JPS6058539B2 - Initial synchronization data reader for magnetic tape reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic tape reader used, for example, as an input device for a microcomputer, and particularly relates to a magnetic tape reader that is used for reading data from a tape on which a digital data waveform of a 1-bit, 1-cycle waveform is recorded. The present invention relates to an initial synchronization data reader for detecting a synchronization level.

Generally, audio cassette magnetic tapes are often used as auxiliary memory, input media, etc. of microcomputers, and digital data is written and read on these magnetic tapes by audio cassette tape recorders.

In this case, if the data is read with a tape recorder that is the same or has the same characteristics as the tape recorder used to write the data, accurate reading is possible, but if a tape recorder with different characteristics is used, data reading errors may occur. There was a risk that this would occur. In other words, in the case of a magnetic tape in which data is recorded using a 1-bit, 1-cycle waveform, the logic levels of ``1'' and ``0'' of the reproduced data seem to be inverted with respect to the logic level of the written data. The present invention has been made to eliminate the above-mentioned drawbacks, and it detects and stores the initial synchronization data level, and uses this storage level as the synchronization level when data is stored. An object of the present invention is to provide an initial synchronization data reading device for a magnetic tape reading device that can accurately read data reproduced by a tape recorder having characteristics different from those at the time of data writing by reading the data.

An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an audio cassette tape recorder, and it is assumed that a magnetic tape (not shown) reproduced by this tape recorder 1 records digital data in a 1-bit, 1-cycle waveform.

In this case, the magnetic tape contains data ``1'' for cueing the digital data, as shown in FIG. 2a, for example.
Initial synchronization data is recorded that serially includes, for example, m pulses at a constant frequency f representing the data "'o" and one pulse at a constant frequency 7 representing the data "'o". The number of pulses represented is 25. The data reproduced by the tape recorder 1 may be transferred to the second pulse depending on the model of the tape recorder 1.
Figure 2 (b) has the same phase as the recorded data in Figure (a) or has the opposite phase (the logic level of the data is reversed).

) as shown in Figure 2c. Such reproduced data is guided to a data reading device 2 and an initial synchronization data reading device 3. This initial synchronization data reading device 3 is configured as shown in FIG. 3, for example. In Figure 3, 3
Reference numeral 1 denotes a level reading circuit that reads the level of input data and inverts the output level every time the logic level of the input data is inverted. 32 is a pulse width measuring circuit for measuring the pulse width of the output "1" from the circuit 31.

Reference numeral 33 denotes a separate circuit 11 (to) which determines whether the pulse width measurement result of the circuit 32 is equal to or greater than a predetermined value, and generates a "1" output when the pulse width measurement result is equal to or greater than a predetermined value, and produces a "0" output when it is not. .

Reference numeral 34 denotes a counter for counting the ``1'' output of the discrimination circuit 33.

Reference numeral 35 denotes a comparison/determination circuit for determining whether or not the count result of the counter 34 has reached a specified value.

A memory 36 stores the output of the level reading circuit 31.

Reference numeral 37 denotes a control circuit, which controls the operation of each of the above-mentioned circuits according to the flow shown in FIG.

On the other hand, the data reading device 2 has a function of reading input data bit by bit while synchronizing with the level supplied from the memory 36.

The data read by the reading device 2 is converted into parallel data by a serial-parallel conversion circuit (not shown) and then sent to a central processing unit (CPU) 4. Next, the operation of the magnetic tape reader having the above configuration will be explained.

First, the initial synchronization data reproduced by the cueing operation of the tape recorder 1 is processed in the initial synchronization data reading device 3 as shown in FIG. That is, in the first step, the input data is read by the level reading circuit 31, and in the second step, the pulse width of the data is measured by the pulse width measuring circuit 32 until the level of the read data changes. In the third step, the discrimination circuit 33 determines whether the input data is ゜゜1゛ or "0゛" based on the magnitude of the measurement pulse width, and when the determination result is "゜0゛", the counter 34 is cleared. Returning to the initial process, the operations of the first to third steps are repeated. When the discrimination result is ゜゜1゛, the fourth
The process moves to step and the counter 34 increments. In the fifth step, it is determined whether the count value of the counter 34 has reached 36 (corresponding to 18×2 because data ゜゛1゛ is determined every half period for each 18 cycles of data ゜1゛). is performed by the determination circuit 35, and when the number 36 has not been reached, the process returns to the initial processing and the operations of the first to fifth steps are repeated. On the other hand, when the "゜1" determination in the third step is performed 36 times or more in a row and the determination result in the fifth step reaches 36, the process moves to the sixth to eighth steps, and the first to eighth steps are performed. The same operation as step 3 is performed.In this case,
In the eighth step, when the determination result is "1" (that is, when the data "1" continues for 18 cycles or more), the process returns to the sixth step and repeats the operations of the sixth to eighth steps. Then, in the 8th step, when the discrimination result is ゛“0゛, the 9th to 1st
Moving to step 1, the same operations as the sixth to eighth steps are performed. In this case, when the determination result in the 11th step is ゜゜0゛ (that is, data ``0'' is determined every half period for one period of data ゜0゛, and in addition, in the 6th to 11th steps, ``0'' is determined. is determined in succession), the data level following the data 6408 is read by the level reading circuit 31 in the twelfth step,
This data level is stored in memory 36 in a thirteenth step. This data level is 1 following the initial synchronization data.
This is the first level of bit 1 cycle data, and is supplied as a synchronization level in the data reading routine by the data reading device 2. Note that the determination result in the 11th step is ゜“1”.
When the waveform of the data ゛0゛ is disturbed, it is determined that the waveform of the data ゛0゛ is disturbed, and at this time, the counter 34 is cleared, the process returns to the initial processing, and the operations of steps 1 to 11 are repeated. The initial synchronization data reading device of the above-mentioned magnetic tape reader measures the pulse width of the initial synchronization data reproduced from the tape recorder to determine data "1゛,゜"O゛. When data ゜゜0゛ is determined a predetermined number of times after being determined a predetermined number of times in succession, the first level of the 1-bit, 1-cycle data following this data ゜゛0゛ is stored, and this level is used as the synchronization level for data reading. .

Therefore, depending on the model of the tape recorder used, the "1", "0" level of the reproduced data may be the same as the "1", "0" level of the tape recording data, or they may be reversed. It is also possible to read the reproduced data accurately.In the above embodiment, the level reading circuit 31
, dedicated circuits for the pulse width measurement circuit 32, 11 (to) separate circuit 33, and the counter 3 determination circuit 35 are used, but the present invention is not limited to this, and the input data is converted into parallel bit data by AID conversion at fixed timings, This data may be subjected to processing as shown in FIG. 4 under program control of an input control microcomputer.

As described above, the present invention can provide an initial synchronous data reading device for a magnetic tape reading device that is capable of accurately reading data reproduced by a tape recorder having characteristics different from those at the time of data writing.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an initial synchronous data reading device of a magnetic tape reading device according to the present invention;
Fig. 2 is a signal waveform diagram shown to explain the operation of Fig. 1, Fig. 3 is a block diagram showing the initial synchronization data reading device of Fig. 1 in detail, and Fig. 4 is the operation of Fig. 3. 31...Lebel reading circuit, 32...Pulse width measuring circuit, 33...11 (to) separate circuit, 34...Counter,
35... Comparison/judgment circuit, 36... Memory, 37...
・Control circuit.

Claims (1)

[Claims] 1 Data is recorded using a 1-bit 1-cycle waveform, and data “1” and “1” with different pulse widths are recorded before the predetermined data.
In a magnetic tape reader that reads data on a magnetic tape in which each serial number 0 is recorded a predetermined number of times, the pulse width of the reproduced data read from the magnetic tape is measured to determine the logical state of the data ``1'' and ``0.'' Discrimination means;
a determining means for determining that a second logical state has been detected a predetermined number of times after the first logical state has been continuously detected a predetermined number of times by the determining means; An initial synchronous data reading device for a magnetic tape reading device, comprising: storage means for storing the first level of the reproduced data; and means for supplying the first level from the storage means as a synchronization level for data reading. .