JPS62157359A - Rotary head type digital tape recorder - Google Patents

Abstract

PURPOSE:To surely control tracking by inverting the logic of a reference pattern so as to control the travel speed of a magnetic tape when a reproduced control signal does not agree with the reference pattern. CONSTITUTION:A counter 8 counts how many times a synchronizing signal is correctly detected out of reproduction signals, and always checks whether said signal is detected by the set number of times. If the set number of synchronizations are not obtained, the output of a latch 6 becomes 'H' in terms of logic. If said output is inputted to terminals J and K of a J-KFF 6d, its output is inverted when a clock pulse enters from a latch 6c. When said output and an original gate signal T1/T2 are passed through a discordance circuit 6e, the later is inverted, and inputted to a length selection circuit, which detects the synchronizing signal by delaying a timing. Thus, even if tracking deviates, an automatic tracking finding ATF system can control the tracking.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a rotary head type digital recorder.

[Technical background of the invention and its problems] In recent years, helical scanning digital audio tape recorders (hereinafter referred to as DAT) using a rotating head have been developed.
This DAT has been developed as an automatic track finding system (hereinafter referred to as
It is equipped with a tracking servo device called ATF.

The ATF reproduces the III control signal recorded on the magnetic tape and uses that control signal to perform tracking control. In a standard AT, for example, the magnetic tape is Deciding on the track pattern above.

In the figure, 1 indicates a pilot signal, and 130.6
It has a frequency of 7 KHz. When this pilot signal f is played back from a magnetic tape, it is reproduced with leakage from the adjacent tracks on both sides, so if we compare the leakage from both tracks, we can see which track the magnetic head is biased toward when reproducing. It is possible to judge whether

In addition, f2 and f3 in the figure indicate synchronization signals, each with 522
．． It has a frequency of 67 KHz, 784.00 KH2.

And in standard AT, one cylinder has A, 82
Since two magnetic heads are mounted, tracking control is performed by distinguishing the respective synchronizing signals based on the difference in frequency.

In order to further improve the detection accuracy, the lengths of the synchronization signals are made different, with the A track having a synchronization signal f2 of one block length, and the A' track having a synchronization signal f2 of 1/2 block length. The B track has a 1 block length synchronization signal f3, and the B' track has a 1/2 block length synchronization signal f3.

The synchronization signal is used to check whether tracking is performed in an orderly and correct manner. When a correct synchronization signal corresponding to a track is detected during playback, a pulse called SH+ (described later) is generated, and a pulse corresponding to the track is generated. When it is determined that the synchronization signal is of the correct quality, SH2
A pulse (described later) is created. These two pulses are then used as a sampling timing signal used to compare the amount of leakage of the pilot signal.

First, the case of reproducing the A track will be explained.

When the synchronization signal f2 is detected, a pulse called SH+ is created, which causes the pilot signal from the B track to
The leakage signal is sampled.

Next, when it is detected that the length of the synchronizing signal f2 is one block length, a pulse SH2 is generated two blocks later than SH+. The pulse leakage signal is now sampled from the B' track, and the difference between both leakage signals is taken and used as an error signal.

This error signal is then sent to the servo circuit to correct tracking. Note that the same applies when reproducing the synchronization signal f3. Below, A −) B −A'→B'→
The magnetic tape is repeatedly played back as A →..., error signals are generated, and servo is applied to proceed with tracking correction.

As described above, there are four types of ATF synchronization signals in standard AT, which are combinations of two types of frequencies and two types of lengths.

By the way, when detecting a synchronizing signal, as described above, the frequency is first detected, and then the block length is detected.

The long synchronization signal and the short synchronization signal are repeatedly reproduced in order, and the detection circuit detects whether the synchronization signal is long or short using a logic gate.

Therefore, if the tracking shifts and the long/short order becomes out of order, the logic in the detection circuit will no longer match, making it impossible to detect the synchronization signal, and the ATF will no longer operate.
Tracking correction will no longer be possible.

If such a situation occurs in a conventional DAT, a speed change signal is output to the capstan motor to forcibly change the tape running speed, and the logic of the synchronization signal detection circuit is matched to synchronize again. It performs a process of detecting signals.

By the way, as mentioned above, in AT, the running speed of the magnetic tape is kept almost constant by an automatic frequency control system (hereinafter referred to as AFC), but in order to detect a synchronization signal when tracking is lost, If the tape speed is forcibly changed by outputting a signal to the capstan motor, playback along the track cannot be performed unless the tape speed is returned to the original speed immediately after synchronization is achieved.

In the conventional device, the running speed of the magnetic tape is restored by the above-mentioned A.
Although this is executed by the operation of the FC, there is a problem in that the processing time becomes considerably long.

Furthermore, even if a signal for changing the running speed of the magnetic tape is output, there is a problem in that it is difficult to follow the operation due to the nature of the circuit of the motor drive system.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and even when tracking is lost and a synchronization signal cannot be detected, the running speed of the magnetic tape can be changed significantly.
The object of the present invention is to provide a rotary head type digital tape recorder that can perform tracking control reliably.

[Summary of the Invention] The rotary head type digital tape recorder of the present invention has the following features:
When tracking is lost and a synchronization signal cannot be detected from the reproduced signal, the timing of the synchronization signal detection circuit is switched to match the timing of the signal being reproduced due to the loss of tracking, thereby detecting the synchronization signal and operating the ATF. The output error signal is used to drive the motor and adjust the running speed of the magnetic tape to ensure accurate tracking.

[Embodiments of the Invention] Hereinafter, details of embodiments of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the overall configuration of the device of this embodiment.

The device of this embodiment includes a pattern detection circuit 1 that detects a synchronization signal from input data, a frequency selection circuit 2 that selectively passes the synchronization signal according to a predetermined logic, and a sampling pulse generation circuit that generates a sampling pulse SH+ to be described later. 3, a synchronization signal length detection circuit 4 that detects the length of the synchronization signal, a length selection circuit 5 that selectively passes the synchronization signal according to a predetermined logic, and a length selection circuit 5 according to specification.
It is comprised of a logic inversion circuit 6 that inverts the logic in , a sampling pulse generation circuit 7 that generates a sampling pulse SH2 to be described later, and a count circuit 8 that counts the number of detected synchronization signals.

FIG. 2 is a diagram showing the track pattern of the magnetic tape in the apparatus of this embodiment.

This track pattern is common to that of a conventional standard AT.

That is, when this track is reproduced, a short synchronization signal f2, a short synchronization signal f3, a long synchronization signal f2, and a long synchronization signal f3 are sequentially detected, and the synchronization signals are repeatedly reproduced. Note that f1 in the figure is a pilot signal.

Further, FIG. 3 is a diagram showing each timing of the apparatus of this embodiment.

In the figure, A indicates a reproduction signal, each cluster of which is output from one magnetic head and corresponds to one track. Also, B is f 2 which is input to the frequency selection circuit 2
/ f 3 signal, C is TI input to logic inversion circuit 6
/T2 signal, D is f2/ which is input to the counter which will be described later.
f3 signal @ (inverted signal of f2/f3 signal), E
is a counter clear pulse to be described later, F is a clock pulse to be described later, and G is a pulse corresponding to the position where the synchronization signal is recorded.

' In the device of this embodiment, a pattern detection circuit M1 first detects a synchronizing signal having a frequency of f2 or f3 from input data, and only the detected signal is output.

Then, the frequency selection circuit 2 applies a gate using the f 2 / f 3 signal shown as B in FIG. 3, and allows the sync signal to pass only when the sync signal is output in the order of f2, f3, . . . . Note that based on this output signal, the sampling pulse generation circuit 3 generates a sampling pulse S.
H+ is created.

Next, the length of the synchronization signal is detected by the synchronization signal length detection circuit 4, and a gate is applied using the T1/T2 signal shown by C in FIG. Let it pass. Note that a sampling pulse SH2 is generated in the sampling pulse generation circuit 7 based on this output signal.

When the tracking becomes out of order, the correspondence between the gated signals B and C and the synchronization signal in the reproduced signal breaks down, making it impossible to detect the synchronization signal.

In the device of this embodiment, this deviation of the synchronization signal is detected and corrected.

FIG. 4 is a circuit diagram specifically showing the configuration of the logic inversion circuit 6 and the count circuit 8 in the device of this embodiment.

As can be seen from this figure, the logic inversion circuit 6 of the device of this embodiment
is a counter 6a, a latch 6b, a flip-flop 6d and a mismatch circuit (exclusive OR gate) 6 to J-.
It is composed of e. The naori counter 8 corresponds to the counting circuit 8.

In this circuit system, a counter 8 counts the number of times a synchronization signal is correctly detected from a reproduced signal, and constantly checks whether a set number of synchronization signals have been detected.

In other words, when correct synchronization is achieved, the sampling pulse generation circuit (described above) 7 generates a sampling pulse 81-12.
is output, so count the number of pulses.

When synchronization is achieved beyond the set number, a latch 6b16c connects the flip-flop 6 to J- in order to prevent the logic of the gate signal T+/T2 from changing.
A logic is set up to set both terminals to "L level" at J and d.

When J- and J%K@ of flip-flop 6d are both at "L level", their Q output terminals are not inverted, so when this output and the original gate signal T+/T2 are passed through mismatch circuit 6e, The gate signals T1/T2 are not inverted and are input as they are to the length selection circuit (described above) 5.
As a result, the length selection circuit 5 continues to detect the synchronization signal.

On the other hand, the logic is set up so that if synchronization cannot be achieved up to the set number, the output of the latch 6b becomes "H level". And J- of flip-flop 6d, @i
When this output is input to the output terminal, the output of the flip-flop 6d is inverted to J- when the clock pulse F is input from the latch 6C.

When this output and the original gate signal TI/T2 are passed through the mismatch circuit 6e, the gate signal Ts/T2 is inverted and inputted to the length selection circuit 5.
starts detecting the synchronization signal with a different timing.

In this way, with the device of this embodiment, even if tracking is lost,
Gate signal T + to match the playback signal at the time when
/T2 is reversed, so tracking can be controlled by the operation of the ATF without significantly changing the running speed of the magnetic tape.

The device of the present invention can quickly stabilize the rotation of the capstan motor and cause the servo to pull the capstan motor when reproducing a signal from a place where there is no signal, for example when starting playback from a stationary state. It is extremely effective.

[Effects of the Invention] As explained above, the rotary head type digital tape recorder of the present invention switches the timing of the synchronization signal detection circuit when tracking is lost and the synchronization signal cannot be detected from the playback signal, and the timing of the synchronization signal detection circuit is changed to detect the synchronization signal when the tracking is lost and the synchronization signal is no longer detected from the playback signal. ATF detects the synchronization signal by matching the timing of the signal
Since the error signal, which is the output of the ATF, is used to move the capstan motor, the synchronization signal can be detected without significantly changing the running speed of the magnetic tape, and accurate tracking control can be performed at all times.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the overall configuration of an apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing a track pattern on a magnetic tape reproduced by the apparatus according to the embodiment, and FIG. 3 is a diagram showing the track pattern in the apparatus according to the embodiment. FIG. 4 is a block diagram showing the specific configuration of the main parts of the device according to the embodiment; FIG. 5 is a diagram showing the track pattern on a magnetic tape reproduced by a standard AT. .

Claims (1)

[Claims] (1) While rotating a cylinder equipped with a magnetic head for recording and reproducing, a magnetic tape is run, and data and control signals are reproduced from tracks diagonally and alternately recorded on the magnetic tape. In a rotary head type digital tape recorder configured to adjust the running speed of the magnetic tape so that the control signal reproduced from a track coincides with a reference pattern, the reproduced control signal matches the reference pattern. 1. A rotary head type digital tape recorder, characterized in that the rotary head type digital tape recorder is configured to invert the logic of the reference pattern and adjust the running speed of the magnetic tape when the magnetic tape does not match.