JPH0256754B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field The present invention records index data related to the information at the beginning of the information recorded on the tape of a tape recorder, so that it can be used in fast forward mode or rewind mode. The present invention relates to a method for reading index data when the tape recorder is controlled by reading the index data.

(b) Background of the technology Conventionally, when recording information in a tape recorder, index data related to the information is recorded at the beginning of the information, and the index data is stored in fast forward mode or rewind mode. It is used to read data and control tape recorders. For example, when recording music, record the song number of the music as index data,
It is used for searching songs, etc.

In such a tape recorder, a pulse train is created in which a start bit pulse or a stop bit pulse is provided before and after index data, and this pulse train is recorded at the beginning of information.
FIG. 1 shows a case where the index data consists of 4 bits. That is, index data
A start bit pulse _P1 is provided before _D4 to _D1 , and a stop bit pulse _P2 is provided after. For index data _D4 to _D1 , if the bit content is "1", a pulse is generated, and if the bit content is "0", no pulse is generated. Therefore, in the case of the pulse train indicated by the solid line, the index data is "0001".

When recording the pulse train shown in Figure 1, if the pulses P ₁ and P ₂ and the index data D ₄ to _{D 1} and their intervals are recorded with a length of 50 ms, when this pulse train is detected in fast forward mode, The waveform shown in FIG. 2 is obtained. Near the end of the tape in fast-forward mode, the tape speed is about 20 times that of recording, so the width and interval of pulse and index data is about 2.5 ms. At this time, a start bit pulse is required to read the index data.
Starting from the middle of P ₁ , that is, 1.25 ms after the rise of the start bit pulse P ₁ ,
Signals are read at time points T ₁ , T ₂ , T ₃ , and T ₄ every 5 ms.

However, if there is an error in the setting of the reference point and the reading interval, the error will be accumulated at later reading times, and there is a risk that a discrepancy with the index data will occur, resulting in a reading error. Also, at the beginning of winding in fast forward mode, the tape speed is approximately 10 times that of recording, the width and interval of pulse and index data are 5 ms, and the detected pulse train in Figure 2 is expanded twice in the direction of the arrow. will be done. Therefore, in this case, reading is not possible with the reading interval shown in FIG. 2, and it is necessary to reset the base point and the reading interval.

(C) Disclosure of the Invention The present invention has been made in view of the above points, and includes a cue signal consisting of a plurality of pulses, index data of a plurality of bits, and a signal provided before each bit of the index data. In this method, a pulse train consisting of a synchronization bit is recorded on a tape, and index data is read from this tape.By continuously counting a predetermined number of multiple pulses, the queue signal detection means detects a queue signal. When this is recognized, the synchronization bit detection means detects the falling edge of each synchronization bit, the timer means creates a predetermined time from the fall of each synchronization bit, and at each point in time when the predetermined time has elapsed, By reading the data with the data judgment means,
The present invention provides a reading method that can accurately read index data.

(D) Embodiment FIG. 3a shows a pulse train containing index data to be detected in the embodiment described below. This pulse train is a track different from the track on which information is recorded, and the information is recorded at the beginning of. Also, this pulse train has pulses P ₁ ′~
A queue signal consisting of P ₉ ′ and index data
_{The last pulse of the} queue signal _{P 9} ' and the first synchronization bit S ₁ ' are separated by one pulse. Furthermore, pulses P ₁ ′ to _{P 9} ′, index data D ₄ ′ to D ₁ ′, and synchronization bits S ₁ ′ to _{S 4} ′ are
Pulses are recorded on tape with equal pulse width and at equal intervals, and the recording method is to record the pulses directly, by frequency modulating them, or by converting them into sine waves. However, from the viewpoint of noise etc., sine wave conversion using a low frequency is suitable, and a pulse width and interval of 50 ms is used.

On the other hand, FIG. 3b shows a waveform obtained by detecting and extracting the pulse train of FIG. 3a from a tape recorded in fast forward mode, but the time axis is ignored in order to correspond to FIG. 3a. Pulse P ₁ that constitutes the queue signal
_-P9 , index data _D4 - _D1 , and synchronization bits _S1 - _S4 are waveform-shaped at the time of detection so that the widths are longer than the intervals. More details will be given later. In fast forward mode, the tape speed at the beginning of winding is approximately 10 times the tape speed during recording, so a pulse recorded at 50ms will be detected with a pulse width of 5ms, and after waveform shaping, it will become, for example, 7ms. ,
The pulse interval is 3ms. On the other hand, the tape speed near the end of the winding is approximately 20 times faster than during recording.
A pulse recorded at 50 ms is detected with a pulse width of 2.5 ms, and after waveform shaping, the pulse width becomes, for example, 3.5 ms, and the pulse interval becomes 1.5 ms.

The reason for waveform shaping when detecting a pulse train is that index data is read a predetermined time after the falling edge of the synchronization bit, and that predetermined time is equal to the pulse width _tP of the cue signal pulse _P8 . By lengthening the pulse width and shortening the interval through waveform shaping, the time point t _P elapsed from the base point will always fall within the pulses of index data D ₄ to _{D 1} . It exists.

FIG. 4 is a block diagram showing an embodiment of the present invention, in which 1 is a reproduction head, 2 is an amplifier circuit, 3 is a waveform shaping circuit, 4 is a cue signal detection means, 5 is a pulse width measurement means, and 6 is a synchronization bit. A detection means, 7 a timer means, 8 a data determination means, and 9 a register.

In the fast forward mode, the reproduction head 1 detects a sine wave signal corresponding to FIG. 3a, which signal is amplified by the amplifier circuit 2. The waveform shaping circuit 3 converts the sine wave signal output from the amplifier circuit 2 into a shape shown in FIG.
The pulse train shown in FIG. 1 is created by slicing a sine wave signal at a predetermined slice level so that the pulse width becomes longer than the pulse interval by a predetermined ratio. Output of waveform shaping circuit 3
POUT is applied to queue signal detection means 4, pulse width measurement means 5, synchronization bit detection means 6, and data determination means 8.

The queue signal detection means 4 counts the pulses generated at the output POUT, and when a predetermined number of pulses are continuously counted, it is recognized as a queue signal, detects the end of the queue signal, and detects the next arriving synchronization bit. This is to perform the detection operation. The queue signal detection means 4 includes a counter 10 that counts the pulses of the output POUT, and a timer circuit 1 that detects whether or not the pulses applied to the counter 10 are continuous.
Consists of 1. When a pulse occurs on the output POUT,
This pulse is counted by the counter 10 and
The timer circuit 11 is reset and the applied clock φ is counted. The timer circuit 11 counts the clock φ for a predetermined time, e.g.
Make 10ms. In other words, if the applied pulse constitutes a cue signal, even at the slowest tape speed in fast forward mode, the time until the next pulse arrives is within 10 ms, and if it is 10 ms or more, the cue signal is They are not the pulses that make up the signal. Its operation is such that when pulses arrive consecutively within 10ms, the timer circuit 11 is reset for each pulse.
The timer output Re is not output from the counter 10.
continues counting pulses. On the other hand, if the pulses do not arrive continuously, the timer circuit 11 outputs the timer output Re, the counter 10 is reset, and the counted pulses become invalid. counter 1
When 0 counts the 7th pulse P ₇ , the pulse P ₇
At the falling edge of , control signal C ₇ is output,
The control signal C ₇ stops the operation of the timer circuit 11 and also activates the pulse width measuring means 5 .
Further, when the pulse _P9 is counted, a control signal _C9 is output at the falling edge of the pulse P9, and the synchronization bit detection means 6 is operated.

The pulse width measuring means 5 measures the time from the rise to the fall of the eighth pulse _P8 , and has an input to which the pulse output POUT and clock φ are applied, and is controlled by the control signal _C7 . It consists of a circuit 12 and a counter 13 that counts and holds pulses applied from the input circuit 12. When the control signal C ₇ is output, the input circuit 12 passes the clock φ for the pulse period t _P of the next arriving pulse P ₈ and applies it to the counter 13 . Therefore, the counter 13 holds the count corresponding to the pulse period _tP .

The bit detection means 6 outputs a control signal ^C9 output when the queue signal detection means 4 detects the end of the queue signal, that is, at the falling edge of the ninth pulse _P9 , and an output T of the timer means 7. It consists of a rise detection circuit 14 controlled by _P and a fall detection circuit 15 controlled by the output of the rise detection circuit 14. When the control signal C ₉ is applied,
The rising edge detection circuit 14 detects the rising edge of the synchronization bit _S1 that comes after the pulse _P9 , and activates the falling edge detecting circuit 15. Falling detection circuit 15
When detecting the fall of the synchronization bit _S1 , it applies a control signal _Ts to the timer means 7.

The timer means 7 is controlled by the control signal T _S outputted from the synchronization bit detection means 6 at the falling edge of the synchronization bits S ₁ to S ₄ , and when the control signal T _S is applied, the timer means 7 is held in the counter 10 . The content of the count is taken in, and the content is subtracted by the clock φ counted by the counter 10. When the count becomes zero, the timer means 7 outputs the timer output.
Output T _P. The timer output T _P operates the data determining means 8 and also operates the rising edge detection circuit 14 in order to detect the rising edge of the next arriving synchronization bits S ₂ to _{S 4} .

The data determining means 8 is composed of, for example, a gate circuit, and when the timer output T _P is applied, the data determining means 8 stores the pulse output POUT at that time in a predetermined bit of the register 9 as index data D _o . The register 9 is composed of 4 bits, and holds index data _D1 to _D4 by storing the result _Do of the data determining means 8 in predetermined bits.

In such a configuration, the queue signal is recognized as a queue signal by the queue signal detecting means 4 when seven pulses P ₁ to _{P 7} are counted continuously, and the eighth pulse P of the queue signal is detected. Pulse width t _P of ₈
is measured and held as a count value of the clock φ by the pulse width measuring means 5 which is activated by the control signal _C7 . When the end of the queue signal is detected by counting the pulses _P7 , the synchronization bit detection means 6 is put into operation by the control signal _C9 , and the first synchronization bit _S1 that follows the queue signal is detected. Detected. When the falling edge of the synchronization bit _S1 is detected and the control signal _TS is output, the timer means 7 starts counting the pulse width measured by the pulse width measuring means 5.
The count value corresponding to the pulse width of pulse _P8 is taken in, and the clock φ used in the pulse width measuring means 5 is
By subtracting and counting, create a time t _P equal to the pulse width of pulse P ₈ . The index data _D4 is fetched by the data determining means 8 which operates according to the timer output T _P output when the timer means 7 measures the time t _P , and the contents of the index data _D4 are stored in the register 9. is stored in the fourth bit of Further, the synchronization bits S ₂ to _{S 4} are detected by the timer output T _P operating the synchronization bit detection means 6, and the synchronization bits S 2 to S 4 are
D ₃ to _{D 1} are similarly read at each time produced by the timer means 7 from each falling edge of the synchronization bits S ₂ to _{S 4} and the third bit of register 9, the second
bit, stored in the first bit. In this embodiment, "0001" is stored in register 9.

Therefore, the time t _P created by the timer means 7, that is, the time t _P from the fall of each of the synchronization bits S ₁ to S ₄ to the data reading time, is equal to the pulse of the queue signal.
Since the result of measuring the pulse width of _P8 with the pulse width measuring means 5 is used, even if the tape speed differs between the beginning of winding and near the end of winding in fast forward mode, the index data is always read at the time of data reading. It is within the range of D ₄ to D ₁ .
In addition, in order to perform independent reading operations based on the falling edge of synchronization bits S ₁ to _{S 4} , the pulse
Even if there is a small or large error in the pulse width measurement of _P8 , the error is integrated and the reading time point does not deviate from the signal range of index data _D4 to _D1 .

In this embodiment, the pulse width of the pulse _P8 was measured, but the pulse interval or pulse period may be used instead of the pulse width, and corresponding processing may be performed. Further, each means in this embodiment can be configured by a program using a microcomputer or the like.

(e) Effects As described above, according to the present invention, it is possible to prevent malfunctions due to noise and errors in reading index data due to changes in tape speed, so that the tape recorder can be controlled as intended by the user. There are things you can do.

[Brief explanation of drawings]

1 and 2 are pulse waveform diagrams showing a conventional example, FIGS. 3a and 3b are pulse waveform diagrams used in the present invention, and FIG. 4 is a block diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Reproduction head, 2... Amplification circuit, 3... Waveform shaping circuit, 4... Queue signal detection means, 5... Pulse width measurement means, 6... Synchronization bit detection means, 7... Timer means, 8... Data determination means, 9... register.

Claims (1)

[Claims] 1 Formed at the beginning of the recorded information by a cue signal consisting of a plurality of pulses, a plurality of bits of index data related to the information, and a synchronization bit provided before each bit of the index data. In the method of reading the index data from a tape on which a pulse train has been recorded, a queue signal detection means recognizes that it is a queue signal by continuously counting a predetermined number of the plurality of pulses; pulse measuring means for measuring and holding the pulse width or pulse period of the queue signal; synchronization bit detection means operated by the output of the queue signal detection means to detect the synchronization bit; and the synchronization bit detection means and a data judgment means for reading data using the output of the timer means, the time from each synchronization bit measured by the timer means to the data judgment. is determined based on the measurement result of the pulse measuring means.