JP3717032B2 - IC card - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes, on a card, a control circuit using a semiconductor integrated circuit, a memory, a modulation / demodulation circuit, and an antenna connected to the modulation / demodulation circuit, and realizes non-contact information communication and power transmission by electromagnetic induction coupling. Or something like that.
[0002]
[Prior art]
An IC card that realizes information communication and power transmission to an IC card by electromagnetic inductive coupling, and particularly relates to an IC card that simultaneously transmits information and power using the same coil, is disclosed in, for example, Japanese Patent Laid-Open No. 6-96300. No. “Non-contact IC card and reader / writer by electromagnetic induction coupling”.
[0003]
According to the publication, an IC card includes a coil for transmitting information and power, a modulation / demodulation circuit for information connected to the coil, a power supply circuit for extracting power to obtain power for IC card operation, and IC card processing It consists of a processing circuit that executes processing in accordance with information from the device and a memory that stores the information. Transfer of information from the IC card processing device to the IC card is realized by amplitude modulation of the carrier wave. Transfer of information to the card processing device is realized by so-called load modulation that changes a load equivalently connected in parallel to the communication coil of the IC card.
[0004]
The IC card processing apparatus operates as follows. When information is transmitted to an IC card, amplitude modulation of a carrier wave is realized by changing a voltage or current that drives a coil that performs information communication and power transmission corresponding to the information transmitted to the IC card. When information transmitted from an IC card is received, information reception is realized by detecting and demodulating a change in the current flowing through the coil that changes corresponding to load modulation on the IC card side.
[0005]
The IC card operates as follows. The power required for the operation of the IC card is obtained by extracting and rectifying the carrier wave sent from the IC card processing device and then stabilizing it. Information transmitted from the IC card processing device is received by demodulating an amplitude-modulated carrier wave. When information is transmitted to the IC card processing device, load modulation is performed using a resistor equivalently connected in parallel to the coil in accordance with the information to be transmitted.
[0006]
[Problems to be solved by the invention]
As described above, an IC card that implements information communication and power transmission using the same coil and applies load modulation as a method of transmitting information from the IC card has the following problems. .
[0007]
A change in current consumption when each means (circuit) in the IC card operates appears as a current change in the communication coil, and equivalently, the same action as load fluctuation occurs. The IC card processing apparatus that has received this detects the load fluctuation as a modulation signal, and a phenomenon occurs in which correct communication is not performed as incorrect information. In particular, during the read, write or erase operation of the memory, current consumption increases and the equivalent load fluctuation is also detected.
[0008]
When such a phenomenon occurs when load modulation corresponding to information to be transmitted starts, in other words, immediately before information is transmitted, the frequency of reception errors on the IC card processing device side increases.
[0009]
[Means for Solving the Problems]
In the present invention, in the IC card, modulation of information to the IC card processing device is started from the start of the read operation for the memory storing the information, or the end of the read operation, the end of the write operation, or the end of the erase operation. In the meantime, a non-modulation period of time of 2 bits or more represented by the bit rate of information is provided. The IC card processor side detects this non-modulation period so that the time when the modulation signal from the IC card is started can be recognized accurately.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of a non-contact IC card according to the present invention. The IC card 1 includes an antenna unit 101 that performs signal transmission / reception, a demodulation unit 102 that demodulates a received signal to obtain information, a modulation unit 103 that modulates information to be transmitted, and passes received information to the processing unit 105 and the processing unit 105. Control unit 104 that delivers information from the modulation unit 103, a processing unit 105 that executes processing according to the received information, a memory control unit 106 that implements reading, writing, and erasing from the processing unit 105 to the memory unit 107, The memory unit 107 that stores information and the power source unit 108 that rectifies the carrier wave and is necessary for the internal operation of the IC card as described above.
[0011]
Although not particularly illustrated, the antenna unit 101 includes an antenna coil, a means for extracting a carrier wave, a means for extracting modulated reception information, and a resistor that realizes load modulation necessary for transmitting information. Yes. In general, a rewritable nonvolatile semiconductor memory element is used for the memory unit 107.
[0012]
For easy understanding, the IC card processing device 2 constituting the system will be described. The IC card processing device does not operate independently, but is used by being connected to a device (such as a personal computer) that is externally controlled from the host.
[0013]
The IC card processing device 2 includes an antenna unit 201 that transmits / receives information to / from an IC card, a demodulation unit 202 that demodulates a received signal to obtain information, a modulation unit 203 that modulates information to be transmitted, and processes received information A communication control unit 204 that delivers the information to the modulation unit 203 and delivers the information from the processing unit 205 to the modulation unit 203; a processing unit 205 that executes processing according to the received information; and a communication control that realizes communication with an external control device The unit 206 and the like. A memory unit is added as necessary.
[0014]
Although not particularly illustrated, the antenna unit 201 includes an antenna coil, a driving unit that drives the antenna coil by an output from the modulation unit 203, and a current that detects a change in the current flowing through the antenna coil that changes due to load modulation of the IC card 1. A detection means and a means for extracting information from the current detection means are included. This detection signal is equivalently an amplitude modulation signal.
[0015]
A basic communication operation will be described. As a modulation method between the IC card 1 and the IC card processing device 2, amplitude modulation, phase modulation, and load modulation are used, but the application of the present invention is mainly when transmitting to the IC card processing device. It is applied to non-contact communication by electromagnetic inductive coupling using the following load modulation method. Further, data modulation for adapting the information to the load modulation method is performed. In the present application, a method of modulating an NRZ code into a modified mirror code is used. This modified mirror code has a feature that there is no unmodulated portion of 2 bits or more indicated by the bit rate of communication between the start bit and the stop bit when normal communication is performed. .
[0016]
FIG. 3 shows a signal state of communication between the IC card 1 and the IC card processing device 2. First, a case where information is transmitted from the IC card processing device 2 to the IC card 1 will be described. (1) in FIG. 3 shows information on the NRZ code delivered from the communication control unit 204 of the IC card processing apparatus 2 to the modulation unit 202. Normally, the start-stop synchronization method is adopted for communication in the non-contact IC card system. First, a start bit is output, followed by a data portion (8 bits in this embodiment), a parity bit is added as necessary, and finally a stop bit is output. (2) in FIG. 3 shows a modified mirror code for the information to be transmitted modulated by the modulation unit 202. FIG. 3 (3) shows a received signal in the antenna unit 101 of the IC card 1. The carrier wave is amplitude-modulated according to the modified mirror code. In the IC card 1, information is extracted from this signal to obtain a signal shown in (4) of FIG. This signal is a modified mirror code. This code is demodulated by the demodulator 103 to obtain the NRZ code shown in (5) of FIG.
[0017]
Next, a case where information is transmitted from the IC card 1 to the IC card processing device 2 will be described. Basically, it is the same form as the transmission of the IC card 1 from the IC card processing device 2. Therefore, it demonstrates using FIG.
[0018]
(1) of FIG. 3 shows information of the NRZ code delivered from the communication control unit 104 of the IC card 1 to the modulation unit 102. First, a start bit is output, followed by a data portion (8 bits in this embodiment), a parity bit is added as necessary, and finally a stop bit is output. (2) in FIG. 3 shows a modified mirror code for the information to be transmitted modulated by the modulation unit 102. (3) in FIG. 3 shows a reception signal output from the current detection means in the antenna unit 201 of the IC card processing device 2. The carrier wave is amplitude-modulated according to the modified mirror code. Actually, load modulation is performed using a resistance for load modulation of the antenna unit 101 corresponding to the output of the modulation unit 103 of the IC card 1. The IC card processing device 2 extracts information from this signal to obtain a signal shown in (4) of FIG. This signal is a modified mirror code. This code is demodulated by the demodulator 203 to obtain the NRZ code shown in (5) of FIG.
[0019]
As described above, in the case of the load modulation method, a change in the current flowing through the antenna coil causes a phenomenon equivalent to load modulation. This phenomenon is a major cause of information communication errors. Further, the current consumption of the memory unit included in the IC card 1 increases when reading, writing, or erasing is performed. In particular, the current consumption changes greatly at the start and end of reading.
[0020]
The problem of non-contact communication by electromagnetic induction coupling using a load modulation method will be described with reference to FIG. A problem occurs when information is transmitted from the IC card 1 to the IC card processing device 2.
[0021]
(1) in FIG. 4 is an NRZ code corresponding to information to be communicated input to the modulation unit 103 of the IC card 1. (2) in FIG. 4 is a modified mirror code obtained by performing data modulation on the NRZ code output from the modulation unit 103 of the IC card 1. (3) in FIG. 4 is a signal received by the antenna unit 201 of the IC card processing apparatus 2, and (4) in FIG. 4 is modulated into a modified mirror code extracted by the current detection means in the antenna unit 201. Signal. (5) in FIG. 4 is an NRZ code obtained by demodulating the modified mirror code extracted by the current detection means in the antenna unit 201 by the demodulation unit 203. This NRZ code is information transmitted from the IC card 1. (6) in FIG. 4 is a signal that permits reading of information from the memory unit 107 included in the IC card 1, and a high level indicates permission of reading.
[0022]
Here, in the case of a normal semiconductor memory, current consumption is transiently consumed at a portion where a signal for permitting reading of information from the memory unit 107 changes (rising edge in FIG. 4 or falling edge not particularly shown). Flows. When such a state occurs, a current that is not allowed in the power supply unit flows through the antenna coil, causing the same state as the load modulation. This is detected as data of 1 bit or more on the IC card processing device 2 side and appears as a communication error.
[0023]
In particular, if the above problem occurs within the time within one bit indicated by the bit rate before the start bit of the information to be originally communicated, the data error indicated by the dotted frame in FIG. As a result, it becomes impossible to identify the data error and the original information, and the communication error cannot be deleted. In this example, the start bit appears before the original information, and the start bit of the original information is recognized as “0” information.
[0024]
FIG. 5 shows a timing chart of a communication state realized by the present invention in order to solve the problem that it becomes impossible to distinguish the generated data error from the original information. In the figure, the meaning of the signals (1) to (6) is the same as (1) to (6) in FIG.
[0025]
The present invention provides the load modulation caused by the consumption current that flows transiently at a portion where a signal that permits reading of information from the memory unit 107 changes (rising edge in FIG. 5 or falling edge that is not particularly shown). The portion that appears as a communication error due to the same state as in the above is controlled so that the above-mentioned problem does not occur within the time within 2 bits indicated by the bit rate before the start bit of the information to be originally communicated.
[0026]
If there is a non-modulation period of 2 bits or more indicated by the bit rate, the IC card processing apparatus 2 can recognize and delete or correct the generated data error. This is because the modified mirror code has a characteristic that there is no unmodulated portion of 2 bits or more indicated by the bit rate of communication between the start bit and the stop bit when normal communication is performed. Because.
[0027]
In the present application, the modified mirror code has been described. However, the code is not particularly limited as long as there is no unmodulated portion of 2 bits or more indicated by the bit rate of communication between the start bit and the stop bit. .
[0028]
Specifically, as shown in FIG. 5, the start or end of a signal for permitting a read operation given from the memory control unit 106 to the memory unit 107, or the end or erase of a signal for permitting a write operation is permitted. The communication control unit 104 and the memory control unit 106 are provided so as to provide a non-modulation period of 2 bits or more expressed by the bit rate between the end of the signal and the start of modulation of information to the IC card processing device 2. Is controlled from the processing unit 105. By doing so, the IC card processing device 2 side can detect the non-modulation period and ignore the data error, and can accurately recognize the start point (start bit) of the modulation signal from the IC card 1. It becomes like.
[0029]
When the IC card 1 transmits information to the IC card processing device 2 while reading information from the memory unit 107, the timing for providing the non-modulation period is the start of a signal that permits a read operation to be given to the memory unit 107. If the read, write, and erase operations are always completed before information is communicated to the IC card processing device 2, the end of those operations is the target.
[0030]
【The invention's effect】
According to the present invention, an information communication error due to operation noise of an IC card can be easily and inexpensively detected by detecting the non-modulated portion on the card processing apparatus side, and an electromagnetic wave using a highly reliable load modulation method is used. Non-contact communication by inductive coupling can be realized. In addition, the unit price of the IC card can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an IC card according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of an IC card processing apparatus according to an embodiment of the present invention.
FIG. 3 is a timing chart of communication between an IC card and an IC card processing device according to the present invention.
FIG. 4 is a timing chart showing problems of a contactless communication method using a load modulation method.
FIG. 5 is a timing chart of a contactless communication method using a load modulation method according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... IC card, 101 ... Antenna part, 102 ... Receiver / demodulator, 103 ... Modulator, 104 ... Communication control part, 105 ... Processing part, 106 ... Memory control part, 107 ... Memory part, 108 ... Memory part, 109 ... Power supply unit 2... IC card processing device 201. Antenna unit 202 202 Demodulation unit 203 Modulation unit 204 Communication control unit 205 Processing unit 206 Communication control unit

Claims (1)

And means for communicating information to and from the IC card processing apparatus by electrodeposition magnetic inductive coupling,
Means for demodulating the received information;
Memory means for storing information;
Processing means for performing predetermined processing according to information received from the IC card processing device and determining information to be transmitted to the IC card processing device according to a processing result;
Means for modulating information to be transmitted to the IC card processing device;
Means for reading, writing and erasing the memory means in accordance with the processing and processing results of the processing means;
In an IC card provided with an antenna for transmitting information and power by electromagnetic induction coupling of the processing means,
A time of at least two bits indicated by the bit rate of the transmission information from the end of the read operation, write operation or erase operation to the memory means until the start of modulation of the information transmitted to the IC card processing device An IC card characterized by providing a non-modulation period during which reading, writing, and erasing processing of the memory is not performed .

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