1 and so} on. DS at t ₅
Since the sample data (SD) by P is “0”, the sampling output of the same content “0” as this sample data (SD) is used as the front and rear time margin M _E. Like this DS
If the sample data (SD) by P is “0”, EP ₁ ~
EP _n, and LP ₁ ~EP _n of Yotsute time margin measurement data to invert the polarity of the data is obtained. For example, if a sampling output of [1 ... 000] is obtained corresponding to EP _{n to} EP ₁ at t ₅ , it is inverted [0 ... 111].
Is output as data indicating the time margin M _E.

The front side and rear side time margin measurement results, that is, M _E and M _L data are the digital comparator (2) of the decision circuit (14) for each DSP cycle.
2) Given to (23).

Time margin obtained from each measurement circuit (20) (21)
M _E and M _L are predetermined values T _E and T _L sent from the front side and rear side time margin predetermined value (reference value) generation circuits (24) and (25).
(T _E = T _L may be used) and the digital comparator (22) (23) compares, and when M _E ≧ T _E , M _L ≧ T _L , each comparator (22) (23)
Therefore, a high level “1” output is generated, which indicates that the time margin is sufficient. On the other hand, M _E comparator (22) (23)
If the judgment is <T _E , M _L <T _L , a low level output indicating an error is obtained. Since the outputs of the comparators (22) and (23) are input to the AND gate (26), the output of the AND gate (26) becomes low level even if one of them is in error, indicating a time axis error. The signal is output. When a signal indicating a time axis error is generated, the same data or data group is written again after the previous recording area. As for the rewritten data, the time margin is checked in the same manner as described above, and when the time axis error is detected again, the rewriting is performed again. In short, writing of the same data or data group is continued until a sufficient time margin is obtained.

In the reproduction mode, the data or data group related to the first writing is read even when the rewriting is performed. At the time of this reading, the time axis error check is not performed. Even for the data related to the first writing, if an error does not occur due to the CRC check or the like, it is output as valid data and the data related to rewriting is not read. However, if the data relating to the first writing with a small time margin cannot be accurately read due to the instantaneous speed fluctuation during reproduction, an error is detected in the CRC check, so the data relating to rewriting is read. Since the data normally rewritten has a sufficient time margin, the probability of becoming unreadable is low.

[Modification]

The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible, for example.

(1) It is also applicable to the case of recording / reproducing data by the PE (Phase Encoding) system, or the case of recording / reproducing by various other systems.

(2) In the embodiment, when rewriting is performed, the original writing is left as it is, but the original writing may be erased and rewriting may be performed here. When rewriting, a signal indicating an error may be added to the original writing.

〔The invention's effect〕

According to the present invention, the possibility of an error occurring during the subsequent reproduction is determined based on the measurement of the time interval between the pulse indicating the read data and the sampling pulse, and the data is rewritten when there is a possibility. , Highly accurate writing can be easily performed without the conventional complicated control of changing the width of the data pulse or the clock pulse.

[Brief description of drawings]

FIG. 1 is a block diagram showing a part of a magnetic tape device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a part of FIG. 1 in detail, and FIG. 3 is a state of each part of FIG. FIG. 4 is a voltage waveform diagram shown, and FIG. 4 is a waveform diagram showing the relationship between sampling pulses and data. (2) ... Recording head, (3) ... Reproduction head, (8) ... Data sampling circuit, (9) ... Synchronous oscillation circuit, (11)
… Time margin measuring circuit, (14) Time margin judging circuit.

Claims (1)

[Claims] 1. A step of writing data to a recording medium, a step of reading the data, a sampling pulse for sampling the read data obtained in the reading step, and a time of a leading edge of a pulse indicating the read data. Measuring a front side time margin consisting of an interval, and measuring a rear side time margin consisting of a time interval between the sampling pulse and the trailing edge of the pulse indicating the read data, and the front side time margin and the rear side time margin. And a single or two predetermined values for the front side and the rear side, each of which indicates a time axis fluctuation range that may occur in the playback mode, are compared, and the front side time margin and the rear side time margin are equal to or more than the predetermined value. And a step of determining whether the front side time margin or the rear side time margin is less than the predetermined value. When judged, this data is regarded as an error and rewritten to the recording medium, and a data recording method.