JPH0731569B2 - Input/Output Devices - Google Patents

Description

Description: FIELD OF THEINVENTION The present invention relates to an interface circuit for an input/output device capable of transferring data between an input/output device and an external device such as a personal computer.

Summary of the Invention

This invention is an input/output device which performs two-way (send/receive) data transfer with an external device (for example, a concept of exchanging data between an external device such as a personal computer and a watch is disclosed in Japanese Patent Laid-Open Publication No. 57-143663), in which the transmitting output transistor is connected to the input end of the receiving input signal level interface circuit in an open collector configuration with the external device via a diode, thereby commonizing the signal terminals for sending and receiving and thereby reducing the number of connector contacts with the external device.

PRIOR ART

The interface circuit of a conventional portable small information device (a watch which transmits and receives data with the above-mentioned personal computer) was of the configuration shown in FIG. 3, which is already commercially available, or of the configuration shown in FIG. 5, as disclosed in Japanese Patent Application No. 59-36779.

In the conventional interface circuit shown in FIG. 3, 31 is an input signal level interface circuit, 32, 33, 34 are connection terminals between external devices... OUT, GND, IN, 35 is a CPU (central processing unit), 36 is an input/output means, and 37 is a 3V output lithium battery.

When the watch receives data from the computer, the input signal (IN) of the RS-232c signal format of ±12V becomes a signal (S) of GND--3V, as shown in the voltage waveform in Figure 4a.
On _the other hand, when data is sent from the watch to the computer, a GND- to -3V signal is output directly from S _OUT of the CPU 35 to the OUT terminal of the external device connection terminal 32, as shown in Figure 4b.

In this case, three contacts, GND, IN, and OUT, are required for contact with the outside, so a mini stereo pin jack is used as the connector, as shown in Figure 8. In Figure 8, 81 is a mini stereo pin plug, and 82 is the pin jack part stored inside the watch case.

This pin jack portion 82 has a hole shape for receiving a pin plug, and therefore has many problems in terms of moisture resistance, dust resistance, and aesthetics.

FIG. 5 shows another conventional interface circuit, which is configured to transfer data only from a computer to a watch, and is described in detail in Japanese Patent Application No. 59-36779.

In FIG. 5, 51 is an input signal level interface circuit, 53 and 54 are connection terminals between an external device (computer) . . . GND, SIG terminals, 55 is a CPU, 56 is an input/output means, 57 is a 3V
It is a lithium battery with a voltage of

The interface circuit in Fig. 5 is designed to interface not only with RS-232c standard format signals of GND ±12V, but also with TTL level data signals between the two values of GND and +5V. A Zener diode 67 with a Zener voltage of 3.5V is inserted so that the transistor 61 does not turn on when the SIG input terminal is at the GND level. Resistor 5
The constants of 9, 60, 62, diode 58, Zener diode 67, and transistor 61 are set so that the SIG input is between GND+3V and GN
To prevent transistor 61 from turning on within the voltage range of D-12V,
The transistor 61 is set to turn ON when the voltage ranges from GND+3V to GND+12V.

The voltage waveforms of the interface circuit are depicted in Figures 6a and 6b.

The diode 58 in FIG. 5 and the diode 38 in FIG.
It is inserted to protect the base-emitter of the transistor from a large reverse voltage when -12V is applied to the input terminal.

Fig. 7 shows a conceptual diagram of a connector actually used in a watch that employs the interface circuit of Fig. 5. 71 is a data input terminal embedded in the side of the case via an insulator, and the case back is at GND potential. The connector is pushed in from the case back as shown in the conceptual diagram and fixed in place, and pin 72 comes into contact with input terminal 71 and spring contact 73 comes into contact with the case back, establishing electrical continuity between the watch and the connector.

The connector in Figure 7 has a simple structure and is excellent in terms of reliability, aesthetics, and cost because there are no moving parts or holes in the watch section, but its biggest problem is that data transfer is only possible in one direction.

[Problems and Objectives of the Invention]

In the prior art, as described above, it is possible to obtain a highly reliable and practical connector case contact structure with one contact between the GND and the signal terminal, but data can only be transferred in one direction from the external device to the small portable information device. On the other hand, if data transfer in two directions, sending and receiving, is to be performed, two signal terminal contacts are required, which poses the problem that a connector case contact structure that is excellent in terms of reliability, appearance and structure cannot be obtained.

The present invention aims to eliminate such problems, and its purpose is to use an input/output device that uses a different power supply voltage from that of the external device, provide one input/output terminal for data exchanged with the external device, and realize two-way communication between the external device and the input/output device with a simple structure.

[Means for solving the problems]

The input/output device of the present invention has an input/output terminal for connecting to an external device and inputting/outputting data bidirectionally with the external device, and a first input/output device for operating the external device.
an input/output device that operates at a second voltage level different from the voltage level of the first voltage level, the input/output device comprising: a level conversion means for converting the level of input data of the first voltage level input from the external device via the input/output terminal to the second voltage level; a CPU for processing the input data level converted by the level conversion means; and a switching element having one terminal connected to a power supply of the second voltage level and another terminal connected to the input/output terminal, the switching element being turned on and off based on output data output from the CPU to the external device, the switching element causing a current to flow through a load resistance of the external device connected to the input/output terminal when turned on;
The output data of the second voltage level is converted to the first voltage level.

The present invention is also characterized by comprising a first diode for preventing a reverse current from the input/output terminal to the first level conversion means.

The power supply circuit further comprises a second diode for preventing a reverse current from the input/output terminal to the switching element.

[Example]

FIG. 1 shows an interface circuit of a watch according to an embodiment of the present invention. The connection terminal 3 for connecting to an external device is a ground terminal (GND), 4 is a signal terminal (SIG), and 1 is an input signal level interface circuit which is composed of a diode 8, a base resistor 9, a base bias resistor 10, a transistor 11, and a collector load resistor 12.

The output signal interface circuit 2 includes a transistor 14,
It consists of a diode 13.

In the figure, reference numeral 5 denotes a CPU, 6 denotes input/output means, and 7 denotes a lithium battery having a voltage of 3V as a power source.

FIG. 19 shows a simplified model circuit of a receiving circuit required when sending a data signal from a watch to an external device, either in the external device or in an adapter interposed between the external device and the watch.

As can be seen by comparing FIG. 1 with the conventional interface circuit shown in FIG. 3, the embodiment circuit of the present invention adds an output signal interface circuit 2 consisting of a second transistor 14 and a second diode 13 to the conventional interface circuit, and shares the signal OUT and IN terminals to form a single signal terminal.

To explain its operation, when data is input from an external device such as a personal computer to the watch, the first
As shown in Figure 2a, which shows the voltage waveform when data is input to the circuit, the SIG terminal 4 has a voltage level of GND-12V and a voltage level of GND+12V.
When a signal with a voltage level of V is applied, the base voltage Sa after passing through the diode 8 and the base resistor 9 has an amplitude between _VSS and _VSS + 0.8 V. The input signal interface circuit 1 performs voltage level determination and phase inversion amplification, and its output is
The data signal is converted to a binary voltage level of V _SS (-3V) and V _DD (0VGND) and input to the serial signal input 15 (S
_IN ).

In this data signal input mode, the serial signal output from the CPU is kept at a high (V _DD ) level.
Therefore, when data is being input, the PNP transistor 14 remains OFF and has no effect on the input data.
Reference numeral 13 is inserted for the purpose of preventing a current from flowing due to the forward characteristic of the diode between the collector and base of transistor 14 when the SIG input signal level exceeds the GND (V _DD ) level.

In the data output mode from the watch to a personal computer, the serial signal output 16 of the CPU is connected between V _DD and V
The output signal interface circuit 2 outputs a binary signal _SS to control the ON/OFF of the transistor 14.
It is configured as an open collector for external devices,
Power supply 17 in the external device or adapter, load resistor 18,
GND terminal 3, transistor 14, diode 13, SIG terminal 4
The data signal is transferred by a loop through the

Therefore, when the CPU output 16 is high (V _DD ), the transistor
When the SIG terminal 4 (output to the outside) is in the OFF state, the voltage of the power supply 17 of the external device or adapter becomes negative from the GND (V _DD ) level. The CPU output 16 is Low (V _SS ).
When this occurs, transistor 14 turns ON and current flows from power supply 17 through the path of transistor 14, diode 13 and resistor 18, so that the potential of the SIG terminal becomes High (GND - _vDD ; strictly speaking, however, it will be lower by the loss voltage of the transistor Vch and diode voltage _VDI ), and a data signal is sent from the watch to the external device.

The voltage waveform at that time is shown in Figure 2b.

During data output, the output signal also flows into the input signal level interface circuit, but the SIG terminal voltage is G
Since the constants of the input signal level interface circuit are set so that transistor 11 does not turn on at the ND (V _DD ) level, no problems arise.

As described above, according to the present invention, two-way data transmission and reception between a small portable information device such as a watch and an external device such as a personal computer can be realized by using a common ground terminal (GND terminal) and only one signal terminal, so that the system shown in Figure 7 can be adopted for the connector.

A second embodiment of the present invention is shown in FIG.
An output signal interface circuit is added to the conventional system shown in FIG. 5, making it possible to transfer data in both directions using only one signal terminal.

In FIG. 9, the connection terminal 93 with the external device is a common/ground terminal (GND), 94 is a signal terminal (SIG), 91 is an input signal level interface circuit, and includes a diode 98, a Zener diode 90, a base resistor 99, a base bias resistor 100, and a N
It consists of a PN transistor 101 and a collector load resistor 102.

The output signal interface circuit 92 includes a PNP transistor 1
04, and diode 103.

Reference numeral 95 denotes a CPU, 96 denotes input/output means, and 97 denotes a lithium battery power supply having a voltage of 3V.

Fig. 109 is necessary when sending a data signal from a watch to an external device, as in the previous embodiment. It is a simple equivalent model of a data receiving circuit in the external device or in an adapter interposed between the external device and the watch.

The interface circuit of the portable small information device based on Fig. 9 and the operation and function between the device and the external device are almost the same as those of the first embodiment shown in Fig. 1, so they are omitted here. However, the voltage waveforms at the main points are shown in Figs. 10a, 10b, and 10c.
As shown in.

Figure 10a shows the voltage waveform when an RS-232c data signal of GND +12V/-12V is input, Figure 10b shows the voltage waveform when a data signal with a TTL level voltage value of GND (0V)/+5V is input, and Figure 10c shows the voltage waveform when data is output in the watch's data transmission mode.

The second embodiment circuit (FIG. 9) differs from the first embodiment circuit (FIG. 1) in that data transmission is sent to the external device via the base resistor 99. This prevents an excessive current from flowing through the transistor 10 during data transmission, regardless of the circuit of the external device.
4, it has the effect of protecting the diode 103 from current flowing through it. Since the resistor 99 is set to 10 KΩ to 100 KΩ, it is desirable to set the load resistor 108 of the receiving circuit of the external device to several hundreds of KΩ to several MΩ.

5, the Zener diode 90 not only enables reception of a data signal at a TTL voltage level, but also prevents the receiving transistor 101 from being turned on even if the transistor 104 is turned on during data transmission.
It also has the effect of preventing base current from flowing into the

FIG. 11 shows a circuit in which the basic circuit of the present invention shown in FIG. 9 has been partially modified for mass production design.

In FIG. 11, reference numeral 110 denotes a Zener diode that protects the internal circuit from static electricity entering from the outside through the external connection terminal, and two Zener diodes are mounted in one package.

Reference numeral 112 denotes a diode pack in which two diodes are similarly mounted in one package, and reference numeral 115 denotes a transistor package in which a transistor and a base bias resistor are built into one package.

In both Figures 9 and 11, just like the first embodiment described in Figure 1, data can be transferred in both directions between the external device and the device through a single signal terminal, and therefore the connector system shown in Figure 7 can be adopted.

As described above in detail, according to the present invention, a data output signal interface circuit consisting of transistors and diodes is provided and wired to a single signal terminal so as to be an open collector type with respect to an external device, thereby making it possible to share the input signal terminal and the output terminal.

This not only has the benefit of reducing costs by reducing the number of external signal connection terminals by one, but also has the enormous benefit of allowing the adoption of a connector structure such as that shown in Figure 7, which is highly reliable and aesthetically pleasing, by having only one signal connection terminal, especially in small portable information devices such as watches.

The present invention makes it possible for the first time to realize a truly practical, reliable, and aesthetically pleasing portable information device capable of two-way data transfer with an external device.

Needless to say, the portable small-sized information device according to the present invention is not limited to a watch, and the present invention can be applied to portable small-sized information devices of any shape and size that does not deviate from the concept and spirit of the present invention, for example, the size of a credit card.

[Effects of the Invention]

The input/output device of the present invention includes a switching element having one terminal connected to a power supply of a second voltage level and another terminal connected to an input/output terminal, and turned on and off based on output data output from a CPU to an external device, the switching element causing a current to flow through a load resistor of the external device connected to the input/output terminal when the switching element is turned on;
By providing a configuration for converting the level of output data of the second voltage level to the first voltage level, the output level can be converted by utilizing the load resistance of the external device connected to the input/output terminal, and there is no need to provide a separate step-up/step-down power supply for converting to the voltage level of the external device within the input/output device. A single terminal can be used as both the input terminal and the output terminal of the input/output device, resulting in the effect of providing an inexpensive input/output device.

[Brief description of the drawings]

FIG. 1 is an interface circuit diagram of the present invention. FIG. 2(a) is a voltage waveform diagram of the interface circuit of FIG. 1 when data is input. FIG. 2(b) is a voltage waveform diagram of the interface circuit of FIG. 1 when data is output. FIG. 3 is a conventional interface circuit diagram. FIG. 4(a) is a voltage waveform diagram of the interface circuit of FIG. 3 when data is input. FIG. 4(b) is a voltage waveform diagram of the interface circuit of FIG. 3 when data is output. FIG. 5 is another conventional interface circuit diagram. FIG. 6(a) is a voltage waveform diagram of the circuit of FIG. 5 when RS-232c data is input. FIG. 6(b) is a voltage waveform diagram of the circuit of FIG. 5 when TTL level data is input. FIG. 7 is a conceptual diagram of the connection between a watch and a watch connector. FIG. 8 is another conceptual diagram of the connection between a watch and a watch connector. FIG. 9 is a second embodiment of the interface circuit diagram of the present invention. FIG. 10(a) is a voltage waveform diagram of the circuit of FIG. 9 when RS-232c data is input. Fig. 10(b) is a voltage waveform diagram when TTL level data is input to the circuit of Fig. 9. Fig. 10(c) is a voltage waveform diagram when data is output from the circuit of Fig. 9. Fig. 11 is an interface circuit diagram according to the present invention. 1: Input signal level interface circuit 2: Output signal interface circuit 3: GND terminal 4: Signal terminal 5: CPU 6: Input/output means 7: Power supply battery 8, 13: Diode 9, 10, 12: Resistor 11, 14: Transistor

Claims (3)

[Claims] [Claim 1] An input/output device having input/output terminals for connecting to an external device and for bidirectionally inputting and outputting data to and from the external device, the input/output device operating at a second voltage level different from a first voltage level for operating the external device, the input/output device comprising: level conversion means for converting the level of input data of the first voltage level input from the external device via the input/output terminals to the second voltage level; a CPU for processing the input data level-converted by the level conversion means; and a switching element having one terminal connected to a power supply of the second voltage level and another terminal connected to the input/output terminal, the switching element being turned on and off based on output data output from the CPU to the external device, the switching element passing a current through a load resistance of the external device connected to the input/output terminals when turned on,
2. An input/output device comprising: a level converter for converting output data of the second voltage level into the first voltage level. 2. The input/output device according to claim 1, further comprising a first diode for preventing a reverse current from said input/output terminal to said first level conversion means. 3. The input/output device according to claim 1, further comprising a second diode for preventing a reverse current from said input/output terminal to said switching element.