JP3179375B2 - Non-contact data transmission / reception method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to providing a tool, baggage, or person with a transponder such as a non-contact card in a production line or a distribution line in a factory, entering / leaving management in an office, or the like. The present invention relates to a contactless data transmission / reception method for registering a unique ID code, a product number, data at the time of manufacture, and the like, and communicating and managing the data without contact, and a device therefor.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing the configuration of a conventional non-contact data transmitting / receiving apparatus. FIG. 8 is a communication frame transmitted and received in a communication area 3 by an interrogator 1 and a transponder 2, and a power supply voltage of the transponder 2. FIG. In FIG. 7, reference numeral 1 denotes an interrogator, 2 denotes an interrogator 1 in a communication area 3.
A transponder that communicates with the The interrogator 1 includes an oscillator 4, a modulator 5, a transmitter 6, a receiver 7, a demodulator 8, and a controller 9. The output terminal of the oscillation unit 4 is connected to the input terminal of the modulation unit 5, and the output terminal of the modulation unit 5 is connected to the transmission unit 6. The control unit 9 includes a CPU and the like. The controller 9 is connected to the modulator 5 and the demodulator 8.

[0005] The transponder 2 comprises a receiving section 11, a power supply section 12, a demodulation section 13, a control section 14, a memory 15, a modulation section 16 and a transmission section 17. The receiving unit 11 is a power supply unit 1
2 and to the demodulation unit 13. Transmission unit 1
7 is connected to the modulation unit 16 and the control unit 14 is connected to the demodulation unit 1
3, the modulator 16 and the memory 15. As shown in FIG. 8, the conventional non-contact card system sends a read signal from the interrogator 1 to the transponder 2 in a non-contact manner, and the transponder 2 writes data and the like in a memory according to the signal and returns the data. It is. In this case, the arrival area of the read signal from the interrogator 1 is the communication area 3, and only the transponder 2 in the area 3 is allowed to communicate. First, the interrogator 1 sends out a read high-frequency signal to the transponder 2 in the communication area 3. The read signal indicates a command or the like for the transponder 2 by ASK (Ampl
It is modulated by, for example, iterative Shift Keying. The transponder 2 demodulates the read signal from the interrogator 1 received by the receiving unit 11 by convolution detection or the like, rectifies the high-frequency signal, charges the capacitor C2, and uses it as an internal power supply. The high frequency signal is also used as an internal clock of the transponder 2. Then, the data is read from the memory 15 in the transponder 2 according to the content of the command,
The high frequency signal is modulated and returned. It should be noted that, as shown in FIG. 7, the transmission unit and the reception unit may be integrated into one unit, except for the transmission / reception unit and the power supply capacitor C2, which are integrated into one chip in the IC, thereby reducing the size and thickness of the card. Have been.

FIG. 8 shows that the interrogator 1 and the responder 2 are in the communication area 3.
It is a figure which shows the communication frame transmitted / received within, and transition of the power supply voltage of the transponder 2. In FIG. 8, the interrogator 1 sends a header (HD) and a command (CM) to the responder 2.
D) C for checking communication errors due to address (ADDR), data (DATA), noise, etc.
RC (Cyclic Redundancy Chec)
The communication frame to which k) is added is transmitted. Transponder is HD
CMD, ADDR, D
Demodulate ATA. After receiving the CRC frame,
Only when the calculation of C matches, it is determined that communication was possible without an error due to noise or the like, and processing according to CMD is performed. C
The MD includes reading and writing of data from a memory in the transponder 2. Here, the transponder 2 rectifies the high-frequency signal from the interrogator 1 and accumulates power to access the memory. In the non-contact data transmission / reception device, when a transponder exists outside the communication area, the transponder 2 does not receive a high-frequency signal and cannot generate a power supply. Holding. In particular, E which can be electrically written
An EPROM or the like is used. Here, since a high voltage is required at the time of writing in an EEPROM or the like, when a writing operation is started, a power supply voltage is boosted by an internal booster circuit (not shown) to generate a writing voltage.
At this time, the power consumed by the transponder 2 increases, and there is a great possibility that the internal power supply voltage decreases as shown in FIG. 8B. In some cases, the writing voltage decreases during writing and normal writing cannot be performed. .

On the other hand, it is conceivable that the interrogator 2 checks whether the data written by the interrogator 1 matches the written data after reading out the written data after writing to the memory and returning the data back. , Period B in FIG.
As shown in FIG. 9, when there is no high-frequency signal from the interrogator 1 when the transponder 2 is replying, the transponder 2 cannot obtain power, and is seen in periods B and C in FIG. As described above, the power supply voltage in the transponder 2 gradually decreases. When the data written to the transponder 2 is returned, if the number of the written data is large, the response data frame of the transponder 2 becomes longer, and the period C in FIG.
As shown by, there is a possibility that the power supply voltage of the transponder 2 becomes lower than the level of the point P and the transponder stops. Also, as described above, a large amount of power is required when writing to the memory, and the writing time is as long as several milliseconds. Therefore, it is necessary to recharge the power supply capacitor built in the transponder with power again. After a certain period of time, if the written data is returned and returned, the response starts before the capacitor is not sufficiently charged, and the power supply voltage drops during the response as described above, and the transponder may stop There is much sex. In a nonvolatile memory such as an EEPROM, correct data is written immediately after writing, but after a certain period of time, the data is garbled and may be retained as it is. Therefore, as shown in FIG. 9, even if the data read by accessing the written address immediately after writing matches the data to be written,
After a period of time, the data may be stored differently.

In a conventional non-contact transmission / reception device in which the transponder returns only data in the memory, the command frame transmitted by the interrogator changes due to noise in the communication area or the like, and is not correctly processed on the transponder side. In such a case, the transponder resets the error as an error so as not to access or return to the memory, and the interrogator could not know which part of the command frame was not correctly processed.

[0007]

As described above, the problem to be solved by the present invention is that the transponder rectifies the high-frequency signal from the interrogator, stores the power, and accesses the memory. In a nonvolatile memory such as an EEPROM, a high voltage is required at the time of writing. When a writing operation is started, a power supply voltage is boosted by an internal booster circuit (not shown) to generate a writing voltage. At this time, the power consumed by the transponder 2 increases, and there is a great possibility that the internal power supply voltage decreases, and normal writing may not be performed. It is also conceivable that the interrogator checks whether the data written by the interrogator matches the written data after reading out the written data after writing to the memory and returning it back. The power supply voltage in the unit gradually decreases, and if the number of written data is large, the response data frame of the transponder becomes longer, so the transponder may stop in the middle of reply. It is. Furthermore, since a large amount of power is required when writing to the memory, it is necessary to charge the power to the charging capacitor again after the writing. It is highly possible that the reply is started and the power supply voltage drops during the reply as described above, and the transponder stops. In a nonvolatile memory such as an EEPROM, data is written immediately after writing, but after a certain period of time, the data is garbled and is retained as it is. Furthermore, in the conventional non-contact transmission and reception device in which the transponder returns only data in the memory, if the frame transmitted by the interrogator changes due to noise in the communication area and the like, and is not correctly processed on the transponder side, The transponder resets as an error so as not to access or reply to the memory, and it was not possible to know which part of the frame was not correctly processed.

[0008]

According to the first aspect of the present invention, the interrogator prevents the transponder from stopping due to a drop in the power supply voltage during the reply, and the interrogator confirms the processing result of the transponder in response to the command from the interrogator. The purpose of this is to confirm whether the data was successfully written to the memory of the container.

A second object of the present invention is to provide a transponder for confirming whether or not a power supply voltage can be stably written in a memory, and for coding a power supply voltage state and returning it to an interrogator. .

[0011]

[0012]

[0013]

According to a first aspect of the present invention, an interrogator transmits a command frame including a write command to a memory, a write address, and data to be written, and a transponder transmits response data from the interrogator to the response data. A code indicating the processing result for the command is added, and the interrogator stores the address at which the writing was performed when the code added to the response data indicates that the transponder is operating normally. A command frame for reading the area is transmitted.

According to a second aspect of the present invention, the transponder detects whether or not the voltage is such that the memory can be stably written, and encodes the state of the power supply voltage.

[0015]

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a positional relationship between an interrogator 1 and a transponder 2, FIG. 2 is a diagram showing internal configuration blocks of the interrogator and the transponder according to the present invention, and FIG. 3 is a command frame from each interrogator and a transponder 2. Data frame for response from
FIG. 4 is a diagram showing a power supply voltage in a transponder and a transponder. In FIG. 1, it is assumed that the transponder 2 advances in the direction of the arrow in front of the interrogator 1. The transponder 2 passes in front of the interrogator 1 and reaches the communication area 3 of the interrogator 1. The interrogator 1 transmits a command frame as shown in FIG. 3 every predetermined time, and waits for a response from the responder 2. If there is no response from the transponder 2, the same command frame is transmitted again after a predetermined time. Here, the entry of the transponder 2 may be detected by another sensor, and the command frame may be transmitted only during detection by the sensor.

The operations of the interrogator 1 and the responder 2 are shown in FIG.
This will be described with reference to FIG. The interrogator 1 modulates the high-frequency signal from the oscillator 4 to the command frame to the transponder 2 by the modulator 5. The command frame is created by the control unit 9, and the command includes a command for reading data from a memory in the transponder 2 and a command for writing data. As a modulation method, ASK (Amplitude Shift Key) is used.
ing) and FSK (Frequency Shift)
Keying) and PSK (Phase Shift K)
eyeing) can be considered, but this is not the case. The high-frequency signal modulated by the modulator 5 is output from the transmitter 6. The transmission unit 6 may be a series resonance circuit (not shown) including a resistor, a capacitor, and a coil. The resonance circuit can efficiently transmit the high-frequency signal to the transponder by matching the resonance frequency of the high-frequency signal.

On the other hand, the transponder 2 receives the high-frequency signal from the interrogator 1 at the receiving unit 11. In order to efficiently receive the high-frequency signal from the interrogator 1, a parallel resonance circuit (not shown) including a coil and a capacitor, which resonates at the frequency of the high-frequency signal, is used for the receiving unit 11. The high-frequency signal received by the receiver 11 is supplied to the power supply 12 and the demodulator 13.
Is rectified by the rectifier in the power supply unit, converted into DC, and charged in the capacitor C2. On the other hand, the demodulation unit 13 demodulates the received high-frequency signal and transmits the result to the control unit 14. The control unit 14 determines the command transmitted from the interrogator 1 based on the demodulation result, and performs access to the memory 15 and the like.

Here, an example of a command frame transmitted from the interrogator 1 is shown in FIG. The interrogator 1 reads out data stored in the memory in the responder 2 and transmits a command to write data to a specified address. Alternatively, a command for controlling various flags (not shown) held by the transponder may be transmitted. In FIG. 3, the interrogator 1 transmits a command frame for writing to the memory to the responder (A). First, a header (hereinafter, HD) is transmitted to notify the transponder of the start of communication. The transponder 2 understands that communication has started by receiving the HD, and is ready to analyze the subsequent command frame. The interrogator 1 transmits a non-modulated wave before the HD and can operate the responder 2 (see FIG. 3).
P). The transponder 2 is a power supply unit 12 shown in FIG.
The operation becomes possible when the power supply voltage generated in step (1) becomes equal to or higher than the point P, and HD can be determined. After the HD, the interrogator 1 issues a command to the transponder 2 (hereinafter, CM).
Send D). The CMD is a method of accessing the memory as described above, and in FIG. 3, the CMD instructs writing of data to the memory. Responder 2 writes C
Preparation for writing data to the memory is started by receiving the MD. On the other hand, a high frequency signal changes due to noise or the like in the communication area 3 and a CMD which is not set in advance is set.
If it is determined that there is an error, the code generation unit 18
To that effect, and stop the subsequent processing.

The interrogator 1 transmits an address (hereinafter, ADDR) designating writing after the CMD. Here, it is conceivable to transmit all the addresses to be written, but in FIG. 3, the head address of the address to be written is transmitted. This makes it possible to shorten the command frame and shorten the communication time. In order to write to a plurality of addresses, the interrogator 1 transmits the number of writes (hereinafter, NUM) following ADDR. Transponder 2 is ADDR
It is determined from which address and how many bytes (or bits) to write from which address. If it is determined that the address or the number of writes is not set here, it is regarded as an error as in the case of the CMD, and the fact is notified to the code generation unit 18.
Stop the subsequent processing.

The interrogator 1 transmits data to be written (hereinafter, DATA) following NUM. DATA may be transmitted as many data as the number of writes specified by NUM, or may be 1-byte (or 1-bit) data if the same data is set to be written. The transponder 2 holds the received DATA and stores the received data in a CRC frame (hereinafter referred to as a CR frame).
Receive until the end of C). The interrogator 1 calculates the CRC of the command frame, and transmits the result as CRC at the end of the command frame. The CRC calculation method and the number of bits are variable for each system. The transponder 2 similarly performs the CRC calculation of the command frame. If the calculation results match when the last bit of the CRC frame is received, it is determined that there is no communication error due to noise or the like and the reception has been normally performed. The subsequent operations are continued, but if they do not match, it is regarded as an error, the fact is notified to the code generation unit, and the subsequent processing is stopped. In FIG. 3, CR
Although the example using the C code has been described, any method may be used as long as it checks a communication error, such as a sum check. Here, the above-mentioned NUM may not be transmitted, but the DATA to be written may be transmitted following the ADDR, and the number of DATAs may be determined by calculating backward from the frame in which the CRC calculation matches.

Here, in FIG. 1, when the communication distance between the interrogator 1 and the transponder 2 is long, the high-frequency signal received by the transponder 2 is weakened, and the power rectified and stored in C2 is reduced. On the other hand, since the demodulation unit and the control unit operate and use power during reception, the internal power supply voltage may decrease during reception. Therefore, in the transponder 2, the power supply voltage is monitored by the power supply voltage monitoring unit 19, and its state is always grasped. The transponder 2 receives the CRC frame and starts the write operation only when the CRC calculation matches. However, since the EEPROM or the like requires a high voltage at the time of writing, the power supply voltage must be increased. However, when power is used by boosting the power supply voltage, the power supply voltage may be reduced, and the writing to the memory may not be performed normally, or the response may become lower than the point P in FIG. 3 and the transponder 2 may stop. Therefore, a voltage Q point at which the power supply voltage can be held so that normal writing to the memory is guaranteed even when the voltage is boosted is set. If the power supply voltage is lower than the Q point before the voltage boosting, stable writing to the memory is performed. Since it is not guaranteed, the writing operation is stopped, the fact is notified to the code generation unit 18, and the subsequent processing is stopped. Also, when writing is being performed (B in FIG. 3), the power supply voltage drops and the point Q or lower is reached.
Alternatively, when the voltage of writing to the memory becomes equal to or lower than the guaranteed voltage, it is not guaranteed that the writing to the memory has been normally performed as described above, so the fact is notified to the code generator 18. . In this case, if the writing is started once, some memory may cause an abnormality by being interrupted. In this case, the writing operation to the memory is not interrupted. Also, unlike when the power supply voltage drops before writing, the CODE is set to a different one because writing is actually being performed on the memory.

After the end of the write operation, the transponder 2 shifts to a reply operation C. Alternatively, since the memory is not accessed at the time of error, the process shifts to the reply operation C after receiving the CRC frame. In response, the signal coded into the digital value by the control unit 14 is transmitted to the modulation unit 16, and the modulation unit 16 performs modulation in accordance with the digital value. The modulation method is ASK, FSK or the like described above. Transmitting the modulated wave to the transmitting unit 1
7 and output to the communication area 3. First, a header HD2 is transmitted to inform the interrogator 1 of the start of a reply.
Subsequently, the transponder 2 returns a processing result of the command frame up to now (hereinafter, CODE). The CODE is generated by the code generation unit 18 and indicates that a CMD, ADDR, NUM, or the like not set as the CODE has been received, or indicates that the power source voltage was below the Q point before writing. The content also indicates that the power supply voltage has dropped below the Q point during writing, or below the voltage at which writing to the memory is guaranteed. Also, when a normal operation is performed, a CODE for notifying the user is set. The above CODE is composed of several bits or several bytes, and is set to have different codes so that the interrogator 1 can understand the processing result of the responder 2. The transponder 2 performs a CRC calculation of the response data frame, transmits the calculation result following the CODE, and ends the response data frame. By shortening the response data frame in this way, it is possible to prevent the power supply voltage from falling below the point P during transmission and the transponder 2 from stopping operating.

Here, in order to avoid a drop in the power supply voltage during transmission, a method is conceivable in which the interrogator 1 outputs a high-frequency signal even during transmission. An example is shown in FIGS. The transmitting section 17 of the transponder 2 is composed of the FET 20 and the resistor R as shown in FIG. The receiving unit is configured by the above-described parallel resonance circuit of the coil L1 and the capacitor C1. The transponder 2 turns ON / OFF the FET 20 in accordance with the signal of the modulation unit 16.
Let it. Here, the signal from the modulator 16 uses a frequency several times lower than the frequency of the high-frequency signal. FET20 is ON
In this case, the Q value of the parallel resonance circuit decreases and the induced voltage decreases, so that the power supply voltage of the transponder 2 gradually decreases as shown in FIG. 5, but the interrogator 1 as shown in FIG. The power supply voltage can be prevented from lowering than when the high-frequency signal is stopped.

On the other hand, the interrogator 1 is in a receiving state after transmitting the command frame, and waits for a response data frame from the transponder 2. When the HD2 from the transponder 2 is received, it is determined that the response data frame has started, and the control unit 9 analyzes the CODE to be subsequently received. The interrogator 1 performs a CRC calculation of the response data frame, and checks whether the CRC matches the CRC returned by the responder 2. If they do not match, it is determined that communication has not been performed normally, and the same command frame as above is transmitted. On the other hand, when the CRC calculations match, it is determined that the communication has been normally performed, and the processing according to the CODE is performed. That is, the CODE determines what processing the transponder 2 has performed, and transmits a command frame according to the processing. For example, C where CODE is not set
If the contents indicate that MD, ADDR, NUM, etc. have been received, or if the CRC calculation results are inconsistent, it is determined that communication has not been successful and data has not been written to the memory. Check the setting and send the same write command frame again. Also CODE
Is related to an abnormality in the power supply voltage of the transponder 2, since writing to the memory is not guaranteed, the same write command frame is transmitted again to perform writing. By shortening the response data frame in this way, as described above, the power supply voltage during transmission falls below the point P in the transponder 2, and the transponder 2
Can be prevented from stopping, and the interrogator 1
Can grasp what kind of processing the transponder 2 has performed on the command frame.

On the other hand, CODE indicating normal operation
FIG. 6 shows an embodiment in which this is the case. The interrogator 1 transmits a command frame as shown in FIG. 5, and the transponder 2 transmits a response data frame to which a CODE indicating normal operation has been added. Here, the interrogator 1 performs a CRC calculation of the response data frame to confirm that the communication has been normally performed, and then transmits the data from the memory to the responder 2 to confirm whether the data is actually written. Transmit the read command frame. This is EEP
This is because, in a nonvolatile memory such as a ROM, correct data is written immediately after writing, but after a certain period of time, the data is corrupted and may be retained as it is. Here, the interrogator 1 reads the command (CMD) for reading from the memory following the HD and the address (A) to be read.
DDR) and the number of reads (NUM). Where A
The DDR and NUM may be the same as those at the time of writing, and if it is desired to check data other than the written address, if the written address is included, there is no problem if data of other addresses is read together. Transponder 2
Is a read command CMD, a specified address ADDR,
The data is read from the memory when the read number NUM is confirmed or when the CRC calculation matches. Here, as in the case of writing, if CMD, ADDR, and NUM are other than the set values, or if the CRCs do not match, an error is determined, and CODE having each meaning is set. In the case of normal operation, CO indicating normal operation is output.
Although it is conceivable to set DE, on the other hand, even if the data and the CRC read after HD2 are returned,
If the interrogator 1 understands the response frame of the transponder 1, it can determine that the process has been completed normally.

After the transponder 2 receives the CRC frame,
A reply operation is started, and HD2 and CODE are transmitted. If received normally, read data from memory, CR
The C calculation result is transmitted continuously, while the CODE other than normal is
In the case of, since data is not read from the memory, C
Only the RC calculation result is transmitted. In general, reading from a memory such as an EEPROM does not require as much power as writing, so the power supply voltage drop at the time of reply is not much different from that at the time of transmitting the CODE and CRC calculation results at the time of writing. Also, compared to replying after writing,
Since there is no period B in FIG. 5, the power stored in C2 is sufficient, and even if a long DATA frame is transmitted at the time of reply, it is extremely unlikely that the voltage becomes lower than the voltage P point at which the operation of the transponder stops. Become. As in the case of writing, the power supply voltage monitoring unit 19 sets a voltage value for detecting whether stable reading can be performed from the memory, and when the voltage value falls below the voltage value, sets a CODE for notifying that, and returns. It is also possible. As described above, the response from the transponder 2 after the writing is completed is set to a short frame, and the interrogator 1 reads again from the address including the address designated to be written, so that the transponder 2 has a sufficient power supply voltage. , It is possible to start a reply while holding down, and it is possible to prevent the power supply voltage from dropping and stopping during transmission. In addition, since a certain period has elapsed compared to the data read from the written address immediately after the writing, it is possible to read the actually written reliable data.

[0028]

[0029]

According to the first aspect of the present invention, in a communication area, a command frame including a command and data is transmitted from an interrogator to a transponder, and the translator responds to the command by accessing an internal memory. In the non-contact data transmission / reception method of transmitting response data from the transponder to the interrogator, the interrogator transmits a command frame for writing to the memory, a write address and data to be written, and the transponder transmits the response data. To the code indicating the processing result for the command from the interrogator,
When the code added to the response data indicates that the transponder is operating normally, the interrogator transmits a command frame for reading the memory area including the address where the writing was performed. It is possible to prevent the power supply voltage from dropping and stopping while the transponder is responding, and the interrogator can understand what processing the transponder has performed on the command frame And it is possible to check whether the data has been written normally.

According to a second aspect of the present invention, the interrogator detects whether or not the voltage is such that the memory can be stably written and encodes the state of the power supply voltage. It is possible to determine what processing has been performed on the command frame for writing to the memory.

[0031]

[Brief description of the drawings]

FIG. 1 is a diagram showing a communication position of an interrogator and a transponder of a non-contact data transmission / reception method and apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a circuit configuration of an interrogator and a transponder of the non-contact data transmission / reception method and apparatus according to the embodiment of the present invention.

FIG. 3 is a diagram showing a communication frame of an interrogator and a transponder of the non-contact data transmission / reception method and apparatus according to the embodiment of the present invention.

FIG. 4 is a diagram showing an example of a transmission circuit of a transponder of the non-contact data transmission / reception method and apparatus according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating a transition of a communication frame of an interrogator and a transponder and a power supply voltage of the transponder of the non-contact data transmission / reception method and apparatus according to the embodiment of the present invention.

FIG. 6 is a diagram showing a transition of a communication frame of an interrogator and a transponder and a power supply voltage of the transponder of the non-contact data transmission / reception method and apparatus according to the embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a conventional non-contact data transmission / reception device.

FIG. 8 is a diagram showing a transition of a power supply voltage of a communication frame and a transponder in a conventional contactless data transmission / reception device.

FIG. 9 is a transmission / reception waveform diagram in a conventional non-contact data transmission / reception device.

[Explanation of symbols]

 1 Interrogator 2 Transponder 3 Communication area 15 Memory

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 1/59 B60R 25/04 610 G01S 13/74-13/82 G06F 13/00 351 G06K 17/00-19/00 G08B 13/22 H02J 17/00 H04B 5/02 H04B 7/24-7/26

Claims (2)

(57) [Claims] In the communication area, a command frame including a command, data, and the like is transmitted from an interrogator to a transponder. The transponder accesses an internal memory in response to the command and transmits the command frame from the transponder to the transponder. the non-contact data transmission and reception method for transmitting response data to the interrogator, the interrogator sends a command frame containing the data to be written to the address written with the command writing into the memory, the responder is the response data A code indicating the processing result for the command from the interrogator is added.The interrogator performs the writing when the code added to the response data indicates that the transponder is operating normally. Non-contact data transmission / reception, characterized by transmitting a command frame for reading a memory area including an executed address. Law. 2. The non-contact data transmission / reception method according to claim 1, wherein the transponder detects whether or not the voltage is a voltage at which the memory can be stably written and codes a state of the power supply voltage.