JP2000112588A - Optical signal converter for tristate bus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a general purpose optical signal converter for a tristate bus in a simple constitution which can be added to an existing LSI while making it unnecessary to alter the existing LSI or to change any existing optical communication protocol for optically connecting the tristate bus for connecting a personal computer with peripheral equipment. SOLUTION: This device is provided with a light emitting element L2 and a light receiving element P2 connected with an input and output terminal D2 of an input and output circuit B2, gate circuit G1 of the light emitting element L2, and current detecting circuit 42 for detecting the inflow currents or outflow currents of the input and output terminal D2. The current detecting circuit 42 operates output to the gate circuit G1, and prohibits the transmitting operation of the light emitting element L2 at the time of detecting currents which are a prescribed value or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electro-optical converter. In particular, the present invention relates to a technique for optically connecting a tri-state serial bus that controls peripheral devices such as a power supply system and input / output devices used in a personal computer.

[0002]

2. Description of the Related Art As a tri-state serial bus, a power supply system management bus, which has already become a standard for personal computers, has been proposed.
s (hereinafter abbreviated as SMB) and I / O control system Univ
There is an external serial bus (hereinafter abbreviated as USB). These are converted into an optical signal to wirelessly control an external battery in the case of the SMB, and a USB-connected peripheral device is used in the case of the USB. Is performing wireless I / O control.

Conventionally, when converting a tristate serial bus signal used for connection between a personal computer main body and peripheral equipment into an optical signal, an existing bidirectional input / output circuit including a tristate bus is connected. Product L
An enable signal (hereinafter abbreviated as an OE signal) of an output circuit in the SI or an enable signal (hereinafter abbreviated as IE) of an input circuit.
(Abbreviated as signal) and used as a gate signal for the light receiving element and the light emitting element connected to the tristate bus.

However, in the case of such a system, an LS signal of an existing product is required to extract an OE signal or an IE signal.
I need a major correction, and
When the tri-state bus on the personal computer side is composed of a plurality of function-specific LSIs including input / output circuits, it has been virtually impossible to correct the plurality of LSIs.

A configuration example of a conventional optical signal converter for a tri-state bus using an OE signal will be described below with reference to FIGS. 4, 5 and 6. FIG.

FIG. 4A is a timing chart of normal data transfer in USB, FIG. 4B is an explanatory diagram of USB hardware, and FIG. 5 is a diagram showing a bus collision of a simple tri-state bus optical signal converter. FIG. 6 is a configuration diagram of a conventional USB optical signal converter.

FIG. 4A shows the timing of data transfer between two input / output buffers of a personal computer and input / output buffers of peripheral devices via two USB buses D + and D-.

In FIG. 4B, the input / output terminal D1 of the input / output circuit B1 and the input / output terminal D2 of the input / output circuit B2 are connected to each other by wires. Similarly, the input / output terminal D3 and the input / output terminal D4 are connected to each other by wires.

As for the signal on the bus D +, the input / output terminal D1 of the input / output circuit B1 is in a high impedance state (hereinafter abbreviated as Z state), but as shown in FIG. Data is transferred between a transmission / reception switching or standby section in which the state is at a high level (hereinafter abbreviated as H state) and a packet data transfer section including a synchronization field, a data field, and EOP which is a data end signal. You.

The signal on the bus D- is such that the input / output terminal D3 of the input / output circuit B3 is in a high impedance state (hereinafter abbreviated as Z state), but the signal state of the bus is low level (hereinafter abbreviated as L state) by a pull-down resistor. ), And a packet data transfer section composed of a synchronization field, a data field, and an EOP which is a data end signal.

Next, FIG. 5 shows a simple circuit configuration for explaining a bus collision. In FIG. 5, B1 is an input / output circuit on the peripheral device side, which outputs the H and L states of the USB bus D + in synchronization with the activation of the output enable signal OE, and the H and L states in the Z state when OE is not active. Enter the state.

B2 is an input / output circuit on the computer side.
As in the case of 1, H, L, and Z of the USB bus D + are input or output.

L1 is a light emitting element for light transmission connected to the input / output terminal D1 of the input / output circuit B1 and turned on when B1 is in the L state.
P2 is connected to the input / output terminal D2 of the input / output circuit B2 and L1
A light-receiving element that receives the light emission of D2 and changes D2 to the L state, L2 is a light-emitting element connected to D2 and lit when D2 is in the L state, P1
Is a light receiving element which is connected to D1 and receives light emitted from L2 to bring D1 into the L state.

By the combination of L1 and P2 and L2 and P1, bus lines D1 and D2, which are D + buses shown in FIG.
Are optically connected bi-directionally at active L.

B1 and B2 are synchronized with the H and L of the USB bus D- when the output enable signal OE becomes active.
Is output. In the Z state where OE is not active,
Input L state.

L3 is connected to the input / output terminal D3 and emits light when D3 is in the H state. P4 is connected to the input / output terminal D4 to receive light emitted from L3 and set D4 to the H state. A light-emitting element connected to D4 and turned on when D4 is in the H state. P4 is connected to D4 to receive light emitted from L3 and
Is an H state. With the combination of L3 and P4 and the combination of L4 and P3, the D-bus signal shown in FIG. 4 is optically connected to the input / output circuits B3 and B4 bidirectionally and active-H.

However, as shown in FIG.
Simply converting the H state and L state of 1 and D2 into light signals without light emission of the light-emitting element and light-emission, and transmitting and receiving,
A bus collision occurs between the input / output circuits B1 and B2, causing a malfunction.

The cause of the occurrence of the bus collision will be described below with reference to FIG. In FIG. 5, L of the input / output circuit B1
The voltage level of the input / output terminal D1 is L due to the transmission output of the state.
When the state changes, the light emitting element L1 is turned on, the light is received by the light receiving element P2 on the receiving side, and the input / output terminal D2 is set to the L state. When D2 goes to the L state, the light emitting element L2 connected to D2 is turned on, and the light receiving element P1 of the input / output terminal D1 that has received this light conducts to generate feedback that the bus line D1 is held at the L state.

Next, even if an attempt is made to change the voltage level of the input / output terminal D1 to the H state by the transmission output of the H state by the input / output circuit B1, since the light receiving element P1 is conducting due to the above-mentioned feedback, the voltage of the D1 is changed. Since the level is held in the L state, the transmission of the H state of the input / output circuit B1 is not transmitted to the input / output terminal D2 on the receiving side.
Output terminals are short-circuited and a bus collision occurs, which may cause a destruction of the output circuit.

Also at the input / output terminal D3 of the bus D-, when the input / output circuit B3 is in the H state, the bus line D3 is held in the H state by feedback in the same manner as described above.
If 3 attempts to switch from the H state to the L state, a bus collision occurs.

Therefore, in order to avoid the bus collision,
The output enable signal O of the input / output circuit as described next
There is a configuration in which the light emitting element blinks in synchronization with E.

FIG. 6 shows a circuit configuration of a conventional USB bus optical signal converter. Between the light emitting element and the input / output circuits B1 and B3, between the output buffer 211 and the light receiving element and the input / output circuits B1 and B3 so that the USB input / output terminals D1 and D2 and the input / output terminals D3 and D4 are optically connected. Is provided with an input buffer 213. And the existing LS of USB
The output buffer 211 is enabled by the output enable signal OE of the output buffers B1 and B3 inside I, and the OE signal is transmitted by the newly provided light emitting element L7. The other side is a light receiving element P that receives the light emission of the light emitting element L7.
7, the input buffer 212 is enabled to transmit D + and D- signals to the input / output circuits B2 and B4.

However, this OE signal is a signal that does not exist in the USB specification that presupposes wire connection.

In an LSI which is mass-produced as an existing product, the OE terminal is not exposed to an external terminal. Therefore, a large-scale correction is made to the existing LSI, an OE signal is extracted, and the input / output buffer is switched. Needed.

[0025]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. The present invention adds an input / output terminal of a tri-state input / output circuit of an existing LSI as an adapter having a simple configuration and transmits / receives light by light. It is an object of the present invention to provide a tristate bus optical signal converter that can be used.

[0026]

According to the present invention, there is provided a light emitting device which is connected to an input / output terminal of a tristate input / output circuit and transmits an optical signal in accordance with an output voltage of the input / output terminal. A light-receiving element that receives an optical signal and outputs the signal to an input / output terminal; a gate circuit that inhibits a transmission operation of the light-emitting element or a reception operation of the light-receiving element; and a current flowing into or flowing out of the input / output terminal. A current detection circuit for detecting the current, wherein the current detection circuit outputs to the gate circuit and configures an optical signal conversion device for a tri-state bus so as to prohibit the transmission operation of the light emitting element when a current equal to or less than a predetermined value is detected. By doing so, the aforementioned bus collision is avoided.

In order to simplify the circuit configuration, a plurality of the input / output circuits are connected in parallel and the above-described current detection circuit is connected to at least one of the input / output terminals of the input / output circuit.
Another gate circuit can be controlled in parallel by the output of the current detection circuit.

Further, as a specific configuration example of the current detection circuit, a sense resistor having one end connected in series to an input / output terminal, a pull-up resistor and a pull-down resistor connected to the other end of the sense resistor, A current flowing into the terminal or a current flowing out of the input / output terminal may be detected by the sense resistor.

By adopting such a configuration, an optical signal converter for a tri-state bus can be added as an adapter having a simple configuration without modifying the existing LSI for the tri-state bus on the personal computer main body side and the peripheral device side. The device can be realized.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention relates to a light emitting element connected to an input / output terminal of a tristate input / output circuit and transmitting an optical signal in accordance with an output voltage of the input / output terminal. A light receiving element that receives an optical signal and outputs the signal to the input / output terminal, a gate circuit that inhibits a transmission operation of the light emitting element, and a current that detects a current flowing into or flowing out of the input / output terminal An optical signal conversion device for a tri-state bus, comprising a detection circuit, wherein the current detection circuit is configured to output a current to the gate circuit and prohibit a transmission operation of the light emitting element when detecting a current equal to or less than a predetermined value. Since an enable signal of an existing LSI for a tri-state bus is not required, and the signal can be converted into an optical signal simply by adding it to an existing LSI as an adapter, the configuration is simple. Effect that allows the optical transceiver of use, high-performance tristate bus signal.

According to a second aspect of the present invention, a plurality of the input / output circuits are provided in parallel, and the current detection circuit is connected to at least one of the input / output terminals of the input / output circuit.
2. The optical signal converter for a tri-state bus according to claim 1, wherein an output of the current detection circuit is input to another of the gate circuits in parallel, and a light detection operation of a plurality of light emitting elements is performed by one current detection circuit. Alternatively, since the light receiving operation of the light receiving element can be controlled, the configuration of the circuit is simplified, and the effects of miniaturization, power saving, and cost reduction are obtained.

According to a third aspect of the present invention, there is provided a sensing resistor having one end connected in series to the input / output terminal, a pull-up resistor and a pull-down resistor connected to the other end of the sense resistor, 3. The optical signal conversion device for a tri-state bus according to claim 1, further comprising a current detection circuit for detecting a current flowing through the sense resistor, wherein the current detection circuit detects a current flowing into or out of the input / output terminal. The effect of miniaturization and cost reduction can be obtained with a simple circuit configuration.

[0033] The invention described in claim 4 of the present invention provides a system for analyzing Sys.
tem Management Bus or Uni
4. The optical signal for a tri-state bus according to claim 1, wherein the input / output terminal of the input / output circuit is connected to a bus without a dedicated control signal bus line, such as a general serial bus. A conversion device, the optical signal conversion device for a tri-state bus of the present invention is applied to a wired standard bus, thereby eliminating the need for a cable,
It is possible to obtain the effect of reducing the storage property and unnecessary radiation and improving the usability.

Next, specific embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 is a diagram showing a relationship between an optical signal converter for a tristate bus and a bus according to Embodiment 1 of the present invention.

In FIG. 1, the input / output terminal D1 of the tristate input / output circuit B1 on the peripheral device side and the input / output terminal D2 of the tristate input / output circuit B2 on the personal computer side are connected to the optical signal for the tristate bus of the present invention. The conversion device is added as adapters 31 and 32 having the same configuration and optically connected.

The light-emitting element L1 of the adapter 31 flashes in response to a signal from the input / output terminal D1, and the light from the L1 is received by the light-receiving element P2 of the adapter 32 and the input / output terminal D2
Output the signal. Similarly, a signal from the input / output terminal D2 is transmitted to the input / output circuit B1 via the light of the light emitting element L2 of the adapter 32 and the light receiving element P1 of the adapter 31. Thus, bidirectional optical connection is performed.

The input / output terminals D1 and D2 are connected to tristate buses TB1 and TB2 in which input / output terminals of a plurality of input / output circuits are connected in parallel.

FIG. 2 is a circuit diagram of the D + bus of the optical signal converter for a tri-state bus according to the first embodiment of the present invention.

In FIG. 2, a tristate bus optical signal converter 32 includes a current detection circuit 42 including a pull-up resistor RU, a pull-down resistor RD, and a sense resistor RS.
And a light conversion circuit 43.

Pull-up resistor RU and pull-down resistor RD
In the case of active L shown in FIG. 2, by setting the parallel resistance value of RU and RP to be equal to the resistance value of RD, when the input / output terminal is in the Z state, H is set as specified in the bus D +.
To level.

One end of the sense resistor RS has an input / output circuit B2.
The other end of the input / output terminal D2 is connected to the optical conversion circuit 43, the pull-up resistor RU, and the pull-down resistor RD.

The current detection circuit 42 includes a differential amplifier I1 connected to both ends of the sense resistor RS, a filter I2 connected to the output of the differential amplifier I1, and a comparator I3 for comparing the output voltage of the filter I2 with a reference voltage. , I4
And NOR for ORing outputs of comparators I3 and I4
And a circuit G4.

Next, the operation of the current detection circuit will be described. Whether a current has flowed between the pull-up resistor RU or the pull-down resistor RD and the input / output terminal D2 is converted by the sense resistor RS and the differential amplifier I1 into a constant positive and negative reference voltage V.
The two comparators determine whether the voltage swings to 1, V2 or more (current detection is performed). If the positive and negative voltage values are within a predetermined range (current detection is not performed), the input / output terminal D2 The current detection circuit 42 outputs an H level logic signal voltage from the NOR circuit G4, assuming that the current is in the Z state with neither inflow nor outflow of current.

The light conversion circuit 43 is connected to the input / output terminal D2, and includes a light emitting element including a resistor RL and an LEDL2 for transmitting an optical signal according to the output voltage of the input / output terminal D2, and an optical input / output terminal for receiving the optical signal. It comprises a light receiving element comprising a resistor RP and a photodiode P2 input to D2, and a gate circuit G1 which receives the H level output of the NOR circuit and inhibits the transmission operation of the light emitting element. Therefore, when there is no inflow or outflow of current to the input / output terminal D2, that is, when the current detection circuit 42 detects the Z state and provides an H-level output to the gate circuit G1, the light emitting element is turned off.

When the current detection circuit 42 detects that a current flows in when the input / output terminal D2 is in the L state or a current flows out when the input / output terminal D2 is in the H state, and provides an L level output to the gate circuit G1, the light emitting element L2 , RL are in a blinkable state, ie, transmittable, according to the signal of the input / output terminal D2.

Optical signal converter 31 for tristate bus
Has the same configuration and operation as the above-described optical signal converter 32 for a tri-state bus.

(Embodiment 2) FIG. 3 is a block diagram showing the optical signal converters 62 and 61 for a tristate bus according to the present invention.
In the circuit diagram of the second embodiment applied to the invention, the adapters are added to the input / output terminal D2 of the input / output circuit of the personal computer main body and the input / output terminal D1 of the input / output circuit of the peripheral device so that both can be optically connected. 3 shows a configuration example in the case of realization.

In FIG. 3, the pull-down resistor (15 KΩ) of the personal computer and the pull-up resistor (1.5 K
Ω) is moved to the insertion positions 52 and 51 of the external resistors.

In FIG. 3, another bus D- has a pull-down resistor (15K) of the personal computer main body.
Ω) is moved to the insertion positions 54 and 53 of the external resistors.

In FIG. 3, since the two USB buses D + and D- are internally controlled by the enable signal OE of one output buffer similarly to the conventional example of FIG. 6, the Z state of the bus signal is detected. The current detection circuit 42 is provided only on the bus D + side, and is omitted in the other bus D−.

However, since the other bus D- is active H, the detection output of the Z state of the input / output terminal by the current detection circuit 42 is inverted and input to the gate circuit G4 of the light emitting element L4.

Therefore, the OE signal 22 inside the existing LSI as shown in the conventional example of FIG. 6 can be obtained simply by adding the optical signal converters 61 and 62 for USB tristate bus having the configuration shown in FIG. 3 as adapters. Without taking out, the detection of the Z state of the input / output terminals of the personal computer main body and the peripheral devices can be performed without being influenced by the voltage level of the bus signal by light reception.

Then, the light emission of the light emitting element is inhibited by the detection signal of the Z state, so that when the L level of the active L is fed back and input to one bus D +, the transmission side is changed from the L level to the H level. In this case, it is possible to avoid the collision of the bus which occurs when the voltage drive is changed.

On another bus D-, active H
When the level is fed back and the voltage drive is changed from the H level to the L level on the transmitting side, it is possible to avoid a bus collision that occurs when the voltage drive is changed.

Further, to make the two buses D + and D- in the Z state (H level and L level) as specified in the USB specification, a pull-up / pull-down resistor on one bus D + and another bus D- Is moved to the insertion positions 54 and 53 of the external resistors, and the two buses D + and D- are inhibited from turning on the light emitting element when the input / output terminals are in the Z state.

In the second embodiment, the current detection circuit is provided on the active L bus D + side.
The same effect can be obtained by providing a current detection circuit on the side of the bus D− and controlling the gate circuit on the active D bus D + side.

[0057]

By adopting the configuration of the present invention, the operability and storage efficiency can be improved by making the tri-state serial bus connecting the personal computer main body and the peripheral device wirelessly connected to improve the operability and storage. It is possible to realize a tristate bus optical signal conversion device that can be added as an adapter having a simple configuration without modifying the general-purpose LSI of the tristate bus on the side and peripheral devices.

[Brief description of the drawings]

FIG. 1 is a configuration diagram when a tri-state bus connection between a personal computer main body and a peripheral device according to a first embodiment of the present invention is wirelessly connected by optical connection;

FIG. 2 is a circuit diagram of an optical signal converter for a tri-state bus according to the first embodiment of the present invention;

FIG. 3 is a circuit diagram of an optical signal converter for a tri-state bus according to a second embodiment of the present invention for optically connecting a personal computer main body and peripheral devices;

FIG. 4 (a) USB timing diagram (b) USB wire connection configuration diagram

FIG. 5 is a circuit diagram of a simple optical signal converter for a tri-state bus.

FIG. 6 is a circuit diagram for optically connecting a personal computer main body and peripheral devices with a conventional optical signal converter.

[Explanation of symbols]

32 Optical signal conversion device for tristate bus 42 Current detection circuit 43 Optical conversion circuit 51, 52, 53, 54 Insertion position of external resistor (Embodiment 2) B1, B2, B3, B4 Input / output circuit L1, L2 L3, L4 LED D1, D2, D3, D4 Input / output terminal G1 Gate circuit OE Output buffer enable signal P1, P2, P3, P4 Photodiode RS Sense resistance RU Pullup resistance RD Pulldown resistance

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 10/06

Claims (4)

[Claims] A light emitting element connected to an input / output terminal of a tri-state input / output circuit for transmitting an optical signal in accordance with an output voltage of the input / output terminal; and receiving an optical signal and outputting the signal to the input / output terminal. A light receiving element, a gate circuit for inhibiting a transmission operation of the light emitting element, and a current detection circuit for detecting a current flowing into the input / output terminal or a current flowing out of the input / output terminal, wherein the current detection circuit has a predetermined value or less. An optical signal conversion device for a tri-state bus, configured to output a current to the gate circuit when detecting a current to inhibit a transmission operation of the light emitting element. 2. An input / output circuit comprising: a plurality of said input / output circuits connected in parallel; at least one of said input / output terminals of said input / output circuit being connected to said current detection circuit; 2. The optical signal converter for a tri-state bus according to claim 1, wherein the optical signal converter is input in parallel to the optical disk. 3. A sense resistor having one end connected in series to the input / output terminal, a pull-up resistor and a pull-down resistor connected to the other end of the sense resistor, and a current detector for detecting a current flowing through the sense resistor. 3. The optical signal converter for a tri-state bus according to claim 1, further comprising a circuit. 4. System Management B
us or Universal Serial Bu
4. The optical signal converter for a tri-state bus according to claim 1, wherein the input / output terminal is connected to a bus having no dedicated control signal bus line such as s.