JPH1031807A - Read-after-write circuit and magnetic recording and reproducing circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the cost of a circuit by reducing the circuit scale of the read-after-write reproducing system. SOLUTION: Recording data, with error correction coded by ECC (error correcting circuit) 5, is modulated by a digital modulating/demodulating circuit 4, and then recorded on a magnetic tape 50 by a recording head 1. Immediately after that, the data reproduced by a reproducing head 8, after a rotary transformer 9 and a reproducing amplifier 10, is provided with a constant amplitude level by an automatic gain control circuit (AGC) 11; an exclusive logical sum of the signal, for which the detection voltage of the AGC thus obtained is binarized by a DC comparator, and the sink clock of a sink clock generating circuit 20, is discriminated if it is an error to be rewritten, by counting with a counter circuit 21 the omission of the data obtained by an exclusive OR circuit 19. At the time of the reproduction, the data decoded by an equalizer circuit 12 is demodulated by the digital modulating/demodulating circuit 4, with errors also corrected by the ECC 5, thereby passing into error-free reproduced data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording / reproducing apparatus such as a data streamer having a read-after-write function, and more particularly to a read-after-write circuit.

[0002]

2. Description of the Related Art A conventional magnetic recording device such as a data streamer is equipped with a read-after-write circuit and has a configuration as shown in a block diagram of FIG. Record data 1
00 is temporarily stored in the buffer memory circuit 7 and then input to the error correction circuit (ECC) 5 of the recording system. ECC
5 encodes the error correction by delaying the input data using the memory 6 and then comparing it with the newly input data. In this manner, the data in which the error correction is coded is input to the digital modulation / demodulation circuit 4 (DCI), where it is modulated. The modulated data is amplified by the recording amplifier 3 and then input to the recording head 1 via the rotary transformer 2 and recorded on the magnetic tape 50 by the recording head 1.

The data recorded on the magnetic tape 50 is immediately reproduced by the reproducing head 8 and the rotary transformer 2
After being input to a reproduction amplifier 10 and amplified, the amplitude level is made constant by an automatic gain control circuit (AGC) 11, and then input to an equalizer (EQ) circuit 12 having a partial response decoding function. The equalizer circuit 12 decodes the reproduced data into data and a clock, and outputs the obtained data and clock to a digital modulation / demodulation circuit (DCI) 13. The digital modulation / demodulation circuit 13 demodulates input data by a clock input at the same time, and demodulates the demodulated data by an error correction circuit (ECC) 14 of a reproduction system.
Output to After delaying the input data using the memory 15, the ECC 14 decodes the error correction by comparing the input data with newly input data, and performs data error correction if necessary.

At this time, the ECC 14 issues a rewrite request to the ECC 5 and the buffer memory circuit 7 of the recording system when the error is too large to correct the error due to too much data loss or the like. As a result, the buffer memory circuit 7 returns to the stored rewrite-requested recording data portion,
Data is read, and the read data is stored in ECC5
Output to The ECC 5 encodes the error correction again into the recording data to be rewritten, and this is recorded on the magnetic tape 50 again by the recording head 1 so that the magnetic tape 50 has an error such as a data loss (the ECC cannot be repaired). Data without any significant error) will be recorded.

However, the conventional read-after-write circuit as described above requires two independent digital modulation / demodulation circuits 4, 13, ECCs 5, 14 and memories 6, 15 for the recording system and the reproduction system. Therefore, the circuit scale becomes large, and in particular, the ECCs 5, 14 and the memories 6, 1,
Since the price of No. 5 was high, there was a problem that the cost of the circuit also increased.

[0006]

As described above, when performing read-after-write in a conventional magnetic recording / reproducing apparatus, the digital modulation / demodulation circuits 4 and 1 are provided for the recording system and the reproduction system, respectively.
3, the ECCs 5, 14 and the memories 6, 15 need to be duplicated, so that there is a problem that the circuit scale is increased and the cost of the circuit is increased.

Accordingly, the present invention has been made to solve the above-mentioned problems, and a read-after-write circuit and a read-after-write circuit capable of reducing the circuit scale of a read-after-write reproducing system to reduce the circuit cost. It is an object of the present invention to provide a magnetic recording / reproducing device using a circuit.

[0008]

According to the first aspect of the present invention, a recording head and a reproducing head are provided independently, and errors in reproduced data obtained by immediately reproducing data recorded on a magnetic tape by the recording head with the reproducing head are eliminated. It is determined whether or not the error should be rewritten. If the error is to be rewritten, the amplitude level of the reproduced data reproduced by the reproducing head is changed in a read-after-write circuit for recording the data again on the magnetic tape by the recording head. A missing portion detecting means for detecting a portion having a predetermined value or less, and a judging means for determining whether or not the amplitude level of the reproduction data detected by the missing portion detecting portion should be rewritten based on the size of the portion having a predetermined value or less. Is provided.

According to a second aspect of the present invention, a recording head and a reproducing head are independently provided, and whether data recorded on a magnetic tape by the recording head is reproduced immediately by the reproducing head is an error to be rewritten. In the read-after-write circuit for recording the data again on the magnetic tape by the recording head if the error to be rewritten is determined, an error correction circuit for adding an error correction code to the recording data, and the error correction circuit A modulation circuit that modulates the data to which the error correction code is added and converts the data into data to be recorded by the recording head; a detection circuit that obtains a detection signal of an outline level of the reproduction data reproduced by the reproduction head; Is converted into a binary signal by comparing the detection signal obtained by
A binarizing circuit, a sync clock generating circuit for generating a sync clock having the same cycle as a sync clock of a sync area added to data as an error correction code by the error correction circuit, and a binarized circuit by the binarization circuit An exclusive-OR circuit for performing an exclusive-OR operation on the binary signal and the sync clock generated by the sync clock generating circuit;
A counting circuit that counts the difference between the number of clocks of the exclusive OR result of the exclusive OR circuit and the number of sync clocks generated by the clock generation circuit, and determines whether an error to be rewritten based on the count number of the counting circuit. And a judgment circuit.

According to a third aspect of the present invention, a function of decoding data error correction is added to the error correction circuit, and the modulation circuit is a modulation / demodulation circuit capable of demodulation. A reproduction system for demodulating the reproduced data by the modulation / demodulation circuit, and then performing error correction of the data by the error correction circuit to correct the data error as necessary to obtain reproduced data without error. It is.

According to a fourth aspect of the present invention, the detection circuit grounds, via a capacitor, an automatic gain control circuit for making the amplitude of reproduced data reproduced by a reproducing head constant, and detects the detected signal from a terminal voltage of the capacitor. It has a configuration to obtain.

According to a fifth aspect of the present invention, there is provided a magnetic recording / reproducing apparatus having a read-after-write function, comprising a configuration in which the read-after-write circuit according to any one of the first to fourth aspects is mounted.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of a magnetic recording / reproducing apparatus equipped with a read-after-write circuit of the present invention. 1 is a recording head for recording the recording data on the magnetic tape 50, 2 is a rotary transformer for inputting the data to the recording head, 3 is a recording amplifier for amplifying the recording data and outputting it to the rotary transformer 2, and 4 is a recording amplifier. A digital modulation / demodulation circuit (DCI) 5 that modulates and demodulates reproduction data, and an error correction circuit (EC) 5 that encodes error correction in recording data.
C) and 6 are memories for delaying recording data for error correction, 7 is a buffer memory circuit for temporarily storing recording data, 8 is a reproducing head for reproducing data from the magnetic tape 50, and 9 is a reproducing head for reproducing data. A rotary transformer for inputting to the amplifier 10; a reproducing amplifier 10 for amplifying the reproduced data reproduced by the reproducing head 8; an automatic gain control circuit (AGC) 11 for keeping the amplitude level of the reproduced data constant; An equalizer (EQ) circuit having a partial response decoding function for decoding
Reference numeral 16 denotes a capacitor connected to the automatic gain control circuit 11 for extracting a detection voltage waveform from its terminal. Reference numeral 17 denotes a detection voltage comparison circuit that compares the detection voltage waveform extracted from the automatic gain control circuit 11 with the threshold voltage of the threshold voltage source 18. A DC comparator for binarizing the voltage waveform; 18, a threshold voltage source for generating a threshold voltage; 19, an exclusive OR of data binarized by the DC comparator 17 and a sync clock output from the sync clock generation circuit 20 20 is a sync clock generation circuit that generates a sync clock synchronized with the clock of the sync area added to the data by the ECC 5, and 21 is the exclusive OR obtained by the exclusive OR circuit 19. Includes a determination circuit that counts the number of clocks of the result and determines whether error correction is possible Counter circuit, 22 is a data processing unit for processing the reproduction data.

Here, the automatic gain control circuit 11, the capacitor 16, the DC comparator 17, the exclusive OR circuit 19
And the sync clock generation circuit 20 includes a missing part detecting means,
The counter circuit 21 constitutes a determination unit. The automatic gain control circuit 11 and the capacitor 16 constitute a detection circuit,
The comparator 18 forms a binarizing circuit, and the counter circuit 21 forms a counting circuit and a determination circuit.

Next, the operation of this embodiment will be described. The recording data 100 is temporarily stored in the buffer memory circuit 7 and then input to the recording ECC 5. ECC5
Encodes the error correction by delaying the input data using the memory 6 and then comparing it with the newly input data. In this manner, the data in which the error correction is coded is input to the digital modulation / demodulation circuit 4, where it is modulated. The modulated data is amplified by the recording amplifier 3 and then input to the recording head 1 via the rotary transformer 2 and recorded on the magnetic tape 50 by the recording head 1.

The data recorded on the magnetic tape 50 is immediately reproduced by the reproducing head 8 and the rotary transformer 2
2 is input to the reproduction amplifier 10 and amplified.
The reproduced data is input to the automatic gain control circuit 11 as shown in FIG. The automatic gain control circuit 11 sets the amplitude level of the input reproduction data to a constant value, and then outputs the same to the equalizer circuit 12 having a partial response decoding function. For this reason, the input reproduced data is decoded into data and a clock by the equalizer circuit 12, but at the time of read-after-write, the obtained data and clock are discarded as they are and are not sent to the digital modulation / demodulation circuit 4.

On the other hand, the detected voltage waveform of the reproduced data as shown in FIG. 2B obtained from the automatic gain control circuit 11 is as follows:
It is input to the DC comparator 17, where it is compared with the threshold voltage Vref, binarized as shown in FIG. 2C, and the binary signal is input to the exclusive OR circuit 19. The threshold voltage Vref when converting to a binary signal is
It is determined whether the sync (synchronization) area added to the data by ECC5 can be detected from the reproduced data,
If the level of the reproduction data is a level at which a sync area can be detected, the level is binarized to an "H"level;

The exclusive OR circuit 19 receives the input signal shown in FIG.
An exclusive OR of the binary signal shown in FIG. 2C and the sync clock shown in FIG. 2D input from the sync clock generation circuit 20 is obtained, as shown in FIG. And outputs the result to the counter circuit 21. Here, the sync clock generation circuit 20 is an EC
At C5, a sync clock having the same cycle as the sync clock added to the recording data is generated. The counter circuit 21 counts the number of clocks of the exclusive-OR result input, and determines the difference between the number of clocks included in one track and the number of sync clocks within a certain period, for example, as the number m of sync detection errors. Error count m is ECC during playback
Nothing is performed if the error number is within the error number n which is the limit of errors that can be corrected in step 5. However, if the error number n is exceeded, it is determined that there is an error that needs to be rewritten, and the rewrite request is sent to the ECC4 and ECC4. Output to the buffer memory circuit 7.

As a result, the buffer memory circuit 7 returns to the stored recording data portion to be rewritten, reads the data, and outputs the read data to the error correction circuit 5. The error correction circuit 5 codes the error correction again into the recording data in which the error is detected, and this is recorded on the magnetic tape 50 again by the recording head 1. For this reason, data free from errors such as data loss (errors that cannot be repaired by ECC) are recorded on the magnetic tape 50.

When reproducing the data recorded on the magnetic tape 50 as described above, the data is reproduced by the reproducing head 8.
The reproduced data input to and amplified by the reproduction amplifier 10 via the rotary transformer 9 is supplied to the automatic gain control circuit 11.
After that, the amplitude level is made constant, and then input to the equalizer circuit 12 having a partial response decoding function. The equalizer circuit 12 decodes the data and clock from the reproduced data, and outputs the obtained data and clock to the digital modulation / demodulation circuit 4.

The digital modulation / demodulation circuit 4 demodulates the input data by a clock input at the same time,
Output to CC5. The ECC 5 delays the input data by using the memory 6, and then decodes the error correction by comparing it with the newly input data, corrects the error of the data as needed, and reproduces the data without error. The data is sent to the processing unit 22 and various processes are performed.

According to the present embodiment, the missing part of the clock obtained by taking the exclusive OR of the binary signal obtained by binarizing the detection voltage of the automatic gain control circuit 11 and the sync clock is counted. By doing so, it is determined whether or not the error should be rewritten. Therefore, the dedicated digital modulation / demodulation circuit, the ECC and the memory are omitted from the reproduction system at the time of read-after-write, and the ECC and the digital modulation / demodulation circuit are integrated into one system. The circuit scale of the afterlight circuit can be reduced, and the circuit can be made inexpensive. Therefore,
A magnetic recording / reproducing device such as a data streamer equipped with the read-after-write circuit can be miniaturized and its cost can be reduced.

[0023]

As described above, according to the first, second, and fourth aspects of the present invention, the circuit scale of the read-after-write reproducing system can be reduced, and the circuit cost can be reduced.

According to the third aspect of the present invention, the digital modulation / demodulation circuit, ECC, and the like can be provided as only one system of the recording system, and the circuit scale of the reproducing system can be reduced, thereby reducing the cost of the circuit.

According to the fifth aspect of the present invention, the apparatus can be reduced in size and inexpensive.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a magnetic recording / reproducing apparatus equipped with a read-after-write circuit of the present invention.

FIG. 2 is an operation waveform diagram showing a rewrite determination operation at the time of read-after-write shown in FIG.

FIG. 3 is a block diagram showing a configuration example of a magnetic recording / reproducing device equipped with a conventional read-after-write circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Recording head 2, 9 ... Rotary transformer 3 ... Recording amplifier 4 ... Digital modulation / demodulation circuit 5 ... Error correction circuit 6 ... Memory 7 ... Buffer memory circuit 8 ... Reproduction head 10 ... Reproduction amplifier 11 ... Automatic gain control circuit 12 ... Equalizer circuit DESCRIPTION OF SYMBOLS 16 ... Capacitor 17 ... DC comparator 19 ... Exclusive OR circuit 20 ... Sync clock generation circuit 21 ... Counter circuit 22 ... Data processing part 50 ... Magnetic tape

Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location G11B 20/18 572 G11B 20/18 572B 572G

Claims (5)

[Claims] 1. A recording head and a reproducing head are provided independently,
The data recorded on the magnetic tape by the recording head is immediately reproduced by the reproducing head, and it is determined whether or not the error of the reproduced data is an error to be rewritten. In a read-after-write circuit for recording on a magnetic tape again, a missing portion detecting means for detecting a portion where the amplitude level of the reproduced data reproduced by the reproducing head is equal to or less than a predetermined value; and a reproducing data detected by the missing portion detecting means. A determination means for determining whether or not to perform rewriting based on the size of a portion where the amplitude level is equal to or smaller than a predetermined value. 2. A recording head and a reproducing head are independently provided,
The data recorded on the magnetic tape by the recording head is immediately reproduced by the reproducing head, and it is determined whether or not the error of the reproduced data is an error to be rewritten. In a read-after-write circuit for recording on a magnetic tape again, an error correction circuit for adding an error correction code to recording data, and data for modulating data to which an error correction code is added by the error correction circuit and recording the data with the recording head A detection circuit that obtains a detection signal of the contour level of the reproduction data reproduced by the reproduction head; a detection signal obtained by the detection circuit is compared with a separately provided threshold voltage to generate a binary signal. A binarizing circuit for performing the processing, and a system which is added to the data as an error correction code by the error correction circuit. A sync clock generating circuit for generating a sync clock having the same cycle as the synchronization clock of the sync area; a binary signal binarized by the binarizing circuit and a sync clock generated by the sync clock generating circuit. An exclusive-OR circuit for performing an OR operation, a counting circuit for counting a difference between the number of clocks of the exclusive-OR result of the exclusive-OR circuit and the number of sync clocks generated by the clock generation circuit, and the counting circuit A determination circuit for determining whether or not an error to be rewritten from the count number of the read / write operation. 3. A modulation / demodulation circuit which can add a function of decoding error correction of data to the error correction circuit and can also demodulate the modulation circuit. When reproducing data on a magnetic tape, the modulation reproduction circuit decodes the reproduced data. After demodulation by a modulation / demodulation circuit, a reproduction system is provided for performing error correction decoding of data by the error correction circuit and performing data error correction as necessary to obtain reproduced data without error. Item 2. A read-after-write circuit according to Item 2. 4. The detection circuit according to claim 1, wherein an automatic gain control circuit for making the amplitude of reproduction data reproduced by a reproduction head constant is grounded via a capacitor, and the detection signal is obtained from a terminal voltage of the capacitor. 4. The read-after-write circuit according to claim 2, wherein 5. A magnetic recording / reproducing apparatus having a read-after-write function, wherein the read-after-write circuit according to claim 1 is mounted.