JPH0680548B2 - Servo controller - Google Patents

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 for DAT etc. for recording / reproducing digital data on a magnetic tape by a rotary head.

[0002]

2. Description of the Related Art Magnetic signals are produced by converting audio signals into PCM.
In a rotary head type DAT for recording and reproducing on a tape, the tape is transferred at a speed of, for example, 200 times the normal reproduction speed, and during this time, a recording signal is reproduced to find the beginning of the music. It is considered to conduct a search. During normal reproduction, the magnetic tape is always transferred at a constant rated speed by the capstan and pinch roller, but at the 200 times tape transfer speed as described above, the pinch roller is removed and the reel tape is removed. -Transfer the magnetic tape only with the tape.

In this case, if the relative speed between the rotary head and the magnetic tape is not within a predetermined range, the rotary head cannot be read because the digital data recorded on the magnetic tape cannot be read. After changing the provided drum to a high speed rotation speed and fixing the rotation speed, head and tape
The reel motor is controlled so that the tape relative speed is approximately constant and the tape transfer speed is 200 times.

[0004]

If the DAT is a battery-powered portable type, the reel motor, which has a heavy load during high-speed search when the battery voltage drops, is a problem. The side reaches the limit first. As a result, the relative speed between the rotary head and the magnetic tape may deviate from a predetermined width, making it impossible to read data.

The present invention has been made in view of the above situation, and is a rotary head type magnetic tape recorder capable of reading data even when the voltage of a battery as a power source drops during high speed search. -The purpose of the present invention is to provide a servo control device for a playback device.

[0006]

SUMMARY OF THE INVENTION The present invention comprises a detection circuit for detecting the relative speed of a magnetic tape and a rotary head drum from a reproduction signal, and detects a decrease in relative speed during high speed search. When the drum speed is increased, the drum speed is increased or decreased stepwise according to the tape transfer direction at the time of high speed search, and at the time of high speed reproduction according to the detection result of the relative speed detection circuit. The magnetic tape speed is controlled so that the data can be read even if the voltage of the battery, which is the power source, drops during high speed search.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a portable type 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 of the circuit.
Are a playback button, a fast-forward search button, and a rewind search button for instructing operations of the playback, fast-forward search, and rewind search. When these are operated, the operation signal is the control unit.
Sent to 14.

The control unit 14 controls the entire other circuits. The preset value memory 15 is provided with a designated address, the relative speed detection circuit 16 is provided with a control signal, and the driver 17 is provided with a drive signal. The gate signals a and b are supplied to the circuits 18 and 19, the addition / subtraction command S is supplied to the addition / subtraction circuit 20, the write pulse and the read pulse are supplied to the latch circuit 21, the preset pulse and the reset pulse are supplied to the speed error detection counter 22, and the latch circuit 23. To the driver 24, and a drive signal to the driver 24.

The preset value memory 15 is a drum motor 25 for rotationally driving a drum (not shown) provided with a rotary head.
The preset values corresponding to the respective rotation speeds during playback, fast-forward search and rewind search are stored and set.The preset values read according to the designated address of the control unit 14 -Sent to the circuit 18.

The gate circuit 18 opens the gate in response to a gate signal a from the control section 14 to set the preset value memory 15 therein.
The preset value of is passed and sent to the latch circuit 21. The latch circuit 21 writes / writes the preset value sent by the write pulse and the read pulse of the control unit 14.
Read out. The preset value read from the latch circuit 21 is added to the addition / subtraction circuit 20 and the speed error detection counter 22.
Sent to.

The adder / subtractor circuit 20 performs addition or subtraction on the preset value from the latch circuit 21 by using an appropriate value in accordance with the add / subtract instruction S of the control section 14, and outputs the operation result to the gate circuit 19. Output.

The gate circuit 19 passes the calculation result from the adder / subtractor circuit 20 according to the gate signal b of the control section 14,
It is sent to the latch circuit 21 again. Speed error detection counter 22
Resets the preset value sent from the latch circuit 21 by the preset pulse, counts up by the reference clock CK, and resets the count value when the reset pulse is input. The count value of the speed error detection counter 22 is sequentially sent to the latch circuit 23.
The latch circuit 23 latches the read pulse from the control unit 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 causes the drum motor to rotate at a rotational speed instructed by the drive signal of the control unit 14. Servo control according to the voltage signal is performed so that 25 is driven to rotate. This drum motor 25
The rotation speed of is 2000 [rpm] during playback, fast-forward
3000 [rpm] at the time of a reach, 1000 at the rewind search
It becomes [rpm]. The rotation of the drum motor 25 is detected by a frequency generator (denoted as "FG" in the figure) 27 attached to the drum motor 25. The FG pulse which is the detection pulse of the frequency generator 27 is It is sent to the control unit 14.

When 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 halves, and is obliquely wound around the drum at a central angle of 90 ° and is run. This tape is run at a constant rated speed (8.15 mm / sec) by a capstan and pinch roller during normal reproduction.

When the signal recorded on the tape is reproduced by the rotary head, the reproduced data is sent to the circuit of the audio processing system and the filter 28. Filter 28
Is composed of, for example, a BPF (band pass filter),
Only the frequency component of the pilot signal recorded at a constant frequency (130 kHz in the rotary head type DAT) in the recording track is extracted and output to the relative speed detection circuit 16.

The relative speed detection circuit 16 is for detecting the relative speed between the magnetic tape and the rotary head at the time of high speed search by being on / off controlled by a control signal from the control section 14, and is a filter. Compare the pulse spacing of the frequency signal from 28 to a reference value. Then, the comparison result is applied to the driver 17 as an error voltage, and a decrease detection signal is sent to the control unit 14 when a decrease in the relative speed at which the high speed search becomes impossible is detected.

The driver 17 follows the rotation speed instructed by the drive signal from the control unit 14, and if an error voltage is applied from the relative speed detection circuit 16, the driver 17 responds to the rotation speed accordingly.
Rotate 29.

The operation of the above embodiment will be described below.

First, the operation for normal reproduction will be described with reference to FIG.

When the play button 11 is operated from the stopped state, the control unit 14 responds to the operation signal to specify the preset value address for reproduction to the preset value memory 15 as shown in FIG. 2 (a). And gate to the gate circuit 18.
Signal a is set to the "1" level as shown in FIG.
The gate circuit 18 is opened.

The preset value memory 15 has a
Preset values for playback, fast-forward search, and rewind search that correspond to the rotation speed of the drum motor 26 that differs during fast-forward search and rewind search are set and stored. When the speed error detection counter 22 counts based on these preset values, the count value of the speed error detection counter 22 is set to be a constant value even if the rotation speed of the drum motor 25 is different. .

The magnitude of these preset values depends on the drum motor.
It corresponds to the number of rotations of 25, and the relationship is rewind search <normal playback <fast forward search. Here, the preset value for reproduction is read from the preset value memory 15 by the address designation of the control unit 14,
It passes through the gate circuit 18 and is sent to the latch circuit 21.

Immediately after the addressing to the preset value memory 15 and the gate signal a to the gate circuit 18, the control section 14 writes a write pulse to the latch circuit 21 as shown in FIG. Then, as shown in FIG. 2 (d), the read pulse is transmitted at a timing slightly delayed from the write pulse timing. Gate circuit 18 with these pulses
The preset value sent via the 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 starts to rotate at the rotation speed for normal reproduction that is instructed, the frequency generator 27 moves from the frequency generator 27 to that shown in FIG.
The FG pulse as shown in (e) is input to the control unit 14.

The control unit 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. Speed error detection counter
At 22, the preset value from the latch circuit 21 is preset by this preset pulse as shown in FIG. 2I, and thereafter the reference clock CK is counted. 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 at the falling edge of the FG pulse as shown in FIG.

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

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

Further, thereafter, in synchronization with the fall of the FG pulse, a write pulse is also sent to the latch circuit 21 at the same time as the read pulse. The latch circuit 21 writes the preset value from the preset value memory 15 having the same value as the above with this write pulse, and the preset value written with the read pulse input at a timing slightly delayed from the write pulse causes a speed error. Output to the detection counter 23 and others.

Thereafter, in the same manner as above, the preset value from the preset value memory 15 is applied to the gate circuit 18 and the latch circuit 21.
The speed error detection counter 22 is preset as it is, and while the drum motor 25 makes a half rotation, it is counted up by the reference clock CK. Then, the count value is converted into an analog voltage signal by the D / A conversion circuit 26 via the latch circuit 23 as control data including an error and sent to the driver 24 to reproduce the drum motor 25 during normal reproduction. It is driven to rotate at the rotation speed of.

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

At this time, the relative speed detection circuit 16 from the control unit 14
The control signal to the driver is at "0" level, the relative speed detection circuit 16 does not operate, and the driver 18 drives the reel motor 29 at a constant speed based on only the drive signal from the control unit 14. To do. During this normal reproduction, the tape transfer speed is kept constant by the capstan and the pinch roller, and the rotation of the reel motor 29 is transmitted to the take-up side reel, and the tape is transferred.
It gives a certain amount of tension to the pump.

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

FIG. 3 shows an example in which the fast-forward search button 12 is operated from the stopped state. When the fast-forward search button 12 is operated, the control unit 14 responds to the operation signal.
As shown in FIG. 3A, the preset value memory 15 sends the designated address of the preset value for the fast-forward search to the preset value memory 15 and the gate signal to the gate circuit 18. As shown in FIG. 3B, "a" is set to "1" level, and the gate circuit 18 is opened.

The preset value for the fast-forward search is read from the preset value memory 15 by the address designation of the control unit 14, and is sent to the latch circuit 21 through the gate circuit 18. Further, the control unit 14 sends a write pulse as shown in FIG. 3C to the latch circuit 22 immediately after the addressing to the preset value memory 15 and the gate signal a to the gate circuit 19. A read pulse having a timing as shown in FIG. 3D, which is slightly delayed from the timing of the write pulse, is transmitted.

The preset value sent through the gate circuit 18 by these pulses is written / read by the latch circuit 22, and then sent to the adder / subtractor circuit 20 and the speed error detection counter 22. In this state, when the drum motor 25 starts to rotate at the rotation speed during the fast-forward search, the frequency generator 27 inputs an FG pulse as shown in FIG. To be done.

The control unit 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. In the speed error detection counter 22, this preset pulse causes the latch circuit 22 to
The preset value from 1 is preset as shown in FIG. 3 (i), and the reference clock CK is counted thereafter. Then, when a read pulse is sent to the latch circuit 23 in synchronization with the fall of the FG pulse, as shown in FIG. 3 (g), the count value of the speed error detection counter 22 at this point is the latch circuit.
Latched to 23. The counted value is read by the D / A conversion circuit 26, converted into an analog voltage signal, and then the driver 24
Applied to.

The driver 24 uses this voltage signal as a speed error signal to rotationally drive the drum motor 25 at the number of revolutions (here, 3000 [rpm]) instructed by the drive signal of the controller 14. 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".

Further, thereafter, in synchronization with the fall of the FG pulse, a write pulse is also sent to the latch circuit 21 at the same time as the read pulse. The latch circuit 21 writes the preset value for the fast-forward search from the preset value memory 15 which is the same value as the above by this write pulse, and then the preset value written by the read pulse slightly delayed from the write pulse. The speed error detection counter
22 Output to other.

Thereafter, in the same manner as above, the preset value from the preset value memory 15 is applied to the gate circuit 18 and the latch circuit 21.
The speed error detection counter 22 is preset as it is, and while the drum motor 25 makes a half rotation, it is counted up by the reference clock CK. Then, the count value is converted into an analog voltage signal by the D / A conversion circuit 26 via the latch circuit 23 as control data including an error, and is sent to the driver 24 to send the drum motor 25 to the fast-forwarding described above. It is driven to rotate at the number of rotations during search.

At this time, the relative speed detection circuit 16 from the control unit 14
The control signal to the controller is at "1" level, and the relative speed detection circuit 16 keeps the reel motor 29 constantly rotating at a constant speed according to the tape winding diameter of the winding side reel. -Take control. That is, 130 recorded in the recording track of the tape.
Only the frequency component of the pilot signal of kHz is filtered 28
When it is extracted by and output to the relative speed detection circuit 16,
The relative speed detection circuit 16 compares the pulse interval with a reference value and applies the comparison result to the driver 17 as an error voltage.

The driver 17 drives 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 when the tape is reproduced. Rotate so that it is sent at a speed of about 200 times.

In such a state, when the battery as the power source is exhausted and the voltage supplied to each circuit drops, the rotation speed of the drum motor 25 rotating at 1.5 times the rotation speed during normal reproduction. First, about 20 times the rotation speed during normal playback.
The rotation speed of the reel motor 29 rotating at 0 times decreases.

Due to the decrease in the rotation speed, the tape transfer speed decreases, and the relative speed between the magnetic tape and the rotary head decreases to such an extent that the data cannot be read. To detect.

That is, if the frequency component of the pilot signal in the reproduction data input to the relative speed detection circuit 16 via the filter 28 changes due to the relative speed decrease, the relative speed detection circuit 16 determines that the relative speed has decreased. Judge, Figure 3 (j)
As shown in, the drop detection signal to the control unit 14 which has been at the "0" level until then is set to the "1" level.

At the same time when this drop detection signal is input, the control unit 14 sets the gate signal a to the gate circuit 18 to the "0" level, and as shown in FIG. The gate signal b to the gate circuit 19 which was at "0" level is set to "1" level. As a result, the preset value for the fast-forward search newly read from the preset value memory 15 does not pass through the gate circuit 18.

On the other hand, when the gate circuit 19 is opened, the preset value for the fast-forward search from the latch circuit 21 is subtracted by "-1" according to the add / subtract instruction S of the control unit 14 to perform the addition / subtraction circuit 20. Is output to the latch circuit 21 again via the gate circuit 19. The latch circuit 21 latches this preset value with a write pulse, and an adder / subtractor circuit with a read pulse sent with a slight delay to the write pulse.
20, read to speed error detection counter 22.

The speed error detection counter 22 includes a latch circuit 21.
The preset value obtained by the subtraction process is preset by the preset pulse of the control unit 14, and thereafter the reference clock C
Count K. Then, when the read pulse synchronized with the falling edge of the FG pulse is input, the latch circuit
23 latches the count value of the speed error detection counter 22.

This latched speed error detection counter 22
Since the preset value is once subtracted by the adder / subtractor circuit 20, the count value of is slightly smaller than the count value at the time of reproduction, and the count value of the D / A conversion circuit 26 is an analog value. Driver after being converted to a voltage signal
When it is sent to the driver 24, the driver 24 drives the drum motor 25 to rotate in accordance with this voltage signal at a speed slightly slower than that in the fast forward search. After that, the count value of the speed error detection counter 22 is reset 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 preset value read from the latch circuit 21 is added / subtracted by the adder / subtractor circuit 20. Then, the subtraction process is performed, and the value gradually decreases to be written in the latch circuit 21 again.

The preset value of the latch circuit 21 is sequentially sent to the speed error detection counter 22 and is preset and counted as shown in FIG. 3 (i).
When the count value of the speed error detection counter 22 is latched by the latch circuit 23, converted into a voltage signal by the D / A conversion circuit 26 and applied to the driver 24, the driver 24 rotates the drum motor 25 accordingly. To do. Therefore, the drum mode
The rotation speed of the motor 25 gradually decreases. This drum mode
As the rotational speed of the 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 rotation speed of the drum motor 25 also decreases sufficiently, and the relative speed between the magnetic tape and the rotary head becomes smaller. When the fast-forward search becomes possible again, the pilot signal in the playback data is filtered again.
Is extracted and input to the relative speed detection circuit 16. When the relative speed detection circuit 16 detects this and sets the decrease detection signal to the control unit 14 to the “0” level as shown in FIG. 3 (j), the control unit 14 simultaneously stops this operation and changes to the state shown in FIG. 3 (k). As shown, the gate signal b to the gate circuit 19 is also lowered to "0" level. At this point, both the gate circuit 18 and the gate circuit 19 are closed, and a new preset value is not input to the latch circuit 21. At the same time, the control unit 14 stops sending the write pulse and the read pulse to the latch circuit 21.

Therefore, the latch circuit 21 continues to output the preset value at the time when the read pulse was input before that. After that, the speed error detection counter 22 presets the preset value from the latch circuit 21 and performs counting, and based on the counted value, the latch circuit 23, D / A
The conversion circuit 26 and the driver 24 serve to servo-control the drum motor 25.

In FIG. 3, the rotational speed control of the drum motor 25 is described when the relative speed between the magnetic tape and the rotary head is lowered in the fast-forward search state by operating the fast-forward search button 12. Rewind search button Rewind search button 13 operation
The same is true in the H state.

In this case, when a decrease in the relative speed is detected, the control unit 14 causes the addition / subtraction circuit 20 to add a preset value by the addition / subtraction instruction S to the addition / subtraction circuit 20, and the speed error detection counter 22 is preset. Control so that the preset value gradually increases. According to the count value, the driver 24 determines that the number of rotations of the drum motor 25 until then is 1000
[Rpm] will be gradually increased.

[0055]

As described above in detail, 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 the relative speed is detected during high speed search, the drum rotation is rotated during high speed search. The magnetic tape speed during high-speed reproduction is controlled according to the detection result of the relative speed detection circuit while increasing or decreasing stepwise from the speed according to the tape transfer direction at that time. It is possible to provide a servo control device of a rotary head type magnetic tape reproducing device which can read data even when the voltage of a battery as a power source is lowered during the search.

[Brief description of drawings]

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 reproduction shown in FIG.

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

[Explanation of symbols]

11 ... Play button, 12 ... Fast forward search button, 13 ... Rewind search button, 14 ... Control section, 15 ... Preset value memory, 16 ... 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. In a rotary head type magnetic tape reproducing apparatus, a relative speed detecting means for detecting a relative speed between a magnetic tape and a rotary head drum from a reproduction signal, and the relative speed detecting means during a high speed search. When a decrease in relative speed is detected by the means, the drum rotation is changed from the rotation speed during high-speed search to high-speed search.
Drum control means for gradually increasing or decreasing in accordance with the tape transfer direction of the chain, and magnetic tape transfer for controlling the magnetic tape speed during high speed reproduction according to the detection result of the relative speed detecting means. A servo control device comprising a control means.