JPH03280263A - Index detector for floppy disk device - Google Patents

Abstract

PURPOSE:To make it possible to generate normal index pulses even at the time of using a recording medium with high light transmissivity by detecting the output level of a photodetecting means, and when the detection level more than a prescribed level is continued for a prescribed period, deciding an abnormal state. CONSTITUTION:When the recording medium with high light transmissivity is inserted, the light of an LED 13a is leaked and an intermediate level is generated in an emitter signal E outputted from a phototransistor(TR) 13b. Thereby, a comparator 24 outputs an H level signal F to an abnormality detecting circuit 22 for a prescribed period. The circuit 22 decides the existence of abnormality in the signal E from the level state of the signal F, and after the lapse of a prescribed period, outputs a signal G to the TR 21. The TR 21 is turned on by the signal G. Thereby, parallel resistors R1, R2 are selected as the external resistors of the photo-TR 13b and the level of the signal E is determined by the parallel resistance of the resistors R1, R2. A receiver circuit 16 inputs the signal E after the lapse of a prescribed period and generates an index pulse based upon a threshold level corresponding to the level of the signal E.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an index detection device used in, for example, an 8-inch floppy disk device.

(Prior art) Conventionally, for example, in an 8-inch floppy disk device,
As shown in FIG. 3, an index hole 12 is formed in the recording medium 11, and this hole 12 is optically detected by an index sensor consisting of a light emitting diode 13a and a phototransistor 13b. That is,
A hole 15 is formed in the jacket 14 that houses the recording medium 11, and the index hole 12 of the recording medium 11 can be detected through this hole 15.

As a result, when the recording medium 11 rotates and the index pole 12 and hole 15 face each other, the light emitting diode 13
The light a is received by the phototransistor 13b, and it is detected that the recording medium l has rotated once.

FIG. 4 is a diagram showing the configuration of a conventional index detection device. As described above, when the index hole 12 and the hole 15 of the jacket 14 face each other, the light from the light emitting diode 13a is received by the phototransistor 13b.

At this time, the phototransistor 13b receives light from the light emitting diode 13a on the base side and turns on, and outputs an rHJ level emitter signal from the emitter side.

On the other hand, when the index hole 12 and the hole 15 do not face each other, the light from the light emitting diode 13a is blocked, so the phototransistor 13b does not operate and the emitter signal is at the rLJ level. Receiver circuit 16 receives this emitter signal and generates an index pulse based on a threshold corresponding to the level of the emitter signal at this time. As a result, index pulses are periodically output every time the recording medium 11 rotates once.

Note that the resistor 17 connected to the light emitting diode 13a
is a fixed resistor for determining the current value to be passed through the light emitting diode 13a and controlling the amount of light emitted.

Incidentally, the emitter level of the phototransistor 13b is determined by the voltage division ratio between the internal resistance r and the external resistance R. Here, the phototransistor 13b is irradiated with light,
When the transistor 13b is on, the resistance value of the internal resistor r decreases, so rH is approximately equal to the power supply voltage.
J level will be secured.

On the other hand, when the phototransistor 13b is off, the resistance value of the internal resistor r becomes extremely high, and the emitter level becomes the ground level, that is, the rLJ level.

Here, if a recording medium II having a high light transmittance is used, the light from the light emitting diode 13a may leak to the base side of the phototransistor +3b, and the resistance value of the internal resistor r may decrease, causing the emitter level to become high.

In such a case, the emitter signal, which should normally be at the rLJ level, will exceed the input threshold of the receiver circuit 16, resulting in an inaccurate index pulse.

(Problems to be Solved by the Invention) As described above, when a recording medium with high light transmittance is used, the output level of the light receiving element that constitutes the inch sensor becomes abnormal, resulting in inaccurate index pulses. There was a problem that occurred.

The present invention has been made in view of the above points, and provides an inch-socks detection device for a floppy disk drive that can prevent the occurrence of inaccurate index pulses due to the use of recording media with high light transmittance. The purpose is to

[Structure of the Invention] (Means and Effects for Solving the Problems) That is, the present invention provides a flowchart that optically detects index holes formed in a recording medium to detect that the recording medium has rotated once.・In the index detection device of the SOBE disk device, the output level of the light receiving means that receives the light from the light emitting means via the recording medium is detected, and if this detection level is above a predetermined level for a predetermined period, an abnormality is detected. This is to prevent the occurrence of inaccurate index pulses due to the use of a recording medium with high light transmittance.

(Embodiment) Hereinafter, an index detection device for a floppy disk drive according to an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, this index detection device optically detects an index hole in a recording medium and generates an index pulse using an index sensor consisting of a light emitting diode 13a and a phototransistor 13b. The light emitting diode 13a emits light toward the recording medium.

The light emitted from the light emitting diode 13a is received by the base side of the phototransistor 13b via the recording medium. The phototransistor 13b is turned on by receiving light from the light emitting diode 13a, and outputs an emitter signal E from the emitter side.

The receiver circuit 16 receives this emitter signal E and generates an index pulse based on a threshold corresponding to the level of the emitter signal E at this time.

Here, the level of the emitter signal E is determined by the voltage division ratio between the internal resistance r of the phototransistor 13b and the external resistance. In this embodiment, as an external resistor, R1 or a parallel resistor of R1 and R2 is selectively used. This external resistor RI R2 is the transistor 21
The phototransistor 13b is connected in parallel to the emitter terminal of the phototransistor 13b. The transistor 21 is turned on/off by the output signal G of the abnormality detection circuit 22. When it is off, the external resistor R1 is connected to the emitter terminal of the phototransistor 13b, and when it is on, the external resistor R1 and R2 are connected to the same terminal. Transistor 1 is connected in parallel to the emitter terminal.
The external connection 3b switches the resistance value.

The abnormality detection circuit 22 is a circuit that detects an abnormal state of the emitter signal E of the phototransistor 13b, and during the input period of the output signal of the monostable 23, the comparator (
When the output signal F of the non-inverting buffer (non-inverting buffer) 24 is higher than a predetermined level, a signal G is output to the phototransistor 13b as an abnormal state.

The monostable 23 is set by a door close signal B that is output when a medium insertion door (not shown) is closed, and a motor on signal C that is output when a spindle motor (not shown) is started, and is set by a resistor and a capacitor. A signal is output to the tarok terminal of the abnormality detection circuit 22 for a period of T1 determined by the time constant of . This period Tl corresponds to the time required for the recording medium to rotate once after the spindle motor is started. Furthermore, the monostable 23 and the abnormality detection circuit 22 are reset by an inverted signal A of the disk sensor signal output when a recording medium is inserted or ejected.

The comparator 24 inputs the emitter signal E of the phototransistor 13b, and outputs the signal F to the data terminal of the abnormality detection circuit 22 when the level of the emitter signal E is equal to or higher than an internally set predetermined level SL.

Next, the operation of this embodiment will be explained with reference to the timing chart shown in FIG. In order to make it easier to understand, the following explanation assumes that a Type I recording medium with normal light transmittance is loaded and a Type ■ recording medium with high light transmittance is loaded. .

When a disk sensor (not shown) is turned on by inserting a recording medium, the abnormality detection circuit 22 and monostable 23 are cleared (initialized) by the inverted signal A of this sensor signal.
be done. At this initial stage, the transistor 21 is off, and only R1 is selected as the external resistor of the phototransistor 13b.

Here, when chucking of the recording medium is completed and the door close signal B and motor on signal C are output, the second
As shown in the figure, the monostable 23 is set at the rising edge of the door close signal B and the falling edge of the motor on signal C. As a result, the monostable 23 outputs a signal to the abnormality detection circuit 22 for the period TI.

At this time, if the recording medium is of type I and has a normal light transmittance, the light from the light emitting diode 13a is received by the phototransistor +3b every time the recording medium rotates once, and as shown in FIG. The emitter signal E is correctly outputted from the phototransistor 13b at the period T2.

The period T2 corresponds to one revolution of the recording medium. The comparator 24 sets this emitter signal E to a predetermined level SL.
When the emitter signal E is higher than the level SL, the signal F is outputted to the abnormality detection circuit 22. The abnormality detection circuit 22 checks the level of the signal F during the signal input period T1, and if the level of the signal F is higher than a predetermined level during this period TI (if it is "H" level). Then, it is determined that an abnormality has occurred in the emitter signal E of the phototransistor 13b, and the signal G is output to the transistor 21 after a period TI.

The specific configuration of the abnormality detection circuit 22 is as follows:
For example, it is equipped with a counter that counts the input of the signal F of a predetermined level or higher at the input timing of the signal, and for a period T
A signal G is output when the count value of the counter up to l exceeds a predetermined value.

In this case, if the recording medium is of type I, the signal F will never be higher than the predetermined level during the period T1. Therefore, the abnormality detection circuit 22 determines that the correct emitter signal E is being output.

As a result, only R1 is selected as an external resistor of the phototransistor 13b in its initial state, and the level of the emitter signal E is determined by this external resistor R1. The emitter signal E at this time is a signal corresponding to an index pulse. Thereafter, the above resistance condition is maintained until the recording medium is ejected. The receiver circuit 16 receives the emitter signal E after the period Tl and generates an index pulse based on a threshold corresponding to the level of the emitter signal E at this time.

On the other hand, in the case of a type H recording medium with high light transmittance,
Light from the light emitting diode 13a leaks, and an intermediate level as shown in FIG. 2 occurs in the emitter signal E of the phototransistor 13b. Therefore, the comparator 24 outputs a signal F of a predetermined level or higher (“H” level) to the abnormality detection circuit 22 during the period Tl. The abnormality detection circuit 22 determines that there is an abnormality in the emitter signal E based on the level state of the signal F, and outputs the signal G to the transistor 21 after a period Tl. Transistor 21 is turned on by this signal G.

As a result, parallel resistors R1 and R2 are selected as external resistors of the phototransistor 13b, and the level of the emitter signal E is determined by the parallel resistors R1 and R2. The resistance condition at this time is maintained until the recording medium is ejected. The receiver circuit 1B inputs the emitter signal E after the period T1, and generates an index pulse based on a threshold corresponding to the level of the emitter signal E at this time (lower threshold than in type I).

In this way, the abnormal state of the emitter signal E of the phototransistor 13b is detected during the detection period determined by the output period T2 of the signal. Therefore, by switching the resistance value of the phototransistor 13b according to the detection result, a normal index pulse can be generated even when a recording medium of type (2) with high light transmittance is used.

[Effects of the Invention] As described above, according to the present invention, an abnormality in the output level of the light receiving element (phototransistor) can be detected during a predetermined detection period. Therefore, generation of inaccurate index pulses can be prevented after this detection period. In addition, by switching the resistance value of the external resistor connected to the light receiving element according to the detection result, it is possible to generate a normal index pulse even when using a recording medium with high light transmittance. It is something.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an index detection device according to an embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation of the embodiment, and FIG. 3 is a diagram for explaining index detection. , FIG. 4 is a diagram showing the configuration of a conventional index inspection device. 13a... Light emitting diode, I3b... Phototransistor, 16... Receiver circuit, 21... Transistor, 22... Abnormality detection circuit, 23... Monostable, 24... Comparator, r.・Internal resistance,
R1 and R2...external resistors.

Claims (1)

[Scope of Claims] An index detection device for a floppy disk device that optically detects an index hole formed in a recording medium to detect that the recording medium has rotated once, wherein the index detecting device emits light toward the recording medium. light-emitting means; light-receiving means for receiving light from the light-emitting means via the recording medium; level detection means for detecting the output level of the light-receiving means; An index detection device for a floppy disk drive, characterized in that it comprises an abnormality determining means for determining an abnormal state in the above cases.