JP2008293167A - Random number generation circuit, non-contact type ic tag, reader/writer and ic tag system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly maintain data communication with a reader/writer. <P>SOLUTION: An IC tag 20 is provided with a random number generation circuit 26 for generating a basic clock signal CL for a logic control circuit 25; a transmission means for repeatedly transmitting an initial signal to a reader/writer in every random interval time according to the establishment of a power supply voltage Vd; and a reception means for receiving a command including the ID information from the reader/writer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a random number generation circuit incorporated in an IC chip for a contactless IC tag, a contactless IC tag, a reader / writer for a contactless IC tag, and a contactless IC tag system.

  A contactless IC tag that performs two-way data communication with a reader / writer via radio waves may incorporate a random number generation circuit for encryption in order to improve security.

  Conventional random number generation circuits amplify the thermal noise of an electric circuit (for example, Patent Document 1), use a single electron phenomenon in a special semiconductor element (Si dot MOSFET) (for example, Non-Patent Document 1), etc. There are known physical random number generation circuits. In addition, software-like pseudo-random number generators based on mathematical methods and random number generators that combine high-frequency oscillators with low-speed counters and smoothing circuits tend to be excessive in circuit scale and power consumption. It is said to be unsuitable for mounting on small devices such as tags.

On the other hand, in a contactless IC tag system, a data communication between an IC tag and a reader / writer is generally a synchronous communication method that uses a carrier wave from the reader / writer to generate a basic clock signal for a logic control circuit in the IC tag. (For example, Patent Documents 2 and 3).
JP 2002-41281 A JP-A-7-105330 JP-A-9-214366 Satoshi Tanamoto et al., Ultra-small random number generator, Internet information, www.toshiba.co.jp/tech/review/2006/02/61_02pdf/a05.pdf

  When using such conventional technology, among the conventional physical random number generation circuits, those that use thermal noise of the electric circuit tend to overload the amplifier circuit and filter circuit, and the required circuit area tends to be excessive. Those using the electronic phenomenon have a problem that a special semiconductor element is required and is not general. In addition, since the conventional data communication system has no flexibility in the frequency of the carrier wave from the reader / writer, the application may be limited depending on the region or application, and communication is complicated when multiple IC tags respond simultaneously. As a result, there is a problem that normal data communication cannot be performed.

  Accordingly, an object of the present invention is to provide a random number generation circuit that can be suitably incorporated in an IC chip for a contactless IC tag, combined with a simple standard circuit element, and a reader Provided are a contactless IC tag, a reader / writer, and an IC tag system that operate without depending on the frequency of a carrier wave from a writer and can maintain appropriate data communication even when a plurality of IC tags respond simultaneously. There is to do.

  In order to achieve the above object, the first invention of the present application (referring to the invention according to claim 1, the same applies hereinafter) is a random number generation circuit incorporated in a contactless IC tag, which generates a clock signal. Serially input a first pulse source, a second pulse source that generates a clock signal having a longer pulse period than the clock signal from the first pulse source, and each clock signal from the first and second pulse sources. And a shift register for inputting to the clock input terminal. The shift register samples the level of the clock signal from the first pulse source based on the clock signal from the second pulse source, and outputs binary data. As a gist, the data is stored in time series and output in parallel as a random number of a predetermined number of bits.

  Note that the first pulse source may be capable of selectively outputting either the output of the pulse oscillator or the waveform shaping output of the carrier wave from the reader / writer, and the clock signal from the first pulse source is the IC It may be usable as a basic clock signal for the logic control circuit of the tag, and the clock signal from the second pulse source is used as a clock signal for the booster circuit that generates the write voltage of the memory mounted on the IC tag. It may be possible.

  The configuration of the second invention (referred to the invention according to claim 5, the same applies hereinafter) is a non-contact IC tag that performs bidirectional data communication with a reader / writer via radio waves, and is a basic clock for a logic control circuit A clock generation means for generating a signal; a transmission means for repeatedly transmitting an initial signal including a synchronization signal and ID information to the reader / writer at random intervals upon establishment of a power supply voltage; and a command including ID information from the reader / writer. Receiving means for receiving, the transmitting means determines the bit rate of the initial signal based on the basic clock signal from the clock generating means, the receiving means is a command from the reader / writer is a selection command for its own IC tag If there is, the transmission of the initial signal by the transmission means is stopped and the reception of the normal command for the own IC tag from the reader / writer is waited. , If the command for the other IC tag, and its gist that to suspend repeated transmission of the initial signal by the transmission means.

  The random number generation circuit according to the first aspect of the invention is attached, and the transmission means can set the interval time based on the random number from the random number generation circuit every time the initial signal is repeatedly transmitted. A clock signal from one pulse source can be output as a basic clock signal.

  The configuration of the third invention (referring to the invention according to claim 8, the same applies hereinafter) is a reader / writer that performs bidirectional data communication with a plurality of contactless IC tags via radio waves, and is synchronized with the IC tags. A receiving means for receiving an initial signal including a signal and ID information; a measuring means for measuring a bit rate of a synchronization signal received by the receiving means; and storing each ID information; and ID information for a specific IC tag. And transmitting means for transmitting the command including the command. The transmitting means sets the bit rate of the command in accordance with the bit rate for each stored ID information.

  The receiving means receives a response signal including ID information from the IC tag, and the measuring means measures the bit rate of the response signal received by the receiving means, and stores the bit rate stored for each ID information. Can be updated.

  The gist of the configuration of the fourth invention (referring to the invention according to claim 10, the same applies hereinafter) is that the plurality of IC tags according to the second invention and the reader / writer according to the third invention are combined.

  According to the first aspect of the invention, the shift register inputs the high frequency clock signal from the first pulse source to the serial input terminal, and the low frequency clock signal from the second pulse source to the clock input terminal. By inputting, the level of the former clock signal is sampled based on the latter clock signal, stored in a time series as binary data of 1 or 0, and output in parallel as a random number of a predetermined number of bits. When sampling the clock signal from the first pulse source with the clock signal from the second pulse source, the level of the clock signal from the first pulse source is either 1 or 0 and is unpredictable. Because there is. Therefore, according to the first aspect of the present invention, the random number data can be greatly increased by minute frequency fluctuations of one or both of the clock signals from the first and second pulse sources without adding a special smoothing circuit to the shift register. In addition, the power consumption and the required circuit area can be reduced, and it can be suitably incorporated into an IC chip for a contactless IC tag.

  Note that the number of bits of the shift register is preferably set to about 16, 32, 64, or 128 bits in consideration of using a random number output in parallel as an encryption key for security. The first and second pulse sources are independent of each other in their clock signals, and at least one of the pulse sources is used for operating parameters such as power supply voltage and ambient temperature. It is preferable that the stability of the oscillation frequency is not so high. Further, when arranging both pulse sources in the same circuit configuration, it is preferable to cause a difference in frequency stability by, for example, changing the form of the circuit element.

  Instead of using an independent pulse oscillator, the first pulse source may waveform the carrier wave from the reader / writer and output it. Since the second pulse source is naturally an independent pulse oscillator, the clock signals from the first and second pulse sources are completely independent from each other by not using the independent pulse oscillator as the first pulse source. Random number characteristics can be improved. However, the second pulse source at this time has a circuit configuration with low stability of the oscillation frequency.

  If the clock signal from the first pulse source is used as the basic clock signal for the logic control circuit of the IC tag, there is no need to separately provide clock generating means for generating the basic clock signal in the IC tag. If the clock signal from the second pulse source is used as a clock signal for generating a write voltage in a memory (for example, a rewritable nonvolatile memory such as an EEPROM) mounted on an IC tag, dedicated clock signal generating means Need not be separately provided in the IC tag.

  According to the configuration of the second invention, when the IC tag enters the communicable area of the reader / writer and the power supply voltage is established, the transmission means repeatedly transmits an initial signal every random interval time. Therefore, even if a plurality of IC tags enter the communicable area of the reader / writer at the same time, the reader / writer reliably receives an initial signal from any one of the IC tags transmitted at least the second time or later. The IC tag can be specified based on the ID information included in the initial signal. This is because the initial signal from each IC tag is repeatedly transmitted every random interval time. On the other hand, if the command from the reader / writer is a selection command for the own IC tag, the receiving unit determines that communication with the reader / writer has been established, stops the repeated transmission of the initial signal, and determines the own IC from the reader / writer. It is only necessary to wait for the reception of a normal command for data communication with the tag. If the command is for another IC tag, data communication between the reader / writer and the other IC tag is prevented from being interrupted by temporarily interrupting the repeated transmission of the initial signal. To do.

  The commands from the reader / writer include a selection command that responds to the initial signal from the IC tag and a normal command for data communication (for example, a read command and a write command). It is assumed that ID information specifying a tag is included. In addition, since the transmission means determines the bit rate of the initial signal based on the basic clock signal from the clock generation means, it depends on the frequency of the carrier wave from the reader / writer by measuring it in the reader / writer and reflecting it in the command. Data communication can be realized.

  If the random number generation circuit according to the first aspect is added, the transmission circuit can set the interval time of the repeated transmission at random every time the initial signal is repeatedly transmitted based on the random number from the random number generation circuit. Further, if the clock signal from the first pulse source of the random number generation circuit is output as the basic clock signal for the logic control circuit, it is not necessary to provide a special clock generation means.

  According to the configuration of the third invention, the measuring means measures the bit rate of the synchronization signal included in the initial signal from the IC tag received by the receiving means, and stores it for each ID information. Further, when transmitting a command to a specific IC tag, the transmission means adds the ID information of the IC tag to the command, and sets the bit rate of the command according to the bit rate stored for each ID information. Set. Therefore, on the IC tag side, it is only necessary to receive a command having the same bit rate as that of the initial signal transmitted by itself, and bi-directional data communication independent of the carrier frequency from the reader / writer can be realized. it can. Since the measuring means stores the bit rate for each ID information, the bit rate may be different for each IC tag, and a plurality of IC tags having the same bit rate may exist.

  The measuring means measures the bit rate of the response signal from the IC tag received by the receiving means, and updates the bit rate stored for each ID information. Commands can be sent according to the latest bit rate of the tag. In other words, even when the basic clock signal on the IC tag side fluctuates with time, reliable data communication can always be realized by reflecting the latest bit rate.

  According to the configuration of the fourth invention, by combining the plurality of IC tags according to the second invention and the reader / writer according to the third invention, a plurality of IC tags can be obtained without depending on the frequency of the carrier wave from the reader / writer. Even if they simultaneously enter the communicable area of the reader / writer, appropriate two-way data communication can be maintained without complication of mutual communication.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The non-contact type IC tag system is a combination of a reader / writer 10 and a plurality of non-contact type IC tags 20, 20,... (FIG. 1).

  In order to perform data communication with the IC tags 20, 20... Via the radio wave W, the reader / writer 10 is provided with a transmission / reception antenna 10 a. However, in FIG. 1, the IC tags 20, 20,... Are individually attached to articles (not shown) on a conveyor (not shown) and are conveyed in the direction of arrow K. The reader / writer 10 has a communicable area S that intersects with the traveling paths of the IC tags 20, 20,... Data communication.

  The reader / writer 10 includes a receiving circuit 11, a transmitting circuit 12, and a microcomputer 13 connected to the antenna 10a (FIG. 2). The microcomputer 13 has a built-in memory 14. The output of the reception circuit 11 is connected to the microcomputer 13, and the output of the microcomputer 13 is connected to the transmission circuit 12. The microcomputer 13 is bidirectionally connected to an external host computer (not shown).

  The IC tag 20 includes a parallel resonance circuit 21 including a coil L and a capacitor C, a power supply circuit 22, a transmission circuit 23, a reception circuit 24, a logic control circuit 25 including a microcomputer, and a random number generation circuit 26. However, a rewritable nonvolatile memory 25a such as an EEPROM is connected to the logic control circuit 25 bidirectionally. The random number generation circuit 26 includes pulse oscillators 26a and 26b, a shift register 26c, a waveform shaping circuit 26d, and a switch 26e. In FIG. 3, each component of the IC tag 20 can be integrated into an IC chip for the IC tag 20. However, one or both of the coil L and the capacitor C may be provided outside the IC chip.

  The power supply circuit 22, the transmission circuit 23, and the reception circuit 24 are connected in parallel to the parallel resonance circuit 21. Note that the output of the reception circuit 24 is connected to the logic control circuit 25, and the output of the logic control circuit 25 is connected to the transmission circuit 23. The output of the power supply circuit 22 is fed to each component of the IC tag 20 as a DC power supply voltage Vd.

  One end of the parallel resonant circuit 21 is connected to one switching terminal of the switch 26e via the waveform shaping circuit 26d, the output of the pulse oscillator 26a is connected to the other switching terminal of the switch 26e, and the common terminal of the switch 26e is Are connected to the serial input terminal ST of the shift register 26c. The common terminal of the switch 26e is branched and input to the logic control circuit 25 as the basic clock signal CL. The output of the pulse oscillator 26b is connected to the clock input terminal CT of the shift register 26c, and is branched and input to the logic control circuit 25 as a clock signal WR for a booster circuit (not shown) that generates a write voltage of the memory 25a. The parallel output terminal PT of the shift register 26 c is connected to the logic control circuit 25.

  The reader / writer 10 can transmit the radio wave W to the IC tags 20, 20,... Via the transmission circuit 12 and the antenna 10a (FIGS. 1 and 2). However, in the radio wave W, arbitrary pulse data D is superimposed on the high-frequency carrier wave W1 (FIG. 4), and the pulse data D is prepared by the microcomputer 13 (FIG. 2), and is shown in the transmission circuit 12. Is superimposed on the carrier wave W1 via a modulation circuit that does not. Note that the modulation factor of the radio wave W by the pulse data D may be set to less than 100% as shown in FIG. 4, or may be set to 100%.

  When the IC tag 20 enters the communicable region S of the reader / writer 10, a high-frequency voltage Vf due to the carrier wave W1 of the radio wave W from the reader / writer 10 is generated at both ends of the coil L and capacitor C of the IC tag 20 (FIG. 3). ). Therefore, the power supply circuit 22 rectifies and smoothes the high-frequency voltage Vf to generate a DC power supply voltage Vd, which is supplied to each part of the IC tag 20 to operate the IC tag 20. For example, the receiving circuit 24 receives the high frequency voltage Vf, demodulates the pulse data D superimposed on the radio wave W from the reader / writer 10, and sends it to the logic control circuit 25. D can be decoded and a predetermined operation can be executed according to the contents of the pulse data D.

  In addition, the logic control circuit 25 sends data to be transmitted to the reader / writer 10 as another pulse data D1 to the transmission circuit 23 as necessary, and the transmission circuit 23 receives the pulse data D1 from the reader / writer 10. The carrier wave W1 is load-modulated and transmitted to the reader / writer 10. Therefore, the receiving circuit 11 of the reader / writer 10 demodulates the pulse data D1 and sends it to the microcomputer 13 (FIG. 2). The microcomputer 13 can decode the pulse data D1 and execute a predetermined operation. .

  In FIG. 3, the logic control circuit 25 operates based on the basic clock signal CL from the random number generation circuit 26. When the memory 25a needs to be rewritten, the logic control circuit 25 uses the clock signal WR from the random number generation circuit 26. A high voltage for rewriting is created by a booster circuit (not shown). The basic clock signal CL selects the output of the pulse oscillator 26a by switching the switch 26e to the pulse oscillator 26a side, and switches the switch 26e to the waveform shaping circuit 26d side, so that the high-frequency voltage Vf, that is, from the reader / writer 10 is selected. The waveform shaping output of the carrier wave W1 can be selected. Note that the pulse periods Tc and Tw of the basic clock signal CL and the clock signal WR are set to Tw >> Tc (FIG. 5). However, the oscillation frequency of the pulse oscillator 26a is lower than the frequency of the high frequency carrier wave W1, and the switch 26e switches to the pulse oscillator 26a side when the frequency of the carrier wave W1 is too high as the basic clock signal CL.

  The shift register 26c samples the level of the basic clock signal CL at every rising or falling edge of the clock signal WR by inputting the basic clock signal CL and the clock signal WR to the serial input terminal ST and the clock input terminal CT, respectively. Then, it is stored in time series as binary data of 1 or 0. However, in FIG. 5, the arrow from the clock signal WR to the basic clock signal CL indicates that the level of the basic clock signal CL is sampled at the rising edge of the clock signal WR.

  On the other hand, the shift register 26c can output the binary data having the predetermined number of bits stored in this way to the logic control circuit 25 as a random number R from the parallel output terminal PT. The basic clock signal CL and the clock signal WR are a clock signal from the first pulse source including the pulse oscillator 26a, the waveform shaping circuit 26d, and the switch 26e, and a clock signal from the second pulse source including the pulse oscillator 26b, respectively. This is because the two clock signals are not correlated with each other, and the level at each sampling point of the former clock signal sampled based on the latter clock signal is unpredictable. Note that the random number generation circuit 26 may be operated at all times to continuously generate different random numbers R for each cycle of the clock signal from the second pulse source. It may be operated by a command signal (not shown), and a new random number R may be generated each time.

  When the IC tag 20 enters the communicable area S of the reader / writer 10 and the power supply voltage Vd from the power supply circuit 22 is established, the IC tag 20 operates, for example, according to the program flowchart of FIG.

  The logic control circuit 25 of the IC tag 20 first reads the random number R from the random number generation circuit 26, and sets an interval time for repeated transmission of the initial signal based on the random number R (program step (1) in FIG. Simply write as (1)). Subsequently, the logic control circuit 25 transmits an initial signal to the reader / writer 10 via the transmission circuit 23 (2). However, the logic control circuit 25 operates based on the basic clock signal CL from the random number generation circuit 26, and determines the bit rate of the initial signal based on the basic clock signal CL. Next, the logic control circuit 25 determines whether or not a command for any one of the IC tags 20 is superimposed on the radio wave W from the reader / writer 10 received via the receiving circuit 24 (3). Unless the command from is detected, the interval time elapses (6), the random number R is newly read from the random number generation circuit 26 (1), and the same operation is repeated thereafter ((1) to (3), (6), (1)).

  Here, the format of the initial signal from the IC tag 20 and the command from the reader / writer 10 is, for example, as shown in FIG. The initial signal is, for example, a start signal composed of 4 to 16 periods of a regular bit pattern such as the pulse data D in FIG. 4, a sync signal having a fixed pattern such as a binary value 11001110, and the IC tag 20 Specific ID information, a synchronization signal, CRC (Cyclic Redundancy Check) information for error check for ID information, and a fixed pattern end signal are cascaded. The command includes a start signal, a command code indicating the type of command, ID information designating the IC tag 20, necessary command data, command code, ID information, CRC information for the command data, The end signal is cascaded.

  In FIG. 7, in addition to a necessary response signal from the IC tag 20 for responding to a command from the reader / writer 10, a selection command from the reader / writer 10, a read command from the reader / writer 10, and a write command These formats are shown together. However, the command from the reader / writer 10 includes a selection command and a normal command, and the normal command includes a read command and a write command. Therefore, the logic control circuit 25 of the IC tag 20 executes the program steps (1) to (3), (6), and (1) in FIG. 6 repeatedly, based on the random number R from the random number generation circuit 26. The initial signal including the synchronization signal and ID information can be repeatedly transmitted to the reader / writer 10 through the transmission circuit 23 at random intervals, and the bit rate of the initial signal can be determined based on the basic clock signal CL.

  On the other hand, when the logic control circuit 25 detects a command (selection command or normal command) from the reader / writer 10 via the reception circuit 24 during the interval time (3), the command is a selection command for the own IC tag 20. If there is ((4), (5)), the repeated transmission of the initial signal is stopped and the reception of the normal command from the reader / writer 10 is awaited (8). If the command from the reader / writer 10 is not a command for the own IC tag 20 but a command for the other IC tag 20 (4), the interval time longer than usual is set and the repeated transmission of the initial signal is suspended. ((7), (6)). Further, when the command from the reader / writer 10 is not the selection command for the own IC tag 20 ((4), (5)), the repeated transmission of the initial signal with the normal random interval time is continued ((6), ( 1) to (6)).

  When the logic control circuit 25 receives a normal command (read command or write command) from the reader / writer 10 via the receiving circuit 24 in the program step (8) of FIG. 6, it executes it (9). That is, if it is a read command, the content of the designated read address in the memory 25a is read and transmitted as a response signal to the reader / writer 10 via the transmission circuit 23. If it is a write command, it is sent to the designated write address in the memory 25a. Write the specified write data.

  Therefore, in FIG. 3, a pulse oscillator 26 a, a waveform shaping circuit 26 d, and a switch 26 e serve as clock generation means for generating a basic clock signal CL for the logic control circuit 25. The functions of the transmission circuit 23 and the logic control circuit 25 corresponding to the program steps (1), (2), and (6) in FIG. The transmission means repeatedly transmits to the reader / writer 10 every time, and the transmission means determines the bit rate of the initial signal based on the basic clock signal CL from the clock generation means. Further, the functions of the reception circuit 24 and the logic control circuit 25 corresponding to the program steps (3) to (5), (7), and (8) in FIG. 6 receive a command including ID information from the reader / writer 10. If the command from the reader / writer 10 is a selection command for the own IC tag 20, the receiving means stops the repeated transmission of the initial signal, waits for the normal command for the own IC tag 20, If it is a command for the tag 20, the repeated transmission of the initial signal is temporarily suspended.

  When the power is turned on, the reader / writer 10 operates according to the program flowchart of FIG. 8, for example.

  First, the microcomputer 13 of the reader / writer 10 operates the transmission circuit 12 to continuously transmit the carrier wave W1 of the radio wave W from the antenna 10a, and then enters an arbitrary IC tag 20 that enters the communicable area S via the reception circuit 11. Waiting for the reception of the initial signal from the program (program step (1) in FIG. 8, hereinafter simply referred to as (1)). On the other hand, when an arbitrary IC tag 20 enters the communicable area S of the reader / writer 10, the IC tag 20 transmits an initial signal (program step (2) in FIG. 6). The start signal of the initial signal is recognized through (1), each data included in the initial signal is read, and the bit rate of the synchronization signal is measured (2).

  Subsequently, the microcomputer 13 checks whether the CRC information and ID information read from the initial signal are correct ((3), (4)). If the CRC information is normal and the ID information is valid, the ID information At the same time, the bit rate is stored in the memory 14 (5), but if one or both of the CRC information and the ID information are not correct, the initial signal itself from the IC tag 20 is ignored ((3), (4), (1 )). Since the IC tag 20 in the communicable area S repeatedly transmits an initial signal at random intervals, even if the initial initial signal is ignored, any subsequent initial signal is correctly received and the reader When communication between the writer 10 and the IC tag 20 is established ((1) to (4)), the bit rate of the synchronization signal at that time is stored for each ID information (5).

  Next, the microcomputer 13 transmits a selection command including the ID information of the IC tag 20 to the IC tag 20 via the transmission circuit 12 (6). It is assumed that the bit rate of the selection command at this time is measured from the initial signal from the IC tag 20 and matches the bit rate stored in the memory 14. Therefore, the logic control circuit 25 of the IC tag 20 can easily and reliably detect a selection command addressed to itself having the same bit rate as the initial signal transmitted by itself (program step (3) in FIG. 6). (5)).

  When the IC tag 20 receives the selection command for its own IC tag 20, the IC tag 20 stops the repeated transmission of the initial signal and waits for the reception of the normal command from the reader / writer 10 (program steps ((4), (5) in FIG. 6). Therefore, the microcomputer 13 of the reader / writer 10 transmits a normal command (read command or write command) to the IC tag 20 as necessary (7), especially when reading (8). In the case of a command, the normal command is repeatedly transmitted until a normal response signal is obtained from the IC tag 20 via the receiving circuit 11 ((8), (9), (8)). The bit rate of the normal command is also matched with the bit rate previously stored for each ID information.

  Therefore, the functions of the receiving circuit 11 in FIG. 2 and the microcomputer 13 corresponding to the program step (1) in FIG. 8 are receiving means for receiving an initial signal from the IC tag 20. Further, the function of the microcomputer 13 corresponding to the program steps (2) to (5) in FIG. 8 is a measuring unit that measures the bit rate of the synchronization signal received by the receiving unit and stores it for each ID information. . 2 and the microcomputer 13 corresponding to the program steps (6) and (8) in FIG. 8 are the transmission means for transmitting a command including ID information to the specific IC tag 20. Thus, the transmission means can set the bit rate of the command in accordance with the bit rate for each stored ID information.

  When the IC tag 20 recognizes that the command from the reader / writer 10 is a selection command for its own IC tag 20 (program steps (3) to (5) in FIG. 6), the program step (8) in FIG. Prior to awaiting a normal command from the reader / writer 10, a response signal indicating that the selection command has been correctly received may be transmitted to the reader / writer 10. At this time, when the reader / writer 10 transmits a selection command in the program step (6) of FIG. 8, for example, the selection command is repeatedly transmitted until the response signal from the IC tag 20 is confirmed, and the response signal is confirmed. It is possible to proceed to transmission of the normal command in the program step (8).

  Similarly, the IC tag 20 transmits a response signal to the reader / writer 10 when the normal command from the reader / writer 10 is not only a read command but also a write command in the program steps (8) and (9) of FIG. May be. At this time, the reader / writer 10 can repeatedly transmit the normal command until the response signal from the IC tag 20 is obtained even when the normal command is a write command in the program steps (8) and (9) of FIG. it can.

  When the response signal from the IC tag 20 is obtained as described above, the microcomputer 13 of the reader / writer 10 remeasures the bit rate of the response signal from the IC tag 20, and the ID information included in the response signal. Accordingly, by updating the bit rate stored in the memory 14 for each ID information, the bit rate of the subsequent command can be matched with the latest bit rate. That is, the measuring unit can measure the bit rate of the response signal received by the receiving unit, update the bit rate stored for each ID information, and reflect the updated bit rate in the subsequent command.

  Note that this system avoids the complication of data communication between the reader / writer 10 and each IC tag 20 even when a plurality of IC tags 20, 20 are simultaneously present in the communicable area S of the reader / writer 10 (FIG. 9). can do.

  For example, even if a plurality of IC tags 20 and 20 enter the communicable region S at the same time (FIG. 9A), the IC tags 20 and 20 repeatedly transmit initial signals for each random interval time ( The program steps (1) to (6) and (1)) of FIG. 6 and the transmission timing of the initial signal from each IC tag 20 at least the second and subsequent times are shifted in time. Communication with each IC tag 20 can be easily established. When communication with one IC tag 20 is established in this way, the other IC tags 20 temporarily suspend the repeated transmission of the initial signal (program steps (3), (4), ( 7), (6)), there is no possibility of hindering communication of the IC tag 20 with which communication has been established previously. Similarly, even if a plurality of IC tags 20 and 20 enter the communicable area S of the reader / writer 10 in succession (FIG. 9B), they are established between the previous IC tag 20 and the reader / writer 10. The prior communication is prioritized, and there is no possibility that the subsequent IC tag 20 will interfere with the communication of the previous IC tag 20.

  In the above description, the logic control circuit 25 of the IC tag 20 can be constructed by a hardware logic circuit instead of being configured by software in the microcomputer. At this time, the function of detecting the command from the reader / writer 10 in the program step (3) in FIG. 6 is not limited to the interval time of the repeated transmission of the initial signal, but the program step (see FIG. 1) to (3) and (6) are valid during the entire period. When detecting a command from the reader / writer 10, the logic control circuit 25 interrupts the initial signal being transmitted, and the program step (4) in FIG. ) And (5) shall be prioritized. At this time, in order to distinguish the command from the reader / writer 10 from the initial signal from the IC tag 20, the radio wave W from the reader / writer 10 may be set to a modulation rate of 100% or close to 100%. preferable. However, the detection of commands from the reader / writer 10 as described above and the preferential operation of the determination associated therewith can be realized by using the interrupt function of the microcomputer, for example, even in the logic control circuit 25 by software. .

  Further, when sending the initial signal and the response signal, the logic control circuit 25 of the IC tag 20 improves the communication security by encrypting the initial signal and the response signal using the latest random number R from the random number generation circuit 26 as an encryption key. Can be made. At this time, the IC tag 20 transmits an encryption key based on the random number R added to the initial signal and the response signal, and the reader / writer 10 uses the encryption key transmitted in this way to Signals and response signals are decoded. Further, the reader / writer 10 can also encrypt the command with the encryption key from the IC tag 20 and transmit it. However, it is assumed that the encryption logic is previously stored in common in both the IC tag 20 and the reader / writer 10.

Overall schematic configuration diagram Block diagram of reader / writer IC tag block diagram Waveform diagram of radio waves for data communication Basic clock signal, clock signal waveform diagram IC tag program flowchart Signal format for data communication Reader / Writer Program Flowchart 1 equivalent explanatory drawing explaining the operation state

Explanation of symbols

W ... Radio wave W1 ... Carrier R ... Random number Vd ... Power supply voltage CL ... Basic clock signal WR ... Clock signal Tc, Tw ... Pulse cycle ST ... Serial input terminal CT ... Clock input terminal 10 ... Reader / writer 20 ... IC tag 25 ... Logic control Circuit 25a ... Memory 26 ... Random number generator 26a, 26b ... Pulse oscillator 26c ... Shift register

Patent applicant F.C. Co., Ltd.
Gyxis Corporation
Attorney Tadaaki Matsuda, Attorney

Claims (10)

  A random number generation circuit incorporated in a contactless IC tag, wherein a first pulse source that generates a clock signal, and a second pulse signal that generates a clock signal having a pulse period longer than the clock signal from the first pulse source A pulse source; and a shift register for inputting each clock signal from the first and second pulse sources to a serial input terminal and a clock input terminal, respectively. A random number generating circuit which samples the level of the clock signal from the first pulse source based on the clock signal, stores it in a time series as binary data, and outputs it in parallel as a random number of a predetermined number of bits. .   2. The random number generation circuit according to claim 1, wherein the first pulse source can selectively output either an output of a pulse oscillator or a waveform shaping output of a carrier wave from a reader / writer.   3. The random number generation circuit according to claim 1, wherein the clock signal from the first pulse source can be used as a basic clock signal for a logic control circuit of an IC tag.   4. The clock signal from the second pulse source can be used as a clock signal for a booster circuit that generates a write voltage of a memory mounted on an IC tag. The random number generator described.   A contactless IC tag that performs two-way data communication with a reader / writer via radio waves, a clock generating means for generating a basic clock signal for a logic control circuit, and a synchronization signal and ID information by establishing a power supply voltage. A transmitting means for repeatedly transmitting the initial signal including the reader / writer at random intervals, and a receiving means for receiving a command including ID information from the reader / writer, the transmitting means from the clock generating means If the command from the reader / writer is a selection command for the own IC tag, the receiving means stops the repeated transmission of the initial signal by the transmitting means and determines the bit rate of the initial signal based on the basic clock signal. Wait for reception of the normal command for the own IC tag from the writer, and if it is a command for another IC tag, IC tag, characterized in that to suspend repeated transmission of the initial signal by the serial transmission means.   5. The random number generation circuit according to claim 1, wherein the transmission means sets an interval time based on a random number from the random number generation circuit every time an initial signal is repeatedly transmitted. The IC tag according to claim 5.   7. The IC tag according to claim 6, wherein the clock generation means outputs a clock signal from the first pulse source as a basic clock signal.   A reader / writer for bidirectional data communication with a plurality of contactless IC tags via radio waves, receiving means for receiving an initial signal including a synchronization signal and ID information from the IC tag, and receiving by the receiving means Measuring means for measuring the bit rate of the synchronized signal and storing it for each ID information, and transmitting means for transmitting a command including ID information to a specific IC tag. A reader / writer characterized by setting a bit rate of a command in accordance with a bit rate for each ID information.   The receiving means receives a response signal including ID information from the IC tag, the measuring means measures the bit rate of the response signal received by the receiving means, and the bit rate stored for each ID information The reader / writer according to claim 8, wherein the reader / writer is updated.   A contactless IC tag system comprising a combination of the plurality of IC tags according to any one of claims 5 to 7 and the reader / writer according to claim 8 or 9.

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