JP2619528B2 - Error track pointer control method - Google Patents

Description

[Contents] Outline Industrial application field Conventional technology (FIGS. 4 and 5) Problems to be Solved by the Invention Means for Solving the Problems (FIG. 1) Operation (FIG. 1) FIG. 1) Embodiment (FIGS. 2 and 3) Effects of the Invention [Overview] Regarding the error track pointer control method, the error track pointer reset control is appropriately performed when reading data in a magnetic tape device using the AXP code method. An error track pointer control method that controls the reset of the error track pointer when reading a data block in a magnetic tape device that adopts the AXP (adaptive cross parity) code method with the aim of improving the data read performance by performing , A deskew buffer, an ECC processor, and a read control Unit, a read data discriminating unit, an error track holding circuit, and a microprogram control unit. When there is an error in the read data, the error track holding is performed in the process of re-reading the data for the same data block. The control as to whether or not the error track pointer held in the circuit is reset in the resynchronization frame is performed by the processing of the microprogram of the microprogram control unit.

[Industrial applications]

The present invention relates to an error track pointer control method, and more particularly, to an error track pointer control method, which is used for a magnetic tape device employing an AXP code (conforming cross parity code) method, and particularly, a data block recorded using the AXP code. The present invention relates to an error track pointer control method in which whether or not to reset an error track pointer can be arbitrarily changed at the time of reading data, thereby improving data reading performance.

[Conventional technology]

Conventionally, when recording and reproducing data in a magnetic tape device, various error correction methods for data, that is,
ECC (Error Checking and Correction) was adopted.

As a general ECC, there is a method using an ECC character depending on only one data frame.

ECC that relies only on one such data frame
When reading data recorded by the method, even if there is a re-synchro frame, the data frames before and after the re-synchro frame have no effect.

Therefore, EC that depends only on one data frame
In the case of the C system, the error track pointer could be reset by the resynchronization frame.

However, recently, GCR ECC (Group Coded Recording EC
A system using an AXP (Adaptive Cross Parity) code (adaptive cross parity code), which is one type of C), has been developed. Hereinafter, this will be described.

FIG. 4 is a diagram showing an example of a data block format on a magnetic tape.

In the figure, SYNC indicates a synchronization signal, and Re-SYNC indicates a resynchronization signal.

This resynchronization signal is a code added every fixed period (72 frames), and is a special code (O421 = 100010001).
Is used.

 The number of tracks uses 18 tracks in this example.

FIG. 5 is an explanatory diagram of an AXP code (AXP code on a magnetic tape).

As shown in the drawing, this magnetic tape has tracks divided into upper and lower A and B, each of which is composed of 9 tracks,
It has a total of 18 tracks.

1 is the VRC bit (Vertical Redundancy) of the A side track
check bit: vertical redundancy check bit), 2 indicates a VRC bit of the B-side track.

3 is the DRC bit (Diagonal Redu
ndancy check bit; opposite line direction redundancy check bit), 4
Indicates the DRC bit of the B-side track.

The DRC bits 3 and 4 are diagonal redundancy check bits over three frames, and the DRC bit 3 and the DRC bit 4 are check bits on lines that cross each other.

Such check bits are added to the upper and lower two tracks on the magnetic tape at different locations.

One of the features of the 18-track magnetic tape device that adopts the AXP code method described above is that the current E
Data of 3 frames from the CC bit is required.

In addition, a special code called a re-synchronization frame (Re-SYNC) is added every fixed period (72 frames).

Therefore, when reading data on magnetic tape,
Even if a resynchronization frame is read, data for two frames from the resynchronization frame is required to perform ECC on a data frame before the present frame.

Therefore, it is not possible to reset the error track pointer immediately after reading the synchronous frame.

Also, when the length of the resynchronization bit is long (for example, 20 bits), the reliability is relatively high. However, in the case of using the above AXP code method, the length of the resynchronization bit is short (9 bits). ).

In such a case, even if the resynchronization frame is correctly detected, there is a possibility that there is a high possibility that a subsequent data frame has an error.

Therefore, in the case of using the AXP code method, the method of resetting with a resynchronization frame, which has been conventionally used, cannot be directly used.

[Problems to be Solved by the Invention] The above-mentioned conventional one has the following disadvantages.

That is, when reading data in a magnetic tape device employing the AXP code system, the error track pointer cannot be reset immediately upon detection of a resynchronization frame.

The present invention solves such a conventional drawback and improves the data reading performance by appropriately performing reset control of an error track pointer when reading data in a magnetic tape device adopting the AXP code system. Aim.

[Means for solving the problem]

FIG. 1 is a diagram showing the principle of the present invention. Hereinafter, the principle of the present invention will be described with reference to FIG.

In the figure, reference numeral 10 denotes a magnetic tape unit (MTU), and 11 denotes a magnetic tape control device (MTC).

12 is a microprogram control unit, 13 is an error track holding circuit, 14 is a deskew buffer, 15 is an ECC processing unit, 16 is a read control unit, 17 is a read data determination unit, 18
Indicates a read head, and 19 indicates a magnetic tape.

The deskew buffer 14 temporarily stores the data read from the magnetic tape 19 and corrects the skew of the data.

The ECC processing unit 15 receives the data from the deskew buffer 14, performs ECC processing, and sends output information (information such as whether or not the data has been read) to the microprogram control unit 12.

The read data discriminating unit 17 discriminates by inputting the data from the deskewing buffer 14 and sends information to the error track holding circuit 13 when detecting a resynchronization signal. The signal to be set is sent to the error track holding circuit 13.

The microprogram control unit 12 determines whether or not to reset the error track pointer in the resynchronization frame in the process of retrying the data read based on the information from the ECC processing unit 15, and the error track holding circuit 13
Send a signal to

[Action]

 The configuration described above has the following effects.

When reading a data block on a magnetic tape recorded by the AXP code, if the data block is written in a bad state, data cannot be read correctly.

In such a case, the magnetic tape is returned and the same data block is read again (retry).

In the course of this retry, the error track pointer is reset by a re-sync frame (Re-SYNC frame) by the microprogram control unit 11, or
It is determined whether or not to hold the resynchronization frame, and an instruction is issued to the error track holding circuit 13.

That is, by processing the reset condition of the error track pointer by the microprogram in the microprogram control unit 12, the data reading performance is improved.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram of one embodiment of the present invention, and the same reference numerals as those in FIG. 1 indicate the same components.

In the figure, reference numeral 10 denotes a magnetic tape unit (MTU), and 11 denotes a magnetic tape control device (MTC).

12 is a microprogram control unit, 13 is an error track holding circuit, 14 is a deskew buffer, and 15 is
An ECC processing unit, 16 is a read control unit, 17 is a read data discrimination unit, 18 is a read head, 19 is a magnetic tape, 20 is a demodulator, 21 is an amplifier, and 22 is a preamplifier.

The deskew buffer 14 temporarily stores the read data to correct the skew of the data, and sends the re-sync frame (Re-SYNC) to the error track holding circuit 13.
(I) frame).

When the magnetic tape has 18 tracks, the resynchronization frame outputs a signal for 18 tracks corresponding to each track.

The error track holding circuit 13 includes an AND gate 18 and a JK flip-flop 19, and the AND gate 1
The output of 8 resets the JK-flip-flop 19.

Further, the error holding circuits 13 are provided in the same number as the number of tracks (18 sets corresponding to each track in the case of 18 tracks).

The read data discriminating section 17 inputs and judges data from the deskewing buffer 14, and inputs the detected resynchronization frame (Detect Re-SYNC) to the AND gate 18 of the error track holding circuit 13.

In addition, a signal for setting an error track is input to the JK flip-flop 19 of the error track holding circuit 13 and set (send Set Error Track (i)).

This signal is also the number of tracks (18 for 18 tracks)
It is output and input to each JK flip-flop 19.

The ECC processing unit 15 receives the data from the deskewing buffer 14, performs ECC processing, and sends information related to a data error, for example, information that the data could be read or could not be read, to the microprogram control unit 12. .

In the microprogram control unit 12, the above-described ECC
Based on the information from the processing unit 15, the processing by the microprogram is performed, and the AND gate 1 of the error track holding circuit 13 is processed.
Send a signal to 8.

In this process, a process is performed to determine whether or not the error track pointer is reset in the resynchronization frame, and the error track holding circuit 13 is controlled.

FIG. 3 is a diagram showing an operation flowchart of the above embodiment.

First, when there is a data block reading instruction (a),
A signal from the microprogram control unit 12 instructs the error track holding circuit 13 to reset the error track pointer ETP (i).

Next, the data block is read from the magnetic tape (c), and the read data discriminating unit 17 determines whether there is a data check error, for example, an uncorrectable error, a CRC error, or the like (d).

If there is no error, the process ends normally (f). If there is an error, a retry to read data of the same block is performed again, and the counter is incremented by 1 (e).

Then, it is determined whether or not the retry has been performed a predetermined number of times (g). If the retry has been performed a predetermined number of times, it is determined that the operation is abnormally ended, and an error report is made (l).

However, if the predetermined number of retries has not been performed, it is determined whether or not a predetermined number of ETP reset instructions have been issued (H). If the predetermined number of ETP reset instructions have been issued, the microprogram control unit 12 Instruct AND gate 18 to hold ETP (nu).

Thereafter, the process proceeds to the position before the error block, and the data block is read again for the same block.

As described above, the data block on the magnetic tape is read, and if there is an error, the data is retried.
The micro program control unit 12 processes the error track pointer reset condition.

That is, by reading the error track pointer ETP with a microprogram to determine whether to reset the error track pointer ETP in the resynchronization frame or hold the error track pointer ETP in the resynchronization frame, the data reading performance is improved.

〔The invention's effect〕

As described above, the present invention has the following effects.

(1) Regarding reading of a data block recorded by the AXP code, if the data is written in a bad state, an error track pointer having an error is reset at a resynchronization frame, or retained even at a resynchronization frame. You may be able to read by changing what you do.

(2) If data can be read in the process of retrying several times, data reading performance is improved.

[Brief description of the drawings]

FIG. 1 is a principle diagram of an error track pointer control system according to the present invention, FIG. 2 is a block diagram of one embodiment of the present invention, FIG. 3 is a flowchart showing the above embodiment, and FIG. FIG. 5 shows an example of a data block format on a tape. FIG. 5 is an explanatory diagram of AXP codes. 10 Magnetic tape unit (MTU) 11 Magnetic tape controller (MTC) 12 Microprogram control unit 13 Error track holding circuit 14 Deskew buffer 15 ECC processing unit 16 Read control Unit 17 Read data discriminating unit 18 Read head 19 Magnetic tape

Continued on the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical display location G11B 20/18 572 9558-5D G11B 20/18 572G

Claims (1)

(57) [Claims] An error track pointer control method for controlling resetting of an error track pointer when reading a data block in a magnetic tape device adopting an AXP (adaptive cross parity) code method. , A deskew buffer (14) that temporarily holds the read data, and an ECC processor (15) that performs error processing on the read data
, A read control unit (16) for controlling data reading, and a read data determining unit (1) for determining read data.
7), an error track holding circuit (13) for holding an error track pointer, and a microprogram control unit (12) for processing reset control conditions for the error track holding circuit (13). If there is an error, in the process of reading data from the same data block again, whether the error track pointer held in the error track holding circuit (13) is reset by a resynchronization frame or not is determined. An error track pointer control method wherein control is performed by processing of a microprogram of the microprogram control unit (12).