JPH0283861A - Synchronous signal detection device - Google Patents

Abstract

PURPOSE:To correctly detect sector mark signals even when two sector mark signals or above are outputted concerning one sector by providing a detecting window to limit an hourly position when a synchronizing signal is detected and outputting only one out of signals as the synchronizing signal when plural signals are detected in the window. CONSTITUTION:A header signal is a signal which becomes an 'L' at a header area and an 'H' at the area where a sector mark should be detected. Such a header signal is first inputted to a D-FF 1, always latched to the 'H' at the end of the header area and reset by a sector mark gate signal. Next, when the inverting output signal of FF 1 becomes the 'H' are resetting is released, FF 2 becomes active. Here, by the fall of a first signal after a sector mark gate becomes active, the FF 2 is latched to the 'H', an output Q becomes the 'H', a NOR circuit 4 is closed and a mark SM before correction detected after the second is not outputted as a mark signal after correction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a synchronization signal detection device that detects a synchronization signal from a signal in which a synchronization signal pattern is recorded.

[Prior Art] Although there are various devices that use synchronization signals, detection of a synchronization signal (sector mark signal) in a conventional optical disk device for recording and reproducing digital information will be described.

When handling data in an optical disk device, the optical disk is divided into several areas called sectors S, as shown in FIG. 3, and the data is handled with each sector S as one unit.

Each sector is divided into a header section in which information such as a track address and sector address is recorded in advance, and a data section in which information is recorded and reproduced.

The header section has a format as shown in FIG.

A pattern for detecting the starting position of the sector is recorded in the sector mark SM.

The VFO selects the next recorded track address TA,
This is a synchronization pattern for a synchronization clock necessary for reading the sector address SA, cyclic redundancy check code CRC, etc., and the ID section is a section for recording position information regarding the sector.

In the address mark AM, a pattern indicating a data break is recorded when reading the next recorded track address TA, sector address SA, and cyclic redundancy check code CRC. The track address TA records the track number of the track where the sector exists, and the sector address SA records the number of the sector.

The cyclic redundancy check code CRC is
It is a code for error detection, and its track address TA,
A code is recorded that determines whether or not there is an error in the data when reading information such as sector address SA, and includes address mark AM, track address TA, sector address SA, and cyclic redundancy check code CRC. The part is written four times in one header H.

FIG. 5 is a diagram showing an example of a pattern of sector marks SM.

Next, a basic sector mark pattern detection method will be explained.

First, the pattern of the sector mark SM is composed of a pattern that does not normally appear in other areas of the disk. For example, in the above case, the data area is recorded with 2-7 modulation, but only the sector mark SM is recorded with a pulse interval of 12T, as shown in FIG. , 9T, and BT, and pulses other than 6T do not appear in the data area.

The read signal input to the sector mark detection circuit is sent to the synchronization circuit 51 of the detection circuit and synchronized with the reference clock. The read signal synchronized with the reference clock is input to the pulse interval detection circuit 52, and the pulse interval (the number of 0s between one pulse and the next pulse) is 9 clocks and 12 clocks.
clock, and 6 clocks. Each signal is input to the shift register 53 and shifted by the reference clock. Here, the signal with a pulse interval of 12 and a7 is extracted by 21 clocks and a 40 clock delay, the signal with a 6 clock pulse interval is delayed by 10 clocks, and the signal with a pulse interval of 9 clocks is delayed by 53 clocks and 17 clocks. The delayed and non-delayed outputs of the Oth clock are respectively sent out and input to the majority circuit 16.

FIG. 6 is a diagram showing the timing of each signal in the conventional example.

The majority circuit 56 outputs a signal only when three or more of the six signals shown in FIG. AND is performed and output as a sector mark signal. This sector mark signal is a gate that opens only at the position where the sector mark SM is detected, and prevents the sector mark SM from being detected at a completely different position.

In FIG. 7, all six signals become rHJ at the point indicated by A, and the sector mark SM is detected here.

However, due to defects on the optical disc, this is always 6
Although not all of the marks are rHJ, by setting it to 376 or more by the majority circuit 56, it is possible to detect the sector mark SM even if there are some defects.

By the way, increasing the detection probability also increases the possibility of false detection. Also, regarding the sector mark gate which is gated at the approximate position of the sector mark SM,
Considering the uneven rotation of the spindle motor that rotates the optical disk, a width of a byte is required, so what is detected within this gate must be recognized as a sector mark SM.

[Problems to be Solved by the Invention] As shown in FIG. 8, in the case of a normal sector mark pattern, after the sector mark pattern there is a VFO "lOO".
The pattern 81 is repeated, but if pattern 82 is detected due to a defect on the optical disk, the output of each shift register will be at point B other than point A, as shown in FIG. In, pattern 83.8
The output of the 4.85 shift register becomes "H", and the 3/85 shift register becomes "H".
6 or more, it is recognized as a sector mark pattern.

Furthermore, since it is located within one byte and close to the original sector mark position, it will be inside the sector mark gate and will be output as the sector mark SM.

When two sector mark signals are output, if these signals are used to reset the operation, recording may be stopped at a completely different position than usual, or other malfunctions may occur. Furthermore, since the sector mark SM is a signal that should serve as a reference for the entire operation, such a decrease is not desirable.

The present invention provides two sector mark signals for one sector.
It is an object of the present invention to provide a synchronization signal detection device that does not stop recording at a position different from normal even when more than one synchronization signal is output, and does not cause other malfunctions.

[Means for Solving the Problems] The present invention provides a synchronization signal detection device that detects a pattern of synchronization signals and has a detection window that limits the temporal position at which the synchronization signal is detected. When signals are detected, only one of the detected signals is output as a synchronization signal, and output of the other detected signals is prohibited.

[Operation] The present invention provides a synchronization signal detection device that detects a synchronization signal pattern and has a detection window that limits the temporal position at which the synchronization signal is detected, in which a plurality of signals are detected within the detection window. When two or more sector mark signals are output for one sector, only one of the above detected signals is output as a synchronization signal and output of other detected signals is prohibited. However, recording does not stop at an unusual position, and other malfunctions do not occur.

[Example] FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a timing diagram in the above embodiment.

This embodiment has a D flip-flop 1.2, an inverter 3.5 and a NOR circuit 4.

The slip-flop 1 inputs a header signal to a clock terminal K, and the flip-flop 2 receives an inverted signal of the flip-flop as a reset signal. The inverter 3 inverts the sector mark gate signal and sends the inverted signal to the reset terminal of the flip-flop 1. The inverter 5 inverts the sector mark signal before correction and sends the inverted signal to the clock input terminal of the 7-lip flop 2 and to the N0R4. N0R4 receives the Q output of flip-flop 2 and the output of inverter 5.

Next, the operation of the above embodiment will be explained.

First, the header signal is a signal that becomes "L" in the header region of the signal, and the sector mark signal is a signal that becomes rHJ in the region where the sector mark is to be detected. The sector mark signal before correction is a sector mark signal detected by a pattern, and a plurality of sector mark signals may be output.

First, the D slip-flop l is always latched to "H" at the end of the header area, and is reset by the sector mark gate signal, the inverted output signal of the flip-flop l becomes rHJ, and the reset of the flip-flop 2 is released. Flip-flop 2 becomes active.

Here, the first fall of the sector mark signal after the sector mark gate becomes active causes the flip-flop 2 to be latched to "H", and its output Q is "H".
'', the NOR circuit 4 is closed, and the flip-flop 2 remains closed until the next reset (that is, until the rise of the header signal).

Therefore, the sector mark SM detected after the second
is prohibited by the gate N0R4, and is never output. In other words, the sector mark SM detected after the second one (sector mark signal before correction) is not a sector mark signal after correction. No output.

For this reason, since a plurality of sector marks are not output within one sector, malfunctions of systems operating based on sector marks can be reduced.

Further, in the embodiment described above, priority is given to the sector mark SM detected first in one sector, but more accurate detection may be performed using another inversion method.

[Effects of the Invention] According to the present invention, even if two or more sector mark signals are output for one sector, recording will not be stopped at a position different from normal, and other malfunctions will not occur. play.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a time chart showing the operation of the above embodiment. FIG. 3 is a diagram showing the relationship between sectors and headers on an optical disc. FIG. 4 is a diagram showing an example of the format of a header section in a conventional example. FIG. 5 is a diagram showing an example of a sector mark pattern in the conventional device. FIG. 6 is a diagram showing an example of a sector mark turn detection circuit in a conventional device. FIGS. 7 and 8 are explanatory diagrams of the operation of the above conventional example. 1.2...D flip-flop, 3.5...Inverter, 4...NOR.

Claims (4)

[Claims] (1) In a synchronization signal detection device that detects a synchronization signal pattern and has a detection window that limits the temporal position at which the synchronization signal is detected, when a plurality of signals are detected within the detection window, A synchronization signal detection device characterized in that it outputs only one of the detected signals as a synchronization signal and prohibits output of other detected signals. (2) The synchronization signal detection device according to claim (1), characterized in that among the signals detected within the detection window, the first detected signal is validated. (3) The synchronization signal detection device according to claim (1) or (2), wherein the synchronization signal is a synchronization signal of an optical information recording/reproducing device. (4) The synchronization signal detection device according to claim (3), wherein the synchronization signal is a sector mark of an optical disc device.