JP2009206723A - Firmware update method, distribution system, master station, slave station, and firmware update program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique that facilitates an update work of firmware. <P>SOLUTION: A master station 10 divides firmware into a plurality of divided blocks, imparts identification information to each divided block, and successively transmits the divided blocks to each slave station 20 by broadcast communication. Each slave station 20 receives the divided blocks so as to manage the presence or the absence of missing blocks on the basis of the identification information imparted to each divided block. After the completion of the transmission of all of the divided blocks, the master station 10 makes confirmation of the presence or the absence of the missing blocks in all of the slave stations 20 and retransmits only the missing blocks to the slave stations 20 respectively, in which the presence of the missing blocks is confirmed by a confirmation step. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for transmitting firmware from a master station that performs power line carrier communication to a slave station.

2. Description of the Related Art In recent years, an automatic meter reading system that collects meter reading information by connecting a communication device that performs power line carrier communication to a meter reading meter of each house of an apartment house and transmitting meter reading information by the meter reading meter to the communication device is known (for example, Patent Documents 1 and 2). In such a system, it may be necessary to upgrade the firmware of the communication device connected to the meter-reading meter.
JP 2000-286757 A JP 2001-283370 A

  However, in the conventional system, when the firmware of the communication device connected to each meter-reading device is updated, the maintenance staff connects the maintenance terminal to each communication device and transfers the update firmware. For this reason, there is a problem that it is very time-consuming. In particular, in a large apartment house where a huge number of meter-reading meters are installed, there is a problem that the upgrade work takes a lot of trouble.

  An object of the present invention is to provide a technique capable of easily performing a firmware update operation.

  (1) A firmware update method according to the present invention is a firmware update method for transmitting firmware from a master station that performs power line carrier communication to a slave station, and the master station converts the firmware into a plurality of divided blocks. A dividing step for dividing, an adding step for assigning identification information to the divided blocks divided by the dividing step, and a divided block to which the identification information is given by the adding step are sequentially transmitted to the slave station by broadcast communication The slave station comprises a receiving step for receiving the divided block, and a management step for managing the presence or absence of a missing block based on the identification information given to the divided block, After the transmission of all the divided blocks is completed, the master station sends all of the missing blocks to all the slave stations. A confirmation step of confirming the presence or absence of standing, and further comprising a retransmission step of retransmitting only missing blocks to the slave station that there has been confirmed the block omission by the confirmation step.

  According to this configuration, since the master station transmits the firmware to the slave station using power line carrier communication, the slave station does not need to perform complicated work such as connecting the maintenance terminal to each slave station and loading the firmware. Firmware can be loaded into the station.

  Further, since the divided blocks are transmitted by broadcast communication, the firmware can be quickly loaded into each slave station. Note that if flooding is used as broadcast communication, the firmware can be distributed to the entire slave station more quickly. In addition, identification information is given to each divided block, and the master station and each slave station manage which divided block is missing by the identification information. Since the existence is confirmed, the master station can accurately grasp the existence of the missing block in each slave station. Further, since the master station transmits the grasped missing block only to the slave station where the missing block is confirmed, it is possible to reliably transmit the missing block to the corresponding slave station while reducing the communication amount.

  (2) Preferably, in the transmission step, broadcast communication in one divided block is executed a plurality of times.

  According to this configuration, since the broadcast communication is executed a plurality of times for each divided block, it is possible to increase the probability that the divided block is transmitted to all the slave stations.

  (3) In the confirmation step, confirmation processing for confirming whether or not a missing block exists for each slave station is sequentially executed for all the slave stations. When it fails, it is preferable to execute the confirmation process for the next slave station.

  According to this configuration, when the confirmation process for confirming whether or not a missing block exists in a certain slave station fails, the confirmation process is executed in the next slave station. Can be executed. In addition, as a characteristic of the communication path of the power line carrier communication, the time zone in which the slave station can communicate may vary due to the influence of a noise source (for example, an IH device) generated according to the time. Therefore, when the confirmation process fails in a certain slave station, it is possible to increase the possibility of succeeding in communication with the slave station by retrying after a certain time, such as executing the confirmation process for the next slave station. it can.

  (4) It is preferable that the retransmission step sets a predetermined upper limit number of retransmissions of the missing block.

  According to this configuration, when the number of retransmissions of the missing block in a certain slave station reaches the upper limit, the retransmission process to that slave station is terminated, and therefore the retransmission process for the slave station is not completed. A situation in which the firmware update process is not executed can be avoided.

  (5) Preferably, the master station further includes an instruction step for instructing all the slave stations to update the firmware all at once at a predetermined time.

  According to this configuration, since all the slave stations update firmware at the same time at a predetermined time, it is possible to avoid a situation in which the firmware versions are different among the respective slave stations.

  (6) The master station manages the firmware versions of all the slave stations, and performs an update instruction step for instructing all slave stations to update the firmware only when the versions of all the slave stations match. It is preferable to further provide.

  According to this configuration, it is possible to avoid a situation in which the firmware versions are different between the slave stations.

  (7) A distributed system according to the present invention is a distributed system including a master station and a slave station that perform power line carrier communication, and the master station divides firmware to be transmitted to the slave station into a plurality of divided blocks. Transmitting means for sequentially transmitting the divided blocks assigned identification information by the assigning means to the slave station by broadcast communication. And the slave station includes receiving means for receiving the divided blocks, and management means for managing the presence or absence of missing blocks based on the identification information given to the divided blocks. After the transmission of all the divided blocks is completed, the station confirms the existence of the missing block in all the slave stations, and confirms the existence of the missing block by the confirmation means. And further comprising exit and retransmission means for retransmitting only blocked for child stations.

  According to this configuration, it is possible to provide a distributed system that realizes the firmware update method shown in (1).

  (8) The master station according to the present invention executes the firmware update method according to claim 1.

  According to this configuration, it is possible to provide a master station that realizes the firmware update method shown in (1).

  (9) A slave station according to the present invention executes the firmware update method according to claim 1.

  According to this configuration, it is possible to provide a slave station that realizes the firmware update method shown in (1).

  (10) A firmware update program according to the present invention includes a master station and a slave station that perform power line carrier communication, and is divided by the dividing step of dividing the master station into a plurality of divided blocks, and the dividing step. A granting step for assigning identification information to the divided blocks, and a transmission step for sequentially transmitting the divided blocks to which the identification information has been given in the granting step to the slave stations by broadcast communication. Based on the identification step given to the divided block and the receiving step for receiving the block, it functions as a management step for managing the presence / absence of missing blocks, and after the master station has completed transmission of all the divided blocks, A confirmation step for confirming the presence or absence of the missing block in all slave stations, and the confirmation step Further characterized in that to function as a retransmission step of retransmitting only the block omission against missing slave station exists is confirmed blocks.

  According to this configuration, it is possible to provide a firmware update program that realizes the firmware update method shown in (1).

  According to the present invention, since the master station transmits the firmware to the slave station using power line carrier communication, the slave station does not need to perform complicated operations such as connecting a maintenance terminal to each slave station and loading the firmware. Firmware can be loaded into the station.

  Hereinafter, a distributed system for realizing a firmware update method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of the distributed system. The distributed system includes a master station 10 and a slave station 20, and the master station 10 and the slave station 20 communicate with each other by power line carrier communication. Here, as power line carrier communication, a low-speed PLC with a communication band of 10 kHz to 450 kHz may be employed, or a high-speed PLC with a communication band of 2 MHz to 30 MHz may be employed. In the case of a low-speed PLC, if firmware is transferred on a one-to-one basis, it takes an enormous amount of time to transfer to all the slave stations 20, so it is preferable to apply the present invention based on flooding.

  This distributed system is installed in an apartment house such as an apartment, for example. The master station 10 is installed in an electrical management room of the apartment house, for example, and the slave station 20 is attached to an electric meter installed in each door of the apartment house. Yes.

  One to a plurality of master stations 10 can be provided. In FIG. 1, a distributed system is configured by three master stations 10. The master station 10 and the slave station 20 are connected via a power line. The power line includes, for example, a primary high-voltage trunk line L1 and a low-voltage trunk line L2 of 6600V. There are three high-voltage trunk lines L1 corresponding to the number of master stations 10. One to a plurality of low-voltage trunk lines L2 are connected to one high-voltage trunk line L1 via a transformer 30. One to a plurality of slave stations 20 can be connected to one low-voltage main line L2. In the present embodiment, for example, a maximum of 180 slave stations 20 can be connected to one master station 10. The master station 10 and the slave station 20 are uniquely assigned communication addresses.

  The three master stations 10 are connected to an ONU (optical network unit) 60 via a hub 70. The ONU 60 is connected to the higher system server 50 via the optical communication network NT. In the distributed system configured as described above, each slave station 20 transmits measurement data measured by an electric meter to the master station 10 via a power line. The master station 10 transmits measurement data via the optical communication network NT. Thereby, the upper system server 50 can collect the measurement data measured by the electric meter of each house.

  FIG. 2 shows a block diagram of the master station 10. The master station 10 includes a control unit 110, a storage unit 120, and a communication unit 130. The control unit 110 includes a CPU and the like, and performs overall control of the entire master station 10. In the present embodiment, the control unit 110 includes functions of a division unit 111, a grant unit 112, a transmission control unit 113, a confirmation unit 114, a retransmission control unit 115, and an instruction unit 116.

  The dividing unit 111 divides the firmware transmitted from the master station 10 to the slave station 20 into a plurality of divided blocks. Here, the firmware is a control program of the slave station 20. The firmware includes two types of firmware: application layer firmware that controls various types of control of the slave station 20 and NET layer firmware that controls communication control of the slave station 20. The dividing unit 111 includes the application layer firmware and the NET firmware. Each layer firmware is divided into a plurality of divided blocks. The firmware is divided into a plurality of divided blocks because there is an upper limit on the amount of data that can be transmitted at one time.

  The assigning unit 112 assigns identification information to the divided blocks divided by the dividing unit 111. Here, the identification information is uniquely assigned to each divided block.

  The transmission control unit 113 controls the communication unit 130 to sequentially transmit the divided blocks to which the identification information is added by the adding unit 112 to the slave station 20 by broadcast communication. In the present embodiment, a technique of executing broadcast communication in one divided block a plurality of times is adopted. In addition, flooding in which each slave station 20 that has received a divided block further performs broadcast communication is employed as broadcast communication. Therefore, the probability that the divided blocks are transmitted to all the slave stations 20 can be increased.

  The confirmation unit 114 confirms whether or not there are missing blocks in all the slave stations 20 after the transmission of all the divided blocks to the slave stations 20 is completed. Specifically, the confirmation unit 114 sequentially performs a confirmation process for confirming whether or not a missing block exists for each slave station 20 on all the slave stations 20. In the case where the confirmation process fails, the confirmation process is executed for the next slave station 20. Here, the missing block indicates a divided block that the slave station 20 has failed to receive.

  The retransmission control unit 115 controls the communication unit 130 to retransmit only the missing block to the slave station 20 in which the existence of the missing block is confirmed by the confirmation unit 114. Here, the retransmission control unit 115 provides a predetermined upper limit number of retransmissions of missing blocks.

  The instruction unit 116 instructs all the slave stations 20 to update firmware at a predetermined time. Here, the instruction unit 116 manages the firmware versions of all the slave stations 20, and instructs all the slave stations 20 to update the firmware only when the versions of all the slave stations 20 match. Also good.

  The communication unit 130 is composed of a communication module that executes power line carrier communication such as a PLC modem, and controls communication. The storage unit 120 is configured by, for example, a writable nonvolatile storage device, and includes a firmware storage unit 121 and a firmware transfer result file storage unit 122. The firmware storage unit 121 stores firmware to be transmitted. The firmware transfer result file storage unit 122 stores a firmware transfer result file indicating which divided block has been successfully received in each slave station 20.

  FIG. 3 shows a block diagram of the slave station 20. The slave station 20 includes a control unit 210, a communication unit 220, and a storage unit 230. The control unit 210 includes a CPU and the like, and includes functions of a reception control unit 211 and a management unit 212. The reception control unit 211 controls the communication unit 220 to receive the divided blocks. The management unit 212 manages the presence or absence of missing blocks based on the identification information given to the divided blocks.

  The storage unit 230 is composed of, for example, a rewritable nonvolatile storage device, and stores firmware and the like transmitted from the master station 10 and received by the slave station 20.

  The communication unit 220 includes a communication module that executes power line carrier communication such as a PLC modem, and controls communication.

  Next, an outline of the firmware update method according to the present invention will be described. FIG. 4 is an explanatory diagram of a firmware update method. The upper system server 50 transmits the transfer firmware file to the master station 10 via the optical communication network NT by, for example, FTP (File Transfer Protocol). Here, the transfer firmware file may be one in which the transfer firmware files F1 to F4 and the like are gathered together in a predetermined format, or may be compressed in the tar format. The master station 10 decompresses and disassembles the transfer firmware file to obtain transfer firmware files F1 to F4. The transfer firmware file F1 is the NET layer firmware for the master station 10, the transfer firmware file F2 is the application layer firmware for the master station 10, and the transfer firmware file F3 is the NET layer firmware for the slave station 20. The transfer firmware file F4 is application layer firmware for the slave station 20.

  The master station 10 decomposes the transfer firmware files F3 and F4 line by line to generate divided blocks, and sequentially transmits the divided blocks to each slave station 20 by flooding. The slave station 20 receives the divided block. Then, the master station 10 and the slave station 20 start updating the firmware at a predetermined time.

  Next, details of the operation of the distributed system shown in FIG. 1 will be described. 5 to 8 are sequence diagrams showing the operation of the distributed system shown in FIG. In the sequence diagrams of FIGS. 5 to 8, it is assumed that, for example, 180 slave stations 20 are connected to one master station 10. Further, it is assumed that the transfer firmware file F3 is transmitted first, and then the transfer firmware file F4 is transmitted.

  First, the upper system server 50 transmits a firmware transfer request for notifying the master station 10 of the start of transmission of the transfer firmware file to the master station 10 (step S1). Next, the master station 10 transmits a firmware transfer response to the higher system server 50 (step S2). Next, the higher system server 50 transmits the transfer firmware file to the master station 10 (step S3).

  Next, the master station 10 transmits a firmware transfer completion response to the higher system server to notify the higher system server 50 that the reception of the transfer firmware file has been completed (step S4). Next, the higher system server 50 transmits a firm transfer completion response to the parent station to the parent station 10 (step S5).

  Next, the master station 10 shifts to the update mode. At this time, the master station 10 decompresses and decomposes the transfer firmware file, acquires the transfer firmware files F1 to F4, and stores them in the firmware storage unit 121. The dividing unit 111 divides the transfer firmware files F3 and F4 into divided blocks, and the adding unit 112 adds identification information to the divided blocks. Here, the transfer firmware files F3 and F4 are divided, for example, for each line. Therefore, information indicating the type of the transfer firmware file and the line number can be adopted as the identification information.

  Next, the master station 10 transmits a firmware transfer request (initialization) to each slave station 20 by unicast (step S11). The firmware transfer request (initialization) transmitted in step S11 is a firmware transfer request for initializing each slave station 20.

  The slave station 20 that has received this firmware transfer request (initialization) executes an initialization process such as resetting a counter for counting the number of receptions of the divided blocks.

  As shown in FIG. 5, firmware transfer requests (initialization) are sequentially transmitted from the first slave station 20 to the 180th slave station 20 by unicast, and the slave station 20 that has received the firmware transfer request It can be seen that a firmware transfer response (initialization) is being transmitted to 10. In addition, the 180th slave station 20 shows that the firmware transfer request (initialization) is relayed by the second slave station 20. That is, in this distributed system, packets are transmitted by multi-hop.

  Next, the transmission control unit 113 sequentially transmits firmware transfer requests from the first block to the nth block to the slave station 20 by flooding (step S12). Here, the transmission control unit 113 transmits the divided blocks from the first block to the n-th block by flooding a plurality of times (for example, three times). Therefore, the probability that a firmware transfer request is transmitted to each slave station 20 can be increased. Note that the first block firmware transfer request stores the first block, and the second block firmware transfer request stores the second block. The firmware transfer request up to the nth block stores the divided blocks from the first block to the nth block.

  Next, when transmission of the transfer request for the nth block is completed, the confirmation unit 114 of the master station 10 starts confirmation processing (step S13). Specifically, when the confirmation unit 114 controls the communication unit 130 to transmit a transfer status confirmation request to the first slave station 20 and receives a transfer status confirmation response from the slave station 20, the second slave station 20 The transfer status confirmation request is sequentially transmitted to the slave station 20 by unicast. The transfer status confirmation response includes identification information of the divided blocks that the slave station 20 could not receive.

  Here, when a certain slave station 20 (for example, the third slave station 20) cannot receive the transfer status confirmation response, the confirmation unit 114 transmits a transfer status confirmation request to the slave station 20 again. Without this, a transfer status confirmation request is transmitted to the next slave station 20 (for example, the fourth slave station 20). When the confirmation processing for the 180th slave station 20 as the final slave station 20 is completed, the transfer status confirmation is sequentially performed for the slave stations 20 that have not received the transfer status confirmation response in the first cycle. The confirmation unit 114 cyclically performs confirmation processing such as transmitting a request. Thereby, the confirmation process with respect to all the slave stations 20 can be performed rapidly. And the confirmation part 114 will complete | finish a confirmation process, if a confirmation process is repeated a predetermined cycle (for example, 3 cycles).

  The confirmation unit 114 generates a firmware transfer result file indicating which division block has been successfully received in each slave station 20 from the processing result of the confirmation process, and stores it in the firmware transfer result file storage unit 122 (step S14). The management unit 212 of the slave station 20 also stores data indicating which divided blocks are missing in the storage unit 230.

  Next, in step S15, when the processing result that the missing block exists in a certain slave station 20 is obtained by the confirmation process in step S13, the retransmission control unit 115 of the master station 10 A retransmission process for transmitting the corresponding missing block is executed. In FIG. 6, the second slave station 20 has failed to receive the X-th divided block. Therefore, the retransmission control unit 115 transmits the firmware transfer request storing the X block to the second slave station 20 by unicast.

  In step S13, when there are missing blocks in two or more slave stations 20, the missing blocks are sequentially transmitted to each slave station 20 by unicast. Further, when a plurality of missing blocks exist in one slave station 20, each missing block is sequentially transmitted to the slave station 20 by unicast.

  When transmission of the missing block to each slave station 20 is completed, the confirmation unit 114 of the master station 10 transmits a transfer status confirmation request to the corresponding slave station 20 by unicast, and performs confirmation processing in the same manner as in step S13. Start. Each slave station 20 that has received the transfer status confirmation request transmits a transfer status confirmation response to the master station 10. Then, the confirmation unit 114 adds information to the firmware transfer result file in the same manner as in step S14 based on the result of the confirmation process. Thus, the retransmission process shown in step S15 ends.

  If there is a missing block even after the retransmission process in step S15, the retransmission control unit 115 performs the retransmission process in the same manner as in step S15 (step S16). If there is a missing block even after the retransmission process in step S16, the retransmission control unit 115 performs the retransmission process in the same manner as in step S15 (step S17).

  That is, the retransmission control unit 115 executes the retransmission process three times and ends the retransmission process. When the transfer of the transfer firmware file F3 to all the slave stations 20 is completed by the above processing, the transfer firmware file F4 is transferred to all the slave stations 20 as shown in FIG. 7 (step S18). First, the master station 10 sequentially transmits firmware transfer requests (initialization) to each slave station 20 by unicast in the same manner as in step S11 shown in FIG. 5 to initialize each slave station 20. The slave station 20 that has received the firmware transfer request (initialization) transmits a firmware transfer response (initialization) to the master station 10.

  Next, the transmission control unit 113 of the master station 10 assigns each divided block from the first block to the n-th block of the transfer firmware file F4 to each slave station 20 three times in the same manner as in step S12 shown in FIG. The data are sequentially transmitted to the slave station 20 by flooding (step S19). Next, the master station 10 performs the same process as steps S13 to S17 on the transfer firmware file F3 (NET layer firmware) on the transfer firmware file F4 (application layer firmware) (step S20).

  Next, in step S21 shown in FIG. 8, the instruction unit 116 of the master station 10 starts an instruction process for instructing the slave station 20 that has successfully transferred the transfer firmware files F3 and F4 to update.

  Specifically, the instruction unit 116 transmits a firmware update start request to each slave station 20 by unicast. The slave station 20 that has received the firmware update start request transmits a firmware update start response to the master station 10. The firmware update start request stores data for specifying the update time. For example, the time can be specified using at least one of year, month, day, hour, minute, and second. The firmware update start request may include data for instructing update of at least one of the transfer firmware files F3 and F4 and data for canceling the designation of time.

  Next, at the update time, each slave station 20 updates the firmware with the received divided block (step S22). At this time, the master station 10 also updates the firmware with the transfer firmware files F1 and F2. Thus, since the firmware is updated at the same time in the master station 10 and each slave station 20, it is possible to prevent the firmware versions in the master station 10 and each slave station 20 from being inconsistent.

  When the update is completed, the master station 10 switches the operation mode from the update mode to the normal operation mode (step S23). In addition, about several days is assumed as update time.

  Even in the third retransmission process shown in FIG. S17, if a missing block exists in a certain slave station 20, the maintenance staff connects the maintenance terminal to the slave station 20 and transfers the transfer firmware file F3. Also good. Thereby, the update can be started after the transfer firmware file F3 is transferred to all the slave stations 20.

  Further, in the instruction process shown in step S21, if there is a slave station 20 whose firmware version does not match, the master station 10 does not have to transmit a firmware update start request.

  Then, the correct version of firmware is transferred to the slave station 20 storing the firmware whose version does not match. In this case, the maintenance staff may connect the maintenance terminal to the corresponding slave station 20 and transfer the correct version of firmware.

  When the instruction unit 116 confirms that the firmware versions stored in all the slave stations 20 match, it transmits a firmware update request to each slave station 20. As a result, the firmware versions of the slave stations 20 can be matched.

  Thus, according to this firmware update method, since the master station 10 transmits firmware to the slave stations 20 using power line carrier communication, the maintenance terminal is connected to each slave station 20 and the firmware is loaded. The firmware can be loaded into the slave station 20 without performing such complicated work.

1 is an overall configuration diagram of a distributed system according to an embodiment of this invention. A block diagram of the master station is shown. A block diagram of the slave station is shown. It is explanatory drawing of the update method of firmware. It is a sequence diagram which shows operation | movement of the distributed system shown in FIG. It is a sequence diagram which shows operation | movement of the distributed system shown in FIG. It is a sequence diagram which shows operation | movement of the distributed system shown in FIG. It is a sequence diagram which shows operation | movement of the distributed system shown in FIG.

Explanation of symbols

10 master station 20 slave station 110 control unit 111 division unit 112 transmission control unit 113 addition unit 114 confirmation unit 115 retransmission control unit 116 instruction unit 120 storage unit 130 communication unit 121 firmware storage unit 122 firmware transfer result file storage unit 130 communication unit 210 Control unit 211 Reception control unit 212 Management unit 220 Communication unit 230 Storage unit

Claims (10)

A firmware update method for transmitting firmware to a slave station from a master station that performs power line carrier communication,
The master station is
A dividing step of dividing the firmware into a plurality of divided blocks;
An assigning step of giving identification information to the divided blocks divided by the dividing step;
A transmission step of sequentially transmitting the divided blocks to which the identification information is assigned in the granting step to the slave station by broadcast communication,
The slave station is
A receiving step of receiving the divided blocks;
Based on the identification information given to the divided blocks, comprising a management step for managing the presence or absence of missing blocks,
The master station is
After the transmission of all the divided blocks is completed, a confirmation step for confirming the presence or absence of the missing block in all the slave stations;
A firmware update method, further comprising: a retransmission step of resending only the missing block to the slave station whose existence is confirmed by the confirmation step.   2. The firmware update method according to claim 1, wherein the transmission step executes broadcast communication in one divided block a plurality of times.   In the confirmation step, confirmation processing for confirming whether or not there is a missing block for each slave station is sequentially executed for all the slave stations, and when the confirmation processing fails in a certain slave station The firmware update method according to claim 1, wherein the confirmation process is executed for the next slave station.   The firmware update method according to claim 1, wherein the retransmission step sets a predetermined upper limit number of times of retransmission of the missing block.   The firmware update method according to claim 1, wherein the master station further includes an instruction step for instructing all slave stations to update the firmware all at once at a predetermined time.   The master station further includes an update instruction step for managing firmware versions of all slave stations and instructing all slave stations to update firmware only when the versions of all slave stations match. The firmware update method according to claim 1, wherein: A distributed system including a master station and a slave station that perform power line carrier communication,
The master station is
Dividing means for dividing firmware to be transmitted to the slave station into a plurality of divided blocks;
An assigning means for giving identification information to the divided blocks divided by the dividing means;
Transmission means for sequentially transmitting the divided blocks to which the identification information is given by the grant means to the slave station by broadcast communication,
The slave station is
Receiving means for receiving the divided blocks;
Based on the identification information given to the divided blocks, comprising a management means for managing the presence or absence of missing blocks,
The master station is
Confirmation means for confirming the presence or absence of the missing block in all the slave stations after transmission of all the divided blocks is completed;
The distributed system further comprising: a retransmission means for retransmitting only the missing block to the slave station whose existence is confirmed by the confirmation means.   A master station that executes the firmware update method according to claim 1.   A slave station that executes the firmware update method according to claim 1. It has a master station and a slave station that perform power line carrier communications,
A dividing step of dividing the master station into a plurality of divided blocks;
An assigning step of giving identification information to the divided blocks divided by the dividing step;
The division block to which the identification information is given in the grant step functions as a transmission step for sequentially transmitting to the slave station by broadcast communication,
A receiving step for receiving the divided block of the slave station;
Based on the identification information given to the divided blocks, function as a management step for managing the presence or absence of missing blocks,
After the transmission of all the divided blocks to the master station, a confirmation step for confirming the existence of the missing block in all the slave stations;
A firmware update program that further functions as a retransmission step for retransmitting only a missing block to a slave station whose existence is confirmed by the confirmation step.

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