JP2002344455A - Communications apparatus and communication method and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communications apparatus, capable of improving communicating efficiency from a slave station to a master station. SOLUTION: A master station receives a data packet transmitted from a slave station by a reception managing part 13, in response to the transmission of a patrol packet to the slave station, and extracts a flag indicating which of a division data packet, a division end data packet, and a single data packet is pertinent to the data packet by analyzing the data packet by a packet header analyzing part 14, and determine the flag by a division packet decision part 17. In the case of the single data packet, a timer 15 for normal patrol packet transmission is conducted, and the patrol packet is repeatedly transmitted to the slave station in a first cycle. In the case of the division data packet, a timer 18 for special patrol packet transmission is conducted, and the patrol packet is repeatedly transmitted to the slave station in a second cycle shorter than the first cycle, and in the case of the division end packet, the patrol packet is repeatedly transmitted to the salve station in the first cycle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a Bluetooth device having a device connection management layer (device connection management unit).
oth) It relates to a communication device.

[0002]

2. Description of the Related Art The Bluetooth (Bluetooth) communication standard is a one-to-many wireless communication standard that has been spread worldwide as being used as short-range wireless data communication using radio waves in portable telephones and portable terminals.

[0005] The mechanism of cyclic packet transmission in Bluetooth communication will be described below with reference to FIGS.

FIG. 8 is a block diagram showing a configuration of a device connection management unit (device connection management layer) of a conventional Bluetooth communication device. In the figure, reference numeral 80 denotes a device connection management unit,
87 is an upper layer. Reference numeral 81 denotes a timer management unit for periodically and repeatedly transmitting the cyclic packet and for releasing the connection state with the partner station after a predetermined time. 82
Is a transmission management unit for transmitting the data packet sent from the upper layer 87 to the partner station. 83 is a reception management unit for receiving a data packet transmitted from the partner station. Reference numeral 84 denotes a packet header analysis unit for analyzing the packet header and the like in the data packet and sending the payload in the data packet to the upper layer 87.
Reference numeral 85 denotes a normal cyclic packet transmission timer for transmitting a cyclic packet for maintaining a connection state. Reference numeral 86 denotes a disconnection timer for releasing the connection state after a predetermined time.

FIG. 9 is a flowchart showing the operation of the packet header analysis unit 84, which comprises steps 91 to 96.

FIG. 10 is a schematic diagram showing a data packet in Bluetooth communication. 101 is a packet header part, 102 is a payload part, and the packet header part 101 includes a packet type discrimination flag 103 and a communication address 104.

The operation of the disconnection timer 86, the operation of transmitting a cyclic packet, and the operation at the time of receiving a data packet in the Bluetooth communication apparatus configured as shown in FIG. 8 will be described.

The disconnection timer 86 is used to release the connection with the partner station when there is no transmission from the partner station for a certain period of time.

A cyclic packet is a packet transmitted from a master station to a slave station for maintaining a connection state in a Bluetooth communication system which is wireless communication.
This packet does not include the payload section 102 in FIG. The cyclic packet is transmitted when there is no data to be transmitted from the master station to the connected slave station for a certain period of time (defined by the disconnection timer 86).

The configuration of the device connection management unit 80 is the same for the master station and the slave station, and there is no device dedicated to the slave station. The difference between the master station and the slave station is that the cyclic packet timer does not operate in the slave station. The determination of the master station / slave station is made at the time of connection. That is, the station requesting the connection becomes the master station. In other words, a station that wants to become a master issues a connection request. As a supplementary explanation, in order to obtain authentication as a Bluetooth function, it is necessary to have both master / slave functions, and a device dedicated to the slave cannot obtain authentication.

Next, the flow of processing when data is received from the partner station will be described. Data reception from the partner station is performed as follows. First, the data packet received by the reception management unit 83 is transmitted to the packet header analysis unit 84.

In step 91, the packet header analysis unit 84 sets the communication address 1 of the packet header unit 101.
In step 92, the packet type 102 is analyzed. Thereafter, it is determined in step 93 whether the data packet is a normal packet or an abnormal packet. If the data packet is an abnormal packet, the process ends in step 94.
On the other hand, if it is confirmed that the packet is a normal packet, the payload section 102 is notified to the upper layer in step 95, and at the same time, the disconnection timer 8 of the timer
6 to transmit a reception sensing signal. As a result, the disconnection timer 86 resets the timer value based on the reception sensing signal.

Here, the packet type will be described.
Packets that need to be confirmed by the other station
For example, DM1 / DH1 / DM3 / DH3 / DM5 / D
There is H5. These packets are appended with a CRC,
It is retransmitted until ACK comes from the partner station. These guarantee the arrival of data and are specified by Length.

Packets other than those described above include A from the partner station.
Assuming that no CK is required and no retransmission is performed, a cyclic packet (Poll) and a reply packet (Null)
There is. The reply packet is a reply packet when there is no transmission data.

As described above, in the device connection management unit in Bluetooth, the normal cyclic packet transmission timer 85 is used.
And the receiving operation are not particularly related.

[0016]

The cyclic packet is used by the master station to maintain a connection state when there is no data to be transmitted to the slave station, and is used for short-distance data communication between portable terminals. In many Bluetooth application devices, since the power saving is emphasized, the cyclic packet transmission interval is set to be long.

FIG. 11 shows a communication state in the above-mentioned Bluetooth communication apparatus when the master station has no transmission data packet to the slave station and transmission data exists only in the slave station.

When there is no data to be transmitted from the master station to the slave station, the cyclic packet 111 is transmitted from the master station to the slave station due to overflow of the normal cyclic packet transmission timer 85. The slave station returns the data packet 112 as a reply to the
Can be transmitted. At this time, the cyclic packet transmission section 113 corresponds to the normal cyclic packet transmission timer 8.
According to the value of 5.

As described above, even if there is data to be transmitted by the slave station, data cannot be transmitted from the slave station to the master station unless there is transmission from the master station to the slave station. Communication efficiency to the master station is low.

The present invention has been made in view of the above problems, and has as its object to provide a communication device, a communication method, and a recording medium that can improve the communication efficiency from a slave station to a master station.

[0021]

In order to solve this problem, a communication apparatus according to the present invention comprises a master station and a slave station, and the slave station performs packet transmission only in response to packet transmission from the master station. The master station has the following configuration.

That is, the master station receives the data packet transmitted from the slave station in response to the transmission of the cyclic packet to the slave station, and analyzes the data packet received by the receiving means to obtain the data packet. Data packet analyzing means for extracting a flag indicating whether the packet is a divided data packet, a divided end data packet, or a single data packet; and a first cyclic packet transmission timer and a first regular packet transmission timer. Timer means having a special cyclic packet transmission timer having a short second cycle, and a cyclic packet for each cycle of the activated cyclic packet transmission timer among the normal cyclic packet transmission timer and the special cyclic packet transmission timer Means for repeatedly transmitting data to the slave station and data packet analyzing means Issued flag to determine, by the normal cyclic packet transmission timer is stopped when a divided data packets to start the special cyclic packet transmission timer,
A divided packet that restarts the normal cyclic packet transmission timer when the data packet is a division end data packet, stops the special cyclic packet transmission timer, and continues the operation of the normal cyclic packet transmission timer when the data packet is a single data packet. Judgment means.

According to this configuration, it is determined whether the data packet is a divided data packet, a divided end data packet, or a single data packet based on the flag attached to the data packet transmitted from the slave station. In this case, by activating the special cyclic packet transmission timer, the cyclic packet transmission cycle can be shortened. As a result, a subsequent divided data packet or divided end data packet can be transmitted from the slave station to the master station in a short cycle, and the communication efficiency from the slave station to the master station can be improved. On the other hand, when the data packet is the division end data packet, there is no data packet to be transmitted subsequently, so that the transmission cycle of the cyclic packet can be restored by activating the normal cyclic packet transmission timer. In the case of a single data packet, the operation of the normal cyclic packet transmission timer is continued, so that power consumption can be suppressed as much as possible.

In the communication method of the present invention, the master station arbitrarily transmits a packet to a slave station, and the slave station transmits a packet only in response to a packet transmission from the master station. The station performs the following processing.

That is, the master station receives the data packet transmitted from the slave station in response to the transmission of the cyclic packet to the slave station, analyzes the data packet, and determines whether the data packet is a divided data packet and a divided end data packet. And a flag indicating which of the single data packets is extracted, the flag is determined, and if the packet is a single data packet, the cyclic packet is repeatedly transmitted to the slave station in the first cycle. The cyclic packet is repeatedly transmitted to the slave station in a second cycle shorter than the first cycle, and if the packet is a division end packet, the cyclic packet is repeatedly transmitted to the slave station in the first cycle.

According to this method, it is determined whether the data packet is a divided data packet, a divided end data packet, or a single data packet based on a flag attached to the data packet transmitted from the slave station. In this case, the transmission cycle of the cyclic packet can be shortened from the first cycle to the second cycle. As a result, a subsequent divided data packet or divided end data packet can be transmitted from the slave station to the master station in a short cycle, and the communication efficiency from the slave station to the master station can be improved.
On the other hand, if the data packet is a division end data packet, there is no data packet to be transmitted subsequently, so that the transmission cycle of the cyclic packet can be restored. Since the period is maintained at one, power consumption can be suppressed as much as possible.

Further, in the recording medium of the present invention, the master station executes an algorithm for arbitrarily transmitting a packet to the slave station, and the slave station executes an algorithm for transmitting the packet only in response to the packet transmission from the master station. The following program is recorded.

That is, the master station receives the data packet transmitted from the slave station in response to the transmission of the cyclic packet to the slave station, analyzes the data packet, and divides the data packet into the divided data packet and the divided end data packet. And a flag indicating which of the single data packets is extracted, the flag is determined, and if the packet is a single data packet, the cyclic packet is repeatedly transmitted to the slave station in the first cycle. A program for executing an algorithm for repeatedly transmitting a cyclic packet to a slave station in a second cycle shorter than the first cycle and for repeatedly transmitting a cyclic packet to the slave station in the first cycle when the packet is a division end packet is recorded. ing.

According to this configuration, an operation similar to that of the above communication method is provided.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram showing a configuration of a device connection management unit in a Bluetooth communication device according to an embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes a device connection management unit;
9 is an upper layer. Reference numeral 11 denotes a timer management unit for periodically and repeatedly transmitting the cyclic packet and for releasing the connection state with the partner station after a predetermined time, and functions as timer means. Reference numeral 12 denotes a transmission management unit for transmitting the data packet transmitted from the upper layer 19 to the partner station, and functions as a transmission unit. The master station arbitrarily transmits a data packet, and the slave station transmits a data packet as a reply to the transmission from the master station.

Reference numeral 13 denotes a reception management unit for receiving a data packet transmitted from the partner station, and functions as a receiving unit. Reference numeral 14 denotes a packet header analysis unit for analyzing a packet header portion and a payload header in the data packet and then transmitting the payload portion in the data packet to the upper layer 19, and functions as a data packet analysis unit. Reference numeral 15 denotes a normal cyclic packet transmission timer having a first cycle for transmitting a cyclic packet for maintaining a connection state. Reference numeral 16 denotes a disconnection timer for releasing the connection state after a predetermined time. These are the same as the conventional example of FIG. However, the packet header analysis unit 14 is provided with a payload header analysis function.

Reference numeral 17 denotes a divided packet judging unit for judging whether a data packet is a divided data packet, a division end data packet, or a single data packet based on a divided packet discrimination flag extracted by the packet header analysis unit 14. Functions as a determining means. Reference numeral 18 denotes a special cyclic packet transmission timer for transmitting a cyclic packet in a second cycle shorter than the normal cyclic packet timer. The above configuration is added to the conventional example.

Then, based on the determination result of the fragmentation packet discrimination flag, the fragmentation packet decision unit 17 continues the operation of the normal cyclic packet transmission timer 15 having the first cycle in the case of a single data packet, In the case of a packet, the operation of the normal cyclic packet transmission timer 15 is stopped, and the operation of the special cyclic data packet transmission timer 18 having a second cycle shorter than the first cycle is started. The operation of the special cyclic data packet transmission timer 18 is stopped, and the operation of the normal cyclic packet transmission timer 15 is restarted.

The configuration of the device connection management unit 10 is the same for the master station and the slave station, and there is no device dedicated to the slave station. The difference between the master station and the slave station is that the cyclic packet transmission function does not operate in the slave station. Therefore, the cyclic packet timer, the special cyclic packet timer, and the fragmented packet determination mechanism do not operate. The determination of the master station / slave station is made at the time of connection. That is, the station requesting the connection becomes the master station. In other words, a station that wants to become a master issues a connection request.

FIG. 2 is a flowchart showing the operation of the packet header analysis unit according to the embodiment of the present invention, and comprises steps 21 to 28. In FIG. 2, step 2
Steps 1 to 26 are the same as steps 91 to 96 in FIG. 9 of the conventional example, and the processing of acquiring the fragment packet determination flag of step 27 and the processing of notifying the fragment packet determination unit of step 28 are added to the conventional example. . Steps 21 to 26 are the same as those described in the related art, so description thereof will be omitted.

FIG. 3 is a flowchart showing the operation of the fragmented packet judging unit 17 according to the embodiment of the present invention.
It consists of steps 31-37.

FIG. 4 is a schematic diagram showing a configuration of a payload portion of a Bluetooth data packet. This payload section is a payload section in the Bluetooth data packet of FIG. 10 and is composed of a payload header section 41 and a payload body section 42. The payload header section 41 has a fragment packet discrimination flag 43 for indicating that the upper layer is a fragment packet in order to reconstruct the fragment packet. Here, the divided packet discrimination flag 43 includes a state indicating that the packet is the divided packet data (divided packet flag), a state indicating that the packet is the division end data packet (the division packet end flag), and a single data packet. It is assumed that there are three types of statuses (individual packet flags) indicating the status.

The procedure for creating the fragment packet discrimination flag 43 in the slave station will be described with reference to FIGS.

FIG. 5 is a block diagram showing a configuration of a packet creation unit and a device connection management unit for creating a fragmented packet discrimination flag in the upper layer 19. 5, reference numeral 51 denotes a packet creation unit, and 52, a device connection management unit, which are the same as the device connection management unit 10 of FIG. The packet creation unit 51 creates a packet based on the data transmission request, and gives the device management unit 52 a packet transmission request.

FIG. 6 shows the packet creation unit 51
It is a flowchart which shows the operation | movement at the time of data transmission request, It consists of steps 61-70. Packet creator 5
In response to the data transmission request to No. 1, the packet creation unit 51 performs the following processing.

That is, in the packet creating section 51,
First, in step 61, the transmission request data length is compared with the maximum packet length, and if the transmission request data length is longer than the maximum packet length, a split packet start mode is set in step 62. Transmission data is cut out from the data, and a divided packet flag is added to the transmission data in step 64.

If the transmission request data length is shorter than the maximum packet length in the above step 61, it is next determined in step 65 whether or not the divided packet mode is set. A packet end flag is added.

If the mode is not the divided packet mode in step 65, a single packet flag is added to the transmission data in step 67.

After step 64, step 66, or step 67, the payload header 41 including the fragmented packet flag in step 64, the fragmented packet end flag in step 66, or the single packet flag in step 67 is transmitted to the beginning of the transmission data. To form a payload section.

Thereafter, at step 68, a transmission data packet is created by adding a packet header to the payload. Further, in step 69, a packet transmission request is made to the device connection management unit 52.

Thereafter, in step 70, the remaining data length is 0
It is determined whether it is greater than 0, and if it is greater than 0, the process returns to step 61 to cut out the next transmission data.

When a data packet is received by the reception management unit 13 in FIG. 1, the data packet is sent from the reception management unit 13 to the packet header analysis unit 14. The packet header analysis unit 14 executes the steps from step 21 to step 26 in FIG. 2 in the same manner as in the conventional example, and performs the division packet determination flag acquisition process in step 27 from the payload unit shown in FIG. Only the packet discrimination flag 43 is obtained and sent to the divided packet discrimination unit in step 28.

Next, the divided packet judging section 17 identifies the divided packet discriminating flag 43 in step 31 and
If it is determined that the packet flag is the fragment packet flag added by the fragment packet flag adding process in step 64 shown in FIG. 6, a fragment data packet sensing signal is transmitted to the normal cyclic packet transmission timer 15 in step 32. Accordingly, the normal cyclic packet transmission timer 15 that has received the divided data packet sensing signal stops the timer operation. Next, in step 33, the divided data packet sensing signal is transmitted to the special cyclic packet transmission timer 18. As a result, the special cyclic packet transmission timer 18 that has received the divided data packet sensing signal starts the timer operation with the settable minimum value.

Thereafter, the remainder of the divided data packet is transmitted from the master station to the master station by a short cycle cyclic packet transmission from the master station to the slave station. All the divided data packets from the slave station are transmitted and division is completed (final)
When the master station receives a data packet, it operates as follows.

That is, the divided packet judging section 17 identifies the divided packet discrimination flag 43 in step 34 and judges that the divided packet end flag is added by the divided packet end flag adding process in step 66. In step 35, the end-of-split packet detection signal is transmitted to the normal cyclic packet transmission timer 15. Thereby, the normal cyclic packet transmission timer 15 that has received the fragmented packet end sensing signal resumes its operation. Next, in step 36, an end detection signal is transmitted to the special cyclic packet transmission timer 18, and the special cyclic packet transmission timer 18, which has received the end detection signal, stops operating.

When the fragmented packet judging section 17 determines in step 34 that the packet is not the fragmented packet end flag, that is, it is the single data packet flag,
In step 37, the process ends. As a result, the state in which the normal cyclic packet transmission timer 15 is operating continues.

FIG. 7 shows a state of communication at the time of activation of the special cyclic packet transmission timer in the Bluetooth communication apparatus according to the embodiment of the present invention configured as described above.

With respect to the cyclic packet 71 from the master station,
At the time point 75, the slave station starts transmitting the first divided data packet 72. As a result, when the divided packet flag in step 66 is identified in step 31 in the divided packet determination unit 17 in the master station, the reception of the divided data packet 75 is sensed. The normal cyclic packet transmission timer 15 is stopped, and the special cyclic packet transmission timer 18 is started in step 33 described above.

By activating the special-circular-packet transmission timer 18, the master station subsequently sends a special-packet-packet transmission timer section 74 to the slave station for each special-circular-packet transmission timer section 74.
Is transmitted, and accordingly, the divided data packet 72 is transmitted from the slave station to the master station.

Thereafter, at the time of the reference numeral 77, the last divided data packet 72 is transmitted from the slave station to the master station. As a result, when the fragmented packet judging unit 17 of the master station identifies the fragmented packet end flag in the above step 67 in the above step 34, it detects that the last divided data packet 77, ie, the reception of the fragmented end data packet, is received. At time 78, the special cyclic packet transmission timer is stopped in step 36, and the normal cyclic packet transmission timer is started again in step 35. Thereafter, while there is no data to be transmitted from the master station to the slave station, the normal time is used. A cyclic packet is transmitted from the master station to the slave station in the cyclic packet transmission timer section 73.

As described above, according to the embodiment of the present invention, whether a data packet is a divided data packet, a divided end data packet, or a single data packet is determined based on a flag attached to a data packet transmitted from a slave station. If it is determined that the data packet is a divided data packet, the transmission cycle of the cyclic packet can be shortened by activating the special cyclic packet transmission timer.
As a result, a subsequent divided data packet or divided end data packet can be transmitted from the slave station to the master station in a short cycle, and the communication efficiency from the slave station to the master station can be improved. On the other hand, when the data packet is the division end data packet, there is no data packet to be transmitted subsequently, so that the transmission cycle of the cyclic packet can be restored by activating the normal cyclic packet transmission timer. In the case of a single data packet, the operation of the normal cyclic packet transmission timer is continued, so that power consumption can be suppressed as much as possible.

Here, a communication method using the above Bluetooth communication device will be described. In this communication method, the master station arbitrarily transmits packets to the slave station,
The slave station transmits a packet only in response to a packet transmission from the master station. The master station performs the following processing.

That is, the master station receives the data packet transmitted from the slave station in response to the transmission of the cyclic packet to the slave station, analyzes the data packet, and determines whether the data packet is a divided data packet and a divided end data packet. And a flag indicating which of the single data packets is extracted, the flag is determined, and if the packet is a single data packet, the cyclic packet is repeatedly transmitted to the slave station in the first cycle. The cyclic packet is repeatedly transmitted to the slave station in a second cycle shorter than the first cycle, and if the packet is a division end packet, the cyclic packet is repeatedly transmitted to the slave station in the first cycle.

According to this method, it is determined whether a data packet is a divided data packet, a divided end data packet, or a single data packet based on a flag attached to a data packet transmitted from a slave station. In this case, the transmission cycle of the cyclic packet can be shortened from the first cycle to the second cycle. As a result, a subsequent divided data packet or divided end data packet can be transmitted from the slave station to the master station in a short cycle, and the communication efficiency from the slave station to the master station can be improved.
On the other hand, if the data packet is a division end data packet, there is no data packet to be transmitted subsequently, so that the transmission cycle of the cyclic packet can be restored. Since the period is maintained at one, power consumption can be suppressed as much as possible.

Further, a program for executing the algorithm of the above communication method can be recorded on a recording medium such as a CDROM. In this case, by executing the program recorded on the recording medium by a computer, the same effects as those of the above-described communication method can be obtained.

[0063]

As described above, according to the present invention,
When there is a divided data packet only in the slave station, it is possible to shorten the transmission interval of the cyclic packet, thereby enabling the master station to promote the transmission of the slave station, and improving the communication efficiency from the slave station to the master station. Can be improved. In addition, when there is no divided data packet to be transmitted to the slave station, the transmission interval of the cyclic packet is restored, so that an increase in power consumption can be minimized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a device connection management unit in a Bluetooth communication device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation of a packet header analysis unit according to the embodiment of the present invention.

FIG. 3 is a flowchart illustrating an operation of a fragmented packet determination unit according to the embodiment of the present invention.

FIG. 4 is a schematic diagram showing a configuration of a payload unit according to the embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration of a packet creation unit according to the embodiment of the present invention.

FIG. 6 is a flowchart illustrating an operation of a packet creation unit according to the embodiment of the present invention.

FIG. 7 is a sequence diagram showing a state of communication when a special cyclic packet transmission timer is activated in the embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a device connection management unit in a conventional Bluetooth communication device.

FIG. 9 is a flowchart showing an operation of a packet header analysis unit in a conventional example.

FIG. 10 is a schematic diagram showing a configuration of a data packet in a conventional example.

FIG. 11 is a sequence diagram showing normal cyclic packet communication in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Timer management unit 12 Transmission management unit 13 Reception management unit 14 Packet header analysis unit 15 Normal cyclic packet transmission timer 16 Disconnection timer 17 Divided packet determination unit 18 Special cyclic packet transmission timer

Claims (3)

[Claims] 1. A communication device comprising a master station and a slave station, wherein the slave station performs packet transmission only in response to a packet transmission from the master station, wherein the master station transmits a packet to the slave station. Receiving means for receiving a data packet transmitted from the slave station in response to the transmission of the cyclic packet; analyzing the data packet received by the receiving means to determine that the data packet is a divided data packet and a divided end data packet Data packet analyzing means for extracting a flag indicating which one of the data packets is a single data packet; a normal cyclic packet transmission timer having a first cycle; and a second cycle special timer having a shorter cycle than the normal cyclic packet transmission timer. Timer means having a cyclic packet transmission timer, the normal cyclic packet transmission timer and the special cyclic Transmitting means for repeatedly transmitting a cyclic packet to the slave station in each cycle of the cyclic packet transmitting timer that is activated among the packet transmitting timers; and determining a flag detected by the data packet analyzing means to determine a divided data packet. When the normal cyclic packet transmission timer is stopped, the special cyclic packet transmission timer is started, and when the packet is a division end data packet, the normal cyclic packet transmission timer is restarted so that the special cyclic packet is transmitted. Stop the transmission timer,
A communication apparatus comprising: a divided packet determining unit that continues the operation of the normal cyclic packet transmission timer when the data packet is a single data packet. 2. A communication method in which a master station arbitrarily transmits a packet to a slave station, and the slave station transmits a packet only in response to a packet transmission from the master station. Receiving a data packet transmitted from the slave station in response to the transmission of the cyclic packet to the slave station; analyzing the data packet to determine whether the data packet is a divided data packet, a divided end data packet, and a single data packet. A flag indicating which one of the data packets is extracted, the flag is determined, and if the data packet is a single data packet, the cyclic packet is repeatedly transmitted to the slave station in a first cycle. The cyclic packet is repeatedly transmitted to the slave station in a second cycle shorter than one cycle, and the division end packet is transmitted. Wherein the cyclic packet is repeatedly transmitted to the slave station in the first cycle. 3. The master station arbitrarily transmits a packet to a slave station, and the slave station records a program for executing an algorithm for transmitting a packet only in response to a packet transmission from the master station. A recording medium, wherein the master station receives a data packet transmitted from the slave station in response to transmission of a cyclic packet to the slave station, analyzes the data packet, and divides the data packet into divided data. A flag indicating which of a packet, a division end data packet and a single data packet is extracted is determined. If the flag is determined, a cyclic packet is repeatedly transmitted to the slave station in a first cycle when the packet is a single data packet. If the packet is a divided data packet, the cyclic packet is transmitted in a second cycle shorter than the first cycle. A recording medium recording a program for repeatedly transmitting to a slave station and executing an algorithm for repeatedly transmitting the cyclic packet to the slave station at the first cycle when the packet is the division end packet.