JP4349323B2 - Communication device and communication synchronization state determination method - Google Patents

Description

  The present invention relates to a communication device that performs communication with a data carrier of a non-contact communication method and a method for determining a synchronization state related to the communication.

An IC card, which is one of non-contact communication type data carriers, communicates with a card reader using radio signals, electromagnetic signals, etc., so just hold the IC card over the card reader. Communication is possible, and convenience is extremely high. For example, Patent Document 1 discloses a configuration in which a transponder, which is a data carrier built in an ignition key of an automobile, performs non-contact communication with a transmission / reception ECU provided on the automobile side.
JP-A-9-142257

On the other hand, there are no restrictions on the shape and size of an IC card that performs non-contact communication, and for example, it is relatively easy to configure a circuit for performing internal communication in the same manner. That is, with such a configuration, a response signal similar to that of an IC card can be transmitted to the card reader. Therefore, there is a problem that the card reader side cannot determine whether or not the IC card performing communication is genuine.
The present invention has been made in view of the above circumstances, and an object of the present invention is to determine whether or not a data carrier to be communicated is properly configured based on a communication result. A communication apparatus and a communication synchronization state determination method are provided.

According to the communication device of claim 1, when the measurement unit performs measurement for determining the synchronization state between the response signal from the data carrier and the reference reception signal set based on the carrier wave, the synchronization determination unit Based on the measurement result, it is determined whether or not the response signal and the reference reception signal are synchronized. That is, since the response signal returned by the data carrier is a signal generated based on the carrier wave, if the response signal and the reference reception signal are synchronized, the data carrier receives the carrier wave transmitted by the communication device. A response is returned. Therefore, it can be reliably determined whether or not the communication target is appropriately configured.

According to the communication device of the second aspect, the measuring means measures at least one of the communication speed, the period, and the phase of the response signal. That is, if any of these is measured, it can be easily determined whether or not the response signal is synchronized with the reference reception signal.
According to a third aspect of the present invention, when the synchronization determination unit makes the determination, the command transmission unit transmits a command for returning response data having a bit number larger than that of the ID data to the data carrier. That is, the determination accuracy of the synchronization state is improved as the number of data bits of the response signal is increased. Therefore, if response data exceeding the number of bits of ID data composed of a predetermined number of bytes is returned to the data carrier, the determination accuracy can be improved with certainty.

According to the communication device according to claim 4, when the measuring unit measures the response timing when the response data is returned from the time when the command generated by the command generating unit is transmitted superimposed on the carrier wave, the synchronization is performed. The determination unit compares the response timing with a reference response timing set based on the carrier wave, and determines whether the carrier wave and the response data are synchronized.
That is, as described in claim 1, since the response signal returned by the data carrier is a signal generated based on the carrier wave, the data carrier can receive the carrier wave transmitted by the communication device and return a response. For example, the timing at which the response is returned has a correlation with the reference response timing and should have a synchronization relationship with the carrier wave. Therefore, based on the measured response timing, the synchronization determination can be reliably performed.

According to the communication device of the fifth aspect, the command generation means generates a command for returning response data whose response timing is clearly defined by the communication protocol when the synchronization determination means makes the determination. If comprised in this way, a comparison with a response timing and a reference | standard response timing can be performed easily based on the prescribed | regulated timing.
According to the communication device of the sixth aspect, the command is a request command for responding ID data of a data carrier. That is, the timing at which the data carrier responds to the ID data in response to the transmission of the request command is one of those clearly defined by the communication protocol, so that the timing comparison can be easily performed.

According to the communication device of the seventh aspect, the measuring means measures the timing at which the specific code included in the response data is received. That is, the timing can be easily measured when the specific code is received.
According to the communication device of the eighth aspect, the specific code is the synchronization code. That is, since the synchronization code is a code arranged for synchronization when the communication device receives the response signal, the timing can be easily measured when the synchronization code is received.

  According to the communication device of the ninth aspect, the synchronization determination unit determines whether or not the measurement value measured by the measurement unit changes according to the change in frequency when the carrier frequency generated by the carrier generation unit is changed. Confirm that the synchronization is correct. In other words, if the data carrier receives the carrier transmitted by the communication device and returns a response, the value measured by the measuring means should change as the carrier frequency changes. Therefore, the synchronization determination can be performed more reliably by performing the determination in this way.

According to the communication device of claim 10, when the synchronization determination means determines that “synchronization is established”, the received response data is recognized and accepted as regular data, so that only the response data returned by the regular data carrier is subsequently received. Can be used for processing.
According to the communication device of the eleventh aspect, when the synchronization determination unit determines that “synchronization is not established”, the received response data is discarded, so that data transmitted by an unauthorized device can be reliably excluded.
According to the communication device of the twelfth aspect, when the synchronization determination unit determines that “synchronization is not established”, the alarm unit outputs an alarm signal, so that notification can be performed when an unauthorized device transmits data.

(First embodiment)
A first embodiment in which the present invention is applied to an IC card as a data carrier will be described below with reference to FIGS. FIG. 3 is a functional block diagram showing an electrical configuration of a reader / writer that reads and writes data from and to an IC card using radio signals. The reader / writer (communication device) 1 is controlled by a processing circuit (synchronization determination means, command transmission means) 2 constituted by a microcomputer. The operation power supply circuit 40 is a circuit that generates and outputs an operation power supply for the reader / writer 1 from a commercial AC power supply or a power supply supplied from a battery according to an application.

  The encoding / decoding circuit 3 and the modulation circuit (modulation means) 4 are supplied with a carrier (carrier wave) output from a carrier generator (carrier wave generation means) 5. The encoding / decoding circuit 3 encodes the transmission data output from the processing circuit 2 and outputs it to the modulation circuit 4. The modulation circuit 4 multiplies the carrier and the encoded transmission signal (modulation signal) output from the encoding / decoding circuit 3 to multiply the modulated signal subjected to ASK (Amplitude Shift Keying) modulation to the amplifier 6. The amplifier 6 amplifies the signal and outputs it to the antenna (transmission / reception means) 7. Then, a radio signal is transmitted from the antenna 7 to the outside.

An input terminal of a demodulation circuit 8 is connected to the antenna 7, and a radio wave signal received by the antenna 7 is input to the demodulation circuit 8. The signal demodulated by the demodulation circuit 8 is output to the encoding / decoding circuit 3, and the encoding / decoding circuit 3 processes the analog reception signal demodulated by the demodulation circuit 8, thereby decoding the received data, It outputs to the processing circuit 2 as digital data. The communication speed measuring device (measuring means) 9a and the communication phase measuring device (measuring means) 9b measure the communication speed and phase of the demodulated analog reception signal and output the measurement result to the processing circuit 2. .
Further, the reader / writer 1 includes an alarm device (alarm means) 10. The alarm device 10 is controlled by the processing circuit 2 and outputs an audio message or an alarm sound, or displays an alarm message by displaying a text message on a display or lighting an alarm lamp. It should be noted that only one of these alarms may be performed, or two or more alarms may be performed in combination.

  FIG. 4 shows an electrical configuration of the non-contact type IC card (data carrier) 11. When the IC card 11 receives the carrier transmitted from the reader / writer 1 via the antenna 12, the operation power supply circuit 13 rectifies the carrier to generate the operation power, and the processing circuit 14 constituted by a microcomputer and other Supply to the component. The carrier is supplied to the operation clock extraction circuit 15, and when a clock signal having a carrier period is extracted, a clock signal obtained by dividing the carrier signal by 64 is output to the processing circuit 14 and the encoding / decoding circuit 16.

Then, the transmission data from the reader / writer 1 superimposed on the carrier is demodulated by the demodulation circuit 17, and is decoded by the encoding / decoding circuit 16 and output to the processing circuit 14. When the operation circuit 14 is activated and supplied with power, the processing circuit 14 receives the transmission data from the reader / writer 1 and reads the data stored in the internal memory 14a. When a write command is transmitted, the processing circuit 14 Write the transmitted data.
The transmission data output from the processing circuit 14 is output to the modulation circuit 18 after being encoded into Manchester code in the encoding / decoding circuit 16. The modulation circuit 18 outputs a modulated signal obtained by load-modulating the carrier with the encoded data to the antenna 12.

  FIG. 5 shows an example of a communication sequence performed between the reader / writer 1 and the IC card 11. When the reader / writer 1 (R / W) transmits a request command to the IC card 11, the IC card 11 returns, for example, 22-byte ID data allocated to itself to the reader / writer 1 side (ID response). . When the reader / writer 1 transmits a Read command to the IC card 11, the IC card 11 returns a predetermined amount (for example, 206 bytes) of data to the reader / writer 1 side (data response).

  FIG. 6 is a waveform diagram showing the relationship between the carrier transmitted from the reader / writer 1 and the response signal returned from the IC card 11. The IC card 11 side generates and outputs Manchester encoded data as response data based on the clock signal obtained by dividing the carrier by 64. Accordingly, when the carrier frequency is fc (for example, 13.56 MHz), the response data has a 1-bit transmission time, that is, the communication speed is 64 / fc.

  FIG. 7 assumes the configuration of the IC card simulation device 21 created by simulating the electrical configuration of the IC card 11. That is, instead of the operation power supply circuit 13 and the operation clock extraction circuit 15 of the IC card 11, circuits 22 and 23 for generating an operation power supply and an operation clock regardless of the carrier supply are arranged. Accordingly, the IC card simulation device 21 can independently transmit the response data without receiving the carrier supplied by the reader / writer 1.

  Next, the operation of this embodiment will be described with reference to FIGS. FIG. 2 is a flowchart showing the contents of control performed mainly by the processing circuit 2 when the reader / writer 1 receives the response data of the IC card 11. FIG. 1 is a timing chart corresponding to the control contents of FIG. 2, (a) shows the carrier, and (b) shows the waveform of the response signal demodulated by the demodulation circuit 8 of the reader / writer 1.

  As described above, when the reader / writer 1 superimposes a command on a carrier and transmits it to the IC card 11, the IC card 11 returns a response signal. At the beginning of the response signal, as shown in FIG. For example, a “preamble” for continuously transmitting data “0” is added. Following the preamble, a “synchronization code (data“ 10001000 ”in FIG. 1)” is transmitted. Then, the time point when the data “0” at the end of the preamble is switched to the data “1” at the beginning of the synchronization code becomes the reference position (timing) for data reception, and reception is started from that point.

  When the reader / writer 1 starts reception, it waits for reception of the preamble in the response signal (step S0). The communication speed measuring device 9a of the reader / writer 1 measures the preamble communication speed within the period during which the preamble of the response signal is received (step S1). For example, if the preamble has an 8-bit configuration, the transmission speed is a value obtained by measuring the preamble transmission time and dividing by “8”. Then, the processing circuit 2 determines whether or not the communication speed is “64 / fc ± α” (step S2). “Α” is an allowable error.

In step S2, when the communication speed of the preamble is different from “64 / fc ± α” (“NO”), the response signal is not synchronized with the carrier, that is, generated based on the clock obtained by dividing the carrier. It is determined that the data is not correct. That is, in this case, it can be determined that the data is not a response signal from a legitimate IC card, but data transmitted by the IC card simulation device 21 as shown in FIG. 7 or external noise. Therefore, the processing circuit 2 rejects acceptance of the preamble in the response signal and returns to step S0 again.
On the other hand, when the communication speed of the preamble is “64 / fc ± α” in step S2 (“YES”), the response signal is data generated based on the clock obtained by dividing the carrier and is synchronized with the carrier. It is judged that Next, in the reception after the synchronization code, the communication phase measuring device 9b measures whether or not the phase of the response signal is synchronized with the phase of the reference reception signal.

  Specifically, when the reference position following the preamble is detected (step S3), as shown in FIG. 1C, a 64 / fc reference reception signal is generated by dividing the carrier by 64 in synchronization with the position. To do. After that, the response signal is decoded at a position synchronized with the phase of the reference reception signal to decode the response data (step S4). When decoding, if the phase shift between the reference reception signal and the response signal is large (for example, the allowable phase shift value is about 10 to 25%), the response data cannot be demodulated correctly. This operation enables measurement of whether the phase of the response signal is synchronized with the phase of the reference reception signal.

  When the data reception of the length specified by the data length information is completed (step S5, “YES”), the check code added to the data body (eg, CRC (Cyclic Redundancy Code)) is confirmed. If the confirmation result is “OK” (step S7, “YES”), the processing circuit 2 accepts the response data (step S8) and ends the process. That is, in this case, the received response data maintains the phase synchronized with the reference reception signal (in other words, the carrier) until the reception is completed.

  On the other hand, if the check code confirmation result is “NG” in step S7 (“NO”), the response data is not synchronized with the carrier, and is data transmitted by the IC card simulation device 21 or the like. There is a high possibility. Accordingly, the processing circuit 2 proceeds to step S9, rejects acceptance of response data, and ends the processing. Note that “OK” and “NG” in step S7 are determined based on whether or not the check code value is appropriate. However, if “NG” is determined, even if the returned check code itself is an appropriate value, the carrier This includes the case where the reader / writer 1 cannot properly read the data value as a result of transmission in a state that is not synchronized with the data.

  Therefore, the determination in step S7 can be performed with higher accuracy as the response data length is longer. For example, when the synchronization deviation of the data bits allowed to finally determine “OK” is ± 10%, the response data of 125 bytes = 1000 bits, which is at least longer than the ID response data, is obtained. If a reply is made, it is possible to determine the synchronization shift with an accuracy of ± 0.01% per bit. For example, since the accuracy of the ceramic oscillator is about 0.5%, it is possible to reliably detect the synchronization shift when the operation clock circuit 23 of the IC card simulator 21 is configured using the ceramic oscillator. it can.

  As described above, according to the present embodiment, in the reader / writer 1, when the communication speed measuring device 9a and the communication phase measuring device 9b measure the communication speed and phase of the response signal returned from the IC card 11, the processing circuit 2 Determines whether the response signal and the reference reception signal set based on the carrier are synchronized based on the measurement result. That is, the response signal returned from the IC card 11 is a signal generated based on the carrier. Therefore, if both signals are synchronized, the IC card 11 receives the carrier transmitted by the reader / writer 1 and responds. Is returned. Therefore, it can be reliably determined whether or not the communication target is appropriately configured.

  In addition, when performing the synchronization determination, the processing circuit 2 transmits a command for returning response data having a bit number of about 1000 bits to the IC card 11, so that the determination accuracy can be improved with certainty. The processing circuit 2 recognizes and accepts the received response data as normal data when it is determined that “synchronization is established”, and discards the received response data when it determines that “synchronization is not established” and sends an alarm signal to the alarm device 10. It was made to output. Therefore, only response data returned from the legitimate IC card 11 can be used for the subsequent processing, and data transmitted by an unauthorized device such as the IC card simulation device 21 can be surely excluded. When the unauthorized device transmits data, the alarm device 10 can notify the user.

(Second embodiment)
8 and 9 show a second embodiment of the present invention. The same parts as those of the first embodiment are denoted by the same reference numerals and the description thereof is omitted, and only different parts will be described below. In the second embodiment, the IC card is configured in accordance with JIS X6322-3 (ISO / IEC 14443-3) which is a standard. The IC card 11 differs from the first embodiment in command and response format, communication speed, timing, and the like.
Here, as shown in FIG. 8, when the reader / writer 1 transmits a request command to the IC card 11, the timing until the IC card 11 returns a response is measured. Therefore, in the second embodiment, the communication speed measuring device 9a and the communication phase measuring device 9b are not required for the reader / writer 1.

FIG. 9 is a flowchart showing the control contents of the processing circuit (measuring means) 2. First, when the reader / writer 1 transmits a request command (step S11), it starts timing measurement (step S12). If the appropriate IC card 11 receives the transmitted request command, the processing circuit 14 on the card side performs internal processing and then starts transmitting response data.
Then, the IC card 11 transmits the ID response data, but when the processing circuit 2 detects the head of the response data as the reference position (step S13, “YES”), the timing measurement is completed (step S14). Then, the response data is decoded for each bit unit (step S15). And reception is continued until data reception is completed (step S16). When the data reception is completed, it is confirmed whether or not the measured response timing is a specified value (1172 / fc).

On the other hand, if it is determined that the measured response timing does not match the specified value (step S17, “NO”), the response timing is abnormal although response data is returned. There is a high possibility that the data is transmitted by the IC card simulation device 21 as shown in FIG. Accordingly, the processing circuit 2 proceeds to step S9.
That is, the timing from when the reader / writer transmits a request command to when the IC card returns a response is determined according to the communication protocol defined in JIS X6322-3 (ISO / IEC144443-3). Therefore, if “YES” is determined in step S17, it can be determined that the response data is synchronized with the carrier. That is, in the second embodiment, the response timing set based on the carrier frequency fc becomes the reference response timing.

  As described above, according to the second embodiment, the processing circuit 2 measures the response timing when the ID response data is returned from the time point when the request command is transmitted superimposed on the carrier wave, and the response timing and By comparing the reference response timing set based on the carrier wave, it is determined whether the carrier wave and the response data are synchronized. Therefore, the synchronization determination can be easily performed based on the specified timing. Since the processing circuit 2 measures the response timing with the timing at which the synchronization code, which is a specific code included in the ID response data, is received, the response timing can be easily measured.

(Third embodiment)
10 and 11 show a third embodiment of the present invention, and only the parts different from the first embodiment will be described. As shown in FIG. 10, the reader / writer 31 of the third embodiment includes a processing circuit 2, a processing circuit (synchronization determination means, command generation means) 32 instead of the carrier generator 5, and a carrier generator 33. Yes. The carrier generator (carrier wave generating means) 33 can output the carrier frequency by switching between fc1 and fc2, and the switching control is performed by the processing circuit 32.

  FIG. 11 is a flowchart showing the contents of control performed by the processing circuit 32. The processing circuit 32 first selects the carrier generator 33 so as to output a carrier having the frequency fc1 (step S21), and communicates with the IC card 11 using the carrier (step S22). Then, it is determined whether or not the response data returned from the IC card 11 is synchronized with the carrier frequency fc1 (step S23). This determination may be made, for example, at any one of steps S1 and S2 and steps S6 and S7 in the first embodiment and step S15 in the second embodiment.

  In step S23, if the response of the IC card 11 is not synchronized with the carrier frequency fc1 ("NO"), it is determined as asynchronous (step S28), so that the alarm device 10 is driven to output an alarm in the same manner as in step S10. It performs (step S29). In step S23, when the response of the IC card 11 is synchronized with the carrier frequency fc1 (“YES”), the processing circuit 32 performs selection so that the carrier generator 33 outputs a carrier having the frequency fc2 ( In step S24), communication with the IC card 11 is performed using the carrier (step S25).

Then, the processing circuit 32 determines whether or not the response data returned from the IC card 11 is synchronized with the carrier frequency fc2 (step S26). If not synchronized ("NO"), the processing circuit 32 proceeds to step S28. . On the other hand, if the response data is synchronized with the carrier frequency fc2 (“YES”), it is determined that the response of the IC card 11 is surely synchronized with the carrier at this time (step S27).
As described above, according to the third embodiment, when the carrier frequency generated by the carrier generator 33 is changed, the processing circuit 32 determines whether the measured value changes according to the change in frequency. Since the synchronization determination is performed after confirmation, the synchronization determination can be performed more reliably.

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications are possible.
Instead of the communication speed, the frequency and phase of response data may be measured.
The communication device may be a card reader having only a function of reading data.
The alarm device may be provided as necessary.
The data carrier is not limited to the IC card 11, but may be an RFID tag or a mobile phone having the same function as these.
The communication protocol is not limited to JIS X6322-3, but may be based on a protocol used according to each application.
The frequency division ratio of the carrier is not limited to “64” and may be set as appropriate.
The specific code for measuring the response timing is not limited to the synchronization code, and may be, for example, a preamble (the last bit) or data (the first bit) received after the synchronization code.
For example, when the communication device is applied to an immobilizer for a vehicle, a horn of the vehicle or a light or the like may be blinked as an alarm device.

1 is a first embodiment when the present invention is applied to an IC card, (a) is a carrier, (b) is a diagram showing a waveform of response data demodulated by a demodulation circuit of a reader / writer, and (c) is a reference reception. Diagram showing signal waveform Flowchart showing control contents performed mainly by the processing circuit when the reader / writer receives the response data of the IC card. Functional block diagram showing the electrical configuration of the reader / writer Functional block diagram showing the electrical configuration of the non-contact IC card The figure which shows an example of the communication sequence performed between a reader / writer and an IC card Waveform diagram showing the relationship between the carrier transmitted from the reader / writer and the response signal returned from the IC card A diagram assuming the configuration of an IC card simulation device created by simulating the electrical configuration of an IC card FIG. 1 equivalent view showing a second embodiment of the present invention. Partial equivalent diagram of FIG. FIG. 3 equivalent view showing a third embodiment of the present invention. 2 equivalent diagram

Explanation of symbols

  In the drawings, 1 is a reader / writer (communication device), 2 is a processing circuit (synchronization determination means, command transmission means, measurement means), 4 is a modulation circuit (modulation means), 5 is a carrier generator (carrier wave generation means), 7 Is an antenna (transmission / reception means), 9a is a communication speed measurement device (measurement means), 9b is a communication phase measurement device (measurement means), 11 is a contact IC card (data carrier), 10 is an alarm device (alarm means), 32 Indicates a processing circuit (synchronization determination means, command generation means), and 33 indicates a carrier generator (carrier wave generation means).

Claims (21)

Carrier wave generating means for generating a carrier wave of a predetermined frequency;
A transmitting / receiving means for transmitting the carrier wave to a data carrier of a non-contact communication system and receiving a response signal from the data carrier;
Measuring means for measuring to determine a synchronization state between a response signal from the data carrier and a reference received signal set based on the carrier;
A communication apparatus comprising: synchronization determination means for determining whether or not the response signal and the reference reception signal are synchronized based on a result of the measurement.   The communication device according to claim 1, wherein the measurement unit measures at least one of a communication speed, a period, and a phase of the response signal. A command transmission means for generating a command and superimposing the command on the carrier wave and transmitting the command to the data carrier;
3. The command transmission means, when the synchronization determination means makes a determination, transmits a command for returning response data having a bit number larger than that of ID data to the data carrier. Communication equipment. Carrier wave generating means for generating a carrier wave of a predetermined frequency;
Command generating means for generating a command for returning predetermined response data to a data carrier of a non-contact communication method;
Modulation means for superimposing the command on the carrier;
Transmitting and receiving means for transmitting the carrier wave on which the command is superimposed to the data carrier and receiving response data from the data carrier;
Measuring means for measuring a response timing when the response data is returned from the time when the command is transmitted;
Synchronization determination means for determining whether or not the carrier wave and the response data are synchronized by comparing the response timing with a reference response timing set based on the carrier wave is provided. A communication device.   5. The communication according to claim 4, wherein the command generation unit generates a command for returning response data whose response timing is clearly defined by a communication protocol when the synchronization determination unit makes a determination. apparatus.   6. The communication apparatus according to claim 5, wherein the command is a request command for responding ID data of a data carrier.   The communication device according to claim 4, wherein the measurement unit measures a timing at which a specific code included in the response data is received.   The communication device according to claim 7, wherein the specific code is a synchronization code. The carrier wave generating means is configured to be able to change the carrier wave frequency in two or more stages,
The synchronization determination unit confirms whether or not the measurement value measured by the measurement unit changes according to the change in the frequency when the carrier frequency generated by the carrier generation unit is changed. The communication apparatus according to claim 1, wherein the determination is performed.   10. The communication apparatus according to claim 1, wherein when the synchronization determination unit determines that “synchronization is established”, the received response data is recognized and accepted as regular data.   11. The communication device according to claim 1, wherein when the synchronization determination unit determines that “synchronization is not established”, the received response data is discarded. Comprising alarm means for generating an alarm signal by sound or light;
12. The communication apparatus according to claim 1, wherein when the synchronization determination unit determines that “synchronization is not established”, the alarm unit outputs the alarm signal. Generate a carrier wave of a predetermined frequency and transmit it to a data carrier of a non-contact communication system,
Perform a measurement to determine the synchronization state of the response signal from the data carrier and the reference reception signal set based on the carrier,
A communication synchronization state determination method, comprising: determining whether or not the response signal and the reference reception signal are synchronized based on a result of the measurement.   The communication synchronization state determination method according to claim 13, wherein one or more of the communication speed, period, and phase of the response signal are measured.   When performing the synchronization determination, a command for returning response data having a larger number of bits than ID data to the data carrier is generated, and the command is superimposed on the carrier and transmitted to the data carrier. The communication synchronization state determination method according to 13 or 14. Generate a carrier wave of a predetermined frequency,
Generate a command for returning predetermined response data to a data carrier of a non-contact communication method, superimpose the command on the carrier,
Transmitting the carrier wave on which the command is superimposed to the data carrier and receiving response data from the data carrier;
Measure the response timing when the response data is returned from the time of sending the command,
A communication synchronization state determination method comprising: determining whether the carrier wave and the response data are synchronized by comparing the response timing with a reference response timing set based on the carrier wave .   17. The communication synchronization state determination method according to claim 16, wherein when performing the synchronization determination, a command for returning response data whose response timing is clearly defined by a communication protocol is generated and transmitted.   The communication synchronization state determination method according to claim 17, wherein the command is a request command for responding ID data of a data carrier.   The communication synchronization state determination method according to any one of claims 16 to 18, wherein a timing at which a specific code included in the response data is received is measured.   The communication synchronization state determination method according to claim 19, wherein the specific code is a synchronization code. 21. The synchronization determination is performed by confirming whether or not a measurement value measured when the carrier frequency is changed changes according to the change in the frequency. Communication synchronization status determination method.

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