JPH03187057A - Control signal waveform shaping circuit - Google Patents

Abstract

PURPOSE:To prevent the malfunction of a linear time counter by inputting a positive/negative pulse to a flip flop FF in accordance with the forward/ reverse rotation indicating signal indicating the tape running direction to obtain a wave form shaped reproducing control signal. CONSTITUTION:Switches 7 and 8 are switched to terminals (a) when a forward/ reverse rotation indicating signal F indicating the tape running direction is '0' to indicate forward rotation,and switches 7 and 8 are switched to terminals (b) when the signal F is '1' to indicate reverse rotation, and a set signal and a reset signal are inputted to terminals S and R of an RS-FF 5 rises, and an edge detector 11 detects the edge of the signal F to send a detection signal 50 to an OR circuit 12. Then, the signal 50 is inputted to the terminal R of the FF 5. Consequently, the set signal is prevented from being inputted by connection to the terminal S of the FF 5 at the time of inverting the tape running, and a reproducing control signal having a square waveform is outputted from a terminal Q of the FF 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a control signal waveform shaping circuit that shapes the waveform of a playback control signal in a video tape recorder (VTR) or the like.

(Prior art) In home VTRs, during recording, so that the head can faithfully trace the video track of the recording tape during playback,
A method is adopted in which a control signal for tracking MO4 is recorded on a control track provided on the tape. At this time, the control signal is recorded in the form of a rectangular wave for each frame, and one edge of this rectangular wave is standardized for each VTR system so that it can be used as a reference edge to determine the tracking phase during playback. ing. During tape playback, the control signal recorded as described above is played back and amplified, and then the playback control signal is shaped into a rectangular wave by a hysteresis amplifier such as a Schmitt circuit in order to eliminate malfunctions due to noise. There is.

FIG. 4 is a block diagram showing an example of a conventional control signal waveform shaping circuit of this type. control head 1
reproduces control signals recorded on tape.

Since the control signal 100 reproduced in this way has a minute level, it is amplified approximately 1000 times by the amplifier 2 to become a pulse-like signal as shown in FIG. 5(A), and this signal is detected by the positive pulse detector. 3 and negative pulse detector 4
is input. The positive pulse detector 3 obtains a positive pulse signal as shown in FIG. 5(B) from the input reproduction control signal and outputs it to the set terminal S of the RS flip-flop 5. The negative pulse detector 4 obtains a negative pulse signal as shown in FIG. 5(B) from the input reproduction control signal and outputs it to the reset terminal R of the RS flip-flop 5. Therefore, positive and negative pulses 300 and 400 as shown in FIG. A rectangular wave (shaped control signal>500) as shown in FIG. 5(D) is obtained from
This rectangular wave 500 becomes a final reproduction control signal 600 via an exclusive OR (EXOR) circuit 6.

Here, a forward/reverse rotation instruction signal F (REV) indicating the tape running direction is inputted to the other input of the EXOR circuit 6, and this normal/reverse rotation instruction signal F becomes 1 during normal rotation and 1 during reverse rotation. Therefore, when the tape running direction is normal, the EXOR circuit 86 is a rectangular wave 50 input to one input.
0 is output as is as the reproduction control signal 600, but in the case of reversal, a reproduction control signal 600 in which the polarity of the rectangular wave 500 is inverted is output. this is,
During forward rotation, the positive edge of the square wave 500 (corresponding to the positive pulse 300) serves as the reference edge for head tracking control, while during reverse rotation, the negative edge of the square wave 500 (corresponding to the negative pulse 400) serves as the reference edge for the head tracking control. This is because it becomes the reference edge for

However, in the conventional control signal waveform shaping circuit as described above, when a forward/reverse rotation instruction is given when the tape is stationary, the aforementioned forward/reverse rotation instruction signal F is output to the EXOR circuit 6 even though no playback control signal is generated. It will be output to the next stage via.

In recent years, the playback control signal whose waveform is shaped as described above is not only used as a playback phase feedback signal for the capstan servo, but also the amount of tape consumed is displayed by counting the playback control signal (so-called linear It is also used for time counters.

Therefore, as mentioned above, when a forward/reverse rotation instruction is given when the tape is stationary, a forward/reverse rotation instruction signal is output from the EXOR circuit 6, which causes the problem that the linear time counter erroneously counts. arise.

FIG. 6 is a block diagram showing an example of a control signal waveform shaping circuit for solving the above problems.
The same parts as those in the circuit shown in the figure are given the same reference numerals. In this example, instead of the EXOR circuit 6 used in the circuit of Fig. 4,
A switch 7.8 is provided for switching input of the positive pulse signal 300/negative pulse signal 400 to the set terminal S/reset terminal R of the RS flip-flop 5. These switches 7.8 are controlled by a forward/reverse rotation instruction signal F, and during forward rotation, that is, when F=O, the C terminal of switch 7.8 is switched to the a terminal side, and during reverse rotation, that is, when F=1. , switch 7
．． The C terminal of No. 8 is controlled to switch to the B terminal side. Therefore, the positive pulse signal 300 is selectively input to the set terminal S of the RS flip-flop 5 during forward rotation, and the negative pulse signal 400 is selectively input during reverse rotation, so that the reference edge is always input to the set terminal S, and the RS The reproduction control signal outputted from the Q terminal of the flip-flop 5 can be used regardless of whether the tape is running in the forward or reverse direction. Moreover, since the forward/reverse rotation instruction signal F is used as a control signal for the switch 7.8, even if the forward/reverse rotation instruction signal F is changed as long as the reproduction control signal is not generated, the Q terminal of the RS flip-flop 5 will be can be made so that no signal is generated. Therefore, even if a forward/reverse rotation instruction is given when the tape is stationary, the aforementioned linear time counter will not malfunction.

FIG. 7 is a block diagram showing another example of a control signal waveform shaping circuit for solving the problems of the circuit shown in FIG. 4, and the same parts as in FIG. be. In this example, an inverter 9 for inverting the polarity of the signal 200 is provided between the amplifier 2 and the positive pulse detector 3.4, and the polarity of the signal 200 output from the amplifier 2 is inverted by the inverter 9. A changeover switch 10 is provided to select one of the signals 200 and input it to the positive and negative pulse detectors 3.4, and the EXOR circuit is omitted. When the forward/reverse instruction signal F is 1, the terminal C of the changeover switch 10 is switched to the terminal a side, and when the signal F is O, the terminal C of the changeover switch 10 is switched to the b side, so that the RS flip-flop 5 is set. The reference edge is always set as input to the terminal S, and the circuit operates in the same way as the circuit shown in FIG. Moreover, since the forward/reverse rotation instruction signal F is used as a control signal for the selector switch 10, even if the forward/reverse rotation instruction signal F is changed as long as the reproduction control signal is not generated, the R
No signal is generated from the Q terminal of the S flip-flop 5. Therefore, in this example as well, even if a forward/reverse rotation instruction is given when the tape is stationary, the aforementioned linear time counter will not malfunction.

In this way, in the control signal waveform shaping circuit shown in FIGS. 6 and 7, even if a forward/reverse rotation instruction is given when the tape is stationary, a pseudo playback control signal is not output, and the linear time counter is Inconveniences such as malfunctions can be prevented. However, when the tape running direction is reversed after the tape is stopped, the following disadvantages occur.

FIG. 8 is an example of a signal waveform showing the operating states of FIGS. 6 and 7 described above. Initially, the tape runs in the normal direction, then the tape stops when the recording magnetization state of the control track is at the S pole, and then It shows the states in which various signals occur when the tape is run in reverse. Fig. 8 (A> shows the tape running direction, and Fig. 8 (B) shows the magnetization pattern of the control track, which shows the change in magnetization polarity that reaches the control head 1 according to the tape running.
), S indicates the S pole and N indicates the N pole, and the subscript number corresponds to the frame number shown in FIG. 8(C).

In the example of FIG. 8(B), the magnetization pattern is S1→N1→...
- The tape arrives at the control head 1 in the order of N3 → S4, the tape stops at the magnetized part of S4, and then
It is shown that the magnetized portion arrives in the opposite direction as S4→N3→...N1→S1 due to reverse reproduction. At this time, the playback control signal output from control head 1 is N
→ If the setting is made to generate a positive pulse when the magnetization of S changes, the reproduction control signal will have a waveform as shown in Figure 8 (D>). As shown in FIG. 8(E), the reference edge (set signal) is input to the set terminal S of the switch 7.8 as shown in FIG.
A reset signal is input as shown in Figure (F). Therefore, from the Q terminal of the RS flip-flop 5, as shown in FIG.
) A final playback control signal whose waveform has been shaped as shown in FIG. Here, a linear time counter (not shown) counts frames by counting rising edges of the reproduction control signal shown in FIG. 8(G). Therefore, as shown in Figure 8 (H), the frame count results differ by 1 from the actual frame number shown in Figure 8 (C) after the tape is played in reverse. A problem occurs.

This problem occurs because the tape stops after the reference edge arrives at the RS flip-flop 5, and then when the tape is run in the opposite direction from before it stopped, the reference edge arrives again. flip flop 5
This occurs because the output signal is not inverted by being input to the set terminal S of . Therefore, this phenomenon occurs in the same way when the tape runs in the reverse direction, stops, and then rotates in the forward direction. In the circuit shown in FIG. 7, the linear time counter malfunctions for the same reason as above.

(Problems to be Solved by the Invention) As described above, if a forward/reverse rotation instruction is given when the tape is stopped in the conventional control signal waveform shaping circuit, a pseudo playback control signal is generated and causes a malfunction of the linear time counter. A control signal waveform shaping circuit as shown in Figs. 6 and 7 has been developed to prevent such inconveniences. However, even in this circuit,
If the tape that is rotating in the forward direction stops once and then rotates in the reverse direction, the set signal will be continuously input to the RS flip-flop, so the count value of the linear time counter and the actual frame number will be 1. There was a drawback that it could be misaligned. In particular, for VTRs with advanced editing functions in recent years, tape running is managed in frame units.
In addition, since forward/reverse rotations are frequently performed, the above-mentioned defects become fatal defects.

SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks, and provides a control signal waveform that can accurately reproduce the reference edge of the control signal and prevent malfunctions of the near-time counter even when the tape running is reversed. The purpose is to provide a shaping circuit.

[Structure of the invention]

(Means for Solving the Problems) A control signal waveform shaping circuit of the present invention includes a pulse generating means for generating positive pulses and negative pulses from a signal reproduced from a control head, a flip-flop circuit, and a tape running direction. a switch means for switching whether to input the positive pulse and the negative pulse from the pulse generating means to the set terminal and the reset terminal of the flip-flop circuit, respectively, or to the reset terminal and the set terminal, respectively, according to a forward/reverse rotation instruction signal; comprising a detection means for generating a detection signal at the time of detecting the reversal timing of the forward/reverse rotation instruction signal, and a signal input means for inputting the detection signal generated from the detection means to the reset terminal of the flip-flop circuit, The configuration is such that a waveform-shaped reproduction control signal is obtained from the 79917091 circuit.

Another aspect of the present invention is an inversion control means for switching between outputting the signal reproduced from the control end as it is or inverting it according to a forward/reverse instruction signal indicating the tape running direction; pulse generating means for generating positive pulses and negative pulses from the output of the means; a 79917091 circuit in which the positive pulse from the pulse generating means is input to a set terminal and the negative pulse to a reset terminal; A detection means for generating a detection signal when an inversion timing is detected, and a signal input means for inputting the detection signal generated from the detection means to a reset terminal of the flip-flop circuit, and the waveform is output from the flip-flop circuit. It has a configuration to obtain a shaped playback control signal.

(Function) In the control signal waveform shaping circuit of the present invention, the pulse generating means generates positive pulses and negative pulses from the signal reproduced from the control head. The switch means determines whether to input the positive pulses and negative pulses from the pulse generating means to the set terminal and the reset terminal of the flip-flop circuit, or to the reset terminal and the set terminal, according to a forward/reverse instruction signal indicating the tape running direction. Switch. The detection means generates a detection signal when detecting the reversal timing of the forward/reverse rotation instruction signal. The signal input means inputs the detection signal generated from the detection means to the reset terminal of the flip-flop circuit.

The flip-flop circuit outputs a waveform-shaped reproduction control signal.

As another feature of the structure, the reversal control means switches whether to output the signal reproduced from the control head as it is or to output the signal after inverting it, depending on the forward/reverse instruction signal indicating the tape running direction. The pulse generating means generates positive pulses and negative pulses from the output of the inversion control means. The flip-flop circuit inputs the positive pulse from the pulse generating means to the set terminal and the negative pulse to the reset terminal. The detection means generates a detection signal when detecting the reversal timing of the forward/reverse rotation instruction signal. The signal input means inputs the detection signal generated from the detection means to the reset terminal of the 79717091 circuit.

The flip-flop circuit outputs a waveform-shaped reproduction control signal.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings, in which the same parts as those of the conventional example are denoted by the same reference numerals. FIG. 1 is a block diagram showing an embodiment of the control signal waveform shaping circuit of the present invention. 1 is a control head that reproduces a control signal recorded on a control track of the tape; 2 is an amplifier that amplifies the control signal 100 reproduced by the control head 1; and 3 is an amplifier 2.
4 is a negative pulse detector that generates a negative pulse from the reproduction control signal 200 output from the amplifier 2; 5 is an input set signal; An RS flip-flop 7.8 generates a rectangular waveform playback control signal 600 in addition to the reset signal; 7.8 is a terminal S of an RS flip-flop 5 which switches the output of the positive and negative pulse detector 3.4 by a forward/reverse instruction signal F; The switch 11 inputted to the terminal R detects the changing edge of the forward/reverse instruction signal F and logically ORs the detection signal #112
The edge detector 12 outputs the output signal from the terminal C of the switch 8 and the detection signal from the edge detector 11, and is an OR circuit that outputs the result to the reset terminal R of the RS flip-flop 5.

Here, the edge detector 11 uses the detection means as the logical sum circuit 1
2 constitutes a signal input means.

Next, the operation of this embodiment will be explained. Now, if the tape starts running in the normal direction and stops at the S pole of the magnetization pattern of the control track, and then runs in the reverse direction, the tape running direction becomes the running direction shown in FIG. 2(A), and at this time, The magnetization pattern at the control head 1 shown in FIG. 1 is as shown in FIG. 2(B). FIG. 2(C) shows the frame number at this time. When the tape is run as described above, the reproduction signal 200 reproduced by the control head 1 becomes as shown in FIG. 2 (D>).

Moreover, during normal rotation when the forward/reverse instruction signal F is 0, both switches 7 and 8 are switched to the terminal a side, and when the tape is reversed when the forward/reverse instruction signal F is 1, both switches 7 and 8 are switched to the terminal side. In this example as well, a set signal as shown in FIG. 2(E) is input to the terminal S of the RS flip-flop 5, and a reset signal as shown in FIG. 2(F) is input to the terminal R. .

By the way, at the time when the tape running is stopped, the forward/reverse rotation instruction signal F is as shown in FIG. 2(G).

Since the signal F rises from 1 to 1, the edge detector 11 detects the edge of the signal F and outputs a detection signal 50 as shown in FIG. 2(H) to the OR circuit n12.

Therefore, this signal 50 is input to the reset terminal of the RSS flip-flop 5 to reset this flip-flop, and the reset signal input to the R terminal is as shown in FIG. 2 (1). Become.

This prevents the set signal from being continuously input to the S terminal of the RS flip-flop 5 when the tape running is reversed in this example. A reproduction control signal having a rectangular waveform as shown in FIG. 2(J) is output. Therefore, the result of the counting operation of the linear time counter (not shown) based on the reproduction control signal as shown in FIG. 2(J) is as shown in FIG. 2(K). The operation of this example as described above is the same even when the tape runs in the reverse direction, stops for a moment, and then changes to the forward direction, and from the Q terminal of the RS flip-flop 5, the signal shown in FIG. 2 (J) is also applied. A playback control signal as shown is output.

According to this embodiment, since the edge of the forward/reverse instruction signal generated when the tape direction is reversed is detected and the reset signal is input to the reset terminal R of the RS flip-flop 5, when the tape is reversed, Since it is possible to prevent the set signal from being continuously input to the S terminal of the RS flip-flop 5, the number of generated reproduction control signals 600 output from the Q terminal of the RS flip-flop 5 is increased by one. , erroneous counting of the linear time counter can be prevented. Furthermore, since it is only necessary to add the edge detector 11 and the OR circuit 12 to realize this, the above effect can be obtained at low cost without increasing the circuit scale.

FIG. 3 is a block diagram showing another embodiment of the present invention. This example also has the same effect as the above example due to the same operation.

〔Effect of the invention〕

As described above, according to the control signal waveform shaping circuit of the present invention, even when tape running is reversed, the reference edge of the control signal can be accurately reproduced to prevent malfunction of the linear time counter.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the control signal waveform shaping circuit of the present invention, FIG. 2 is an operational waveform diagram explaining the operation of the circuit shown in FIG. 1, and FIG. 3 is a block diagram showing an embodiment of the control signal waveform shaping circuit of the present invention. 4 is a block diagram showing an example of a conventional control signal waveform shaping circuit, FIG. 5 is an operating waveform diagram of the circuit shown in FIG. 4, and FIG. 6 is a block diagram showing an example of a conventional control signal waveform shaping circuit. A block diagram showing another example of the control signal waveform shaping circuit, FIG. 7 is a block diagram showing still another example of the conventional control signal waveform shaping circuit, and FIG. 8 shows the operation of the circuit shown in FIG. 7. FIG. 1... Control head 2... Amplifier 3... Positive pulse detector 4... Negative pulse detector 5... RS flip-flop 7.8... Switch 1... Edge detector 12 ...OR circuit

Claims (2)

[Claims] (1) Pulse generating means that generates positive pulses and negative pulses from signals reproduced from the control head, a flip-flop circuit, and positive and negative pulses from the pulse generating means according to a forward/reverse instruction signal indicating the tape running direction. are input to the set terminal and reset terminal of the flip-flop circuit, respectively, or to the reset terminal,
a switch means for switching input to the set terminal;
comprising a detection means for generating a detection signal at the time of detecting the reversal timing of the forward/reverse rotation instruction signal, and a signal input means for inputting the detection signal generated from the detection means to the reset terminal of the flip-flop circuit, A control signal waveform shaping circuit characterized in that a reproduction control signal whose waveform has been shaped is obtained from the flip-flop circuit. (2) An inversion control means for switching whether to output the signal reproduced from the control head as it is or inverted according to a forward/reverse instruction signal indicating the tape running direction, and a positive pulse and a signal from the output of this inversion control means. pulse generating means for generating a negative pulse; a flip-flop circuit in which the positive pulse from the pulse generating means is input to a set terminal and the negative pulse is input to a reset terminal; and a point in time when the reversal timing of the forward/reverse rotation instruction signal is detected. and a signal input means for inputting the detection signal generated from the detection means to a reset terminal of the flip-flop circuit, the reproduction control signal having been waveform-shaped from the flip-flop circuit. A control signal waveform shaping circuit characterized in that it obtains the following.