Patent Description:
Conventionally, a RFID communication unit has been known, which reads and writes data from a RF tag attached to an individual and exchanges the data with an industrial control device such as a programmable controller (Programmable Logic Controller, hereinafter abbreviated as "PLC") in order to perform individual management at a manufacturing site or a distribution site. In recent years, information for individual management has increased, and data handled by the RFID communication unit has increased in capacity.

In the RFID communication unit, data is read and written by wireless communication with the RF tag, and it is common to collectively transfer the data between the RFID communication unit and the RF tag even when the data has increased in capacity.

EP patent application no. <CIT> teaches a wireless tag communication apparatus that includes a plurality of communication units configured to communicate with a wireless tag. The communication units are disposed such that communicable ranges of the communication units overlap each other. A control unit controls each of the plurality of communication units to alternate between a communication state and a pause state. When the wireless tag is positioned within communication ranges of both first and second communication units of the plurality of communication units, the control unit controls the first communication unit to be in the communication state and the second communication unit to be in the pause state. <CIT> relates to a method for scheduling communications over a wireless communication subsystem and a radio frequency identification (RFID) communication subsystem, said method comprising determining one or more periods of activity of the wireless communication subsystem; deriving one or more periods of non-activity on the basis of the one or more determined periods of activity; synchronizing an operation of the radio frequency identification (RFID) communication subsystem with the one or more periods of non-activity; and triggering the operation of the radio frequency identification (RFID) communication subsystem in accordance with the one or more derived periods of non-activity to enable substantially concurrent communications operation of the wireless communication subsystem and the radio frequency identification (RFID) communication subsystem. EP patent application no. <CIT> relates to systems and methods that provide electronic data (e.g., Electronic Product Code (EPC) data) obtained from Radio Frequency Identification (RFID) tags by RFID readers and/or from servers to one or more industrial components (e.g., controllers, programmable logic controllers, modules, etc.). The systems and methods employ component that processes, if desired, and stores received electronic data as records within a table. Processing includes filtering for data of interest and/or formatting the data in a suitable structure. Storage can include delineating related electronic data across rows the table and types of data across columns of a row. Upon receiving a subscription and/or request for electronic data from the one or more industrial components, the data can be retrieved and conveyed to the subscribing and/or requesting components. A patent application no. <CIT> teaches apparatuses, systems for, and methods of transporting digital signals and radio-frequency RF signals. An intelligent network and corresponding method are provided for transporting RF signals to an RFID antenna and transporting digital signals to a controller. The intelligent network is implemented with a manager unit for controlling a plurality of network devices to facilitate the efficient management of RFID-enabled devices. The network devices include a combination router/switch, which has the capability of switching both digital data and RF data, RFID readers, RFID reader/writer pads, and other devices.

Optional features of the invention are provided by the dependent claims.

By the way, in order to realize control with high speed and high precision in the PLC, it is necessary to make a control period of the PLC constant and short. However, if the capacity of the data exchanged between the PLC and the RFID communication unit is large, it is necessary to suppress the data exchange capacity at the expense of a transfer speed so that the control period of the PLC becomes short, or to enlarge the data exchange capacity at the expense of the control period of the PLC so as to achieve acceleration.

Meanwhile, there is a demand for a technique capable of achieving both acceleration in the data transfer and uniformity in the control period of the PLC even when a large capacity of data is exchanged between the PLC and the RFID communication unit.

One aspect of the present invention is to realize a technique capable of achieving both acceleration in the data transfer and uniformity in the control period of the PLC.

In order to solve the above-described problems, a RFID communication unit according to one aspect of the present invention includes a higher-order communication control part for performing communication with a higher-order controller in a predetermined communication period, wherein the higher-order controller is external to the RFID communication unit, the higher-order controller is configured to communicate with the RFID communication unit by exchanging a plurality of data, each data having the same fixed data exchange size, and each data being communicated during a fixed communication period, and a RF communication control part for performing at least one of reading and writing of data with a RF tag by wireless communication, the RFID communication unit being characterized in that the RF communication control part is configured to select a division transfer method for dividing data subjected to at least one of reading and writing with the RF tag into a plurality of data packets, each data packet having the same data exchange size and each data package being communicable in one communication period in the higher-order communication control part, and transferring each of the plurality of data packets to the higher-order controller or to the RF tag in the one communication period, wherein the RF communication control part is configured to concurrently execute the wireless communication with the RF tag during the communication period in which communication by the higher-order communication control part is performed; or a batch transfer method for collectively transferring data subjected to at least one of reading and writing with the RF tag, wherein the data is transferred to the RF tag in one single communication period, wherein the data is then transferred to, or was transferred beforehand from, the higher-order controller in another communication session.

Further, in order to solve the above-described problems, a method for controlling the RFID communication unit according to one aspect of the present invention includes a step of performing, by a higher-order communication control part of the RFID communication unit, communication with a higher-order controller in a predetermined communication period, wherein the higher-order controller is external to the RFID communication unit, the higher-order controller communicates with the RFID communication unit by exchanging a plurality of data, each data having the same fixed data exchange size, and each data being communicated during a fixed communication period, and a step of performing, by a RF communication part of the RFID communication unit, at least one of reading and writing of data with a RF tag by wireless communication. The method being characterized in further comprising: a step of selecting, by the RF communication part of the RFID communication unit, a division transfer method or a batch transfer method, wherein the division transfer method for dividing data subjected to at least one of reading and writing with the RF tag into a plurality of data packets, each data packet having the same data exchange size and each data package being communicable in one communication period in the higher-order communication control part, and transferring each of the plurality of data packets to the higher-order controller or to the RF tag n the one communication period, wherein the wireless communication with the RF tag is concurrently executed during the communication period in which the communication with the higher-order controller is performed, and the batch transfer method for collectively transferring data subjected to at least one of reading and writing with the RF tag, wherein the data is transferred to the RF tag in one single communication period, and wherein the data is then transferred to, or was transferred beforehand from, the higher-order controller (<NUM>) in another communication session.

Further, in order to solve the above-described problems, a product including one or more tangible computer-readable non-transitory storage media comprising computer-executable instructions which, when executed by a computer associated with a RFID communication unit, cause the RFID communication unit to carry out all the steps of the method for controlling the RFID communication unit.

According to one aspect of the present invention, it is possible to achieve both acceleration in data transfer and uniformity in a control period of a PLC.

Hereinafter, an embodiment according to one aspect of the present invention (hereinafter, also referred to as "the present embodiment") is described with reference to the drawings.

First, an example of a scene in which the present invention is applied is described with reference to <FIG> shows an example of a main configuration of a RFID communication unit <NUM> according to the present embodiment.

For example, as shown in <FIG>, the RFID communication unit <NUM> according to the present embodiment is used as an input machine of a programmable logic controller (PLC) <NUM> which is a higher-order controller. The RFID communication unit <NUM> performs communication with the PLC <NUM> in a predetermined communication period by the control of a higher-order communication control part <NUM>. Further, the RFID communication unit <NUM> performs at least one of data reading and data writing with a RF tag <NUM> by wireless communication based on the control of a RF communication control part <NUM> in accordance with a command from the PLC <NUM>. Further, the RFID communication unit <NUM> receives response data from the RF tag <NUM> and transfers the received response data to the PLC <NUM>.

The RF tag <NUM> is attached to an object such as a part or a product in order to improve traceability at a production site for example.

The RFID communication unit <NUM> communicates in the predetermined communication period in accordance with a control period of the PLC <NUM>, and divides data into a data exchange size which is communicable in one communication period to transfer the data by a plurality of times of communication. Further, the RFID communication unit <NUM> concurrently executes wireless communication with the RF tag <NUM> for a communication duration in which communication with the PLC <NUM> is performed.

The RFID communication unit <NUM> first receives a command from the PLC <NUM>. Subsequently, the RFID communication unit <NUM> performs at least one of reading and writing with the RF tag. At this time, the RFID communication unit <NUM> divides data subjected to at least one of reading and writing with the RF tag <NUM> into a data exchange size that is communicable in one communication period with the PLC <NUM>, and transfers the divided data to the RF tag <NUM> by a plurality of times of communication. Then, the RFID communication unit <NUM> transfers a transfer result with the RF tag <NUM> to the PLC <NUM>. The RFID communication unit <NUM> concurrently transfers the transfer result with the RF tag <NUM> to the PLC <NUM> when the wireless communication with the RF tag <NUM> is performed for each wireless communication with the RF tag <NUM>.

Thereby, the RFID communication unit <NUM> receives the command from the PLC <NUM>, performs at least one of reading and writing with the RF tag, shortens a total processing time of transferring the transfer result with the RF tag to the PLC <NUM>, and keeps the control period of the PLC <NUM> constant by performing communication with the PLC in the predetermined communication period.

Hereinafter, the configuration of the RFID communication unit <NUM> according to the embodiment of the present invention is described in detail with reference to <FIG>.

Hereinafter, Embodiment <NUM> of the present invention is described in detail.

As described above, the RFID communication unit <NUM> includes the higher-order communication control part <NUM>, the RF communication control part <NUM>, and an antenna <NUM>.

The higher-order communication control part <NUM> executes wired communication with the PLC <NUM> via a bus or a network. The higher-order communication control part <NUM> can exchange data with the PLC <NUM> at a high speed of several microseconds to several milliseconds per byte.

The antenna <NUM> realizes the wireless communication with the RF tag <NUM>. Based on the control of the RF communication control part <NUM>, the antenna <NUM> transmits an electromagnetic wave including a command signal and accepts a response signal from the RF tag <NUM> with respect to the command.

The RF communication control part <NUM> performs at least one of data reading and data writing with the RF tag via the antenna <NUM>. In addition, the RF communication control part <NUM> may be a calculation device having a function of comprehensively controlling each part of the RFID communication unit <NUM>. The RF communication control part <NUM> may control each part of the RFID communication unit <NUM> in a manner that, for example, one or more processors (such as a CPU) execute a program stored in one or more memories (such as a RAM or a ROM).

The RF communication control part <NUM> includes a command decryption part <NUM> and a communication execution part <NUM>.

The command decryption part <NUM> decodes the commands received from the PLC <NUM> by the function of the higher-order communication control part <NUM>. The commands received from the PLC <NUM> include a write command that specifies data writing with the RF tag <NUM> and a read command that specifies data reading with the RF tag <NUM>. The write command and the read command include a data transfer period between the PLC <NUM> and the RFID communication unit <NUM>, a communication period between the PLC <NUM> and the RFID communication unit <NUM>, and data about the data exchange size.

The command decryption part <NUM> converts data included in the write command received from the PLC <NUM> into data writable to the RF tag <NUM>. The command decryption part <NUM> converts, for example, data of octal code, hexadecimal code, <NUM>-ary code or the like included in the write command which is received from the PLC <NUM> into data of ASCII code.

Further, the command decryption part <NUM> converts data read with the RF tag <NUM> into data that can be transferred to the PLC <NUM> as a response to the read command received from the PLC <NUM>. The command decryption part <NUM> converts, for example, numeral string data read from the RF tag <NUM> into the data of octal code, hexadecimal code, <NUM>-ary code or the like.

The communication execution part <NUM> transmits a command signal and receives a response signal with respect to the RF tag <NUM> via the antenna <NUM>. Further, the communication execution part <NUM> may be configured to be capable of executing decoding processing of the response signal received from the RF tag <NUM>. In addition, the wireless communication with the RF tag <NUM> via the antenna <NUM> is communication with a speed of several milliseconds to several tens of milliseconds per byte.

<FIG> is diagram schematically showing the flow of data when the RFID communication unit <NUM> performs data reading with the RF tag <NUM> in accordance with the read command received from the PLC <NUM> and transfers the data to the PLC <NUM>. As shown in <FIG>, when the RFID communication unit <NUM> receives a read command which is the command transferred from the PLC <NUM>, the RFID communication unit <NUM> starts reading data from the RF tag <NUM>. The data exchange size between the PLC <NUM> and the RFID communication unit <NUM> is a data exchange size that is communicable in one communication period in the higher-order communication control part <NUM>, and is fixed. The RF communication control part <NUM> of the RFID communication unit <NUM> divides the data read from the RF tag <NUM> into a size the same as the data exchange size with the PLC <NUM>, and transfers the data by a plurality of times of communication.

The RF communication control part <NUM> of the RFID communication unit <NUM> performs decoding processing and conversion processing on the data read from the RF tag <NUM> by one communication, and transfers the data to the PLC <NUM> according to a communication period (IO period) with the PLC <NUM>. Further, the RF communication control part <NUM> of the RFID communication unit <NUM> concurrently transfers the transfer result with the RF tag <NUM> to the PLC <NUM> and performs the wireless communication with the RF tag <NUM> to read next division data.

In this way, the RF communication control part <NUM> concurrently executes the wireless communication with the RF tag <NUM> during the communication period in which the communication with the PLC <NUM> by the higher-order communication control part <NUM> is performed. Thereby, a total processing time TAT can be shortened compared with the case in which a large capacity of data collectively read from the RF tag <NUM> is divided into a data exchange size that is communicable in one communication period with the PLC <NUM> and is transferred to the PLC <NUM>.

Here, the total processing time TAT is a time that includes a command transfer time required for the transfer of the read command which is a command from the PLC <NUM>, a total RF communication time T3 required when data to be read with the RF tag <NUM> is transferred between the RFID communication unit <NUM> and the RF tag <NUM>, and a response transfer time T2 required when the transfer result with the RFID communication unit <NUM> and the RF tag <NUM> is transferred to the PLC <NUM>.

In this way, the total processing time TAT can be made shorter than T2 + T3 by concurrently performing the wireless communication with the RF tag <NUM> during the communication period with the PLC <NUM>. Therefore, the data transfer time can be shortened, and high-speed data transfer can be realized.

Further, because the wireless communication with the RF tag <NUM> is concurrently performed to read the next division data when the transfer result with the RF tag <NUM> is transferred to the PLC <NUM>, a time T1 from receiving the command from the PLC <NUM> until starting transferring the transfer result to the PLC <NUM> can be shortened, and a response to a control target in the PLC <NUM> can be made faster.

(a) and (b) of <FIG> are diagrams showing the total processing time TAT when the communication period between the PLC <NUM> and the RFID communication unit <NUM> is <NUM>, the data exchange size between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> bytes, and a total data reading size is <NUM> Kbytes. (a) of <FIG> shows an example when the data read using a conventional RFID communication unit is divided into each <NUM> bytes and transferred to the PLC <NUM>. (b) of <FIG> shows an example when the RFID communication unit <NUM> of the present embodiment is used to concurrently perform reading from the RF tag <NUM> and data transfer to the PLC <NUM>.

In the example shown in (a) of <FIG>, the RFID communication unit <NUM> collectively reads data from the RF tag <NUM> by <NUM> Kbytes, divides the read <NUM> Kbytes of data into each <NUM> bytes and transfers the data to the PLC <NUM>. The RFID communication unit <NUM> requires <NUM> to read <NUM> Kbytes of data from the RF tag <NUM>. The total processing time TAT is <NUM> which is the sum of a transfer time of the command from the PLC <NUM> to the RFID communication unit <NUM>, a transfer time of the data from the RFID communication unit <NUM> to the PLC <NUM>, and a read time of the data from the RF tag <NUM>.

In addition, in a conventional transfer method, in order to transfer a response result from the RFID communication unit <NUM> to the PLC, the communication period of the PLC is temporarily extended from <NUM> to <NUM>, and thereby the control period of the PLC is disturbed.

Meanwhile, in the example shown in (b) of <FIG>, the RFID communication unit <NUM> requires <NUM> to divide the data transferred from the RF tag <NUM> by one communication into each <NUM> bytes and read <NUM> Kbytes of data. Then, the total processing time TAT is <NUM> which is the sum of a transfer time of the command from the PLC <NUM> to the RFID communication unit <NUM>, a transfer time of the data from the RFID communication unit <NUM> to the PLC <NUM>, and a read time of the data from the RF tag <NUM>.

In other words, in the example shown in (b) of <FIG>, the wireless communication with the RF tag <NUM> is concurrently executed during the communication period in which the communication with the PLC <NUM> by the higher-order communication control part <NUM> is performed, the reading of the data from the RF tag <NUM> and the transfer of the data to the PLC <NUM> are performed concurrently and the data is transferred by the division transfer method. In this way, in the transfer method according to the present embodiment, while the response result is transferred from the RFID communication unit <NUM> to the PLC <NUM>, the communication period of the PLC <NUM> is not extended and the control period of the PLC <NUM> is not disturbed.

In the example of the conventional transfer method shown in (a) of <FIG>, a large capacity of data collectively read from the RF tag <NUM> is divided into a data exchange size that is communicable in one communication period with the PLC <NUM> and is transferred to the PLC <NUM> by a batch transfer method. Compared with the conventional transfer method, the transfer method of the present embodiment can realize acceleration of <NUM>. In this way, according to the transfer method of the present embodiment, by concurrently executing the wireless communication with the RF tag <NUM> during the communication period in which the communication with the PLC <NUM> by the higher-order communication control part <NUM> is performed, both acceleration in the data transfer and uniformity in the control period of the PLC can be achieved.

<FIG> is a diagram schematically showing the flow of data when the RFID communication unit <NUM> writes the data received from the PLC <NUM> to the RF tag <NUM> in accordance with the write command which is the command received from the PLC <NUM>. As shown in <FIG>, when the RFID communication unit <NUM> receives the write
As shown in <FIG>, when the RFID communication unit <NUM> receives the write command from the PLC <NUM>, the RFID communication unit <NUM> starts writing data to the RF tag <NUM>. The data exchange size between the PLC <NUM> and the RFID communication unit <NUM> is a data exchange size that is communicable in one communication period in the higher-order communication control part <NUM>, and is fixed. The RF communication control part <NUM> of the RFID communication unit <NUM> transfers data having the same size as the data exchange size with the PLC <NUM> to the RF tag <NUM> by one communication and writes the data. In this way, the RF communication control part <NUM> of the RFID communication unit <NUM> transfers and writes data having the same size as the data exchange size with the PLC <NUM> to the RF tag <NUM> by one communication.

The RF communication control part <NUM> of the RFID communication unit <NUM> concurrently writes data to the RF tag <NUM> and receives next data transferred from the PLC <NUM> by concurrently executing the wireless communication with the RF tag <NUM> during the communication period in which the communication by the higher-order communication control part <NUM> is performed.

In this way, the RFID communication unit <NUM> concurrently performs data transfer with the PLC <NUM> and data writing with the RF tag <NUM>. Thereby, compared with collectively writing the data for writing which is transferred from the PLC <NUM> to the RF tag <NUM>, the time T1 from receiving the command from the PLC <NUM> until starting writing the data to the RF tag <NUM> can be shortened.

Thereby, the total processing time TAT can be made shorter than the sum of the total RF communication time T3 required when data to be written with the RF tag <NUM> is transferred between the RFID communication unit <NUM> and the RF tag <NUM>, and the response transfer time T2 required when the transfer result with the RFID communication unit <NUM> and the RF tag <NUM> is transferred to the PLC <NUM>. Therefore, the total processing time TAT can be shortened, and high-speed data transfer can be realized.

Embodiment <NUM> of the present invention is described below. In addition, for convenience of explanation, the members having the same functions as those of the members described in Embodiment <NUM> are designated by the same reference numerals, and the description thereof is not repeated.

<FIG> is a block diagram showing a main configuration of a RFID communication unit <NUM> according to Embodiment <NUM>. As shown in the same diagram, in addition to the configuration of the RFID communication unit <NUM> of Embodiment <NUM>, a RF communication control part <NUM> includes a communication method determination part <NUM>.

The communication method determination part <NUM> divides the data subjected to at least one of reading and writing with the RF tag <NUM> into a data exchange size that is communicable in one communication period in the higher-order communication control part <NUM>, and selects the division transfer method for transferring the data by a plurality of times of communication or the batch transfer method for collectively transferring the data subjected to at least one of reading and writing with the RF tag by one communication.

Further, as for the transfer of the data subjected to at least one of reading and writing with the RF tag <NUM>, the communication method determination part <NUM> calculates each total processing time TAT of the division transfer method and the batch transfer method, and selects a transfer method having the shorter total processing time TAT.

(a) and (b) of <FIG> are diagrams showing the total processing time TAT when the communication period between the PLC <NUM> and the RFID communication unit <NUM> is <NUM>, the data exchange size between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> bytes, and a total data reading size is <NUM> bytes, (a) of <FIG> shows the flow of data when the data is read by the division transfer method. (b) of <FIG> shows the flow of data when the data is read by the batch transfer method.

As shown in (a) of <FIG>, the RFID communication unit <NUM> divides the data read with the RF tag <NUM> into <NUM> bytes which is a data exchange size that is communicable in one communication period in the higher-order communication control part <NUM>, and transfers the data by a plurality of times of communication. The communication time required for the RFID communication unit <NUM> to read <NUM> bytes of data by one communication from the RF tag <NUM> is <NUM>. The RFID communication unit <NUM> performs communication with the RF tag <NUM> by <NUM> times and reads <NUM> × <NUM> times = <NUM> bytes of data. The total communication time required for the RFID communication unit <NUM> to read <NUM> bytes of data from the RF tag <NUM> is <NUM> × <NUM> times = <NUM>.

The RFID communication unit <NUM> concurrently transfers the <NUM> bytes of data read from the RF tag <NUM> to the PLC <NUM> and reads next <NUM> bytes of data from the RF tag <NUM>.

As shown in (a) of <FIG>, the total processing time TAT of reading data from the RF tag <NUM> by the division transfer method is <NUM> which is the sum of a total RF communication time T3 = <NUM>, a command transfer time of <NUM> and a response transfer time of <NUM>.

Meanwhile, as shown in (b) of <FIG>, in the batch transfer method, the RFID communication unit <NUM> receives a read command from the PLC <NUM> and collectively reads <NUM> bytes of data from the RF tag <NUM>. The RFID communication unit <NUM> can collectively read the <NUM> bytes of data from the RF tag <NUM> in <NUM>. Subsequently, the RFID communication unit <NUM> divides the <NUM> bytes of data read from the RF tag <NUM> into each <NUM> bytes which is a data exchange size that is communicable in one communication period in the higher-order communication control part <NUM>, and transfers the data to the PLC <NUM> by <NUM> times. Because the communication period between the PLC <NUM> and the RFID communication unit <NUM> is <NUM>, the time required to transfer data from the RFID communication unit <NUM> to the PLC <NUM> is <NUM> × <NUM> times, that is, <NUM>.

Therefore, the total processing time TAT of reading data from the RF tag <NUM> by the batch transfer method is <NUM> which is the sum of a total RF communication time T3 = <NUM>, a command transfer time of <NUM>, and a time <NUM> of transferring the data read from the RF tag <NUM> from the RFID communication unit <NUM> to the PLC <NUM>.

In this way, when the communication period between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> and the data exchange size between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> bytes, the total processing time TAT is shorter in the case that the data is read by the batch transfer method than in the case that the data is read by the division transfer method.

In this way, the RF communication control part <NUM> calculates, by the function of the communication method determination part <NUM>, a command transfer time required to transfer the command from the PLC <NUM>, a total RF communication time required when the data to be read with the RF tag <NUM> is transferred with the RF tag <NUM>, and a to the PLC <NUM>. Then, the communication method determination part <NUM> calculates each total processing time TAT of the division transfer method and the batch transfer method based on the command transfer time, the total RF communication time and the response transfer time. Based on each total processing time TAT of the division transfer method and the batch transfer method calculated by the function of the communication method determination part <NUM>, the RF communication control part <NUM> selects the transfer method having the shorter total processing time to execute the reading with the RF tag.

As shown in (a) of <FIG>, the RFID communication unit <NUM> divides the data read with the RF tag <NUM> into each <NUM> bytes which is a data exchange size that is communicable in one communication period in the higher-order communication control part <NUM>, and transfers the data by a plurality of times of communication. The communication time required for the RFID communication unit <NUM> to read <NUM> bytes of data from the RF tag <NUM> by one communication is <NUM>. The RFID communication unit <NUM> performs communication with the RF tag <NUM> by <NUM> times and reads <NUM> × <NUM> times = <NUM> bytes of data. The total communication time required for the RFID communication unit <NUM> to read the <NUM> bytes of data from the RF tag <NUM> is <NUM> × <NUM> times = <NUM>.

As shown in (a) of <FIG>, the total processing time TAT of reading data from the RF tag <NUM> by the division transfer method is <NUM> which is the sum of a total RF communication time T3 = <NUM>, a command transfer time of <NUM>, and a response transfer time of <NUM>.

Meanwhile, as shown in (b) of <FIG>, in the batch transfer method, the RFID communication unit <NUM> receives a read command from the PLC <NUM> and collectively reads <NUM> bytes of data from the RF tag <NUM>. The RFID communication unit <NUM> can collectively read the <NUM> bytes of data from the RF tag <NUM> in <NUM>. Subsequently, the RFID communication unit <NUM> divides the <NUM> bytes of data read from the RF tag <NUM> into each <NUM> bytes which is a data exchange size that is communicable in one communication period in the higher-order communication control part <NUM>, and transfers the data to the PLC <NUM> by <NUM> times. Because the transfer period between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> once, the time required to transfer data from the RFID communication unit <NUM> to the PLC <NUM> is <NUM> × <NUM> times, that is, <NUM>.

Therefore, the total processing time TAT of reading data by the batch transfer method is <NUM> which is the sum of a total RF communication time T3 = <NUM>, a command transfer time of <NUM>, and a response transfer time of <NUM>.

In this way, when the communication period between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> and the data exchange size between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> bytes, the total processing time TAT is shorter in the case that the data is read by the division method than in the case that the data is read by the batch method.

In this way, when the data is read from the RF tag <NUM> and transferred to the PLC <NUM> in accordance with the command transferred from the PLC <NUM>, whether the total processing time TAT is shorter when the data is read by the division transfer method or the total processing time TAT is shorter when the data is read by the batch transfer method depends on the data exchange size and the communication period between the PLC <NUM> and the RFID communication unit <NUM>. Therefore, the RF communication control part <NUM> of the RFID communication unit <NUM> determines, by the function of the communication method determination part <NUM>, whether the reading method of the data is the division transfer method or the batch transfer method in order that the total processing time TAT is the shortest. Thereby, the total processing time TAT can be shortened, and high-speed data transfer can be realized.

In addition, the data exchange size and the communication period between the PLC <NUM> and the RFID communication unit <NUM> can be set by a user operating the PLC <NUM>. In initial communication processing between the PLC <NUM> and the RFID communication unit <NUM>, information about the data exchange size and the communication period is passed to the RFID communication unit <NUM>, and a periodic communication between the PLC <NUM> and the RFID communication unit <NUM> starts. The RF communication control part <NUM> of the RFID communication unit <NUM> determines, by the function of the communication method determination part <NUM>, whether to set the transfer method as the division transfer method or the batch transfer method by using the information about the data exchange size and the communication period received from the PLC <NUM> as a parameter.

(a) and (b) of <FIG> are diagrams showing the total processing time TAT when the communication period between the PLC <NUM> and the RFID communication unit <NUM> is <NUM>, the data exchange size between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> bytes, and a total data writing size is <NUM> bytes, (a) of <FIG> shows the flow of data when the data is written by the division transfer method. (b) of <FIG> shows the flow of data when the data is written by the batch transfer method.

As shown in (a) of <FIG>, the RFID communication unit <NUM> divides the data written to the RF tag <NUM> into <NUM> bytes which is a data exchange size that is communicable in one communication period in the higher-order communication control part <NUM> and transfers the data by a plurality of times of communication. The communication time required for the RFID communication unit <NUM> to write <NUM> bytes of data by one communication with the RF tag <NUM> is <NUM>. The RFID communication unit <NUM> performs communication with the RF tag <NUM> twice and writes <NUM> × <NUM> times = <NUM> bytes of data. The total communication time required for the RFID communication unit <NUM> to write <NUM> bytes of data to the RF tag <NUM> is <NUM> × <NUM> times = <NUM>.

The RFID communication unit <NUM> concurrently writes <NUM> bytes of data with the RF tag <NUM> to the RF tag <NUM> and receives next <NUM> bytes of data from the PLC <NUM>.

As shown in (a) of <FIG>, the total processing time TAT of writing data to the RF tag <NUM> by the division transfer method is <NUM> which is the sum of a total RF communication time T3 = <NUM>, a command transfer time of <NUM>, and a response transfer time of <NUM>.

Meanwhile, as shown in (b) of <FIG>, in the batch transfer method, the RFID communication unit <NUM> receives a write command from the PLC <NUM> and collectively writes <NUM> bytes of data to the RF tag <NUM>. The RFID communication unit <NUM> can collectively write the <NUM> bytes of data to the RF tag <NUM> in <NUM>.

When the RFID communication unit <NUM> finishes writing the data for an entire writing size to the RF tag <NUM>, the RFID communication unit <NUM> transfers a response notifying the completion of the writing to the PLC <NUM>.

Therefore, the total processing time TAT of writing data by the batch transfer method is <NUM> which is the sum of a total RF communication time T3 = <NUM>, a command transfer time of <NUM>, and a response transfer time of <NUM>.

In this way, when the communication period between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> and the data exchange size between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> bytes, the total processing time TAT is shorter in the case that the data is written by the batch transfer method than in the case that the data is written by the division transfer method.

As shown in (a) of <FIG>, the RFID communication unit <NUM> divides the data written to the RF tag <NUM> into <NUM> bytes which is a data exchange size that is communicable in one communication period in the higher-order communication control part <NUM> and transfers the data by a plurality of times of communication. The communication time required for the RFID communication unit <NUM> to write <NUM> bytes of data in one communication with the RF tag <NUM> is <NUM>. The RFID communication unit <NUM> performs communication with the RF tag <NUM> twice and writes <NUM> × <NUM> times = <NUM> bytes of data. The total communication time required for the RFID communication unit <NUM> to write <NUM> bytes of data with the RF tag <NUM> is <NUM> × <NUM> times = <NUM>.

As shown in (a) of <FIG>, the total processing time TAT of writing data with the RF tag <NUM> by the division transfer method is <NUM> which is the sum of a total RF communication time T3 = <NUM>, a command transfer time of <NUM>, and a response transfer time of <NUM>.

In this way, when the communication period between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> and the data exchange size between the PLC <NUM> and the RFID communication unit <NUM> is <NUM> bytes, the total processing time TAT is shorter in the case that the data is written by the division transfer method than in the case that the data is written by the batch transfer method.

In this way, when the data is written to the RF tag <NUM> in accordance with a write command from the PLC <NUM>, whether the total processing time TAT is shorter when the data is written by the division transfer method or the total processing time TAT is shorter when the data is written by the batch transfer method depends on the data exchange size and the communication period between the PLC <NUM> and the RFID communication unit <NUM>.

Therefore, the RF communication control part <NUM> of the RFID communication unit <NUM> determines, by the function of the communication method determination part <NUM>, whether the writing method of the data is the division transfer method or the batch transfer method in order that the total processing time TAT is the shortest. Thereby, the total processing time TAT can be shortened, and high-speed data transfer can be realized.

<FIG> is a block diagram showing a main configuration of a RFID communication unit <NUM> according to Embodiment <NUM>. As shown in <FIG>, in the RFID communication unit <NUM>, in addition to the configuration of the RFID communication unit <NUM> of Embodiment <NUM>, a RF communication control part <NUM> includes a communication judgment part <NUM>.

The RFID communication unit <NUM> and the RF tag <NUM> communicate with each other via wireless communication. The wireless communication may be interrupted due to the influence of noise or the like in the surrounding environment. In this case, the communication between the RFID communication unit <NUM> and the RF tag <NUM> fails, and a retry of data transmission/reception occurs.

As shown in (a) of <FIG>, it takes <NUM> for the RFID communication unit <NUM> to read <NUM> bytes of data in the batch transfer method for collectively reading a plurality of data from the RF tag <NUM>. While the data is transmitted from the RF tag <NUM> to the RFID communication unit <NUM>, if the communication between the RFID communication unit <NUM> and the RF tag <NUM> is interrupted and the data transfer fails, a retry of data reading occurs, and the reading of <NUM> bytes of data is performed again. When the communication between the RFID communication unit <NUM> and the RF tag <NUM> is interrupted twice and the data transfer fails twice, the reading of <NUM> bytes of data is performed three times, which takes <NUM> × <NUM> = <NUM>. The RFID communication unit <NUM> performs communication with the PLC <NUM> in a predetermined communication period to divide and transfer the data read from the RF tag <NUM> by the batch transfer method to the PLC <NUM>. In this way, when the data is read from the RF tag <NUM> by the batch transfer method, if the communication between the RFID communication unit <NUM> and the RF tag <NUM> fails, the backtracking time for the retry of data reading is large, and thus the total processing time TAT of data reading becomes long.

Further, as in the case that the data is read from the RF tag <NUM> by the batch transfer method, when the data is written to the RF tag <NUM> by the batch transfer method, if the communication between the RFID communication unit <NUM> and the RF tag <NUM> is interrupted and the data transfer fails, a retry of data writing occurs, and the total processing time TAT of data writing becomes long.

The communication judgment part <NUM> executes retry efficiency processing described below in order to minimize the influence of the communication failure between the RFID communication unit <NUM> and the RF tag <NUM>.

While the data is read and written with the RF tag <NUM>, if the communication between the RFID communication unit <NUM> and the RF tag <NUM> is interrupted and the transfer fails, the communication judgment part <NUM> reduces the data size for batch transfer each time the transfer fails. For example, as shown in (b) of <FIG>, while <NUM> bytes of data is collectively read from the RF tag <NUM>, if the communication between the RFID communication unit <NUM> and the RF tag <NUM> is interrupted and the data transfer fails, the communication judgment part <NUM> halves the data size of the data read from the RF tag <NUM> at the time of retry to <NUM> bytes. Then, a retry is performed to read <NUM> bytes of data from the RF tag <NUM>. If the communication between the RFID communication unit <NUM> and the RF tag <NUM> is interrupted and the data transfer fails again at the time of retry, the communication judgment part <NUM> halves the data size of the data read from the RF tag <NUM> at the time of a next retry to <NUM> bytes.

In this way, while at least one of data reading and data writing is being performed with the RF tag <NUM> by the batch transfer method, if the wireless communication with the RF tag <NUM> fails, the communication judgment part <NUM> reduces the data size of the data transferred with the RF tag <NUM> by one communication. Thereby, the efficiency of the data transfer retry is achieved when the communication with the RF tag <NUM> is interrupted and the transfer fails.

Furthermore, when the data size of the data transferred with the RF tag <NUM> by one communication is reduced to the exchange size of data exchanged with the PLC <NUM> in one communication period, the communication judgment part <NUM> switches the transfer method from the batch transfer method to the division transfer method, and concurrently executes the wireless communication with the RF tag <NUM> during the communication period in which the communication by the higher-order communication control part <NUM> is performed. According to these configurations, the data can be transferred efficiently.

Further, the communication judgment part <NUM> may have a function of measuring a noise level of the surrounding environment with respect to the communication between the RFID communication unit <NUM> and the RF tag <NUM>. Then, when the noise level is high, the communication judgment part <NUM> may perform processing of reducing the data size of the data read and written with the RF tag <NUM> in advance.

Control blocks of the RFID communication unit <NUM> (particularly, the higher-order communication control part <NUM>, and the RF communication control part <NUM>) may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by a software.

Claim 1:
A RFID communication unit (<NUM>, <NUM>, <NUM>), comprising:
a higher-order communication control part (<NUM>) for performing communication with a higher-order controller(<NUM>) in a predetermined communication period, wherein the higher-order controller(<NUM>) is external to the RFID communication unit(<NUM>, <NUM>, <NUM>), the higher-order controller(<NUM>) is configured to communicate with the RFID communication unit(<NUM>, <NUM>, <NUM>) by exchanging a plurality of data, each data having the same fixed data exchange size, and each data being communicated during a fixed communication period; and
a RF communication control part (<NUM>, <NUM>, <NUM>) for performing at least one of reading and writing of data with a RF tag (<NUM>) by wireless communication;
the RFID communication unit (<NUM>, <NUM>, <NUM>) being characterized in that the RF communication control part (<NUM>, <NUM>, <NUM>) is configured to select:
a division transfer method for dividing data subjected to at least one of reading and writing with the RF tag(<NUM>) into a plurality of data packets, each data packet having the same data exchange size and each data package being communicable in one communication period in the higher-order communication control part (<NUM>), and transferring each of the plurality of data packets to the higher-order controller (<NUM>) or to the RF tag (<NUM>) in the one communication period, wherein the RF communication control part (<NUM>, <NUM>, <NUM>) is configured to concurrently execute the wireless communication with the RF tag (<NUM>)during the communication period in which communication by the higher-order communication control part (<NUM>) is performed; or
a batch transfer method for collectively transferring data subjected to at least one of reading and writing with the RF tag (<NUM>), wherein the data is transferred to the RF tag (<NUM>) in one single communication period, and wherein the data is then transferred to, or was transferred beforehand from, the higher-order controller (<NUM>) in another communication session.