JPH04212748A - Servo control device - Google Patents

Abstract

PURPOSE:To read data even when the voltage of a battery being a power source is lowered in the middle of high speed search in the servo controller of a rotating head type magnetic tape reproducing device. CONSTITUTION:A detection circuit is provided, which detects a relative speed between a magnetic tape and a rotating head drum from a reproducing signal, and the rotation of the drum is increased or decreased stepwise from a rotating speed at the time of high speed search according to a tape moving direction in the case of detecting the lowering of the relative speed in the middle of the high speed search, and the speed of a magnetic tape at the time of reproducing at a high speed is controlled in accordance with the detected result by the relative speed detection circuit.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control device used in a DAT or the like for recording and reproducing digital data on a magnetic tape using a rotary head.

0002

[Prior art] Audio signals are converted into PCM and magnetic tape
A rotating head type DAT that records on a tape and plays it back has a high-speed system that transports the tape at, say, 200 times the normal playback speed, and during this time plays back the recorded signal to find the beginning of the song. The idea is to conduct a search. During normal playback, the magnetic tape is always transported at a constant rated speed by the capstan and pinch rollers, but at a tape transport speed of 200 times as described above, the pinch rollers are removed and the reel module is moved. - The magnetic tape is transferred only by the tape.

In this case, unless the relative speed between the rotating head and the magnetic tape is within a predetermined range, the digital data recorded on the magnetic tape cannot be read. After changing the installed drum to a high-speed rotation speed and fixing the rotation speed, the head and tape are
The reel motor is controlled so that the relative speed of the tape is approximately constant and the tape transport speed is 200 times faster.

0004

[Problem to be Solved by the Invention] Here, if the DAT is a battery-powered portable type, when the battery voltage decreases, the reel motor becomes a heavy burden during high-speed searches. The side reaches its limit first. Therefore, there is a risk that the relative speed between the rotary head and the magnetic tape will deviate from a predetermined range, making it impossible to read data.

The present invention was made in view of the above-mentioned circumstances, and provides a rotating head type magnetic tape that allows data to be read even when the voltage of the battery that is the power source drops during high-speed search. The object of the present invention is to provide a servo control device for a playback device.

[0006]

[Means and effects for solving the problem] The present invention includes a detection circuit that detects the relative speed between the magnetic tape and the rotating head drum from the reproduced signal, and detects a decrease in the relative speed during high-speed search. When the drum rotation is detected, the drum rotation is increased or decreased in stages from the rotation speed during high-speed search depending on the tape transport direction at that time, and the drum rotation is increased or decreased during high-speed playback according to the detection result of the relative speed detection circuit. The speed of the magnetic tape is controlled, making it possible to read data even if the voltage of the battery, which is the power source, drops during a high-speed search.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a portable rotary head type DAT using a battery as a power source will be described below with reference to the drawings.

FIG. 1 shows the circuit configuration.
13 are a play button, a fast forward search button, and a rewind search button for instructing playback, fast forward search, and rewind search, respectively.
It's a button. When these are operated, the operation signal is sent to the control section 14.

The control section 14 controls all other circuits, and sends a specified address to the preset value memory 15, a control signal to the relative speed detection circuit 16, a drive signal to the driver 17, and a gate. Gate signals a and b are sent to the circuits 18 and 19, an addition/subtraction command S is sent to the addition/subtraction circuit 20, a write pulse and a read pulse are sent to the latch circuit 21, a preset pulse and a reset pulse are sent to the speed error detection counter 22, and the latch circuit 23 A read pulse is sent to the driver 24, and a drive signal is sent to the driver 24, respectively.

The preset value memory 15 is stored in accordance with the rotational speed of a drum motor 25 that rotationally drives a drum (not shown) provided with a rotary head during playback, fast forward search, and rewind search. The preset values read out according to the designated address of the control section 14 are sent to the gate circuit 18.

The gate circuit 18 receives gate signals from the control section 14.
The gate is opened by the gate signal a, and the preset value in the preset value memory 15 is passed through and sent to the latch circuit 21. The latch circuit 21 writes/reads preset values sent by write pulses and read pulses from the control section 14. The preset value read from the latch circuit 21 is sent to the addition/subtraction circuit 20 and the speed error detection counter 22.

The addition/subtraction circuit 20 adds or subtracts the preset value from the latch circuit 21 using an appropriate appropriate value according to the addition/subtraction instruction S from the control section 14, and sends the result of the operation to the gate circuit 19. Output.

The gate circuit 19 passes the calculation result from the addition/subtraction circuit 20 in accordance with the gate signal b of the control section 14 and sends it to the latch circuit 21 again. The speed error detection counter 22 presets the preset value sent from the latch circuit 21 using a preset pulse, thereafter counts up using the reference clock CK, and resets the counted value when a reset pulse is input. The count value of this speed error detection counter 22 is sequentially calculated by the latch circuit 2.
Sent on 3rd. The latch circuit 23 latches this in response to the read pulse from the control section 14 and outputs it to the D/A conversion circuit 26 .

When the D/A conversion circuit 26 converts the input digital signal into an analog voltage signal and outputs it to the driver 24, the driver 24 drives the drum motor at the rotation speed instructed by the drive signal from the control section 14. Servo control is performed according to the voltage signal so as to rotate the motor 25. The rotation speed of this drum motor 25 is 2000 [rpm] during playback.
, 3000 [rpm] during fast forward search, and 1000 [rpm] during rewind search. This drum motor 25
The rotation of is detected by a frequency generator (denoted as "FG" in the figure) 27 attached to the drum motor 25, and the FG pulse, which is the detection pulse of the frequency generator 27, is sent to the control section 14. Sent out.

As the drum motor 26 rotates, a rotary head provided on the drum scans the magnetic tape. At this time, the magnetic tape is pulled out from the cassette half and is run while being wound diagonally around the drum at an angle of 90° to the center of the drum. During normal playback, this tape is run at a constant rated speed (8.15 mm/sec) by a capstan and a pinch roller.

When the signal recorded on the tape is reproduced by the rotary head, the reproduced data is sent to the audio processing circuit and also to the filter 28. The filter 28 is composed of, for example, a BPF (band pass filter), and has a constant frequency (rotating head type DAT) in the recording track.
In this case, only the frequency component of the pilot signal recorded at 130 kHz is extracted and outputted to the relative speed detection circuit 16.

The relative speed detection circuit 16 is controlled on/off by a control signal from the control unit 14 to detect the relative speed between the magnetic tape and the rotary head during high-speed search, The pulse interval of the frequency signal from 28 is compared with a reference value. Then, apply this comparison result to driver 1.
In addition to applying the error voltage to the control unit 1 when a decrease in relative speed is detected that makes high-speed search impossible,
A drop detection signal is sent to 4.

The driver 17 further operates the relative speed detection circuit 1 according to the rotational speed instructed by the drive signal of the control section 14.
When an error voltage is applied from 6, the reel motor 29 is driven to rotate in accordance with this.

The operation of the above embodiment will be explained below.

First, the operation when performing normal reproduction will be explained using FIG. 2.

[0021] When the playback button 11 is operated from the stopped state,
In response to the operation signal, the control unit 14 specifies the address of the preset value for reproduction in the preset value memory 15 as shown in FIG.
As shown in FIG. 2(b), the gate signal a to the gate is set to "1" level, and the gate circuit 18 is opened.

The preset value memory 15 contains data for playback and fast-forward search corresponding to the rotational speed of the drum motor 26, which differs depending on the operation state, such as during normal playback, fast-forward search, and rewind search. , each preset value for rewind search is stored and set, and when the speed error detection counter 22 counts based on these preset values, the drum motor
Even if the rotational speed of the counter 25 is different, the speed error detection counter 2
The count value of 2 is set to be a constant value.

The magnitude of these preset values corresponds to the number of rotations of the drum motor 25, and the relationship is as follows: during rewind search < during normal playback < during fast forward search. Here, a preset value for reproduction is read out from the preset value memory 15 according to the address designation of the control section 14, and is sent to the latch circuit 21 through the gate circuit 18.

The control section 14 stores the preset value memory 15.
Addressing to and gate signal a to gate circuit 18
Immediately after, a write pulse as shown in FIG. 2(c) is applied to the latch circuit 21, and a read pulse is applied to the latch circuit 21 at a timing slightly delayed from the timing of this write pulse as shown in FIG. 2(d). Send. These pulses
The preset value sent via the gate circuit 18 is written/read by the latch circuit 21, and then sent to the addition/subtraction circuit 20 and the speed error detection counter 22. In this state, when the drum motor 25 begins to rotate at the specified normal playback rotation speed, an FG pulse as shown in FIG. 2(e) is input from the frequency generator 27 to the control unit 14 in accordance with the rotation. be done.

The control section 14 sends a preset pulse as shown in FIG. 2(f) to the speed error detection counter 22 in synchronization with the rise of this FG pulse. The speed error detection counter 22 uses this preset pulse to preset the preset value from the latch circuit 21 as shown in FIG. 2(i), and thereafter counts the reference clock CK. Then, at the timing of the fall of the FG pulse,
), the count value of the speed error detection counter 22 is latched by the latch circuit 23 at the time when the read pulse is sent to the latch circuit 23.

The count value of this speed error detection counter 22 is based on the preset value and the time data for half a rotation of the drum motor 26.
The counted value is read out from the latch circuit 23 to the D/A conversion circuit 28, converted to an analog value voltage signal, and applied to the driver 24.

The driver 24 uses this voltage signal as a speed error signal to rotate the drum motor 25 at the rotational speed (2000 [rpm] in this case) instructed by the drive signal of the control section 14. Then, as shown in FIG. 2(h), when a reset pulse is sent to the speed error detection counter 23 at a timing appropriately delayed from the fall timing of the FG pulse, the count value is reset to "0".

From now on, a write pulse is also sent to the latch circuit 21 at the same time as the read pulse described above in synchronization with the falling edge of the FG pulse. The latch circuit 21 uses this write pulse to write a preset value from the preset value memory 15, which is the same value as above, and uses the read pulse input at a timing slightly delayed from the write pulse to change the written preset value to the speed error. It is output to the detection counter 23 and others.

Thereafter, in the same manner as described above, the preset value from the preset value memory 15 is directly preset in the speed error detection counter 22 via the gate circuit 18 and latch circuit 21, and the drum motor 25 is rotated half a rotation. During this time, the count is counted up using the reference clock CK. Then, the counted value is converted into an analog voltage signal by the D/A conversion circuit 26 via the latch circuit 23 as control data containing an error, and sent to the driver 24 to drive the drum motor.
This is to rotate the rotor 25 at the rotational speed during normal reproduction.

Therefore, the preset value in the speed error detection counter 22 is always the preset value for reproduction.

At this time, the control signal from the control section 14 to the relative speed detection circuit 16 is at the "0" level, the relative speed detection circuit 16 does not operate, and the driver 18
The reel motor 29 is rotated at a constant speed based only on the drive signal from the reel motor 29. During this normal playback, the tape transport speed is kept constant by the capstan and pinch roller, and the rotation of the reel motor 29 is transmitted to the take-up reel, and the tape is It is designed to provide a certain amount of tension.

Next, the operation when changing from a stopped state to a high speed search state will be explained.

FIG. 3 shows an example when the fast forward search button 12 is operated from a stopped state. Fast forward search button 1
When the operation 2 is performed, the control unit 14 stores the preset value memory 1 in response to the operation signal as shown in FIG. 3(a).
5, the specified address of the preset value for fast-forward search is sent to the preset value memory 15, and the gate signal a to the gate circuit 18 is sent as shown in FIG. 3(b).
1'' level, and the gate circuit 18 is opened.

The preset value for fast-forward search is read out from the preset value memory 15 by the address designation of the control unit 14, passes through the gate circuit 18, and is sent to the latch circuit 21.
sent to. The control unit 14 also controls the preset value memory 1.
5 and immediately after the gate signal a to the gate circuit 19, a write pulse is applied to the latch circuit 22 as shown in FIG. 3(c), and the timing of this write pulse is slightly delayed. A read pulse with a timing as shown in FIG. 3(d) is sent out.

The preset value sent via the gate circuit 18 by these pulses is written/read by the latch circuit 22, and then sent to the addition/subtraction circuit 20 and the speed error detection counter 22. In this state, when the drum motor 25 starts rotating at the rotational speed during the fast-forward search, the frequency generator 27 (see FIG. 3) responds to the rotation.
An FG pulse as shown in e) is input to the control section 14.

The control section 14 sends a preset pulse as shown in FIG. 3(f) to the speed error detection counter 22 in synchronization with the rise of this FG pulse. The speed error detection counter 22 uses this preset pulse to preset the preset value from the latch circuit 22 as shown in FIG. 3(i), and thereafter counts the reference clock CK. Then, in synchronization with the falling edge of the FG pulse,
), when a read pulse is sent to the latch circuit 23, the count value of the speed error detection counter 22 at this point in time is latched in the latch circuit 23. The count value is D/A
The signal is read out to the conversion circuit 26, converted into an analog value voltage signal, and applied to the driver 24.

The driver 24 uses this voltage signal as a speed error signal to calculate the rotation speed (
Here, the drum motor 25 is driven to rotate at 3000 [rpm]. Then, when the reset pulse shown in FIG. 3(h), which is appropriately delayed from the falling timing of the FG pulse, is sent to the speed error detection counter 22, the count value is reset to "0".

From now on, a write pulse is also sent to the latch circuit 21 at the same time as the read pulse described above in synchronization with the falling edge of the FG pulse. The latch circuit 21 uses this write pulse to write a preset value for fast-forward search from the preset value memory 15, which is the same value as above, and then writes the preset value using a read pulse slightly delayed from the write pulse. is output to the speed error detection counter 22 and others.

Thereafter, in the same manner as described above, the preset value from the preset value memory 15 is directly preset in the speed error detection counter 22 via the gate circuit 18 and the latch circuit 21, and the drum motor 25 rotates half a rotation. During this time, the count is counted up using the reference clock CK. Then, the counted value is converted into an analog voltage signal by the D/A conversion circuit 26 via the latch circuit 23 as control data containing an error, and sent to the driver 24 to drive the drum motor.
The motor 25 is rotated at the rotational speed during the fast-forward search described above.

At this time, the control signal from the control section 14 to the relative speed detection circuit 16 is at the "1" level, and the relative speed detection circuit 16 controls the reel motor 29 to the winding side reel. - Servo control is performed so that the rotation is always at a constant speed according to the diameter of the roll. That is, when only the frequency component of the 130 kHz pilot signal recorded in the recording track of the tape is extracted by the filter 28 and output to the relative speed detection circuit 16, the relative speed detection circuit 16 detects the pulse interval. is compared with the reference value, and the comparison result is used as the error voltage for driver 1.
7.

The driver 17 moves the reel motor 29 in the forward direction according to the rotational speed instructed by the drive signal of the control section 14 and the error voltage from the relative speed detection circuit 16. Rotate it so that it is fed at about 200 times the speed.

[0042] In such a state, when the battery as a power source is exhausted and the voltage supplied to each circuit is reduced, the rotational speed of the drum motor 25, which is rotating at 1.5 times the rotational speed during normal playback, will decrease. First, the rotation speed during normal playback is approximately 20%.
The rotational speed of the reel motor 29, which is rotating at 0 times, decreases.

When the tape transport speed decreases due to this decrease in rotational speed, and the relative speed between the magnetic tape and the rotary head decreases to such an extent that data cannot be read, the relative speed detection circuit 16 detects this. Detect.

That is, when the frequency component of the pilot signal in the reproduced data inputted to the relative speed detection circuit 16 via the filter 28 changes due to a decrease in relative speed, the relative speed detection circuit 16 detects that the relative speed has decreased. Judgment, Figure 3
As shown in (j), the drop detection signal to the control unit 14, which had been at the "0" level, is set to the "1" level.

At the same time as this drop detection signal is input, the control section 14 sets the gate signal a to the gate circuit 18 to "0".
level, and as shown in Figure 3(k), up to “0”
``The gate signal b to the gate circuit 19, which was at the level ``
1” level. This causes the preset value memory 15
The preset value for fast-forward search newly read from the gate circuit 18 does not pass through the gate circuit 18.

On the other hand, when the gate circuit 19 is in the open state, the addition/subtraction circuit 20 subtracts the preset value for fast-forward search from the latch circuit 21 by "-1" according to the addition/subtraction instruction S of the control section 14. The output is sent to the latch circuit 21 again via the gate circuit 19. A latch circuit 21 latches this preset value by a write pulse, and reads it out to an addition/subtraction circuit 20 and a speed error detection counter 22 by a read pulse sent with a slight delay after the write pulse.

The speed error detection counter 22 presets the subtracted preset value from the latch circuit 21 using a preset pulse from the control section 14, and thereafter counts the reference clock CK. The latch circuit 23 latches the count value of the speed error detection counter 22 at the time when a read pulse synchronized with the falling edge of the FG pulse is input.

This latched speed error detection counter 2
The count value 2 is a slightly smaller value than the count value at the time of reproduction because the preset value has been subtracted once by the addition/subtraction circuit 20, and this count value is used as the D/A.
When the voltage signal is converted into an analog voltage signal by the conversion circuit 26 and sent to the driver 24, the driver 24 rotates the drum motor 25 at a speed slightly slower than during the fast-forward search in accordance with this voltage signal. Thereafter, the count value of the speed error detection counter 22 is reset at the time when the reset pulse is input.

Thereafter, every time a write pulse synchronized with the falling edge of the FG pulse and a read pulse slightly delayed from this write pulse are input to the latch circuit 21, the latch circuit 21
The preset value read from 1 is subtracted by the addition/subtraction circuit 20, gradually becoming a smaller value, and then sent to the latch circuit 21 again.
will be written in.

The preset values of the latch circuit 21 are sequentially sent to the speed error detection counter 22, and are preset and counted as shown in FIG. 3(i). The count value of this speed error detection counter 22 is the latch circuit 2
3 and is converted into a voltage signal by the D/A conversion circuit 26 and applied to the driver 24, and the driver 24 rotates the drum motor 25 accordingly. Therefore, the rotational speed of the drum motor 25 gradually decreases. As the rotation speed of the drum motor 25 decreases, the relative speed between the magnetic tape and the rotary head gradually increases.

Then, the preset value in the speed error detection counter 22 becomes sufficiently small, and accordingly, the rotational speed of the drum motor 25 also decreases sufficiently, so that the relative speed between the magnetic tape and the rotary head decreases. When the fast-forward search becomes possible again, the pilot signal in the reproduced data is again extracted by the filter 28 and input to the relative speed detection circuit 16. The relative speed detection circuit 16 detects this and sends a decrease detection signal to the control unit 14 as shown in FIG. 3(j).
0'' level, the control section 14 simultaneously outputs the gate signal b to the gate circuit 19 as shown in FIG. 3(k).
is also lowered to the “0” level. At this point, the gate circuit 18,
Both gate circuits 19 are closed, and no new preset values are input to the latch circuit 21. At the same time, the control unit 14 stops sending the write pulse and read pulse to the latch circuit 21.

Therefore, the latch circuit 21 continues to output the preset value at the time when the previous read pulse was input. Thereafter, the speed error detection counter 22 presets and counts the preset value from the latch circuit 21, and based on the counted value, the latch circuit 23
, the drum motor 25 is servo-controlled by the D/A conversion circuit 26 and the driver 24.

FIG. 3 describes the rotational speed control of the drum motor 25 when the relative speed between the magnetic tape and the rotary head decreases in the fast-forward search state by operating the fast-forward search button 12. The same applies to the rewind search state by operating the rewind search button 13.

In this case, when a decrease in relative speed is detected, the control section 14 causes the addition/subtraction circuit 20 to add the preset value by an addition/subtraction instruction S to the addition/subtraction circuit 20,
Control is performed so that the preset value preset to the speed error detection counter 22 gradually increases. According to the counted value, the driver 24 gradually increases the rotational speed of the drum motor 25 from 1000 [rpm].

[0055]

[Effects of the Invention] As detailed above, according to the present invention,
Equipped with a detection circuit that detects the relative speed between the magnetic tape and the rotating head drum from the playback signal, and when a decrease in relative speed is detected during high-speed search, the drum rotation will be changed to the rotation during high-speed search. The magnetic tape speed is increased or decreased in stages according to the tape transport direction at that time, and the magnetic tape speed during high-speed playback is controlled according to the detection result of the relative speed detection circuit. It is possible to provide a servo control device for a rotary head type magnetic tape reproducing device that allows data to be read even when the voltage of a battery serving as a power source decreases during a search.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit configuration according to an embodiment of the present invention.

FIG. 2 is a timing chart showing the contents of operation processing during normal playback in FIG. 1;

FIG. 3 is a timing chart showing the contents of operation processing during fast-forward search.

[Explanation of symbols]

11... Playback button, 12... Fast forward search button, 13... Rewind search button, 14... Control section, 15... Preset value memory, 1
6...Relative speed detection circuit, 17, 24...Driver, 18,
19... Gate circuit, 20... Addition/subtraction circuit, 21, 23... Latch circuit, 22... Speed error detection counter, 25... Drum motor, 26... D/A conversion circuit, 27... Frequency generator (FG), 28...filter, 29...reel motor.

Claims (1)

[Claims] 1. A rotary head type magnetic tape playback device, comprising: relative speed detection means for detecting the relative speed between the magnetic tape and the rotary head drum from a playback signal; and a means for detecting the relative speed during a high-speed search. drum control means for increasing or decreasing drum rotation stepwise from the rotational speed during high-speed search according to the tape transport direction during high-speed search when a decrease in relative speed is detected by the means; A servo control device comprising: magnetic tape transfer control means for controlling magnetic tape speed during high-speed reproduction according to the detection result of the relative speed detection means.