JP3041973B2 - Magnetic recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus, and more particularly to a one-field screen switching signal generation.

[0002]

2. Description of the Related Art A servo mechanism of a cylinder motor of a conventional magnetic recording / reproducing apparatus (hereinafter referred to as VTR) will be described. FIG. 9 is a block diagram showing a configuration of a servo mechanism during reproduction of a conventional VTR. Cylinder motor 902 for driving rotary head 903 and cylinder motor 90
2, a frequency generator 905 for detecting the rotation speed, and a phase detector 904 for detecting the rotation phase of the cylinder motor 902.
And a frequency discriminator (CYL-SC) 906 for detecting an error of an output signal of the frequency generator 905 with respect to a reference cycle.
A reference signal generator 909, a phase comparator (CYL-PC) 907 for detecting a phase error between the rotation phase signal 921 obtained from the phase detector 904 and the reproduction reference signal obtained from the reference signal generator 909, The phase error output 919 of the phase comparator 907 and the speed error output 9 of the frequency discriminator 906
20 and an drive circuit (DR) 912 for driving the amplifier 911 and the cylinder motor 902.

With respect to a VTR having the above-described components, an operation of generating a one-field screen switching signal (hereinafter, referred to as an H.SW signal) will be described with reference to a configuration diagram of FIG. 9 and a timing chart shown in FIG. 8A shows the rotation phase signal 921, and FIG. 8B shows the output signal 922 of the frequency generator 905. The rotation phase signal 921 is input to the H.SW generation circuit 915, and the H.SW generation circuit 915 is reset by the rising edge, and the H.SW generation circuit 9 is generated by the next rising edge of the output signal 922 of the frequency generator 905.
The 15 output signal 923 is set (FIG. 8C). Next, FIG. 8D shows the PG mono-multi circuit (PG ·
MM) 916, which is triggered by the rising edge in FIG. 8C and whose delay time can be varied by changing the time constant with the variable resistor 917 in FIG. FIG. 8E shows an output waveform 908 of the PG mono-multi circuit 916 of FIG.
913 of the head amplifier circuit (HA) 913,
The head is switched for each field.

[0004]

By the way, when the above-mentioned conventional H.SW signal generating method is used, since the delay time of the H.SW signal is determined by the variable resistor and the capacitor, the delay time of the variable resistor and the capacitor is determined. Due to the temperature dependency, the delay time changes, the switching timing of the H.SW signal is shifted, and a switching noise bar appears at the top or bottom of the television screen.

An object of the present invention is to solve the above-mentioned problem and to provide a magnetic recording / reproducing apparatus in which a noise bar does not appear on a screen.

[0006]

For the present invention SUMMARY OF THE INVENTION The To achieve the above object, a signal generating means controlled by the rotary head phase information and the rotary head speed information, playback vertical sync signal
Creates a rotary head switching signal with a predetermined phase difference
Means for performing the predetermined phase difference,
The rotary head switching signal obtained by delaying the output signal of the generating means.
Calculating means for adjusting the delay time of the
And nonvolatile memory means for storing data .

[0007]

According to the present invention, by using the above means, the phase difference between the phase reference signal and the H.SW signal can always be kept constant, and a switching noise bar is provided at the upper or lower part of the television screen caused by a temperature change. Not issued.

[0008]

1 to 7 show an embodiment of the present invention.
This will be described with reference to FIG.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the drawing, a block diagram surrounded by a broken line 101 is a block diagram showing a configuration of a cylinder servo mechanism at the time of reproduction of a conventional VTR, and has the same function as each block of the same number already described with reference to FIG. . The master tape is reproduced, the vertical synchronization signal 105 from the video circuit 914 and the output signal 923 of the H / SW generation circuit 915 are input to the microcomputer 104, and the phase difference between the H / SW signal 108 and the vertical synchronization signal 105 is processed by software processing. setting the delay time [Delta] T ₄ so as to 6.5H (Fig. 6 (D)). Next, the H.SW signal 108 is delayed in the positive and negative directions by ΔT (FIGS. 6 (F) and 6 (G)) to determine whether there is a step in the detection signal 114 of the envelope signal 113 near the H.SW or not. It is determined whether or not the mouth is opened due to the discontinuity of the reproduction signal (see FIG. 7). When it is determined that the user is not mouthing, the nonvolatile ROM 112 stores ΔT ₄
Transfer and store the value of When the power is turned on again, the nonvolatile RO
The data of ΔT ₄ of M112
4 and the H · SW signal 108 based on the ΔT ₄ data.
Create 2 to 5 show software processing in the microcomputer 104. When power is on, Fig. 2
The program starts from the main processing of. Processing 20
Reference numeral 1 denotes a determination process. In the test mode, the process proceeds to a process 202, and the other process proceeds to a process 207. The process 202 is an initial setting, and details are shown in FIG. The process 301 is a process of storing the value X _{3 of} the counter latched by the vertical synchronization signal in the ROM 3 and storing the value X _{1 of} the counter latched by the H · SW signal 923 in the ROM ₁ . Process 302 by subtracting the value of X ₁ from the value of X ₃ counters, ROMTi further minus the time alpha ₃ corresponding to 6.5H
This is the process of storing in m1. Tim1 obtained in process 302
Is ΔT ₄ in FIG. 6 (D).
Process 303 is a process for permitting an external interrupt. The external interrupt is assumed to be interrupted at the rising edge of the output signal 923 of the H / SW creation circuit 915. The process 203
A / D conversion of the signal 114 obtained by detecting the envelope signal 113
This is a process of inputting the signal 106 converted by the conversion circuit 103. The process 204 is a judgment process, and is performed based on the envelope detection level V ₁ (FIG. 7D) at the center of the H · SW signal.
It is determined whether or not a value obtained by subtracting the envelope detection level V ₂ (FIG. 7D) near the SW signal is larger than a set threshold value V ₃ . If it is larger, the process proceeds to step 205 and thereafter, and proceeds to the process in which it is determined that the envelope is open.
Proceed to 6. The process 205 is a process when it is determined that a mechanical mounting error has occurred, for example, a process of setting the port to High or notifying the outside. The processing 206 is performed in the ROM Tim1
Is stored in the nonvolatile memory 112 at the address Tim4. Next, when the power is turned on again and the test mode is not set, the main processing first proceeds to processing 207, where the data stored at the Tim4 address of the nonvolatile memory 112 is stored in the RA.
This is the process of transferring to MTim1. Process 208 is a process for permitting an external interrupt. When an external interrupt, that is, a rising edge of the output signal 923 of the H / SW generation circuit 915 is input to the microcomputer 104, the process 401 is performed.
A process 401 is a process for starting a timer, and is performed for a time Δ
Interrupt after T ₄ is a process that enters. When this interrupt occurs, the process 501 is performed and the H / SW signal 108 is output.

The above is the software processing performed by the microcomputer 104. As described above, according to the magnetic recording / reproducing apparatus of the embodiment of the present invention, since the phase of the rotary head switching signal is arranged to be constant at the optimum value, no switching noise bar is displayed on the screen.

[0011]

As is apparent from the above description, according to the present invention, since the phase difference between the phase reference signal and the H.SW signal is arranged to be always constant, the conventional temperature change And a magnetic recording / reproducing apparatus that does not emit a switching noise bar at the top or bottom of the television screen caused by the above.

[Brief description of the drawings]

FIG. 1 is a block diagram of a magnetic recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart of a main processing program of a microcomputer applied to the present invention;

FIG. 3 is a flowchart of a program of a microcomputer initial setting process applied to the present invention;

FIG. 4 is a flowchart of a processing program when an external interrupt occurs.

FIG. 5 is a flowchart of a processing program when a timer interrupt occurs.

FIG. 6 is a timing chart of an output signal of a main part of the circuit shown in FIG. 1;

FIG. 7 is an explanatory diagram showing a change in a detection output signal with respect to opening of an envelope signal of a reproduction signal;

FIG. 8 is a timing chart of a conventional H.SW signal creation.

FIG. 9 is a block diagram of a servo mechanism during reproduction of a conventional magnetic recording / reproducing apparatus.

[Explanation of symbols]

 104 microcomputer 112 EP / ROM 903 rotating head 904 phase detector 905 frequency generator 915 H / SW creation circuit

Claims (1)

(57) [Claims] 1. A signal creating means controlled by the rotary head phase information and the rotary head speed information, playback vertical sync signal
Creates a rotary head switching signal with a predetermined phase difference
Means for performing the predetermined phase difference,
The rotary head switching signal obtained by delaying the output signal of the generating means.
Calculating means for adjusting the delay time of the
Recording / reproducing apparatus having a nonvolatile memory means for storing data