JP5664807B2 - Communication device, communication method, and wireless tag - Google Patents

Description

The present invention relates to a communication device , a communication method , and a wireless tag, and in particular, has a retention characteristic for a non-volatile memory built in a wireless tag such as an IC card or an IC chip that performs proximity communication with a reader / writer, for example. The present invention relates to a communication device , a communication method , and a wireless tag that can be maintained and can shorten a write processing time required for writing.

  In recent years, proximity communication that performs wireless communication in a short distance without contact using an IC (Integrated Circuit) card or the like has been used in, for example, electronic commuter passes and electronic money, and also used proximity communication. Electronic commuter passes and mobile phones having the function of electronic money have become widespread.

  Proximity communication is standardized as, for example, ISO / IEC 14443 or ISO / IEC 18092 (hereinafter also referred to as NFC (Near Field Communication)).

  Proximity communication in response to a signal from a reader / writer with a reader / writer that outputs an RF (Radio Frequency) signal among communication devices that perform proximity communication such as communication conforming to the NFC standard. A communication device such as an IC card or an IC chip that performs the above is also referred to as a wireless tag.

  The wireless tag has a built-in non-volatile memory such as EEPROM (Electrically Erasable Programmable Read Only Memory), for example, by reading and writing data to and from the non-volatile memory through proximity communication, Provide various services.

  Among wireless tags, there is a batteryless wireless tag that operates using RF signals output from a reader / writer as power.

  Since the batteryless wireless tag operates using the RF signal output from the reader / writer as power, sufficient power cannot be obtained when the RFID tag is separated from the reader / writer.

  For this reason, for example, if the wireless tag is moved away from the reader / writer while the built-in nonvolatile memory is being accessed, the wireless tag cannot operate, and the memory corruption (Memory Corruption ) Occurs, that is, the data stored in the non-volatile memory may be inconsistent.

  In addition, even in a wireless tag having a battery (for example, an IC chip built in a mobile phone), the memory corruption receives data to be written to the nonvolatile memory from the reader / writer when the wireless tag is separated from the reader / writer. This can happen when things can no longer be done.

  As a method of dealing with memory corruption, in the nonvolatile memory of the wireless tag, the latest data is not overwritten with the data written immediately before, but a recording area different from the storage area of the data written immediately before (For example, refer to Patent Document 1).

Patent No. 3702923

  In addition to the electronic commuter pass and electronic money described above, the wireless tag can be used for various services such as entry / exit management and inventory management, but provides a service so that the user does not feel stress. Therefore, it is necessary to shorten the write processing time required to write data to the nonvolatile memory built in the wireless tag.

  On the other hand, the memory cell (state) of the nonvolatile memory built in the wireless tag is changed to an erase state where data is not written (erased) or a write state where data is written. In order to enhance the retention characteristic that is retained for a long time, it is necessary to sufficiently accumulate charges (electrons or holes) in the floating gate of the transistor that forms the memory cell.

  FIG. 1 is a diagram for explaining writing of data to an EEPROM which is a nonvolatile memory.

  When data is written to the EEPROM, erase is performed to put the memory cell in an erase state, and then write is performed to put the memory cell in the erase state into a write state.

  For example, in an EEPROM, in order to maintain a certain retention characteristic, the charge accumulation time for accumulating charges in the floating gate is longer than the time for the memory cell to transition to the erase state or the write state.

  If the charge accumulation time is shortened, the writing process time can be shortened. However, if the charge accumulation time is shortened, the retention characteristic is lowered.

  Therefore, there is a trade-off relationship between shortening the write processing time and maintaining the retention characteristics, but if the retention characteristics deteriorate and the write state or erase state cannot be maintained, wireless Since the tag becomes unusable, it is not desirable to shorten the write processing time at the expense of retention characteristics.

  The present invention has been made in view of such circumstances, and is intended to maintain retention characteristics and shorten the writing processing time.

  A communication apparatus according to an aspect of the present invention includes a communication unit that performs near field communication with a reader / writer, and a control unit that controls writing of data to a nonvolatile memory in accordance with a command from the reader / writer. A part of the storage area of the storage memory is a user block which is a minimum unit storage area allocated to a service, the user block has a plurality of units, and the unit stores a predetermined unit in which writing is performed. One or more units of the plurality of units constituting the user block having at least one page as a region is a buffer unit that functions as a buffer for buffering data written to the user block, The nonvolatile memory is management information for managing a storage area of the nonvolatile memory. The management information includes a unit number that identifies the unit, and the control means, in accordance with a command from the reader / writer, transmits data to the buffer unit and a target unit to which data is to be written. Is started by receiving an RF signal from the reader / writer in the communication means, and after the start-up, during a start-up process performed before receiving a command from the reader / writer, It is a communication device that erases all pages.

A communication method or wireless tag according to one aspect of the present invention is a communication method or wireless tag corresponding to the communication device according to one aspect of the present invention described above .

  In one aspect as described above, a part of the storage area of the non-volatile memory is a user block which is a storage area of a minimum unit allocated to a service, and the user block includes a plurality of units, The unit has one or more pages that are storage areas of a predetermined unit in which writing is performed, and at least one of the plurality of units constituting the user block buffers data to be written to the user block The nonvolatile memory stores management information for managing a storage area of the nonvolatile memory, and the management information includes a unit number for specifying the unit. The control means writes data to the buffer unit and a target unit that is a target unit to which data is to be written in accordance with a command from the reader / writer. Further, the control means is activated when the communication means receives an RF signal from the reader / writer, and after the activation, during the activation process performed before receiving a command from the reader / writer, the buffer means Erase all pages of the unit.

  Note that the communication device may be an independent device, or may be an internal block constituting one device.

  According to one aspect of the present invention, the retention characteristic of a nonvolatile memory can be maintained, and the write processing time required for writing can be shortened.

It is a figure explaining writing of the data to EEPROM which is a non-volatile memory. It is a block diagram which shows the structural example of one Embodiment of the communication system to which this invention is applied. 3 is a diagram illustrating an example of a logical format of a memory unit 24. FIG. FIG. 4 is a diagram for explaining data writing to a memory unit 24. It is a figure explaining the response | compatibility with respect to memory corruption. 5 is a flowchart for explaining processing of the wireless tag 20. 6 is a diagram for explaining a write processing time of the wireless tag 20. FIG. 6 is a diagram illustrating another example of the logical format of the memory unit 24. FIG. 5 is a flowchart for explaining processing of the wireless tag 20.

  [One embodiment of communication system to which the present invention is applied]

  FIG. 2 is a diagram of a communication system to which the present invention is applied (a system refers to a logical collection of a plurality of devices, regardless of whether or not each configuration device is in the same housing). It is a block diagram which shows the structural example of embodiment.

  In FIG. 2, the communication system includes a reader / writer 10 and a wireless tag 20.

  The reader / writer 10 has an antenna 11 and outputs an RF signal from the antenna 11 to perform proximity communication with the wireless tag 20 in a contactless manner, and to the wireless tag 20 (the built-in memory unit 24). The data is stored (written), and the data is read from the wireless tag 20.

  When the wireless tag 20 comes close to the reader / writer 10, the wireless tag 20 starts to operate using the RF signal output from the antenna 11 by the reader / writer 10, and performs proximity communication with the reader / writer 10.

  In the near field communication, the reader / writer 10 transmits data by modulating the RF signal according to the data, and the wireless tag 20 receives the data transmitted by the reader / writer 10 using the RF signal and stores it in the built-in memory unit 24. Write.

  In addition, the wireless tag 20 reads data stored in the memory unit 24 and performs load modulation on the RF signal transmitted from the reader / writer 10, thereby transmitting the data to the reader / writer 10.

  That is, the wireless tag 20 includes an antenna 21, an RF unit 22, a command sequencer unit 23, and a memory unit 24.

  The antenna 21 is configured by a resonance circuit including a coil and a capacitor, for example, receives an RF signal from the reader / writer 10, and supplies the RF signal to the RF unit 22.

  The RF unit 22 performs near field communication with the reader / writer 10.

  That is, when the RF signal from the reader / writer 10 is received by the antenna 21 when the reader / writer 10 and the wireless tag 20 are close to each other, the RF unit 22 obtains power as a power source from the RF signal, Supply the necessary blocks.

  Further, the RF unit 22 demodulates the RF signal from the reader / writer 10 into a command and data, and supplies it to the command sequencer unit 23.

  Further, the RF unit 22 transmits data to the reader / writer 10 by load-modulating the RF signal from the reader / writer 10 according to the data supplied from the command sequencer unit 23.

  The command sequencer unit 23 performs sequence control in accordance with commands from the reader / writer 10 supplied from the RF unit 22, thereby performing control such as reading and writing of data with respect to the memory unit 24.

  That is, when the command from the reader / writer 10 is a write command for requesting data writing, the command sequencer unit 23 transmits the data supplied from the reader / writer 10 and supplied from the RF unit 22 together with the write command. Write to the memory unit 24.

  Further, when the command from the reader / writer 10 is a read command for requesting reading of data, the command sequencer unit 23 reads data from the memory unit 24 and supplies it to the RF unit 22.

  The memory unit 24 is, for example, a nonvolatile memory such as an EEPROM, and stores data under the control (management) of the command sequencer unit 23.

  [Logical format of memory unit 24]

  FIG. 3 is a diagram illustrating a logical format of the memory unit 24 included in the wireless tag 20 of FIG.

  A part of the storage area of the memory unit 24 is, for example, a user block which is a minimum storage area allocated to services such as commuter passes, electronic money managed by a predetermined service provider, tickets for events, and the like. Yes.

  The memory unit 24 is provided with one or more user blocks.

  Here, one or more user blocks are allocated to the service, and data for providing the service is stored in the one or more user blocks.

  The user block has a plurality of M + 1 units (M is an integer of 1 or more).

  Data for providing a service is written in the unit. However, one of the M + 1 units constituting the user block functions as a buffer for buffering data written to the user block.

  As described above, since one unit constituting the user block functions as a buffer, the user block includes one unit functioning as a buffer and one or more M for storing data for providing a service. In total, there are a plurality of M + 1 units.

  Hereafter, of the M + 1 units constituting the user block, a unit that functions as a buffer is also referred to as a buffer unit, and a unit that is not a buffer unit is also referred to as a data unit.

  In FIG. 3, of the M + 1 units constituting the user block, the M + 1th unit is a buffer unit, and the other 1st to Mth M units are data units. It has become.

  The unit serving as the buffer unit changes when data is written to the user block, which will be described later.

  A unit has K pages that are one or more.

  A page is a storage area of the minimum unit in which writing to the memory unit 24 is performed. In FIG. 3, one page is a storage area of N bytes.

  Here, in FIG. 3, one page of the pages of the unit is used as a page (management page) for storing management information for managing the storage area of the memory unit 24.

  That is, in FIG. 3, one specific page among the K pages constituting the unit is a management page in which management information for managing the unit is stored.

  Therefore, in FIG. 3, since the unit requires one or more pages (data pages) for storing data and one management page, the number of pages K constituting the unit is plural.

  In FIG. 3, the Kth page among the K pages constituting the unit is a management page. The management page is a fixed page that does not change (like the buffer unit).

  In the management page, a unit number, a (single) sequence number, and an error detection code are written as unit management information.

  The unit number is information for identifying a unit having a management page in which the unit number is written.

  The sequence number is a value that is regularly updated each time data is written to the memory unit 24. For example, a value obtained by incrementing or decrementing a predetermined value such as 1 with respect to the immediately preceding value, A value obtained by calculating a predetermined function as an argument, a table in which an input value and an output value are associated, and an output value obtained using an immediately preceding value as an input value can be employed.

  Here, for example, a value incremented by 1 each time data is written to the memory unit 24 is used as the sequence number.

  The error detection code is an error detection code for detecting an error (error) of data written in the unit, and is, for example, CRC (Cyclic Redundancy Checking).

  [Data writing control to the memory unit 24]

  FIG. 4 is a diagram for explaining control of data writing to the memory unit 24 by the command sequencer unit 23.

  4, a user block having a unit to which data is written has M + 1 units # 1, # 2,..., # M + 1.

  In FIG. 4, immediately before the data is written (before writing), for example, the M + 1-th unit # M + 1 among the M + 1 units # 1 to # M + 1 is The other 1st to Mth units # 1 to #M are data units.

  In FIG. 4, before writing, the unit number S_PAD of the data unit #m is the value m.

  Although the unit number S_PAD is not given to the buffer unit, in FIG. 4, for convenience, the unit number S_PAD of the unit # M + 1 that is the buffer unit is set to 0 as a value representing the buffer unit.

  In FIG. 4, the sequence number SEQ of the data unit # 1 before writing is the value X. Illustration of sequence numbers SEQ of other data units # 2 to #M is omitted.

  Here, one unit #m is composed of K pages. Now, assuming that the first page of the first unit # 1 of the user block is the first page, the unit #m is composed of K pages from the (m-1) K + 1th page to the mKth page. Is done. The m-th page, which is the last page of each unit #m, is a management page.

  Now, for example, it is assumed that a write command for requesting writing of data to a unit whose unit number S_PAD is 1 is transmitted from the reader / writer 10 to the wireless tag 20 together with the data.

  In this case, according to the write command from the reader / writer 10, the command sequencer unit 23 sets the data transmitted together with the write command to the target unit that is the target unit to be written, that is, the unit number S_PAD is 1. Is written in unit # M + 1 which is a buffer unit, not unit # 1 (unit of unit number S_PAD which is requested to be written by a write command).

  Further, the command sequencer unit 23 displays the unit number S_PAD = 1, which is the same as the unit number S_PAD = 1 of the target unit # 1, on the management page of the unit # M + 1 that is the buffer unit, a predetermined value Y The updated sequence number SEQ and error detection code are written.

  Here, in FIG. 4 (the same applies to FIG. 5 described later), the illustration of the error detection code is omitted.

  In FIG. 4, the sequence number SEQ value Y written in the management page of the unit # M + 1 that is the buffer unit is the sequence number SEQ = written in the management page of the unit # 1 that is the target unit. This is a value X + 1 updated by incrementing X by 1.

  As described above, the unit number S_PAD whose value is 1, the sequence number SEQ updated to the predetermined value Y, and the error detection code are written in the management page of the unit # M + 1 that is the buffer unit. Thus, unit # M + 1 is not a buffer unit but a data unit having a unit number S_PAD of 1.

  As a result, at this time, there are two units # 1 and # M + 1 that have a unit number S_PAD of value 1.

  However, the sequence number SEQ = Y of the unit # M + 1 is a newer value than the sequence number SEQ = X of the unit # 1, that is, a value X + 1 obtained by updating the sequence number SEQ = X.

  Therefore, for the two units # 1 and # M + 1 whose unit number S_PAD is 1, the sequence number SEQ is referred to, so that the unit # M + 1 in which the latest data is written and the data are past Can be distinguished from the unit # 1 written in (unit storing the data written immediately before the latest data among the data written in the unit having the unit number S_PAD of 1).

  Here, when there are two units having the same unit number S_PAD, the unit in which the latest data is written out of the two units (in this embodiment, the unit with the larger sequence number). ) Is also called a new unit, and a unit in which data has been written in the past (a unit with a smaller sequence number) is also called an old unit.

  After that, the command sequencer unit 23 erases the management page of the old unit of the two units # 1 and # M + 1 whose unit number S_PAD is 1, ie, the target unit unit # 1. In the erase state, the unit # 1 is newly set as a buffer unit, and the writing process for writing data to the memory unit 24 is completed.

  As described above, the unit number S_PAD is not assigned to the buffer unit. However, in FIG. 4, the unit number S_PAD of the unit # 1 that newly becomes the buffer unit is set to a value 0 indicating that it is a buffer unit. is there.

  As described above, in accordance with the write command from the reader / writer 10, the command sequencer unit 23 writes data to the unit # M + 1 that is the buffer unit, and uses the unit number of the target unit # 1 as the unit number of the buffer unit. Write unit number S_PAD = 1 and make unit # 1 a new buffer unit. As a result, write data to unit # M + 1 whose unit number S_PAD is 1 .

  As a result, regarding the data stored in the unit whose unit number S_PAD is 1 in the memory unit 24, the latest data (data written in the unit # M + 1 in FIG. 4) is the immediately preceding (previous) data. (In FIG. 4, the data written in the unit # 1) is written, leaving the memory tag, that is, for example, while the memory unit 24 is being accessed, the wireless tag 20 is the reader / writer. It is possible to deal with a case where inconsistency occurs in data stored in the memory unit 24 by moving away from 10 or the like.

  FIG. 5 is a diagram for explaining how to deal with memory corruption.

  In FIG. 5, before writing, as in the case of FIG. 4, the M + 1th unit # M + 1 is a buffer unit, and the other 1st to Mth units # 1 to #M Is a data unit.

  Further, before writing, the unit number S_PAD of the data unit #m has a value m, and the unit number S_PAD of the unit # M + 1 that is a buffer unit has a value 0 representing the buffer unit.

  For example, as in the case of FIG. 4, a write command for requesting writing of data with the unit number S_PAD as the target unit is transmitted from the reader / writer 10 to the wireless tag 20 together with the data. Let's say.

  In this case, as described with reference to FIG. 4, the command sequencer unit 23, in accordance with the write command from the reader / writer 10, transfers the data transmitted together with the write command to the unit # M + 1 (unit Write to the unit whose number S_PAD is 0.

  Further, as described in FIG. 4, the command sequencer unit 23 displays the unit number S_PAD = 1 that is the same as the unit number S_PAD = 1 of the target unit # 1 on the management page of the unit # M + 1 that is the buffer unit. S_PAD = 1, updated the sequence number SEQ = X of the unit # 1 which is the target unit Write the sequence number SEQ of the Y = X + 1 and error detection code, and then manage the unit # 1 which is the target unit By erasing the page and setting it to the erased state, the writing process for writing data to the memory unit 24 is completed with unit # 1 as a new buffer unit.

  Now, during the writing process, for example, in the management page of unit # M + 1 which is a buffer unit, the unit number S_PAD = 1, the sequence number SEQ updated to a predetermined value Y, and the error detection code It is assumed that the wireless tag 20 is separated from the reader / writer 10 while the necessary power is not supplied to the wireless tag 20 (power is cut off).

  In this case, the command sequencer unit 23 recovers the storage contents of the memory unit 24 when the reader / writer 10 and the wireless tag 20 are next brought into proximity and activated when power is supplied (at the next activation). To do.

  That is, for example, in the management page of unit # M + 1 which is a buffer unit, at least unit number S_PAD = of unit number S_PAD = 1, sequence number SEQ of predetermined value Y, and error detection code If the power is turned off after the sequence number SEQ updated to 1 and the predetermined value Y is written, two units # 1 and # M + 1 with the unit number S_PAD of 1 and the same value exist To do.

  As described in FIG. 4, for the two units # 1 and # M + 1 whose unit number S_PAD is 1, the unit (new unit) in which the latest data is written by referring to the sequence number SEQ. ) # M + 1 can be distinguished from unit (old unit) # 1 in which data has been written in the past.

  At the next startup, the command sequencer unit 23 performs error detection using the CRC as the error detection code of the management page of the new unit # M + 1, and if no error is detected (error detection code If the data has been successfully written to the new unit # M + 1, erase the management page of the old unit # 1 and put it in the erased state. (In FIG. 5, the unit number S_PAD is set to a value 0 indicating that it is a buffer unit), and unit # 1 is a buffer unit.

  Then, as described with reference to FIG. 4, new data is written to the buffer unit.

  On the other hand, if an error is detected as a result of error detection using CRC as an error detection code of the management page of the new unit # M + 1 (when the error detection code is an error), the command sequencer unit 23 Indicates that the writing of data to the unit # M + 1, which is a new unit, has not been completed normally, the state of the memory unit 24 is changed to, for example, the writing of data to the unit # M + 1, which is a new unit. It returns to the state just before being called.

  That is, the command sequencer unit 23 erases the management page of the unit # M + 1, which is a new unit, and puts it in the erased state (in FIG. 5, the unit number S_PAD is set to a value 0 indicating that it is a buffer unit). Unit # M + 1 is the buffer unit.

  Then, as described with reference to FIG. 4, new data is written to the buffer unit.

  [Processing of the wireless tag 20]

  FIG. 6 is a flowchart for explaining processing of the wireless tag 20 of FIG.

  In the following, attention is given to one user block, and processing for the one user block will be described.

  When the reader / writer 10 and the wireless tag 20 are close to each other, the RF unit 22 of the wireless tag 20 receives an RF signal from the reader / writer 10 and starts supplying power to the necessary blocks of the wireless tag 20. The command sequencer unit 23 is activated.

  Then, the command sequencer unit 23 is a predetermined unit for performing proximity communication with the reader / writer 10 such as initialization of an internal register (not shown) before receiving a command from the reader / writer 10 after starting. Start the startup process.

  Further, the command sequencer unit 23 erases all the pages of the buffer unit in the memory unit 24 during the activation process (only the process of setting the erased state), and puts it in the erased state.

  That is, in step S11, the command sequencer unit 23 confirms the unit number S_PAD of the management page of M + 1 units # 1 to # M + 1 constituting the target user block of interest in the memory unit 24. The process proceeds to step S12.

  In step S12, the command sequencer unit 23 determines whether there is a unit (two units) having the same unit number S_PAD based on the result of the confirmation of the unit number S_PAD in step S11.

  If it is determined in step S12 that no unit of the same unit number S_PAD exists, that is, if there is a unit in which the management page is in an erased state, that is, there is a buffer unit, the process proceeds to steps S13 to S15. Skip to step S16.

  If it is determined in step S12 that a unit having the same unit number S_PAD exists, that is, for example, because the previous write process has not been completed, the management page is erased as described in FIG. If there is no buffer unit that is in the state and there are two units having the same unit number S_PAD, the process proceeds to step S13, and the command sequencer unit 23 determines that the unit number S_PAD has the same unit number S_PAD. Of the two units, error detection is performed using an error detection code of a unit (new unit) having a new sequence number SEQ to determine whether or not the new unit has an error.

  If it is determined in step S13 that there is an error in the new unit (the error detection code is not normal), the process proceeds to step S14, and the command sequencer unit 23 selects one of the two units of the same unit number S_PAD. The unit having the old sequence number SEQ (the old unit) is recognized as the latest unit in which the latest normal writing has been performed.

  Further, in step S14, the command sequencer unit 23 recognizes the other unit (new unit) of the two units having the same unit number S_PAD as a buffer unit, and the process proceeds to step S16.

  If it is determined in step S13 that there is no error in the new unit (the error detection code is normal), the process proceeds to step S15, and the command sequencer unit 23 uses two of the same unit number S_PAD. Among the units, the sequence number SEQ recognizes a new unit (new unit) as the latest unit in which the latest normal writing has been performed.

  Furthermore, in step S15, the command sequencer unit 23 recognizes the other unit (old unit) of the two units having the same unit number S_PAD as a buffer unit, and the process proceeds to step S16.

  In step S16, the command sequencer unit 23 determines whether the management page of the buffer unit is in an erased state.

  If it is determined in step S16 that the management page of the buffer unit is in an erased state, that is, if the management page of the buffer unit is erased in step S22, which will be described later, of the previously performed write processing. The process skips step S17 and proceeds to step S18.

  If it is determined in step S16 that the buffer unit management page is not in the erased state, that is, the buffer unit management page has not been erased in step S22, which will be described later, of the previously performed write processing. Therefore, it is necessary to maintain sufficient retention characteristics for the management page of the latest unit that has been a buffer unit and data has been written during the previous writing process performed in step S21 immediately before step S22. If there is a possibility that the charge has not been accumulated in the floating gate to the extent possible, the process proceeds to step S17, and the command sequencer unit 23 stores the contents of the management page in the management page of the latest unit. Is rewritten, and the process proceeds to step S18. No.

  Here, in the rewriting of the storage content of the management page to the management page of the latest unit in step S17, the command sequencer unit 23 changes the storage content of the management page of the latest unit to only one page of the management page. The management page is written and the charge is accumulated in the floating gate to the extent that sufficient retention characteristics can be maintained.

  As described above, with respect to the management page of the latest unit that has been a buffer unit at the time of the previous writing process and to which data has been written, the charge to the floating gate to such an extent that sufficient retention characteristics can be maintained. If there is a possibility that data has not been stored, the management page of the latest unit will be rewritten. Regarding the management page, the reader / writer 10 and the wireless tag 20 are separated before sufficient charge is accumulated in the floating gate (charge accumulation in the floating gate that can maintain sufficient retention characteristics). Even if sufficient charge cannot be stored in the floating gate due to By the processing of step S17 to be performed, the charge on the floating gate is sufficiently accumulated, it is possible to maintain the retention properties.

  In step S18, the command sequencer unit 23 erases all pages of the buffer unit and puts them into an erased state.

  The above steps S11 to S18 are performed during the startup process.

  When the activation process is completed in the wireless tag 20, the process proceeds from step S <b> 18 to step S <b> 19, and the wireless tag 20 enters a command waiting state waiting for a command from the reader / writer 10.

  Then, after waiting for a command to be transmitted from the reader / writer 10, the process proceeds from step S 19 to step S 20, and the RF unit 22 receives the command from the reader / writer 10 and supplies it to the command sequencer unit 23. Then, the process proceeds to step S21.

  For example, assuming that the command from the reader / writer 10 is a write command, write processing is performed in accordance with the write command in step S21 and subsequent step S22.

  That is, in step S21, the command sequencer unit 23 writes the data transmitted from the reader / writer 20 together with the write command to a page other than the management page of the buffer unit according to the write command from the reader / writer 10 (write state). Only write processing), and set to the write state.

  Here, in the conventional wireless tag, in writing data to the non-volatile memory, after receiving a write command from the reader / writer, erasing is performed to put the memory cell in an erased state, and then the erased memory cell is written. A light is put into a state.

  In FIG. 6, since all the pages of the buffer unit have already been erased in step S18 performed during the activation process, it is not necessary to erase before writing in step S21.

  In step S21, the command sequencer 23 writes data to a page other than the buffer unit management page, and then writes the unit number, sequence number, and error detection code to the buffer unit management page ( Write only) and put it in the light state.

  In step S21, the unit number written in the management page of the buffer unit is the unit number of the target unit to which data is written, and is included in the write command from the reader / writer, for example.

  In step S21, the sequence number written in the management page of the buffer unit is a value obtained by incrementing the sequence number already written in the management page of the target unit by 1.

  Further, in step S21, the error detection code written to the management page of the buffer unit is the data written to a page other than the management page of the buffer unit in the command sequencer unit 23 (or the data and the management page). It is obtained for the written unit number and sequence number).

  In step S21, when data is written to a page other than the management page of the buffer unit, and further, the unit number, sequence number, and error detection code are written to the management page of the buffer unit, the process proceeds to step S22. The command sequencer unit 23 erases the management page of the unit (data unit) having the same sequence number as the sequence number written in the management page of the buffer unit in the immediately preceding step S21, and the writing process is completed.

  That is, when the sequence number is written in the management page of the buffer unit in the immediately preceding step S21, the new unit (the management page is written in the immediately preceding step S21) as the sequence number unit in the user block of interest. , A unit that was a buffer unit) and an old unit that is also a target unit.

  In step S22, the command sequencer unit 23 erases (only erases) the management page of the old unit (target unit) of the new unit and the old unit, thereby replacing the old unit with a new buffer. A unit.

  As described above, in the wireless tag 20, the command sequencer unit 23 is activated when the RF unit 22 receives an RF signal from the reader / writer 10, and after activation, before receiving a command from the reader / writer 10. Since all the pages of the buffer unit are erased during the start-up process to be performed (step S18), after receiving the write command from the reader / writer 10, the data is written in the memory unit 24, which is a non-volatile memory. Instead of erasing the cell to the erased state, it is only necessary to write the memory cell to the write state.

  Therefore, after receiving the write command, erasing is not performed even if it takes the same time as the conventional charge accumulation time (time for accumulating charge in the floating gate) necessary for the retention characteristic to maintain the write state. Therefore, the time (write processing time) from the reception of the write command to the completion of the write processing for writing data into the memory unit 24 can be shortened.

  That is, it is possible to maintain the same retention characteristics as in the prior art and to shorten the write processing time.

  In FIG. 6, when it is determined in step S12 that there is no unit with the same unit number S_PAD, that is, there is a buffer unit in which the management page is in the erased state, and in step S13, a new It is determined that there is an error in the unit, and in step S14, the old unit (the unit with the old sequence number SEQ) of the two units of the same unit number S_PAD is made the latest unit, and the new unit is In either case of being a unit, the process proceeds to step S16. However, in these cases, the process can proceed to step S18 instead of step S16.

  That is, as described above, in step S16, it is determined whether or not the management page of the buffer unit is in an erased state.

  If the management page of the buffer unit is not in the erased state, the management page of the buffer unit is not erased in step S22 in the previous writing process, and therefore, immediately before step S22. The write in step S21 has been completed until a sufficient charge is accumulated in the floating gate for the management page of the latest unit that has been a buffer unit at the time of the previous write process and in which data has been written. In step S17, the management page of the latest unit is rewritten in order to maintain the retention characteristics of the management page of the latest unit.

  On the other hand, in step S12, it is determined that there is no unit with the same unit number S_PAD when there is a buffer unit in which the management page is in an erased state, and that there is a buffer unit. In step S22 as the write process performed last time, the management page of the unit that became the buffer unit is erased. Therefore, for the unit that was the buffer unit at the previous write process, step S21 is performed. As for the management page of the unit, sufficient charge is accumulated in the floating gate.

  Therefore, since the retention characteristics of the management page can be maintained, it is not necessary to rewrite the management page in step S17.

  If there are two units with the same unit number S_PAD, and the old unit of the two units is the latest unit in step S14, management of the old unit to be the latest unit is performed. For the page, if the old unit was the buffer unit last time, the management page is rewritten, if necessary, in step S17 during the startup process performed after the data was written. Therefore, the retention characteristic of the management page can be maintained, and it is not necessary to rewrite the management page in this step S17.

  Therefore, when it is determined in step S12 that no unit with the same unit number S_PAD exists, and when the old unit of the two units with the same unit number S_PAD is the latest unit in step S14. In any case, since the retention characteristic of the management page can be maintained, in these cases, the process can proceed to step S18 instead of step S16.

  [Write processing time]

  FIG. 7 is a diagram for explaining the write processing time of the wireless tag 20.

  Here, as described above, in the data writing to the nonvolatile memory with the conventional wireless tag, after the write command is received from the reader / writer, the memory cell is erased and then erased. Writing is performed to put the memory cell in the state into the write state.

  A method of writing data in the nonvolatile memory by performing erase and write necessary for writing data after receiving the write command is called a simultaneous method.

  On the other hand, as described with reference to FIG. 6, during the activation process of the wireless tag 20, all pages of the buffer unit are erased (only erase and write necessary for data writing are performed). After the write command is received from the reader / writer 10, data is written to the buffer unit (only the erase and write necessary for data writing are performed) and the data is written to the memory unit 24. Is called separation method.

  In the simultaneous method, as shown in FIG. 7, when the wireless tag and the reader / writer are brought close to each other and the output of the RF signal from the reader / writer is started, the wireless tag starts up using the RF signal as a power source. Start the startup process.

  Furthermore, after the activation process is completed, the wireless tag waits for polling to be transmitted from the reader / writer, receives the polling, and returns a response to the polling.

  Note that the time required for the reader / writer to transmit polling after outputting the RF signal is, for example, about several tens of milliseconds. The activation process is completed in about 10 milliseconds, for example.

  Thereafter, when a write command is transmitted from the reader / writer, the wireless tag receives the write command. Further, according to the write command from the reader / writer, the wireless tag performs a writing process of writing the data transmitted from the reader / writer together with the write command to the nonvolatile memory.

  Note that the time from when the reader / writer receives a response from the wireless tag until the next command starts to be transmitted is, for example, 2.4 milliseconds or more.

  When the writing process is completed, the wireless tag returns a response to the write command.

  As described above, in the simultaneous writing process, the wireless tag performs erasing and writing after receiving the write command, and writes data to the nonvolatile memory.

  Therefore, if the unit (buffer unit) is composed of K pages, the time required for erasing one page is set to Te seconds, and the time required to write one page is set to Tw seconds, the simultaneous write processing can be performed. Takes K × (Te + Tw) seconds.

  On the other hand, in the separation method, as shown in FIG. 7, when the reader / writer 10 and the wireless tag 20 are in close proximity and output of an RF signal from the reader / writer 10 is started, the wireless tag 20 Start up with the signal as the power source and start the startup process.

  In the activation process, the wireless tag 20 erases all pages of the buffer unit as described with reference to FIG.

  The wireless tag 20 waits for the polling to be transmitted from the reader / writer 10 after the activation process is completed, receives the polling, and returns a response to the polling.

  Then, when a write command is transmitted from the reader / writer, the wireless tag 20 receives the write command. Further, according to the write command from the reader / writer 10, the wireless tag 20 performs a writing process of writing data transmitted from the reader / writer together with the write command into the memory unit 24 (buffer unit thereof).

  Thereafter, when the writing process is completed, the wireless tag 20 returns a response to the write command.

  In the separation-type writing process, as described with reference to FIG. 6, after receiving the write command, the wireless tag 20 writes only data to the buffer unit (all pages) and writes data to the memory unit 24.

  That is, since the buffer unit is already erased during the activation process, it is not performed after receiving the write command from the reader / writer 10 (it is not necessary).

  In the separation method, the wireless tag 20 performs writing to the buffer unit (step S21), and then erases one page, which is the management page of the target unit (step S22), as described in FIG. Processing is complete.

  Therefore, as described above, when the buffer unit is composed of K pages, the time required for erasing one page is set to Te seconds, and the time required to write one page is set to Tw seconds, the writing of the separation method is performed. The time required for processing (write processing time) is Te + K × Tw seconds.

  From the above, the writing processing time required for the writing method of the separation method is shorter by (K-1) × Te (= K × (Te + Tw) − (Te + K × Tw)) seconds than the simultaneous method. Become.

  As described above, according to the separation method, the erase necessary for writing is performed in advance during the start-up process, so the retention characteristics similar to the simultaneous method are maintained and the write command is received. Can be shortened.

  [Another Embodiment of Logical Format of Memory Unit 24]

  FIG. 8 is a diagram for explaining another embodiment of the logical format of the memory unit 24 included in the wireless tag 20 of FIG.

  The logical format of FIG. 8 is common to the case of FIG. 3 in that a part of the storage area of the memory unit 24 is one or more user blocks allocated to the service.

  However, the logical format of FIG. 8 is that management information is stored in a page (management page) in that another part of the storage area of the memory unit 24 is a management block for storing management information. It is different from the case of.

  Here, in FIG. 3, since the unit requires one or more pages (data pages) for storing data and one management page for storing management information, the unit includes a plurality of pages. In FIG. 8, since the management information is stored in the management block and no management page is required, the unit can be composed of one or more pages.

  In FIG. 8, the unit is composed of one page.

  Thus, in FIG. 8, a unit is equal to a page.

  In FIG. 8, data and CRC as an error detection code of the data are stored in a user block unit (equivalent to a page).

  The management block includes, for example, M ′ units (which are also pages in FIG. 8), which is twice the number of user blocks.

  Accordingly, if the memory unit 24 has, for example, one user block, the management block has two units.

  Management information for each user block is stored in the management block. The management information for one user block is stored in two units of the management block.

  Here, the two units of the management block that store the management information of one user block are also referred to as two units of the management block corresponding to the user block.

  When attention is paid to a certain user block, the attention user block is configured as management information of the attention user block in each of the two units (pages) of the management block corresponding to the attention user block of interest. Unit number S_PAD of M + 1 units, one sequence number, CRC as an error detection code of them (unit number S_PAD of one unit M + 1, and one sequence number), etc. Is memorized.

  Here, every time data is written to the target user block, management information of the target user block is alternately written in the two units of the management block corresponding to the target user block.

  Therefore, the latest management information of the target user block is stored in one of the two units of the management block corresponding to the target user block, and the latest management information is stored in the other unit. Management information immediately before being written is stored.

  As described above, the management information of the user block of interest is written alternately in the two units of the management block corresponding to the user block of interest every time data is written to the user block of interest. The latest management information and the management information immediately before the latest management information is written are stored, so that it is possible to cope with memory corruption.

  The storage area for storing the unit number S_PAD of M + 1 units for each of the two units (pages) of the management block corresponding to the target user block is M + 1 units constituting the target user block. Are divided into M + 1 storage areas (hereinafter also referred to as unit number areas) for storing information for specifying the unit number S_PAD (hereinafter also referred to as unit number specifying information).

  Then, the value m is adopted as the unit number specifying information of the m-th unit #m among the M + 1 units # 1 to # M + 1 constituting the target user block, and M + 1 units In the number area, the unit number identification information #m of the unit #m whose unit number S_PAD is the value i is stored in the i-th unit number area from the top.

  Accordingly, when unit number identification information #m is stored in the i-th unit number area from the top of the M + 1 unit number areas, M + 1 pieces constituting the target user block are stored. Among the units # 1 to # M + 1, the unit number S_PAD of the m-th unit #m is the value i.

  As described above, in FIG. 8, it is specified that the unit number S_PAD of the unit #m has the value i by writing the unit number specifying information #m of the unit #m in the i-th unit number area. Therefore, it can be said that the management information includes the unit number S_PAD # i of the unit #m substantially (equivalently).

  Here, in FIG. 8, as described above, since one sequence number SEQ is included in the management information of the target user block, data is written in any unit of the target user block. Even updated.

  That is, in FIG. 3, management information exists for each unit, and one sequence number SEQ is included in the management information. Therefore, the sequence number SEQ included in the management information of a certain unit includes data in the unit. Updated every time is written.

  On the other hand, in FIG. 8, management information exists for each user block, and since one sequence number SEQ is included in the management information, the sequence number SEQ included in the management information of a certain user block is the user block. The data is updated when data is written to any of the units (updated every time data is written to the user block).

  Note that only one user block can be provided in the memory unit 24, and in this case, only one sequence number SEQ exists for the memory unit 24.

  Even when the memory unit 24 has the logical format of FIG. 8, the command sequencer unit 23 controls data writing to the memory unit 24 in the same manner as in FIG. 3.

  That is, for example, immediately before data is written (before writing), for example, the M + 1-th unit # M + 1 of the M + 1 units # 1 to # M + 1 of the user block of interest Is a buffer unit, and the other 1st to Mth units # 1 to #M are data units.

  Further, it is assumed that the unit number S_PAD of the data unit #m has the value m, and the sequence number SEQ (included in the management information) of the user block of interest has the value X.

  Now, for example, it is assumed that a write command for requesting writing of data to a unit whose unit number S_PAD (value of the user block of interest) is 1 is transmitted from the reader / writer 10 to the wireless tag 20 together with the data. .

  In this case, according to the write command from the reader / writer 10, the command sequencer unit 23 sets the data transmitted together with the write command to the target unit that is the target unit to be written, that is, the unit number S_PAD is 1. Is written in unit # M + 1 which is a buffer unit, not unit # 1 (unit of unit number S_PAD which is requested to be written by a write command).

  Thereafter, the command sequencer unit 23 updates the management information of the user block of interest.

  That is, as the management information of the user block of interest, as described above, the latest management information (hereinafter also referred to as latest management information) and the management information immediately before the latest management information is written (hereinafter referred to as previous management information). Is stored in the memory unit 24.

  Now, the management information C # t is stored as the latest management information of the user block of interest in the memory unit 24, and the management information C # t-1 is stored as the management information immediately before the user block of interest. To do.

  The command sequencer unit 23 uses the management information C # t as the update source management information (hereinafter also referred to as update source management information), and the unit number S_PAD of the unit # M + 1 that is the buffer unit as the target unit. The unit number S_PAD = 1, which is the same as the unit number S_PAD = 1 of a certain unit # 1, is updated so that the unit number S_PAD of the unit # 1, which is a new buffer unit, has a value 0 indicating that it is a buffer unit Update the original management information.

  Further, the command sequencer unit 23 updates the sequence number SEQ included in the update source management information, and calculates a new error detection code.

  Then, assuming that the update source management information obtained as a result is represented as management information C # t + 1, the command sequencer unit 23 uses the management information C # t + 1 as the management information of the user block of interest. The management information C # t-1, which is management information immediately before the unit 24, is written in an overwritten form.

  As a result, the management information C # t + 1 becomes the latest management information of the attention user block, and the management information C # t becomes the management information immediately before the attention user block.

  When the memory unit 24 has the logical format shown in FIG. 8, the command sequencer unit 23 performs the following processing instead of steps S11 to S18 in FIG.

  That is, the command sequencer unit 23 performs error detection using the error detection code of the latest management information.

  When an error is detected in the latest management information, the command sequencer unit 23 recognizes the buffer unit by referring to the latest management information, and all pages of the buffer unit (in FIG. 8, 1). Page) is erased to enter the erased state.

  On the other hand, when an error is detected in the latest management information, the command sequencer unit 23 recognizes the buffer unit by referring to the immediately preceding management information, erases all the pages of the buffer unit, and sets the erased state. .

  As described above, the command sequencer unit 23 performs the process until the buffer unit is placed in the erase state during the startup process.

  After that, for example, when a write command is transmitted from the reader / writer 10, the command sequencer unit 23 controls the writing of data to the memory unit 24 as described above.

  However, when an error is detected in the latest management information, the command sequencer unit 23 updates the immediately previous management information as the update source management information, not the latest management information, and the update source management information obtained as a result Is overwritten on the latest management information.

  [Processing of the wireless tag 20]

  In FIG. 6, the processing of the wireless tag 20 has been described on the assumption that the write command is transmitted only once from the reader / writer 10 to the wireless tag 20. In response to this, the write command may be transmitted one or more times.

  FIG. 9 is a flowchart for explaining processing of the wireless tag 20 in FIG. 2 when a write command is transmitted from the reader / writer 10 to the wireless tag 20 at least once.

  The logical format of the memory unit 24 of the wireless tag 20 is assumed to be the format shown in FIG.

  In the wireless tag 20, the same processes as in steps S11 to S20 in FIG. 6 are performed in steps S41 to S50, respectively.

  In step S50, when the RF unit 22 receives the write command from the reader / writer 10 and supplies it to the command sequencer unit 23, the process proceeds to step S51, and the command sequencer unit 23 stores all pages in the buffer unit. , It is determined whether or not the erase state.

  If it is determined in step S51 that all pages of the buffer unit are in the erased state, the process skips step S52 and proceeds to step S53.

  If it is determined in step S51 that one or more pages of the buffer unit are not in the erased state, the process proceeds to step S52, and the command sequencer unit 23 erases the buffer unit and all the buffer units are erased. The page is erased, and the process proceeds to step S53.

  Here, in step S52, erasure of the buffer unit may be performed on all pages of the buffer unit, or only pages that are not in the erased state among the pages of the buffer unit may be performed.

  In steps S53 and S54, processing similar to that in steps S21 and S22 of FIG. 6 is performed.

  After step S54, the process returns to step S49, and the wireless tag 20 enters a command wait state waiting for a command from the reader / writer 10.

  Then, after waiting for the next write command to be transmitted from the reader / writer 10, the process proceeds from step S49 to step S50. Thereafter, the processes of steps S49 to S54 are repeated in the same manner.

  The processing in steps S49 to S54 is performed when, for example, the wireless tag 20 cannot receive power supply due to the separation from the reader / writer 10, or the reader / writer 10 If no command is transmitted during this period (when the command waiting state in step S49 continues for a predetermined time), the process ends.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

  That is, for example, in the present embodiment, the EEPROM is adopted as the memory unit 24 which is a nonvolatile memory. A non-volatile memory can be employed. However, the separation type writing process is particularly useful for a nonvolatile memory such as an EEPROM having a long charge accumulation time.

  In this embodiment, one unit is a buffer unit, but a plurality of units can be adopted as the buffer unit.

  10 reader / writer, 11 antenna, 20 wireless tag, 21 antenna, 22 RF unit, 23 command sequencer unit, 24 memory unit

Claims (7)

A communication means for performing proximity communication with a reader / writer;
Control means for controlling the writing of data to the nonvolatile memory in accordance with a command from the reader / writer,
A part of the storage area of the nonvolatile memory is a user block that is a storage area of a minimum unit allocated to a service,
The user block has a plurality of units;
The unit has one or more pages that are storage areas of a predetermined unit in which writing is performed,
At least one of a plurality of units constituting the user block is a buffer unit that functions as a buffer for buffering data written to the user block,
The nonvolatile memory stores management information for managing a storage area of the nonvolatile memory,
The management information includes a unit number that identifies the unit,
The control means includes
According to the command from the reader / writer, write the data to the buffer unit and the target unit to which the data is to be written,
The communication means is activated by receiving an RF signal from the reader / writer, and erases all pages of the buffer unit during activation processing performed after activation and before receiving a command from the reader / writer. Communication device. The unit is composed of one page,
The other part of the storage area of the nonvolatile memory is a management block that stores management information for each user block,
The management information of the user block includes a unit number of each of a plurality of units included in the user block and one sequence number whose value is regularly updated each time data is written to the nonvolatile memory. The communication apparatus according to 1. The unit is composed of a plurality of pages,
One of the plurality of pages of one unit is a management page that stores management information for each unit,
The communication apparatus according to claim 1, wherein the management information of the unit includes a unit number of the unit and one sequence number whose value is regularly updated each time data is written to the nonvolatile memory. The control means includes
After writing data to a page other than the management page of the unit, the unit number, the sequence number, and an error detection code for detecting an error in the data written to the unit are written to the management page. Item 4. The communication device according to Item 3. The communication device according to claim 1, wherein the nonvolatile memory is an EEPROM. A communication means for performing proximity communication with a reader / writer;
In a communication method of a communication device comprising: control means for controlling data writing to a nonvolatile memory according to a command from the reader / writer;
A part of the storage area of the nonvolatile memory is a user block that is a storage area of a minimum unit allocated to a service,
The user block has a plurality of units;
The unit has one or more pages that are storage areas of a predetermined unit in which writing is performed,
At least one of a plurality of units constituting the user block is a buffer unit that functions as a buffer for buffering data written to the user block,
The nonvolatile memory stores management information for managing a storage area of the nonvolatile memory,
The management information includes a unit number that identifies the unit,
The control means is
According to the command from the reader / writer, write the data to the buffer unit and the target unit to which the data is to be written,
The communication means is activated by receiving an RF signal from the reader / writer, and erases all pages of the buffer unit during activation processing performed after activation and before receiving a command from the reader / writer. A communication method including steps. An antenna,
Communication means for performing proximity communication with a reader / writer via the antenna;
Control means for controlling the writing of data to the nonvolatile memory in accordance with a command from the reader / writer,
A part of the storage area of the nonvolatile memory is a user block that is a storage area of a minimum unit allocated to a service,
The user block has a plurality of units;
The unit has one or more pages that are storage areas of a predetermined unit in which writing is performed,
At least one of a plurality of units constituting the user block is a buffer unit that functions as a buffer for buffering data written to the user block,
The nonvolatile memory stores management information for managing a storage area of the nonvolatile memory,
The management information includes a unit number that identifies the unit,
The control means includes
According to the command from the reader / writer, write the data to the buffer unit and the target unit to which the data is to be written,
The communication means is activated by receiving an RF signal from the reader / writer, and erases all pages of the buffer unit during activation processing performed after activation and before receiving a command from the reader / writer. Wireless tag.

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