JPS6050755A - Data reproducing circuit - Google Patents

Abstract

PURPOSE:To obtain accurate reproduction data by controlling the phase relation between a read signal and a read window when the read singnal read out of a recording medium during the generation of a data error to obtain the reproduction data. CONSTITUTION:In case a data error is detected after the reproduction data is processed, a signal which is reread is produced from the data processor of a host side. While a reread command given from the host side is supplied to a memory 8. Therefore the memory 8 supplies the information so far stored to a phase detector 1 via a signal line 8a or 8b to an amplifier 2 via an OR circuit 9a or 9b to change the frequency of a VCO circuit 3. In such a way, the phase of a window pulse generated from a window producing circuit 4 is shifted properly forward or backward to extract the data out of the read signal when the read signal which is reread is processd. Thus the margin area of the window pulse is obtained and therefore the accurate data can be read or reproduced by controlling properly the phase of the window pulse even in case a data error arises.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a data reproducing circuit that processes a read signal read from a recording medium and reproduces data, and more particularly relates to a data reproducing circuit that reproduces data by processing a read signal read from a recording medium. The present invention relates to a data reproducing circuit that can reproduce error-free data by re-reading the data even in the case of an error.

BACKGROUND OF THE INVENTION Floppy disk devices are widely used for recording data, and the standard recording methods for floppy disk devices include the FM recording method for single density and the MFMFM recording method for double density. In the single-density FM recording method, recording is performed according to the following criteria: (1) a data bit is written in the center of a bit cell, and (2) a clock bit is written at the beginning of a bit cell. On the other hand, in the MFMFM recording system for double density, (
The criterion for 1) is the same, but the criterion for (2) is different, that is, it uses the criterion of writing a clock bit at the beginning of the current bit cell when no data bit is written in both the previous and current bit cells. be. Therefore, MFM
In the FM recording method, the clock bits on both sides of the data bit are omitted, and for this reason, the interval between bit cells is set to 1.
/2, the recording density is doubled. Incidentally, FIG. 1 shows the case where the bit pattern of hexadecimal number "A1'' is recorded by the FM recording method, and FIG. 2 shows the case where it is recorded by the MFMFM recording method.

As shown in Figure 1(a), the read signal read from the floppy disk is usually a mixture of clock pulses and data pulses, and this read signal is shown in Figure 1(b). As shown in FIG. 1(C), reproduced data consisting only of data pulses must be extracted by processing with a data window. The same applies to the MFMFM recording method shown in FIG. 2. FIG. 3 shows a block diagram of a conventional data reproducing circuit for extracting reproduced data from a read signal read from a floppy disk device (FDD). As shown in FIG. 3, the data reproducing circuit includes a VFO circuit (variable frequency oscillator) 10 to which a read signal read from a floppy disk device is input, and an output of the VFO circuit 10 to which the output is input and generates a wind pulse. Window generation circuit 4
and a data separator 5 to which the output of the window generation circuit 4 and the read signal are both input. The VFO circuit 10 includes a phase detector 1, an amplifier 2, and a VCO (voltage controlled oscillator).
3, and the output of the VCO circuit 3 is connected to the phase detector 1.
Phased-locked loop (PL)
L). The phase detector 1 is connected to the amplifier 2 through a signal line 1a for supplying a pump-up signal to the amplifier 2 and a signal line 1b for supplying a pump-down signal to the amplifier 2. The pump-up signal increases the output from the phase detector 1, while the pump-down signal decreases its output. The oscillation frequency of the vCO circuit 3 changes depending on the voltage level of the signal from the amplifier 2.

The VFO circuit as shown in FIG. 3 is used not only to generate a data window for extracting data but also to generate a clock window for extracting clock pulses. Furthermore, if the floppy disk has an 18M format, an S4-YNC field is provided at the beginning of the ID field and the beginning of the data field, respectively, and this 5YNC field is composed of hexadecimal "o o" data. has been done. Therefore, the 5YNC field consists only of clock pulses, and therefore the pulses are arranged at equal intervals. Therefore, in the 5YNC field, since the interference between pulses is equal in both directions, no peak shift occurs due to interference with other pulses. Therefore, usually this 5Y
A window is generated by the window generating circuit 4 in lock or synchronization with the clock pulse of the NC field. Once synchronization is established in this way, even if disc rotational fluctuations occur, the VFO circuit 10 can follow the bit phase changes, ensuring accurate reproduction of data from the read signal. It is possible to generate a window. However, in the configuration shown in FIG. 3, it is impossible to compensate for bit phase changes caused by individual peak shifts that occur for some reason. This point will be explained in more detail with reference to FIG.

FIG. 4<a) shows the wind pulses periodically generated by the window generating circuit 4 shown in FIG. 3, while FIG. 4(b) shows the read signal read from the floppy disk. There is. In the read signal shown in FIG. 4(b), only the data pulse is shown for the sake of simplicity. The read signal shown in FIG. 4(b) is applied to the phase detector 1 and the data separator 5, and is processed by the window signal shown in FIG. 4(a) generated by the window generating circuit 4 to obtain only desired data. The reproduced data consisting of is extracted. However, as shown in FIG. 4, the wind pulse and the data pulse do not necessarily have a constant phase relationship, and the phase between them differs due to various reasons. For example, the phase between the wind pulse and the data pulse changes due to the effects of jitter when reading from the floppy disk via the head, jitter of the circuit between the phase detector 1 and the window generation circuit 4, and the like. Such a change in the phase T is allowed within a certain range, but if it exceeds such a range, the data separator 5 may not be able to output accurate reproduced data.

In such a case, a data error is discovered by an error detection circuit provided within the data processing device to which the reproduced data is supplied. In such a case, there is a high possibility that a data error will occur again even if re-reading is performed in response to a command from the data processing device.

Purpose The present invention has been made in view of the above points, and is aimed at determining the phase relationship between the read signal and the read window when processing a read signal read from a recording medium to obtain reproduced data due to the occurrence of a data error, etc. An object of the present invention is to provide a data reproducing circuit that can generate accurate reproduced data by controlling the data.

Configuration Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 5(a) shows one wind pulse, while Figure 5(c) shows the 7-data pulses to be extracted by the wind. A phase difference T exists between the rising edge of the wind pulse in FIG. 5(a) and the rising edge of the data pulse in FIG. 5(C).

As described above, ideally, the rising edge of the data pulse relative to the wind pulse should be located at the center of the wind pulse, as shown in FIG. however,
Due to factors such as data jitter and circuit responsiveness during reading, the rising edge of the data pulse, etc.
'), it exists with a certain probability distribution curve with the maximum value at the center of the window. Therefore, Fig. 5(b)
The tail portion of the probability distribution curve where the frequency is low indicates that an extremely large cause of fluctuation such as jitter has occurred.Therefore, in the design, a predetermined value is placed on the rising and falling ends of the wind pulse shown in Figure 5(a). Margin areas α1 and α with width
2, respectively. That is, FIG. 5(C)
The rising edge of the data pulse is the margin α1 in FIG. 5(b).
If it exists in any region of α2 or α2, it indicates that an abnormal pit shift has occurred, and there is a high possibility that a data error will occur in 8- when data processing is performed. What should be noted here is that the existence probability distribution curve of the rising edge of the data pulse shown in FIG. However, this is due to the effects of bit shifts that occur individually due to jitter that occurs when reading data, circuit responsiveness, etc. Further, when the probability curve shown in FIG. 5(b) is a normal Gaussian distribution, the ranges of the rising end side margin area α1 and the falling edge side margin area α2 are substantially equal.

The present invention has been made with attention to such points, and
Using the auxiliary wind pulse shown in FIG. 5(b), check whether the rising edge of the data pulse exists in either the rising edge side margin area 0 or the falling edge side margin area α2. When re-reading data due to a data error or other cause, the phase of the wind pulse shown in Fig. 5(a) is shifted in a desired direction to extract data from the read signal. There is a patent for this.

Incidentally, the phase ΔT+ on the rising edge side and the phase ΔT2 on the falling edge side of the auxiliary wind pulse shown in FIG. 5(b) are appropriately determined with reference to the aforementioned margin areas α1 and α2, respectively.

FIG. 6 shows an embodiment of a data reproducing circuit constructed based on the principle of the present invention shown in FIG. That is, the data reproducing circuit of FIG. 6 consists of phase detector 1, amplifier 2, and V
Co circuit 3, window generation circuit 4, and data separator 5
Each of these elements has the same reference numeral as shown in FIG. 3. Therefore, in the circuit shown in FIG. 6 as well, the phase detector 1, amplifier 2, and VCO circuit 3 constitute a VFO circuit. However, in the circuit shown in FIG. 6, the pump-up signal line 1a and pump-down signal line 2b, which are the outputs from the phase detector 1, are not directly input to the amplifier 2, and the OR circuits 9a and 9b are not directly input to the amplifier 2. are connected to one input terminal of each of the two input terminals. In the data reproducing circuit of FIG. 6, there is an auxiliary window generation circuit 6 that generates the auxiliary window shown in FIG. The output of the auxiliary window generation circuit 6 and the read signal are input, and the rising edge of the data in the read signal is as shown in FIG. 5(d).
It has a data rising position detection circuit 7 that determines whether the data is within the range of ΔT1 and ΔT2 shown in FIG.

Further, the data rising position detecting circuit 7 is connected to the storage device @8, and when it is determined by the data rising position detecting circuit 7 that the rising edge of the data exists within the range of either ΔT+ or ΔT2. The information is stored in the storage device 8. One output terminal of the storage device is the OR circuit 9a.
The other output terminal of the storage device 8 is connected to the other input terminal of the OR circuit 91]. Furthermore, the storage device 8 is connected so as to be able to input a reread command supplied from a processing device on the host side.

Therefore, if a data error occurs in the reproduced data by a data processing device on the host side (not shown), a reread command is supplied from the host side to the storage device 8, and the storage device The information stored in relation to the position 11- where the
to control the phase of the wind pulse to be generated.

Next, the operation of the data reproducing circuit shown in FIG. 6 will be explained in detail. A read signal read from a floppy disk (not shown) is input to the input end of the phase detector 1. This read signal includes not only data pulses but also clock pulses as described above. In this specification, the expression "data pulse" includes both the case where a pulse is present and represents a binary state "1" and the case where no pulse is present and a binary state "0" is represented. When the read signal is supplied to the phase detector 1, the output from the phase detector 1 is sent to the amplifier 2 via the OR circuits 9a and 9b.
Further, the output of the amplifier 2 is input to the VCO circuit 3, and the output from the VCO circuit 3 is input to the phase detector 1.
Since the signal is fed back, an output with a phase synchronized with the read signal is input to the window generation circuit. Therefore, the window generation cycle 1 is performed based on the read signals synchronized in this way.
2-path 4 periodically generates wind pulses and supplies them to data separator 5; On the other hand, since the read signal is simultaneously applied to the data separator, the data separator 5 extracts data in response to the wind pulse supplied from the window generation circuit 4 and outputs reproduced data. The reproduced data thus output is supplied to an arbitrary data processing device (not shown) on the host side, and data processing is performed according to a predetermined program. In the data reproducing circuit of the present invention shown in FIG. 6, since the auxiliary window generating circuit 6 is provided,
The auxiliary wind pulse shown in FIG. 3(d') is generated and supplied to the data rising position detection circuit 7. The data rising position detection circuit 7 simultaneously receives the output of the window generation circuit 4, the output of the auxiliary window generation circuit 6, and the read signal, and detects that the rising edge of the data pulse exists within the range of either ΔT+ or ΔT2. Determine whether or not. If it is determined that the rising edge of the data exists at either ΔT1 or ΔT2, the location is stored in the storage device 8 in relation to the data position.

If no data error is detected when the reproduced data output from the data reproducing circuit of FIG. 6 is processed in a data processing device (not shown), it means that all the data has been read accurately. In that case, it is preferable to configure the system so that a signal is sent from the data processing device on the host side to the storage device 8 to erase the information stored up to that point. On the other hand, if a data error is detected when the reproduced data is processed, a signal for re-reading is generated from the data processing device on the host side. This signal is supplied to a reading device (not shown) to reread data from the location where the data error has occurred. On the other hand, such a reread command from the host side is also supplied to the storage device 8. Therefore, when the reread read signal is supplied to the phase detector 1, the storage device 8 transfers the previously stored information via either the signal line 8a or 8b to the OR circuit 9a or 9b. is supplied to amplifier 2 to change the vCO00 circuit frequency. In this manner, when processing a read signal that has been reread, data is extracted from the read signal by appropriately shifting the phase of the wind pulse generated from the window generation circuit 4 in the forward or backward direction. With such a configuration, even if a data error occurs due to entering the margin area of the wind pulse; accurate data reading or reproduction can be performed by appropriately controlling the phase of the wind pulse. becomes possible. Furthermore, when the rising edge of the data pulse enters 8T1, a pump-up signal is sent through the signal line 8a to shift the phase of the wind pulse in the forward direction, while when the rising edge of the data pulse enters ΔT2. supplies a pump-down signal via signal line 8b to shift the phase of the wind pulse in the backward direction.

Effects As explained in detail above, according to the present invention, even if data bits are individually shifted for some reason and a data error occurs during data processing, rereading is not necessary. When data is separated from a read signal, the data is extracted by appropriately shifting the phase of the data separation window, thereby making it possible to reduce the occurrence of data errors as much as possible. Therefore, even if there is data with individual large bit shifts, it is possible to reliably save the data by re-reading.

Although specific embodiments of the present invention have been described in detail above, the present invention should not be limited only to these specific examples, and various modifications may be made without exceeding the technical scope of the present invention. Of course it is possible.

[Brief explanation of drawings]

Figures 1 and 2 show typical recording systems in floppy disk devices, with Figure 1 being an explanatory diagram of the FM recording system, Figure 2 being a clear diagram of the MFMFM recording system, and Figure 3 The figure is a block diagram showing a conventional data reproducing circuit.
The figure is an explanatory diagram showing the phase relationship between the window and the data, FIG. 5 is an explanatory diagram for explaining the present invention in detail, and FIG. 6 is an explanatory diagram showing one embodiment of the data reproducing circuit of the present invention. This is a block diagram. (Explanation of symbols) 1: Phase detector 2: Amplifier 3: VCO circuit 4: Window generation circuit 5: Data separator 6: Auxiliary window generation circuit 7: Data rising position detection circuit 8: Storage device 9: OR circuit 10: VFO Circuit patent applicant Ricoh Co., Ltd.

Claims (1)

[Scope of Claims] 1. In a data reproducing circuit that processes a read signal read from a recording medium and reproduces data, a wind pulse generating means that periodically generates a wind pulse having a predetermined pulse width; data pulse separation means for separating a data pulse from the read signal in response to the wind pulse; and storage means for storing that a rising edge of the data pulse exists in a preset margin area of the wind pulse; A data reproducing circuit comprising: a wind pulse phase control means for controlling the phase of the wind pulse according to an output from the storage means in response to a reread command. 2. The data reproducing circuit according to item 1 above, wherein the margin area has a rising margin area adjacent to the rising edge of the wind pulse and a falling margin area adjacent to the falling edge of the wind pulse. 3. The data reproducing circuit according to item 2 above, wherein the phase control means controls the phase of the wind pulse according to the read signal when the re-read command does not exist. 4. In the above item 3, the phase control means comprises a phase detector to which the read signal is input, an amplifier to which the output of the phase detector is input, and a VCO to which the output of the amplifier is input. A data reproducing circuit comprising a VFO circuit connected to feed back the output of the vCO circuit to the phase detector. 5. The data reproducing circuit according to item 4 above, wherein the recording medium is a floppy disk.