JP2008262590A - Interface circuit and information processor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interface circuit with an IR (Infrared) interface circuit and a serial interface circuit, and to provide an information processor using the same. <P>SOLUTION: This interface circuit comprises an output terminal, an optical interface circuit part generating an optical driving signal to drive an optical driver, a serial interface circuit part generating a serial driving signal to drive a serial output driver, an interface selection circuit selecting the optical interface circuit part or the serial interface circuit part, and a switch circuit that is provided among the optical interface circuit part, the serial interface circuit part and the output terminal and that becomes off at the time of reset. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an interface circuit and an information processing apparatus using the interface circuit, and more particularly to an interface circuit equipped with an IR (Infrared) interface circuit and a serial interface circuit, and an information processing apparatus using the interface circuit.

In recent years, with the development of computer systems and electronic devices, data communication between a plurality of devices has been frequently performed, and a communication function using infrared rays that does not require connection of a cable or the like is required. Yes. When performing data communication, it is desirable to be able to communicate with devices of various manufacturers regardless of the manufacturer. For this reason, IrDA (Infrared
Data Association) establishes regulations regarding communication functions using infrared rays.

On the other hand, a serial interface circuit and an IrDA interface circuit are mounted in advance so as to be compatible with various interfaces in computer systems, electronic devices, and the like, and can be switched and used.

FIG. 10 shows a block diagram of a conventional personal computer. The conventional personal computer 1 has an interface compliant with IrDA, and outputs from the CPU 2 that processes data, the I / O controller 3 that performs signal conversion for connecting the CPU 2 and an external device, and the output from the I / O controller 3. DC component removing circuit 4 that removes a DC component from the transmitted signal, IR driver 5 that emits infrared light in accordance with the transmission signal from which the DC component has been removed by the DC component removing circuit 4, and detection of power-on. A system reset circuit 6 that generates a system reset signal to be reset and supplies it to the CPU 2 is configured.

The I / O controller 3 includes a CPU interface circuit unit 3a for connecting to the CPU 2, an IR interface circuit unit 3b for generating a transmission signal for driving the IR driver 5, and a serial for generating a transmission signal for driving the serial driver. The interface circuit unit 3c, the IR interface circuit 3b, or the serial interface circuit 3c are configured by a switch 3d and an interface selection circuit unit 3e that switches the switch 3d in response to an instruction from the CPU interface circuit 3a.

FIG. 11 shows an operation waveform diagram of a conventional example. 11A is a power supply, FIG. 11B is a reset signal, FIG. 11C is an output transmission signal TxD ₁ of the I / O controller 3, FIG. 11D is an interface switching signal of the interface selection circuit unit 3e, and FIG. An operation waveform diagram of the output transmission signal TxD ₂ of the component removal circuit 4 is shown.

When the personal computer 1 is turned on at time t ₁ , the system reset circuit 8 outputs a reset signal at time t ₂ delayed by a predetermined time T ₁ . When the reset signal is supplied from the system reset circuit 8 at time t2, the CPU ₂ executes the startup software.

The reset signal from the system reset circuit 8 is also supplied to the interface selection circuit unit 3e of the I / O controller 3 to select the serial interface circuit unit 3c. The interface selection circuit unit 3e switches the switch 3d to the contact b in response to a selection signal from the interface selection circuit unit 3e, and selects the serial interface circuit unit 3c. Since the serial interface circuit 3 which is a standard, such as to output the normal high level, the output drive signal of the I / O controller 3 at time t ₂ as shown in FIG. 11 (C) becomes a high level. Time t ₃
When the startup software of the CPU 2 is finished, the CPU 2 supplies a command for selecting the IR interface circuit unit 3b set by the software to the CPU interface circuit 3a.

The CPU interface circuit 3a issues a command for selecting the IR interface circuit unit 3b to the interface selection circuit unit 3e in accordance with a selection command from the CPU 2. The interface selection circuit unit 3e switches the switch 3d to the contact point a in response to a selection command from the CPU interface circuit unit 3a, and selects the IR interface circuit unit 3b.

The IR interface circuit unit 3b generates a driving signal that does not continuously emit the infrared light emitting element of the IR driver 5 from the data supplied from the CPU 2 via the CPU interface circuit 3a according to the IrDA standard. To the IR driver 5.

CPU2 is time T ₂ in the serial interface circuit 3c between times t ₂ ~t ₃ is selected by the activation software when it starts. Serial interface circuit 3c is a standard on the normal state of the RS232C are configured to output a high level, the transmission signal TxD ₂ at time T ₂ are set to the high level sequentially.

On the other hand, IR driver 5 is designed such that the output drive signal standards on the I / O controller 3 is the infrared light emitting element emits light at a high level, in this state, the IR driver 5 at the time t ₁ ~ time t ₂ The built-in light emitting element continues to emit light. For this reason, since the life of the light emitting element is reduced or damaged, the direct current component removing circuit 4 is provided on the input side of the IR driver 5 in order to prevent the light emitting element from continuously emitting light.

The DC component removal circuit 4 is composed of a differentiation circuit or the like, and prevents DC components from continuing in response to rising and falling of the transmission signal TxD ₁ shown in FIG. When the DC component removal circuit 4 is provided, the transmission signal is distorted as shown in FIG. 11E, and the current value to be supplied to the IR driver cannot be satisfied.

In order to remove the DC component removal circuit, it is desired that the output signal does not continuously become a constant value.

The present invention has been made in view of the above points, and an object of the present invention is to provide an interface circuit that can output an output signal without making the signal continuously high, and an information processing apparatus using the interface circuit.

The interface circuit of the present invention includes an output terminal, an optical interface circuit unit that generates an optical drive signal for driving the optical driver, a serial interface circuit unit that generates a serial drive signal for driving the serial output driver, An interface selection circuit that selects the optical interface circuit unit or the serial interface circuit unit; and a switch circuit that is provided between the optical interface circuit unit and the serial interface circuit unit and the output terminal and is turned off at the time of reset. Have.

According to the present invention, when reset, the output of the serial interface circuit unit is not supplied to the output terminal by the switch circuit. Therefore, when the optical driver connected to the output terminal is selected as the interface, the optical driver Therefore, a continuous high-level signal is not supplied to the light-emitting diode, so that the light-emitting diode built in the optical driver connected to the output terminal does not emit light longer than necessary and the life of the light-emitting diode is extended. Can do.

As described above, according to the present invention, the signal from the serial interface circuit unit is inverted and output at the time of reset, and the signal from the optical interface circuit unit can be output in a non-inverted state at the end of the reset. It has the feature of being able to output without making it a signal that goes high continuously.

FIG. 1 shows a block diagram of a first embodiment of the present invention. In this embodiment, the case where the interface circuit of the present invention is mounted on a personal computer having an interface compliant with IrDA will be described.

The personal computer 11 of this embodiment is connected to a CPU 12 that processes data, an I / O controller 13 that performs signal conversion for connecting the CPU 12 to an external device, and an I / O controller 13. An interface determination circuit 14 that determines an interface to be used, an IR driver 15 that emits infrared light in accordance with a transmission signal output from the I / O controller 13, and a system reset signal that detects power-on and resets the system is generated. The system reset circuit 16 is supplied to the CPU 2.

The I / O controller 13 is a one-chip IC, and is used to drive a CPU interface circuit unit 13a that connects to the CPU 12, an IR interface circuit unit 13b that generates a transmission signal for driving the IR driver 15, and a serial driver. The interface selection circuit unit 13e for switching the switch 13d in response to an instruction from the CPU interface circuit unit 13a, the switch 13d for selecting the serial interface circuit unit 13c, the IR interface circuit unit 13b, or the serial interface circuit unit 13c that generates the transmission signal Consists of.

I / O controller 13 is newly provided external control terminal T _C for controlling the interface selection circuit unit 13e, the internal IR interface circuit 13b or the serial interface by the interface determination signal supplied to the external control terminal T _C Any one of the circuit portions 13c can be selected. The output signal of the interface determination circuit 14 is supplied to the external control terminal T _C newly set in the I / O controller 13.

The interface determination circuit 14 is connected to the CPU 12, generates a determination signal for selecting the IR interface circuit unit 13 b or the serial interface circuit unit 13 c in accordance with a selection command supplied from the CPU 12, and the I / O controller 13 supplied to the external control terminal T _C.

FIG. 2 shows an operation flowchart of the first embodiment of the present invention. When the power is turned on, the system reset circuit 16 detects this and supplies a reset signal to the CPU 12, the I / O controller 13, and the interface determination circuit 14. When receiving a reset signal from the system reset circuit 16, the CPU 12 is reset and starts a program (steps S1-1, S1-2, S1-3).

When the interface determination circuit 14 receives the reset signal supplied from the system reset circuit 16, the interface determination circuit 14 turns on a selection flag for selecting a preset interface circuit and sends a determination signal for selecting the IR interface circuit unit 13b to the I / O controller. 13 for supplying the external control terminal T _C of.

I / O interface selection circuit 13e of controller 13 switches the switch 13d in accordance with the determination signal to select the IR interface circuit 13b supplied via the external control terminal T _C from interface determination circuit 14 to the contact b selection signal Is supplied to the switch 13d. The switch 13d is switched to the contact b in response to a selection signal for switching to the contact b supplied from the interface selection circuit unit 13e, and connects the CPU interface circuit unit 13a to the IR interface circuit unit 13b (step S1-4).

According to this embodiment, since the I / O controller 13 such as at power-on be reset, the choice of the interface is determined by the signal supplied to the external control terminal T _C, the serial interface circuit by the reset operation 13c is no longer selected. For this reason, a continuous high level signal is not supplied to the IR driver 15, so that the light emitting diode or the like built in the IR driver 15 does not emit light longer than necessary, thereby extending the life of the light emitting diode. Can do.

FIG. 3 shows a block diagram of the second embodiment of the present invention. The personal computer 21 of this embodiment is connected to a CPU 22 that processes data, an I / O controller 23 that performs signal conversion for connecting the CPU 22 to an external device, and an output terminal T _OUT of the I / O controller 23. An inversion circuit 24 that inverts the output signal of the / O controller 23, an IR driver 25 that emits infrared light in response to the transmission signal inverted by the inversion circuit 24, and a system reset signal that detects power-on and resets the system The system reset circuit 26 supplies the CPU 2.

The I / O controller 23 is formed of a one-chip semiconductor device, and drives a CPU interface circuit unit 23a for connecting to the CPU 22, an IR interface circuit unit 23b for generating a transmission signal for driving the IR driver 25, and a serial driver. Of the serial interface circuit unit 23c for generating a transmission signal for switching, the switch 23d for switching the connection between the CPU interface circuit unit 23a and the IR interface circuit unit 23b or the serial interface circuit unit 23c, the IR interface circuit unit 23b, and the serial interface circuit unit 23c. One of the switch 23e that switches the path of the output signal, the interface selection circuit unit 23f that controls the switches 23d and 23e in accordance with an instruction from the CPU interface circuit unit 13a, and the switch 23e. It provided the road, composed of inverting circuit 23g for inverting the output signal.

The interface selection circuit unit 23f of the I / O controller 23 switches connection contacts of the switches 23d and 23e according to a command supplied from the CPU interface circuit unit 23a. When a command for selecting the IR interface circuit unit 23b is supplied from the CPU interface circuit unit 23a, the contact of the switch 23d, 23e is switched to the contact b side, and when a command for selecting the serial interface circuit unit 23c is supplied, the switch 23d, The contact of 23e is switched to the contact a side.

FIG. 4 shows an operation flowchart of the second embodiment of the present invention. When the power is turned on, the system reset circuit 26 detects this and supplies a reset signal to the CPU 22 and the I / O controller 23. When receiving a reset signal from the system reset circuit 16, the CPU 22 is reset and starts a program (step S2-1).

The I / O controller 23 also receives the reset signal (step S2-2), and the interface selection circuit unit 23f outputs a signal for selecting the serial interface circuit unit 23c. When receiving the reset signal, the interface selection circuit unit 23f switches the contacts of the switches 23d and 23e to the contact a side. When the contact of the switch 23d is switched to the contact a side, the output of the serial interface circuit unit 23c is supplied to the switch 23e. At this time, the serial interface circuit unit 23c is set to high level because the output is normally set to be fixed at high level.

The output high level signal of the serial interface circuit unit 23c is supplied to the switch 23e, and is output from the I / O controller 23 without being output from the inverting circuit 23g via the contact a. The output high level signal of the serial interface circuit unit 23 c output from the I / O controller 23 is inverted to a low level by the inversion circuit 24 and supplied to the IR driver 25.

When the reset is completed, the CPU 22 supplies the I / O controller 23 with an instruction for selecting an interface set in advance in the program, in this embodiment, the IR interface circuit unit 23b (steps S2-3 and S2-4). When the CPU interface circuit unit 23a of the I / O controller 23 receives an instruction to select the IR interface circuit unit 23b from the CPU 22, the CPU interface circuit unit 23a issues an instruction to switch the switches 23d and 23e to the contact point b to the interface selection circuit unit 23f. When the interface selection circuit unit 23f receives a command to switch the contacts of the switches 23d and 23e to the contact b from the CPU interface circuit unit 23a, the interface selection circuit unit 23f switches the contacts of the switches 23d and 23e to the contact b.

When the contact of the switch 23d is switched to the contact b, the CPU interface circuit unit 23a and the IR interface circuit unit 23b are connected, and a signal that does not have a high level compliant with IrDA is output from the IR interface circuit unit 23b. The output signal of the IR interface circuit unit 23b is supplied to the switch 23e.

Since the contact of the switch 23e is switched to the contact b, the output signal of the IR interface circuit unit 23b is supplied to the inverting circuit 23g and inverted. The signal inverted by the inverting circuit 23g is returned to the original state via the inverting circuit 24 and supplied to the IR driver 25. Therefore, the IR driver 25 is supplied with the output signal of the IR interface circuit unit 23b.

According to the present embodiment, when the I / O controller 13 is reset at the time of power-on or the like, even if the serial interface circuit unit 23c is selected by the reset operation, the output high level signal of the serial interface circuit unit 23c is switched 23d and 23e are supplied to the IR driver 25 via the inverting circuit 24, so that they are inverted and supplied as a low level signal, and the IR driver 25 is not supplied with a signal that continuously becomes high level.

After the reset, the IR interface circuit unit 23b is selected by the switches 23d and 23e, and a signal whose high level is not continuous in accordance with IrDA is supplied to the IR driver 25 through the inverting circuits 23g and 24. A signal based on IrDA in the IR interface circuit unit 23b is supplied to the IR driver 25 without being inverted by the inverter circuits 23g and 24.

As described above, when the IR driver 25 is selected as an interface, a continuous high-level signal is not supplied to the IR driver 25. Therefore, a light emitting diode or the like built in the IR driver 25 emits light longer than necessary. Thus, the lifetime of the light emitting diode can be extended.

FIG. 5 shows a block diagram of a third embodiment of the present invention. The personal computer 31 of this embodiment is connected to a CPU 32 that processes data, an I / O controller 33 that performs signal conversion for connecting the CPU 32 to an external device, and an output terminal T _OUT of the I / O controller 33. The switch circuit 34 that controls the switching of the output signal of the / O controller 33, the interface selection circuit 35 that controls the switching of the switch circuit 34 according to the signal supplied from the CPU 32 to the I / O controller 33, and the switch circuit from the I / O controller 33 In response to a signal supplied via 34, an IR driver 36 that emits infrared rays, a system reset signal that detects power-on and resets the system is generated, and is sent to the CPU 2, the I / O controller 33, and the interface selection circuit 35. Supply system reset circuit 37 Configured.

Since the CPU 32, the I / O controller 33, the IR driver 36, and the system reset circuit 37 have the same configuration as the conventional one, description thereof is omitted. The switch circuit 34 is provided between the I / O controller 33 and the IR driver 36 and turns on / off the connection between the I / O controller 33 and the IR driver 36 in accordance with a selection signal from the interface selection circuit 35.

The interface selection circuit 35 turns off the switch circuit 34 when the I / O controller 33 is reset, and turns on the switch circuit 34 when the IR driver 36 is selected. FIG. 6 shows an operation flowchart of the interface selection circuit of the third embodiment of the present invention.

When the power is turned on, the system reset circuit 37 detects this and supplies a reset signal to the CPU 32, I / O controller 33, and interface selection circuit 35. When the CPU 32 receives a reset signal from the system reset circuit 37, the CPU 32 is reset and starts a program.

When the interface selection circuit 35 detects the reset signal, it turns off the switch circuit 34 (steps S3-1 and S3-2). At this time, when the interface selection circuit unit 33e of the I / O controller 33 receives the reset signal, the contact of the switch 33d is switched to the contact a side in order to select the serial interface circuit unit 33c. When the contact of the switch 33d is switched to the contact a side, the I / O controller 33 outputs a signal of the serial interface circuit unit 33c. At this time, the serial interface circuit unit 33c is set to the high level because the output is normally set to be fixed at the high level.

The interface selection circuit 35 turns off the switch circuit 34 when receiving the reset signal, and turns on the switch circuit 34 when the IR driver 36 of the I / O controller 33 is selected (steps S3-3 and S3-4). For this reason, the output signal of the I / O controller 33 is supplied to the IR driver 36.

According to the present embodiment, when the I / O controller 33 is reset at the time of power-on or the like, the connection between the I / O controller 33 and the IR driver 36 is disconnected, and the output of the serial interface circuit unit 33c is the IR driver 36. Therefore, when the IR driver 36 is selected as an interface, a continuous high level signal is not supplied to the IR driver 36. Therefore, a light emitting diode or the like built in the IR driver 36 is required. It is possible to extend the life of the light emitting diode without emitting light longer than that.

For example, the switch circuit 34 is generally constituted by an IC of a buffer circuit of model number HC125, and the interface selection circuit 35 is connected to the gain control terminal of the IC, and a low-level control signal is supplied at the time of reset, and the reset is completed. This can also be realized by supplying a high-level control signal at that time.

FIG. 7 is a block diagram showing the main part of the fourth embodiment of the present invention. The personal computer 41 of this embodiment has an interface compliant with IrDA. The CPU 42 processes data, the I / O controller 43 performs signal conversion for connecting the CPU 42 to an external device, and the I / O controller 43. IR driver 44 that emits infrared light in response to a transmission signal output from the CPU, a system reset signal that detects the power-on to reset the system and generates a system reset signal that is supplied to the CPU 2, and a clock that generates a clock signal The generating circuit 46 is configured.

The present embodiment is characterized by the IR driver 44 and the clock generation circuit 46, and the other configurations are the same as those of the conventional configuration, and the description thereof is omitted. FIG. 8 is a block diagram of an IR driver according to the fourth embodiment of the present invention. The IR driver 44 of this embodiment includes a driver 47 that amplifies a transmission signal supplied from the I / O controller 43, a light emitting diode 48 that generates infrared light in accordance with an output signal of the driver 47, and between the driver 47 and the light emitting diode 48. The count is started by the rise of the transmission signal from the switch 49 and the I / O controller 43 that controls the supply of the signal from the driver 47 to the light emitting diode 48, and the clock signal from the clock generation circuit 46 is counted. The counter 50 is configured to turn off the switch 49 when a predetermined count value is reached.

FIG. 9 shows an operation waveform diagram of the fourth embodiment of the present invention. 9A is an output clock signal of the clock generation circuit 46, FIG. 9B is an output transmission signal of the I / O controller 43, FIG. 9C is a switch control signal that is an output of the counter 50, and FIG. The lighting state of is shown.

According to this embodiment, when the I / O controller 43 is reset and the signal from the serial interface circuit unit 43c is supplied to the IR driver 44, the counter 50 counts the clock supplied from the clock generation circuit 46. Start. A predetermined digit of the counter 50 is supplied to the switch 49 as a switch control signal. When the predetermined value is reached, the switch control signal becomes a high level and the switch 49 is turned off. For this reason, the light emitting diode 48 is turned off after the high level period of the transmission signal reaches a predetermined value.

Therefore, according to this embodiment, when the high level exceeds a predetermined time, the switch is turned off and the supply of the drive signal to the light emitting diode 48 is stopped, so that the light emitting diode 48 emits light for a predetermined time or longer. There is no.

It is a block block diagram of 1st Example of this invention. It is an operation | movement flowchart of 1st Example of this invention. It is a block block diagram of 2nd Example of this invention. It is an operation | movement flowchart of the I / O controller of 2nd Example of this invention. It is a block block diagram of 3rd Example of this invention. It is an operation | movement flowchart of the interface selection circuit of 3rd Example of this invention. It is a block block diagram of 4th Example of this invention. It is a block block diagram of IR driver of 4th Example of this invention. It is an operation | movement waveform diagram of IR driver of 4th Example of this invention. It is a block block diagram of an example of the past. It is an operation | movement waveform diagram of an example of the past.

Explanation of symbols

11, 21, 31, 41 Personal computer 12, 22, 32, 42 CPU
13, 23, 33, 43 I / O controllers 15,25,36,44 IR driver 16,26,37,45 system reset circuit 14 interface determination circuit T _C external control terminals 23d, 23e switches 23 g, 24 inverting circuit 34 switches Circuit 35 Interface selection circuit 46 Clock generation circuit 47 Driver 48 Light emitting diode 49 Switch 50 Counter

Claims (2)

An output terminal;
An optical interface circuit unit for generating an optical drive signal for driving the optical driver;
A serial interface circuit unit for generating a serial drive signal for driving the serial output driver;
An interface selection circuit for selecting the optical interface circuit unit or the serial interface circuit unit;
An interface circuit comprising: a switch circuit which is provided between the optical interface circuit unit and the serial interface circuit unit and the output terminal and which is turned off at reset. An information processing apparatus comprising the interface circuit according to claim 1.

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