JP3048816B2 - 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 (hereinafter referred to as "VTR"), and particularly to setting a delay time of a head switching signal using a digital value obtained by A / D converting a voltage value of a variable resistor. It relates to a VTR of the system.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram schematically showing a head switching signal generating circuit and a drum phase comparing circuit in a conventional VTR. In the figure, 1 is a variable resistor, 2 is a capacitor, 3 is a PG-MM (PG Monostable Multivibrat
or) 4 is an output signal (hereinafter simply referred to as PG) of a PG (Pulse Generator) for detecting the rotation phase of the drum, which is input from the PG input terminal 5, and the rotation of the drum, which is input from the FG input terminal 6. FG (Frequency Gen) for detecting speed
a timing signal generating circuit for generating a timing signal for the PG-MM3 based on two input signals of an output signal (hereinafter, simply referred to as FG) of the PG-MM3.
A flip-flop 8 for generating a head switching signal based on both the output of PG 3 and the PG, a head switching signal output terminal 8 for outputting a head switching signal generated by the flip-flop 7, and a Vsync input terminal 9 for recording. A reference phase signal generating circuit for generating a reference phase signal from an internal clock at the time of reproduction from Vsync inputted from 10, a phase comparing circuit 11 for comparing the phase of the head switching signal and the reference phase signal, 12
Indicates the pulse width modulation (Pulse Width) of the output of the phase comparison circuit 11.
Modulation (PWM): A PWM generation circuit for converting to an output, and 13 is a PWM output terminal.

Next, the operation will be described with reference to a timing chart shown in FIG. When the drum on which the rotary magnetic head is mounted rotates, one pulse of PG (a) per rotation and FG (b) of 16 pulses per rotation are generated, and these pulses are respectively supplied to the PG input terminal 5 and the FG input terminal 6. And supplied to the timing signal generation circuit 4. In the timing signal generation circuit 4, the period of the FG3 pulse from the rising edge of the first FG after the PG is input, and the period of the FG3 pulse from the rising edge of the FG pulse of the ninth pulse after the PG is input. , And a timing signal (c) that is "L" during the other periods is generated and supplied to the PG-MM3. When the timing signal (c) is "L", the contact of the PG-MM 3 with the variable resistor 1 and the capacitor 2 connected to the PG-MM 3 is fixed at "L", and the timing signal (c) Becomes "H", the contact is released from being fixed to "L" and the variable resistor 1
To charge the capacitor 2. Voltage of this contact
(d) is input to the PG-MM, and when the threshold level is exceeded, a PG-MM output (e) having a constant pulse width is output. In the flip-flop 7, the head switching signal (f) which is cleared by PG (a), becomes "H" at the next PG-MM output (e), and becomes "L" at the next PG-MM output (e). )
Create The delay time t from the rising edge of FG (b) to the rising edge or falling edge of the head switching signal (f) is adjusted by adjusting the resistance value of the variable resistor 1 so that the charging current of the capacitor 2 changes. The charging time changes and is adjusted. The head switching signal (f) is output from the head switching signal output terminal 8 and supplied to a video signal processing system and the like, and is also supplied to the phase comparison circuit 11. In the phase comparison circuit 11, the phase of the head switching signal (f) is compared with the reference phase signal created by the reference phase signal creation circuit 9, and is output as a phase error.
Is converted into a PWM signal and output from the PWM output terminal 13 to form a phase control system.

In the drum servo system, the rotation of the drum is controlled by the operation of a speed control system (not shown) and the above-described phase control system. At the time of assembling and adjusting the VTR, when the rotating magnetic head comes to a predetermined position, a head switching signal
(f) rises or falls, the resistance value of the variable resistor 1 is adjusted, the delay time t of the PG-MM is adjusted,
The head switching timing, that is, the switching point is adjusted. As a result, at the time of recording, Vsync and the head switching signal (f) have a predetermined phase relationship, Vsync is recorded at a predetermined position on the magnetic tape, and at the time of rotation the magnetic head comes to a predetermined position at the time of reproduction. The reproduction signal is switched.

[0005] On the other hand, as described above, the dedicated digital hardware that constitutes the speed detector, the phase detector, and the like is constituted by dedicated hardware.
FIG. 6 is a block diagram showing an outline of a software servo system in which a speed detector and a phase detector are formed by a microcomputer with respect to the servo system. In the figure, 2
1 is a variable resistor for creating a variable voltage, 22 is an A / D converter for converting the voltage value of the variable resistor 21 into a digital value, 23 is a PG input terminal, 24 is an FG input terminal, and 25 is
Vsync input terminal, 26 is a free running counter for measuring the input time of PG, FG, Vsync and other output signals and the output time of an output signal, 27 is a central processing unit (CPU) of a microcomputer, 28 is a PWM creation circuit, 29 is PWM
An M output terminal 30 is a head switching signal output terminal.

Next, the operation will be described with reference to the timing chart shown in FIG. Each time the drum rotates and a PG is input, the voltage value of the variable resistor 21 is converted into a digital value by the A / D converter 22 and transmitted to the CPU 27. Assuming that this digital amount is N, the CPU 27 calculates a delay time t by multiplying N by an appropriate coefficient K (t
= N × K). In the free running counter 26, PG,
The time when FG and Vsync are input is measured and transmitted to the CPU 27. After PG (h) is input, the CPU 27 calculates a time T2 (= T1 + t) obtained by adding a delay time t to the time T1 when the first FG (i) is input, and the free running counter 26 calculates T2. When it becomes, the head switching signal (j) rises. Next, when PG (h) is input and then FG (i) of the ninth pulse is input, a time T4 (= T3 + t) obtained by adding a delay time t to the input time T3 of this FG (i).
Is calculated, and the head switching signal (j) falls when the free running counter 26 reaches T4. The head switching signal (j) is output from the head switching signal output terminal 30 and supplied to a video signal processing system. Further, in the CPU 27, every time FG (i) is input, FG (i)
The cycle of (i) is obtained, and the speed error is calculated. Vsyn when recording
The reference phase is calculated from the input time of c, the reference phase is calculated independently at the time of reproduction, the phase difference between the reference phase and the head switching signal (j) is obtained, and the phase error is calculated. The speed error and the phase error are appropriately weighted and added, and the PWM
M and output from the PWM output terminal 29. Similarly to the digital servo system, in the stage of assembling and adjusting the VTR, the resistance value of the variable resistor 21 is adjusted so that the head switching signal (j) rises or falls when the rotary magnetic head comes to a predetermined position. The adjustment is performed, the delay time t is adjusted, and the switching point is adjusted. As a result, during recording, Vsync and the head switching signal (j) have a predetermined relationship,
Vsync is recorded at a predetermined position, and at the time of reproduction, the reproduction signal is switched when the rotary magnetic head comes to the predetermined position.

[0007]

Since the conventional VTR is configured as described above, if the accuracy of the A / D converter 22 is not sufficient, even if the resistance value of the The value N converted into a digital quantity will fluctuate. If this variation is ΔN, the delay time t is Δ
t = ΔN × K, the head switching signal
The timing at which (j) occurs varies by Δt.
In the phase control system, the fluctuation of the head switching signal (j) is detected as a phase error, which causes uneven drum rotation. In order to solve this, for example, the voltage value of the variable resistor 21 may be A / D converted and taken in only once when the microcomputer is reset.
When adjusting the switching point, the variable resistor 21
The microcomputer must be reset every time the resistance value is changed, and there is a problem that adjustment of the switching point takes a lot of trouble.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the switching point can be adjusted without any trouble as in the prior art, and the fluctuation of the head switching signal can be eliminated. It is an object of the present invention to obtain a magnetic recording / reproducing apparatus of a software servo system which can eliminate drum rotation unevenness due to fluctuation.

[0009]

A magnetic recording / reproducing apparatus according to the present invention comprises a measuring means for measuring an input time of an input signal, and a frequency generator (Frequen) for detecting a rotation speed of a drum.
The output signal of a pulse generator (hereinafter referred to as PG) which detects the rotation speed of the drum from the input time of the output signal of the cy generator (hereinafter referred to as FG) and detects the rotation phase of the drum or the output of the FG Control means for detecting the rotational phase of the drum from the input time of the signal to control the rotational speed and rotational phase of the drum; voltage variable means for generating a variable voltage; and A / D for A / D converting the variable voltage
Conversion means and whether or not the generation time of the head switching signal is being adjusted
To output either the first level or the second level signal
Switching means for switching and inputting to the control means;
To set the delay time in response to D conversion output, head switching which sets the time of occurrence of the head switching signal from the input time of the output signal of the output signal or the FG of this delay time and the PG, it generates a head switching signal Signal control means, wherein the control means sets the delay time according to the A / D conversion means at the time of reset, and sets the delay time by the switching means.
Time of occurrence of the head switching signal according to the level of the force signal
It is determined whether or not is being adjusted, and if the generation time of the head switching signal is being adjusted, the delay time is set variable, and if the generation time of the head switching signal is not being adjusted, The delay time is fixed to the previously set delay time .

[0010]

In the present invention, the head switching timing,
That is, when it is determined that the switching point is being adjusted, the voltage value of the voltage variable unit is changed to A / each time PG is input, and only once when the control unit is reset.
D-conversion is performed to set a delay time for generating a head switching signal. When it is determined that the switching point is not being adjusted, A / D conversion is not performed, and head switching is performed using the previously set delay time. Since the signal is generated, no trouble is required for adjusting the switching point, and the fluctuation of the head switching signal is eliminated.

Further, in the present invention, the determination as to whether or not the generation time of the head switching signal is being adjusted is made only in accordance with the operation of the switching means, so that an increase in the cost of the apparatus can be minimized. it can.

[0012]

【Example】

Embodiment 1 FIG. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a magnetic recording / reproducing apparatus according to one embodiment of the present invention. The embodiment shown in FIG. 1 differs from the conventional VTR shown in FIG. 6 except for the following points.
Is the same as That is, reference numeral 31 denotes a changeover switch for switching to the "H" side when adjusting the switching point and to "L" side when not adjusting the adjustment, and 32 denotes an input port for inputting the level of the changeover switch to the CPU 27.

Next, the operation will be described with reference to the flowchart shown in FIG. The timing chart is the same as the conventional one shown in FIG. When the microcomputer is reset in step 40, first, in step 41, the voltage value of the variable resistor 21 is converted into a digital value by the A / D converter 22 and is set to N.

In step 42, N is taken into the CPU 27 and the delay time t = N × K is calculated. Step 4
At 3, it is determined whether or not FG has been input.
If G has not been input, the process proceeds to step 44. In step 44, it is determined whether PG has been input. If PG has not been input, the process returns to step 43.
Thereafter, step 43 until FG or PG is input.
The determination in step 44 is repeated.

When the FG is input from the FG input terminal 24, the process proceeds to step 45, in which the time when the FG is input is measured by the free running counter 26, and the CPU 27 determines the period of the FG from the time difference from the immediately preceding FG input time. Then, the speed error is calculated, the phase error and weighted addition are performed, and the output is converted to PWM by the PWM generation circuit 28, and
Output from the M output terminal 29.

Next, at step 46, the value of the FG counter for counting the number of FG pulses is increased by "1", and at step 47, it is determined whether or not the value of the FG counter is "1". If "1", that is, if the FG input at that time is the first FG after PG input, step 48
Then, the delay time t is added to the FG input time T1 to calculate the rise time T2 (= T1 + t) of the head switching signal. In step 49, after calculating a phase error from the time difference between T2 and the reference phase, the process returns to step 43. If the value of the FG counter is not "1" in step 47, the process proceeds to step 50, and it is determined whether the value of the FG counter is "9". If it is "9", that is, if the FG at that time is the FG of the 9th pulse after the PG input, the process proceeds to step 51, where the delay time t is added to the FG input time T3, and the falling time T4 (= After calculating (T3 + t), the process returns to the step 43. In step 50, if the value of the FG counter is not "9", the process returns to step 43. Although not shown in the flowchart of FIG. 2, when the time of the free running counter 26 becomes T2 or T4, the "H" and "L" levels of the head switching signal output from the head switching signal output terminal 30 are switched.

Here, in step 44, if PG has been input, the flow proceeds to step 52, where the value of the FG counter is set to "0". Then, in a step 53, it is determined whether or not the level of the input port 32 is "H". Here, when the switching point which is the head switching timing is being adjusted, the changeover switch 31 is set to “H” by the adjuster.
The switch 31 is switched to the "L" side except when the switching point is being adjusted. If the level of the input port 32 is “L”, that is, if the switching point is not being adjusted, step 4
3, if it is "H", that is, if the switching point is being adjusted, the process proceeds to step 54, where the voltage value of the variable resistor 21 is A / D converted, and in step 55, the delay time t (= N × K ), And then returns to step 43.

Therefore, the switching point can be adjusted without any trouble as in the past, and the switching point is fixed to the previous value when the switching point is not being adjusted.
The A / D conversion value of the voltage value of the variable resistor can be prevented from fluctuating.
It is possible to prevent the rotation of the drum from becoming uneven due to the fluctuation of the A / D conversion value.

Embodiment 2 FIG. In the above-described embodiment, the level of the input port 32 is switched by the changeover switch 31. However, as shown in FIG. And the input port 32 is set to “H” in this state when the switching point is being adjusted.
The input port 32 may be switched to the “L” level by cutting the wiring 33 after the adjustment of the switching point is completed.

In the above embodiment, the level of the input port 32 is determined every time a PG is input. However, the level may be determined at another timing such as a timer interrupt. In the above-described embodiment, the case where one cycle of the head switching signal is generated for one rotation of the drum is shown. However, the case where one cycle of the head switching signal is generated for one rotation of the drum 1.5, or the head switching signal is generated at another rate. The same effect as in the above embodiment can be obtained.

In the above-described embodiment, the generation time of the head switching signal is set by adding the delay time to the input time of the predetermined FG after the input of the PG. The generation time of the head switching signal may be set by adding a delay time.

[0022]

As described above, according to the magnetic recording and reproducing apparatus of the present invention, the measuring means for measuring the input time of the input signal and the frequency generator (Fre
The output signal of a pulse generator (hereinafter, referred to as PG) or the output signal of the FG that detects the rotation speed of the drum from the input time of the output signal of the FG (frequency generator: hereinafter FG) and detects the rotation phase of the drum. Control means for detecting the rotational phase of the drum from the input time to control the rotational speed and rotational phase of the drum, voltage variable means for generating a variable voltage, and an A / D converter for A / D converting the variable voltage.
D conversion means, and whether or not the generation time of the head switching signal is being adjusted
The signal of one of the first level and the second level
Switching means for switching and inputting to the control means;
/ To set the delay time in response to D converter output, and sets the occurrence time of the head switching signal from the input time of the output signal of the output signal or the FG of this delay time and the PG, generates a head switching signal head Switching signal generating means, wherein the control means sets the delay time according to the A / D conversion means at the time of reset, and sets the delay time by the switching means.
Time of occurrence of the head switching signal according to the level of the force signal
It is determined whether or not is being adjusted, and if the generation time of the head switching signal is being adjusted, the delay time is set variable, and if the generation time of the head switching signal is not being adjusted, Since the delay time is fixed to the previously set delay time, the switching point can be adjusted as before, and at other times, the fluctuation of the A / D conversion value of the voltage value of the voltage variable means. possible to prevent the results, the effect called Ru prevents the rotation unevenness occurs in the drum by the fluctuation of the a / D conversion value.

[0023] Moreover, using just easily determine device whether being adjusted providing easy single such switching means, there is an effect that the cost of the apparatus can be minimized.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a drum controller of a software servo of a magnetic recording and reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an algorithm of the software shown in FIG. 1;

FIG. 3 is a block diagram showing a magnetic recording / reproducing apparatus according to another embodiment of the present invention.

FIG. 4 is a block diagram schematically showing a drum control unit of a conventional digital servo.

FIG. 5 is a timing chart for explaining the operation of the device shown in FIG. 4;

FIG. 6 is a block diagram schematically showing a drum controller of a conventional software servo.

FIG. 7 is a diagram showing a timing chart for explaining the operation of the device shown in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Variable resistor 22 A / D converter 23 PG input terminal 24 FG input terminal 25 Vsync input terminal 26 Free running counter 27 CPU 28 PWM creation circuit 29 PWM output terminal 30 Head switching signal output terminal 31 Changeover switch 32 Input port 33 Wiring 34 Resistor

Claims (1)

(57) [Claims] 1. A measuring means for measuring an input time of an input signal, and a frequency generator (Frequency G) for detecting a rotation speed of a drum.
The output signal of a pulse generator (hereinafter referred to as PG) or the output signal of the FG that detects the rotation speed of the drum from the input time of the output signal of the FG (enerator: FG) and detects the rotation phase of the drum. Control means for detecting the rotational phase of the drum from the input time of the input and controlling the rotational speed and rotational phase of the drum; voltage variable means for generating a variable voltage; and A / D converting means for A / D converting the variable voltage. The first level is determined by whether or not the generation time of the head switching signal is being adjusted.
The signal of one of the first level and the second level by the control means.
A switching means for switching and inputting, and a delay time is set in accordance with the A / D conversion output, and the generation time of the head switching signal is determined from the delay time and the input time of the output signal of the PG or the output signal of the FG. And a head switching signal generating means for generating a head switching signal, wherein the control means sets the delay time according to the A / D conversion means at the time of resetting, and sets an input signal by the switching means.
The generation time of the head switching signal is adjusted according to the signal level.
It is determined whether or not the head switching signal is being generated, and if the time at which the head switching signal is generated is being adjusted, the delay time is set variable. A magnetic recording / reproducing apparatus characterized in that a time is fixed to a previously set delay time.