JPH05135219A - Non-contact type ic card system - Google Patents

Abstract

PURPOSE:To effectively transmit abnormality detection information generated by a non-contact type IC card to a reader/writer, and to reduce a power consumption for transmitting the abnormality detection information. CONSTITUTION:At the time of transmitting data RX to an IC card 3, a high frequency signal running through a coil 23 is a constant level, and at the time of transmitting data TX to a reader/writer 2, the high frequency signal currents are amplitude-modulated by the data TX. When an abnormal state is detected by an abnormal state detecting means 13, abnormality detecting information AL in the data transmitting period is supplied to a modulation circuit 6, and the high frequency currents running through the coil 23 are amplitude modulated. The high frequency signal is amplitude-demodulated, and the abnormality detection information is extracted and transmitted to a CPU 28 by a receiving circuit 27. The CPU 28 fetches an output of the receiving circuit 27 in the transmitting period of the data RX and TX. When the data TX are transmitted from the IC card 3, the receiving circuit 27 extracts the data TX, and transmits the data TX to the CPU 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type IC card and a reader / writer which are magnetically coupled to each other by a coil means and modulates a high frequency signal sent from the reader / writer to the non-contact type IC card with data. The present invention relates to a system that enables data transmission between the reader / writer and the non-contact type IC card.

[0002]

2. Description of the Related Art A conventional IC card has an electric contact, and the electric contact is brought into contact with the electric contact of a recording medium writing / reading device (reader / writer) to connect to the reader / writer. However, there has been proposed a non-contact type IC card in which a coil is used instead of an electrical contact, and the reader / writer and the coil are magnetically connected in a non-contact manner. An example of a conventional non-contact type IC card and its reader / writer will be described below with reference to FIG. However, 1 is a host, 2 is a reader / writer, 23 is a coil, 24 is a driver, 25 is a transmission circuit, 26 is an oscillation circuit, 27 is a reception circuit, 28 is a CPU (central processing unit),
29 is a current detecting means, 3 is a non-contact type IC card (hereinafter,
4 is a transmitting / receiving circuit, 40 is a coil, 41 is a rectifying circuit, 42 is a power supply circuit, 43 is a receiving circuit, 44 is a transmitting circuit, 45 is a timing circuit, 46 is a reset circuit, and 5 is a CPU. ..

In the figure, when data is transmitted from the reader / writer 2 to the IC card 3, the data from the host 1 or the like is processed by the CPU 28 in the reader / writer 2 and sent to the transmission circuit 25. In the transmission circuit 25, a high-frequency signal having a constant amplitude is supplied as a carrier from the oscillation circuit 26, the carrier is modulated with data, and a modulated high-frequency signal is output. In this case, the modulation method may be any modulation method such as frequency modulation or phase modulation as long as the amplitude is constant. The modulated high frequency signal output from the transmission circuit 25 is supplied to the coil 23 via the driver 24.

At this time, the IC card 3 is mounted on the reader / writer 2, and the coil 23 of the reader / writer 2 and the coil 40 of the IC card 3 are electromagnetically coupled.

Therefore, in the IC card 3, the modulated high frequency signal is supplied from the coil 23 of the reader / writer 2 to the transmitting / receiving circuit 4 via the coil 40 of the IC card 3. The modulated high frequency signal is rectified by the rectifier circuit 41 and supplied to the power supply circuit 42 to generate a predetermined power supply voltage required for each part of the IC card 3. The output signal of the coil 40 is also supplied to the receiving circuit 43, the data is demodulated, and the CPU 5
Is supplied to. The CPU 5 operates based on the outputs of the timing circuit 45 and the reset circuit 46, processes the supplied data, and writes a predetermined one in a memory (not shown).

When data is sent from the IC card 3 to the reader / writer 2, the transmitter circuit 25 of the reader / writer 2 outputs a high-frequency signal having a constant amplitude without modulation.
IC card 3 via driver 24 and coils 23 and 40
Sent to. In the IC card 3, the high frequency signal is rectified by the rectifier circuit 41 and the power supply circuit 42 is operated as in the above.
And the predetermined power supply voltage is generated.

On the other hand, in the IC card 3, the data read from the memory (not shown) is processed by the CPU 5 and supplied to the transmission circuit 44. The transmission circuit 44 is composed of, for example, an additional resistance and a switch, and has data "1" and "0".
This switch turns on and off depending on the bit.

In the reader / writer 2, when the switch of the transmission circuit 44 is turned on and off as described above, the coil 2
The load on No. 3 changes, and thus the amplitude of the high-frequency current flowing through the coil 23 changes. That is, this high frequency current is amplitude-modulated by the data supplied from the CPU 5 of the IC card 3 to the transmission circuit 44. This high frequency current is detected by the current detecting means 29 and demodulated by the receiving circuit 27 to obtain data. This data is processed by the CPU 28 and sent to the host 1 or the like.

By the way, in the conventional contact type IC card, when an abnormal state occurs, the CPU detects it and sends the detection result to the reader / writer. As a result, the host can determine the abnormal state of the IC card and its type.

By the way, in such an IC card 3,
The transmission / reception circuit 4 may be in an abnormal state, and the IC card may be operated in this abnormal state.
In this worst case, the IC card 3 may be destroyed.

On the other hand, the applicant of the present invention has provided a system in which an abnormal state detecting means is provided in the IC card and the detected information is transmitted to the reader / writer in the same manner as the data (special feature). Japanese Patent Application No. 3-205693).

[0012]

By the way, in the above system, when the detecting means detects an abnormal state, the detection information is always continuously sent to the reader / writer. For this reason, power consumption increases.

An object of the present invention is to provide a non-contact type IC card system which solves such a problem, enables effective transmission of abnormal state detection information, and reduces power consumption.

A second object of the present invention is to separate the second data different from the normal data transmitted from the IC card to the reader / writer, for example, the abnormality detection information and the like from the normal data to ensure the data. Non-contact type IC that can detect
To provide a card system.

Furthermore, a third object of the present invention is to simultaneously perform data transmission from the reader / writer to the IC card and data transmission from the IC card to the reader / writer, that is, to ensure the function of full-duplex data transmission. Another object of the present invention is to provide a non-contact type IC card system that can be carried out.

[0016]

In order to achieve the above object, the present invention provides a high-frequency signal sent from a reader / writer in synchronization with the timing of data transmission between the reader / writer and the IC card. Modulation is performed with the second information from the abnormal state detecting means or the like, and the detection information is extracted from the high frequency signal by the reader / writer.

Further, according to the present invention, in the reader / writer, the presence / absence of the second information is determined from the relationship between the level at the terminal end of the data period of the high frequency signal and the level immediately after the terminal end. , The second information is extracted.

[0018]

The CPU in the reader / writer operates according to an instruction from the host, and captures the output of the receiving circuit only during data transmission. Therefore, by sending the detection information to the reader / writer only during this data transmission period, the detection information is surely taken into the CPU, and further, the detection information is not transmitted during the period when the CPU is not taken in, so that there is no waste in this period. Unnecessary power consumption.

Whether the high-frequency signal is transmitted by a modulation method of constant amplitude such as phase modulation or frequency modulation, or whether the data is transmitted by the amplitude method, if the data is transmitted only, the data of the high-frequency signal is transmitted. It is possible to make a part of the modulation period, for example, the level of the terminal end equal to the level of the non-modulation part of the high frequency signal. On the other hand, the detection information is sent to the reader / writer in the same manner as the data sent from the IC card to the reader / writer during the data transmission period, so that the high frequency signal current in the reader / writer is amplitude-modulated by the detection information. Therefore, the level of the specific portion of the data transmission period of the high frequency signal current is equal to the level of the non-modulated portion of the high frequency signal when the detection information is not transmitted, and is different from the level of this non-modulated portion when the detection information is transmitted. It will be. Therefore, the presence / absence of detection information can be reliably determined from the relationship between the level of the specific portion of the data transmission period of the high frequency signal and the level of the non-data transmission period.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a non-contact type IC card system according to the present invention. In the transmitting / receiving circuit section 4 of the IC card 3, 6 is a modulation circuit, 7 is a comparator, 8 is a demodulation circuit, 13 Is an abnormality detection means, and
In the reader / writer 2, 9 is a detection circuit, 10 is an LPF (low-pass filter), 11 is an amplifier, and 12 is a demodulation circuit, and the parts corresponding to those in FIG.

In the figure, when data is sent from the reader / writer to the IC card 3, here, the transmission circuit 25 sends the carrier from the oscillation circuit 26 to "1" from the CPU 28,
It is assumed that the data RX consisting of "0" bits is modulated by a constant amplitude modulation method such as frequency modulation or phase modulation. Therefore, as shown in FIG. 2B, a modulated high frequency wave voltage having a constant amplitude is applied to the coil 23 from the driver 24 with respect to the data RX shown in FIG. Sent to the IC card 3.
In the IC card 3, similar to the IC card 3 shown in FIG. 9, the power supply circuit 42 generates a power supply voltage from the modulated high frequency voltage. Further, the modulated high frequency voltage from the coil 40 is waveform-shaped by the comparator 7, and then supplied to the demodulation circuit 8 and the timing circuit 45, and the timing circuit 45.
Generates a clock. This clock is supplied to the CPU 5 and the demodulation circuit 8 to demodulate the data RX with the "1" and "0" bits from the waveform-shaped modulated high frequency voltage. This data RX is processed by the CPU 5 and stored in a memory (not shown).

When data is sent from the IC card 3 to the reader / writer 2, the data TX consisting of "1" and "0" bits is sent from the CPU 5 to the modulation circuit 6, and this modulation circuit 6 causes the data TX in FIG. As explained, Figure 2
As shown in FIG. 2B for the data TX of FIG.
The high frequency current flowing through the coil 23 is amplitude-modulated by this data TX.

Here, the receiving circuit 27 is the detection circuit 9 and the LP.
F10, amplifier 11, demodulation circuit 12, coil 2
When the high frequency current flowing in 3 is amplitude-modulated, it is demodulated. In this case, this high frequency current is generated by the IC card 3
Since the data TX has been amplitude-modulated, the data TX is demodulated and taken into the CPU 28.

The CPU 28 takes in the output of the data transmission period receiving circuit 27 between the reader / writer 2 and the IC card 3 in response to a command from the host. However,
When only data is transmitted from the reader / writer 2 to the IC card 3 as described above, the amplitude of the high frequency current flowing through the coil 23 varies depending on the transmitted data (see FIG. 2).
(Not shown in FIG. 9B), since it is the self-transmitted data, there is no output from the receiving circuit 27.

By the way, when there is an abnormality in the IC card 3, the abnormality detecting means 13 detects this. So CP
When the anomaly detection means 13 detects an anomaly in U5, the U5 in FIG.
As shown in (d), in synchronization with the period in which the data RX is supplied from the demodulation circuit 8 and the period in which the data TX is supplied to the modulation circuit 6 (that is, the data transmission period between the reader / writer 2 and the IC card 3). , Abnormality detection information AL is supplied to the modulation circuit 6. In the reader / writer 2, data TX from the CPU 5
In the same manner as when is supplied, the high frequency current flowing through the coil 23 is amplitude-modulated by the abnormality detection information AL.
This is shown in FIG. 2C for the data RX of FIG. 2A, but when data is transmitted from the reader / writer 2 to the IC card 3, as shown in the left part of FIG. The high-frequency current that flows is amplitude-modulated only by the abnormality detection information AL, and when transmitting data from the IC card 3 to the reader / writer 2, the high-frequency signal current becomes the abnormality detection information AL as shown in the right part of FIG. Data TX
Amplitude is modulated by and.

The receiving circuit 27 in the reader / writer 2 is
When the data RX is transmitted from the reader / writer 2 to the IC card, only the abnormality detection information AL is output, and when the data TX is transmitted from the IC card 3 to the reader / writer 2, the abnormality detection information AL and the data TX are respectively demodulated. Output. FIG. 2E shows the abnormality detection information A output from the receiving circuit 27.
L is shown.

As described above, in this embodiment, the abnormality detection information AL is sent in synchronization with the data transmission period between the reader / writer 2 and the IC card 3, and the abnormality detection information AL is also sent to the reader / writer 2. Therefore, the abnormality detection information AL is not transmitted except during such a data transmission period, so that the power consumption is significantly reduced as compared with the conventional case where the abnormality detection information is always transmitted.

The CPU in the reader / writer takes in the output of the receiving circuit in accordance with a command from the host, but the conventional half-duplex communication function cannot take in the second data such as the abnormality detection information during data transmission. ..

On the other hand, in the above embodiment, the power consumption due to the wasteful transmission of the abnormality detection information is lost as described above, and the CPU 28 causes the reader / writer 2 to the IC card 3 to operate.
Even in this case, the abnormality of the IC card 3 can be detected by fetching the output of the receiving circuit 27 during the data transmission to and from.

FIG. 3 is a block diagram showing the details of the receiving circuit 27 in FIG. 1, in which 9a and 9b are diodes and 9 is a diode.
c is a resistor, 14 is an S / H (sample hold) circuit, 1
5 is a timing circuit, 16 is a start bit detection circuit,
17 is a flip-flop circuit, 18 is an input terminal, 24
Reference numerals a and 24b are switching transistors, and parts corresponding to those in FIG.

In the figure, the driver 24 outputs a high frequency current i to the coil 23 by alternately turning on and off the switching transistors 24a and 24b.
These switching transistors 24a and 24b are shown in FIG.
It is turned on and off according to the output signal of the transmission circuit 25.

The detection circuit 9 is composed of diodes 9a and 9b and a resistor 9c. When the switching transistor 24a of the driver 24 is turned on, the switching transistor 24a is connected to the coil 23 and the diode 9
When the switching transistor 24b is turned on and the current i flows through the resistor a and the resistor 9c, the current i flows from the diode 9b through the coil 23 and the switching transistor 24b. The detection circuit 9 takes out the voltage v generated in the resistor 9c as a detection output voltage. Therefore, the detected output voltage v is obtained as a voltage when the high frequency current i has one polarity.

Now, looking at the period of data transmission from the IC card 3 to the reader / writer 2, in contrast to the data TX shown in FIG. 4 (a), the high frequency current i is this data TX as shown in FIG. 4 (b). Is amplitude-modulated by. Here, it is assumed that the high-frequency signal i has a large amplitude at the “0” bit of the data TX and maintains the original amplitude of the high-frequency signal at the “1” bit.

Each block of the data RX and TX is 1
It is made up of a START (start) bit, 8-bit data, 1-bit parity, and 1-bit STOP (stop) bit. The START bit is a "0" bit and the STOP bit is a "1" bit. Figure 4 (c)
Indicates the detected output voltage v.

Further, the resistance value of the resistor 9c is set to about the ON resistance of the switching transistors 24a and 24b, and the resistor 9c has almost no influence on the waveform of the high frequency current i.

The detected output voltage v is filtered by the LPF 10 and amplified by the amplifier 11 to generate a signal having a level corresponding to each bit of the data TX (FIG. 4 (a)) as shown in FIG. 4 (d). can get. This signal is a demodulation circuit 12
And is demodulated to the original data TX (FIG. 4 (e)).

This demodulated data TX is also supplied to the start bit detection circuit 16 and the STA is read from the first edge.
Detect RT bit. Timing circuit 15 is this ST
The carrier is reset by the ART bit pulse, the carriers from the oscillation circuit 26 are counted, and the output signal of the amplifier 11 (see FIG.
A sampling clock φk is generated for each bit in (d). This sampling clock φk causes S / H
The circuit 14 samples and holds the output signal of the amplifier 11 and outputs a signal (FIG. 4 (g)) delayed by about 1 bit. This signal is supplied to the demodulation circuit 12.

Further, the timing circuit 15 generates the comparison timing clock φC at the timing immediately after the STOP bit in the output signal of the amplifier 11 (FIG. 4 (d)). The demodulation circuit 12 compares the levels of the output signal of the amplifier 11 and the output signal of the S / H circuit 14 (FIG. 4 (g)) at the timing of the comparison timing clock φc. In this case, the STOP bit of the output signal of the amplifier 11 (FIG. 4 (d)) and the level immediately after it are equal to “L”.
Comparison timing clock φ of signals shown in (d) and (g)
The timing levels of c are the same, and the demodulation circuit 12 determines that there is no abnormality detection information AL.

In the above, only the data TX is transmitted from the IC card 3 to the reader / writer 2, but when the abnormality detection information AL is transmitted at the same time, the high frequency current i is transmitted.
Since the abnormality detection information AL (FIG. 3) is also amplitude-modulated, the output signal of the amplifier 11 differs in the level of the STOP bit period by ΔV depending on the level immediately after that, as shown in FIG. 5 (a). Therefore, this and the output signal of the S / H circuit 14 shown in FIG. 5B differ in level by ΔV at the timing of the comparison timing clock φc (FIG. 5C). If there is such a difference in level, the demodulation circuit 12 determines that there is abnormality detection information AL, and sends a pulse to the flip-flop circuit 17 to trigger it. As a result, the output of the flip-flop circuit 17 becomes "H" as shown in FIG.

Even when the abnormality detection information AL is transmitted during the transmission of the data RX from the reader / writer 2 to the IC card 3, the high frequency current i is amplitude-modulated by the abnormality detection information AL, and the abnormality is similarly detected. The detection information AL can be extracted. However, in this case, the data RX is not demodulated by the demodulation circuit 12. Therefore, the reader / writer 2
Since the CPU 28 of FIG. 1 (FIG. 1) knows that the transmission of the data RX has started, it supplies the pulse synchronized with the START bit of the data RX from the input terminal 18 to the timing circuit 15.

In this way, the abnormality detection information AL sent simultaneously with the data RX, TX can be extracted from the IC card 3. Moreover, in FIG. 3, the data STOP
Since the presence or absence of the abnormality detection information AL is determined by whether the level in bits is equal to or different from the level immediately after that, for example, the coupling state between the coils 23 and 40 varies and the amplitude of the high frequency current i is Even if it is not constant, the presence / absence of the abnormality detection information AL can be surely determined.

FIG. 6 is a block diagram showing the main part of another specific example of the receiving circuit 27 in FIG. 1, in which 19 is a current transformer, 19a is a detection coil, 19b is a resistor, 19c is a magnetic coupling element, and 20 is. The amplifier 21 is an envelope detection circuit, and the parts corresponding to those in the above drawings are designated by the same reference numerals.

In the figure, a current transformer 19 composed of a magnetic coupling element 19c, a detection coil 19a and a resistor 19b for detecting a current (coil current) flowing in the coil 23.
Are provided in series with the coil 23. Magnetic coupling element 1
Reference numeral 9c is, for example, an annular magnetic core, and an electric wire passing through the center hole of the magnetic core serves as a primary coil and is connected to the coil 23. The detection coil 19a is wound around a magnetic core N times (where N is an integer of 1 or more), and a resistor 19b for converting the detection current of the detection coil 19a into a voltage is connected between both terminals of the detection coil 19a. Thus, a so-called current transformer 19 is formed. The high frequency current (FIG. 7A) flowing through the coil 23 is detected by the detection coil 19a, and the resistance 1
After being converted into a high frequency voltage by 9b, it is amplified by the amplifier 20, and the envelope detection circuit 21 performs envelope detection and waveform shaping as shown in FIG. 7B to extract a signal including the data TX and the abnormality detection information AL. It This signal is the third
It is sent to the demodulation circuit 12 and the S / H circuit 14 as shown in the figure.

The magnetic coupling element 19c, the detection coil 19a,
In the current transformer 19 including the resistor 19b, its input impedance is sufficiently small and its voltage drop is sufficiently small regardless of the flowing current, so that the amplitude of the high frequency current applied to the coil 23 is kept substantially constant.

Thus, also in this specific example,
The same effect as the specific example shown in FIG. 3 is obtained.

In FIG. 6, the envelope detection circuit 21
The diode detection circuit and filter are used instead of
As shown in (c), the center level may be detected.

FIG. 8 shows an example of the modulation circuit 6 in FIG. The demodulation circuit 6 includes variable current sources 22a and 22b.
The variable current source 22a is ON / OFF controlled by the data TX from the CPU 5 (FIG. 1).
2b is on / off controlled by the abnormality detection information AL from the CPU 5.

The variable power source 22a is held in the off state when the data TX is not supplied, and the variable current source 22b is turned on during the abnormality detection information AL. Variable power sources 22a, 22
When b is turned on, the amplitude of the high frequency current flowing through the coil 23 in FIG. 1 changes.

[0049]

As described above, according to the present invention,
Since the second information such as the abnormality detection information is sent to the reader / writer in synchronization with the data transmission period between the reader / writer and the IC card, it is effectively transmitted without waste, resulting in significant power consumption. Can be reduced to

Further, according to the present invention, it is possible to realize a full-duplex communication function capable of surely detecting the abnormality detection information even when the second information is transmitted overlapping with the data, and further,
Even if the amplitude of the high-frequency signal is not held constant due to variations in the coupling state of the coil between the reader / writer and the IC card, there is no effect on the detection of the second information.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a non-contact type IC card system according to the present invention.

FIG. 2 is a timing chart showing a transmission operation of data and abnormality detection information of the embodiment shown in FIG.

3 is a configuration diagram showing a specific example of a receiving circuit of the reader / writer in FIG.

FIG. 4 is a timing chart showing the operation of the specific example shown in FIG.

5 is a timing chart showing an operation of extracting abnormality detection information of the specific example shown in FIG.

FIG. 6 is a configuration diagram showing another specific example of the receiving circuit of the reader / writer in FIG.

FIG. 7 is a signal waveform diagram showing an operation of the specific example shown in FIG.

8 is a configuration diagram showing a specific example of a modulation circuit in the non-contact type IC card in FIG.

FIG. 9 is a block diagram showing an example of a conventional non-contact type IC card.

[Explanation of symbols]

 2 reader / writer 3 non-contact type IC card 6 modulation circuit 8 demodulation circuit 9 detection circuit 10 LPF 12 demodulation circuit 13 abnormal state detection means 14 sample hold circuit 15 timing circuit 16 start bit detection circuit 17 flip-flop circuit 19 current transformer 21 envelope Detector circuit 23 coil 27 receiver circuit 40 coil

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunen Ito, Toranomon 1-26-5, Minato-ku, Tokyo, NTT Data Communications Corp. (72) Inventor Takashi Takeuchi Toranomon, Minato-ku, Tokyo 1-26-5 NTT DATA Communications Co., Ltd.

Claims (2)

[Claims] 1. A reader / writer and a non-contact type IC card are magnetically coupled by a coil means, and data transmission between the reader / writer and the non-contact type IC card is performed from the reader / writer to the non-contact type IC card. In a non-contact type IC card system, which is performed by modulating a high-frequency signal transmitted to a device with data, the non-contact type IC card has a second data generating means such as an abnormal state detecting means. , The second information is transmitted to the reader / writer by modulating the high frequency signal with the information from the second data generating means in synchronization with a data transmission period between the reader / writer and the non-contact type IC card. The non-contact type IC card system, wherein the reader / writer has information detecting means for detecting the second information from the high frequency signal. 2. The information detecting means according to claim 1, wherein the information detecting means detects a data modulation period in the high-frequency signal, and the information is detected based on a relationship between a level at a terminal end of the data modulation period and a level immediately after the terminal end. A non-contact type IC card system characterized by determining the presence or absence of second information.