JPH073717B2 - ATF control circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ATF control circuit of a rotary head type digital audio tape recorder, and is particularly suitable for preventing an error accompanying generation of a pilot signal detection timing. Regarding the protection circuit.

Conventionally, as a tracking control system of a rotary head type digital audio tape recorder (hereinafter, R-DAT), as described in JP-A-60-214415, one track area is divided into several parts and pilot signals are generated. Including ATF
It adopts the ATF control method in which signals are spatially arranged. However, no consideration was given to the protection of the capstan servo system when the ATF control loop becomes abnormal due to an error accompanying the detection timing of the pilot signal when the ATF signal is not recorded.

[Problems to be solved by the invention]

The above-mentioned conventional technology does not consider the point of preventing an error accompanying the detection timing of the pilot signal,
There is a problem of malfunction due to the dropout of the pilot signal due to dropout or the like.

The object of the present invention is to prevent malfunctions due to the loss of pilot signals, etc., and thus to perform stable tracking control, and to prevent equipment damage due to drive motor runaway.
It is to provide an ATF control circuit.

[Means for solving problems]

The above object is achieved by using the detection timing signal of the pilot signal and disconnecting the ATF control loop in the capstan system from the main servo loop and performing only speed control if the signal is not detected for a certain period of time.

[Work]

When the detection timing signal of the pilot signal based on the ATF signal is not detected for a predetermined period, a specific signal (referred to as ATF-NG signal) is generated to disconnect the ATF control loop and It is possible to prevent abnormal control operation.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples. FIG. 1 is a block diagram showing an embodiment of an ATF control circuit of a rotary head type digital audio tape recorder (R-DAT) to which the present invention is applied. FIG. 2 is a circuit diagram for generating an ATF-NG signal. The figure is a timing diagram for explaining the operation of the ATF-NG signal.

In FIG. 1, reference numeral 1 is an input terminal for a signal reproduced and amplified by the head. From the signal input from this input terminal 1, only a low frequency pilot signal component is selected by a low pass filter 2 and an envelope detector 3 The envelope waveform is extracted. The envelope waveform is
S / H1 timing signal 13, which will be described later, passes through buffer 4 to S /
It is held by the H1 circuit 5. S / H2 timing signal described later
By 14, the difference between the buffer 4 and the S / H1 circuit 5 is held in the S / H2 circuit 6. This hold voltage is used as a tracking error signal. Reference numeral 8 is a bandpass filter for extracting a synchronizing signal which gives a timing for generating the timing signals 13 and 14 of the S / H1 and S / H2 respectively. The synchronizing signal having a constant frequency is passed by the comparator 9 after passing through the BPF8. The waveform is shaped and converted into a square wave. The output of the comparator 9 is judged by the sync signal pattern detector 10 to be a sync signal or not, and a pulse signal is sent to the sync signal counter 12 of the next stage every time the pattern is detected. The sync signal counter 12
A signal is transmitted to the ATF area counter 11 to inform that the pattern of the synchronization signal is detected, and the timing 13 of S / H1 and the timing 14 of S / H2 are generated from this signal. On the other hand, the count result of the synchronization signal counter 12 is the digital comparator 15
Is input to and compared with the comparator threshold, and the result is
Transfer to the ATF area counter 11. ATF area counter 11
Determines whether to generate the S / H2 timing signal 14 based on this result. The signal output from the circuit 6 by the signal 14 is the ATF error signal 11 and the switch 18 via the buffer 7.
Sent to. The S / H2 timing 14 is input to the ATF-NG signal generation circuit 16 and is switched by the output 17.
Switch 18 The phase error signal from the switch 18 and the speed error signal from the terminal 20 are added via the resistors 30 and 31, respectively, and output to the terminal 21.

FIG. 2 shows one embodiment of the ATF-NG signal generation circuit,
It consists of a bit counter. The S / H2 timing 14 is input to the reset, and the clock 24 inputs the signal of 33.3 Hz. The MSB output of the counter is the ATF-NG signal 17. CI is a carry-in terminal, which is connected to ▲ ▼ and prohibits counting operation until the ATF-NG signal becomes “H” until it is reset.

FIG. 3 is a timing chart showing the operation of the embodiment shown in FIG. When the S / H2 timing signal 14 is output as in 25, that is, when the S / H2 timing does not occur continuously for about 1 second, the ATF-NG signal is output. (Experimental results indicate that about 1 second is appropriate.) This signal switches the switch 18 in FIG. 1 back to disconnect the ATF control system (capstan phase system). In other words, the control signal output terminal 19 has a constant voltage that is approximately the center value of the phase error voltage. Is output. This output is supplied to the motor together with the speed error signal, and the servo loop becomes only the speed system.

According to the present embodiment, there is an effect that the malfunction can be prevented relatively easily by operating the 6-bit counter by using the S / H2 timing signal.

The ATF-NG signal generation circuit is not limited to the counter shown in FIG. Also, the clock used for the counter
Not limited to 33.3 Hz, other frequency signals may be used.

〔The invention's effect〕

According to the present invention, there is an effect that stable tracking control can be realized without adversely affecting the drive motor even when there is a non-recording portion and a dropout of the ATF signal due to dropout.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an ATF.
-A block diagram showing an embodiment of an NG signal generating circuit, and Fig. 3 is a timing chart showing an operation when the configuration of Fig. 2 is adopted. 11 …… ATF area counter, 6 …… S / H2 circuit, 16 …… ATF
-NG signal generation circuit, 12 ... synchronization signal counter, 18 ... switch.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiji Noguchi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Hitachi, Ltd. Consumer Electronics Research Laboratory (72) Inventor Harushige Nakagaki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa (56) Reference JP-A-61-26956 (JP, A) JP-A-60-171658 (JP, A) JP-A-61-187149 (JP, A) JP-A-62 -183049 (JP, A)

Claims (1)

[Claims] 1. An ATF (automatic track following) control circuit for controlling a rotation phase of a capstan motor for driving a magnetic tape in a rotary head type magnetic recording / reproducing apparatus, wherein the ATF is obtained from a signal reproduced by the rotary head. A low-pass filter that extracts a pilot signal for control, a band-pass filter that extracts a synchronization signal that gives detection timing of the pilot signal, a comparator that shapes the waveform of the synchronization signal, and a synchronization signal pattern after waveform shaping A sync signal pattern detector, a sync signal counter that counts the number of pulse signals that are detection signals from the pattern detector, and a digital comparator that compares the count value of the sync signal counter with a predetermined threshold value, Triggered by the detection signal output from the pattern detector first within a first predetermined period And a first detection timing signal generating means for generating a first detection timing signal of the pilot signal, and a first predetermined time after the first detection timing signal from the first detection timing signal generating means, Second detection timing signal generating means for generating a second detection timing based on the output signal from the digital comparator; and a specific detection signal if at least the second detection timing signal does not occur for a second predetermined period. A specific signal generating means for generating a signal and a specific signal from the specific signal generating means separate the ATF control loop from the main servo loop, and instead of the servo control voltage to the main servo loop, a substantially phase error center voltage value An ATF control circuit comprising: