JP2001333001A - Data transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency by switching transmission methods in accordance with the characteristic of transmission data. SOLUTION: When a master station 1 transmits a polling signal to respective slave stations 1 to N, in the respective slave stations, a transmission control part 21 decodes the polling signal, and performs transmission when the polling signal is a transmission request to its own station. When data transmitted from the master station are a packet request signal, a receiving timing controller 44 first outputs the information to a transmission timing controller 45, prepares packet data for transmission data with a packet data composing device 46 and transmits the packet data to a power line 18 through a transmission data switching device 47. Meanwhile, when the data transmitted from the master station are a time slot request signal, the controller 44 sequentially transmits a time slot to the respective slave stations. In such a case, the controller 45 switches the switching device 47 to transmit the transmission data to the power line 18. Thus, transmission is performed by switching a packet method and a time slot method in accordance with the requests from the master station.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission system for transmitting and receiving data between one master station and a plurality of slave stations connected via the same transmission line.

[0002]

2. Description of the Related Art Conventionally, in a system for performing 1: N communication between a master station and a plurality of (N) slave stations, the master station controls data transmission. When the master station transmits to the slave station, data obtained by adding transmission control data such as information for specifying the slave station of the transmission destination to the data to be transmitted is transmitted from the master station to the slave station. When the master station receives data from the slave station, the master station transmits a transmission request signal to the slave station, and the slave station transmits the data to the master station after reception. Such a transmission request signal is called a polling signal, and in a 1: N communication system, the polling signal is transmitted and controlled by a master station. There are two data formats for transmitting the polling signal after receiving it. One is a method of combining data to be transmitted and transmission control data such as information for specifying a slave station as a transmission source to form a series of transmission data packets, and transmitting the packets in packet units. As a known example thereof, there is JP-A-56-86041. The other is a method of transmitting a polling signal or a synchronization signal indicating the head of transmission data to the slave station from the master station, and subsequently transmitting data of each slave station. A time slot in which each slave station can transmit is called a time slot, and by determining a time slot in which each slave station can transmit in advance, each slave station can transmit data following a polling signal from the master station without error. Transmit. Known examples of this include:
There is JP-A-10-92588 and the like.

[0003]

As described above, since a packet consists of transmission control data and transmission data, the data to be actually received at the transmission destination is the transmission data, and the ratio between the two is the transmission efficiency. Become. For example, if the data length of the polling signal is 10 bytes, the transmission control data length of the packet is 10 bytes, and the data length is x bytes,
The transmission efficiency is x / (20 + x). This shows that the efficiency can be improved as the data length x is increased. If the transmission data length is set in the transmission control data section of the packet, the transmission data length can be varied for each packet. The transmission efficiency of the packet system is poor when the transmission data length is short.For example, when a system that monitors devices connected to each slave station transmits only normal or abnormal information of the device from the slave station. It is. On the other hand, in the time slot method, only the data of each slave station is transmitted after the polling signal, so that the ratio of transmission data to the polling signal increases in proportion to the number of slave stations. Therefore, when the number of slave stations is large and the data transmission length is the same for each slave station, the transmission efficiency is higher than that of the packet system. However, when the data lengths transmitted and received by the slave stations are different, the time slot width needs to be adjusted to the maximum data length. For this reason, transmission data and a portion without data are generated in a time slot, and there is a problem that transmission efficiency is reduced. The above problem does not cause any practical problem if a communication system with a high transmission speed is used in consideration of the transmission efficiency. However, in a communication system using an optical fiber or a dedicated communication line capable of high-speed transmission, there is a possibility that the installation cost of the communication line may be increased.
A power line carrier system using an existing power line as a communication line does not require the cost of laying the communication line, but has large signal attenuation and noise and cannot increase the transmission speed.

[0004] An object of the present invention is to provide a data transmission system in which the transmission speed is relatively slow and data collection of slave stations in a fixed period and data collection from a specific slave station are required suddenly. Another object of the present invention is to provide a data transmission method effective for improving the data transmission.

[0005]

In order to solve the above-mentioned problems, in order to solve the above-mentioned problems, a packet system for transmitting and receiving a packet of transmission control information and transmission data between a master station and a slave station, After the transmission control information to be transmitted, the time slot method in which each slave station continuously transmits data in a predetermined order is switched according to the transmission control information transmitted from the master station. Here, information indicating the length of data transmitted from the slave station is added to the transmission control information. Further, after the transmission control information transmitted from the master station, the procedure in which each slave station transmits data in a predetermined order is repeated a plurality of times, and the transmission data from each slave station received a plurality of times by the master station is compared. The data with the highest frequency is assumed to be data without transmission errors. When each slave station transmits data in a predetermined order after the transmission control information, information for detecting an error at the time of transmission is added to the transmission data. Also, the identification information of the slave station to be transmitted and received is added to the transmission control information, and the identification information designates one slave station, a plurality of slave stations, and all slave stations. In addition, a constant voltage source or a constant current source is connected to the power line, and a device including a lamp, a sensor, or a display panel is connected, and the presence or absence of a device failure is transmitted to a master station.
The FF command is transmitted from the master station, or the display information is transmitted to the display board from the master station.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. One embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows (a) the overall configuration of a power line carrier according to an embodiment of the present invention, and (b)
The configuration of the master station and slave stations is shown. In FIG. 1A,
The master station 1 includes a power combining unit 19 for superimposing and separating a transmission signal on a power line 18, a modulation / demodulation unit 20 for modulating a transmission signal and demodulating a reception signal, and decoding and controlling reception data and generating transmission data. Transmission control unit 2 that performs transmission control
One. Slave station 1 (3a), slave station 2 (3b), slave station 3
(3c) to slave station N (3d) are also realized by the same configuration as the master station 1. FIG. 1B shows a detailed configuration of the power coupling unit 19, the modem unit 20 and the transmission control unit 21 of the master station 1 and each slave station 3. The power coupling unit 19 includes a capacitor 31, a coil 32, and a transformer 33, and the modulation / demodulation unit 20 includes an amplifier 34, a power supply cycle detection circuit 35, a modulator 36, a BPF (bandpass filter) 37, and a demodulator 38, and a transmission control unit. 2
Reference numeral 1 denotes a synchronization detector 39, SOF detector 40, address discriminator 41, control information decoder 42, CRC detector 43, reception timing controller 44, transmission timing controller 45, packet data assembler 46, and switch 47. Become. The power line carrier is connected to devices such as a lamp 24, a sensor 25, and a display board 26 from a constant voltage source 17 via a power line 18, and a monitoring / control device 22 controls and monitors each device. The master station 1 and the slave stations 1 to N are connected to the power line 1
8 for transmitting information for controlling and monitoring each device between the master station 1 and the slave stations N. Lamp 24,
Devices such as the sensor 25 and the display board 26 are controlled by the control device 23 based on information transmitted from the master station 1.

FIGS. 6A and 6B show time waveforms at various parts in FIG. 1. FIG. 6B shows a power supply waveform supplied from the constant voltage source 17, and FIG. 6E shows a transmission signal waveform. The waveform (a) of FIG. 7 shows the waveform on the power line 18. In the present embodiment, a case where data is transmitted in synchronization with a power supply waveform will be described. However, a clock signal shown in FIG. 6C is generated by the power supply cycle detection circuit 35 shown in FIG.
The time-series data to be transmitted as 0 and 1 in FIG. 6D is modulated by the modulator 36 and transmitted on the power line 18 via the amplifier 34 and the power line coupling unit 19. On the receiving side,
The transmission signal is extracted by passing only the frequency component of the transmission signal by the BPF 37 shown in (b), and is demodulated by the demodulator 38 into time series data of 0 and 1. Note that there are various modulation methods such as amplitude modulation, frequency modulation, and phase modulation, and any of these methods can be adopted.

FIG. 2 shows a transmission data format in the embodiment of the present invention. FIG. 2 (a) shows a data transmission format of a polling signal and a reception confirmation signal, FIG. 2 (b) shows a data transmission format at the time of packet communication, FIG. 2C shows a transmission data format at the time of time slot communication. As shown in the figure, the polling signal includes a synchronization signal 6 for synchronizing bits on the slave station side,
To perform a cyclic redundancy check (CRC) for checking a start-of-frame signal (SOF) 7, a control signal 8, an address signal 9 indicating an address of a transmission destination, and transmission data transmission error used for indicating a head of transmission data. CR
It consists of a C signal 10. The control signal 8 is, as shown in FIG.
ck information 13, M / S information 14, P / T information 15, and data length information 16. The Ack information 13 is information indicating whether or not the transmission source requests a reception acknowledgment signal from the reception source. The M / S information 14 indicates that the transmission source is a master station (Master).
r) or information for identifying a slave station (Slave), P / T information 15 is identification information for requesting selection of packet or time slot communication, which is a feature of the present invention, and data length information 16 is for packet data. Data section 11
Represents the data length to be transmitted, and in the case of a time slot, is information indicating the data length to be stored and transmitted in one time slot 12 transmitted by the slave station.

Hereinafter, a case will be described with reference to FIGS. 1 and 2 where the master station 1 polls (transmits a request) a specific slave station and the slave station transmits a packet. The master station 1 transmits a polling signal shown in FIG. When the polling signal transmitted from the master station 1 shown in FIG. 2A is transmitted to each slave station, the polling signal is output in time series from the demodulator 38 shown in FIG. 1 in each slave station. The transmission control unit 21 decodes the polling signal, and if it is a transmission request to its own station, performs transmission. The head of the polling signal is a synchronization signal 6 whose data string is, for example, "1010".
1010 ", the synchronization detector 39 detects the synchronization signal 6 when the data string is input. The synchronization signal 6 is used to synchronize the data string in 1-bit units. In the present embodiment, since the bit synchronization of the data string is extracted from the power supply waveform, there is no need to provide a synchronization signal in particular. Can be synchronized by adjusting.
The signal 7 confirms that it is the head of the transmission data.
Accordingly, the SOF signal 7 is detected by the SOF detector 40, and the received timing controller 44 determines that the transmitted data is transmitted as a polling signal or packet data, and the address discriminator 41 and the control information decoder 4
2 to determine whether the signal is addressed to the own station. If the transmitted data is a polling signal, the control signal 8
Ack information 13 included in the ACK indicates a reception confirmation request, and M /
The S information 14 indicates a master station, and the P / T information 15 stores information indicating a packet. Since the address of the slave station requesting transmission is stored in the address signal 9, the address discriminator 41 determines that the corresponding slave station is a polling signal for its own station. C
The RC signal 10 detects an error in the transmission data, and the soundness of the transmission data after the SOF signal 7 is confirmed. Accordingly, if the slave station determines that the transmission error is detected by the CRC signal 10 after the slave station determines the polling signal to the own station based on the information up to the address signal 9 by the above-described procedure, the slave station determines that the polling signal is incorrect. Judgment is not performed from the slave station. In the case where no error is detected by the CRC signal 10, FIG.
The transmission from the slave station to the master station is started in the format of the packet data shown in (b). When a packet transmission request is detected by the reception timing controller 44, the information is output to the transmission timing controller 45, and the transmission timing controller 45 performs transmission control. Transmit data to packet data assembler 4
6. The packet data is created by the transmission data switch 4
7. The signal is transmitted to the power line 18 via the modulator 36, the amplifier 34, and the power coupling unit 19. At this time, the roles of the signals below the synchronization signal 6 and the information are the same as those of the above-described polling signal. In this embodiment, since there is only one master station, the address of the slave station to be transmitted is stored in the address signal 9, and the master station transmits the address from the slave station according to the M / S information 14 of the control signal 8. The master station determines that the data is data, and receives the packet data at the master station. Further, since the data length to be transmitted by the data section 11 can be changed by the data length information 16, even if the data length to be transmitted differs for each slave station, transmission can be performed efficiently.

Next, a case of transmission by a time slot method will be described with reference to FIGS. 1, 2 and 3. FIG. The time slot request signal shown in FIG. 3A is transmitted from the master station 1 to the slave station. This time slot request signal is
The data format is exactly the same as the polling signal described above,
The P / T information 15 of the control signal 8 indicates a time slot. Each of the slave stations determines the received signal received via the power line coupler 19 shown in FIG. 1 as a time slot request signal by the modem unit 20 and the transmission control unit 21. The control information decoder 42 determines the data length of the time slot from the data length information 16 of the control signal 8, and the transmission timing controller 45
A transmission request in the time slot format. In the time slot method, as shown in FIG. 2C, each slave station sequentially transmits a time slot following a time slot request signal composed of signals from a synchronization signal 6 to a CRC signal 10. The transmission order of the slave stations is determined in advance so that the slave station 1 transmits in the first time slot and the slave station 2 transmits in the next time slot.
, The transmission timing is determined from the order and the data length information 16, the switch 47 is switched, and the transmission data is transmitted to the power line 18 via the modem 20 and the power combiner 19. Accordingly, as shown in FIG. 3, after the time slot request signal, the time slots 12 are sequentially transmitted from each slave station, that is, the time slot 12a from the slave station 1, the time slot 12b from the slave station 2, and the time slot 12n from the slave station n. I will do it. The master station receives the data shown in FIG. 3D in chronological order, determines that the received data is of the time slot type in the same procedure as that of the slave station, and receives transmission data from the slave station. The width of the time slot can be changed by the data length information 16 transmitted from the master station.

As described above, in the present embodiment, since information relating to packet transmission and time slot transmission which can be determined by a slave station is transmitted to a signal requested to be transmitted from the master station, the slave station transmits data according to both types according to the request. Becomes possible. Therefore, when the transmission data is short and the data is collected from all the slave stations, the reduction in the transmission efficiency that occurs in the packet communication is as follows.
The problem can be solved by switching to the time slot method. Further, when the length of data transmitted / received between the master station and the specific slave station is significantly different, the decrease in transmission efficiency caused by the time slot method can be eliminated by similarly switching to the packet method.

As shown in FIG. 2B, the format of the packet data is such that the CRC signal 10 is added to the end of the data 11, so that even if the data in the data portion is erroneous during transmission due to noise or the like, it is not detected. Can be. Therefore, when an error is detected on the packet data receiving side, a retransmission request can be issued to the transmission source, and a highly reliable communication system can be provided. On the other hand, in the above-described time slot method, as shown in FIG. 2C, since each slave station transmits a time slot after the CRC signal 10, an error in data transmitted in the time slot cannot be detected. . Therefore, after transmitting the time slot request signal from the master station 1 and receiving the time slots from the respective slave stations, the same transmission request is again transmitted from the master station, and the reception of the time slots by the master station is repeated a plurality of times. . Since the noise generated in the transmission path is either random in time due to the thermal noise of the equipment or bursts within a certain period of time in bursts, transmission errors occur in all the time slots received multiple times. It is unlikely that they are. Therefore, the reliability of communication can be improved by comparing the transmission data a plurality of times for each time slot and making the most frequent data true data.

As described above, the reliability of communication in the time slot system can be improved, but the transmission efficiency decreases because the same data is transmitted a plurality of times. Hereinafter, another embodiment of the present invention that solves this problem will be described with reference to FIG. FIG. 4 shows (a) the data format at the time of time slot transmission and (b) the configuration of the transmission control unit 21 of the master station and slave station. The difference from the embodiment of FIG.
The purpose is to add a parity 122 for detecting a signal error to the transmission data from the slave station stored in each time slot 12, and to provide a parity bit addition circuit 48 and a parity check circuit 49. When there is a transmission request in the time slot from the master station, the transmission control unit 21 of each slave station inputs the transmission data 121 to the parity bit addition circuit 48 and adds the parity bit 122 to the transmission data 121. Now, when the even parity is adopted, the parity bit 122 is added with 0 when the transmission data 121 is “1010”, the number 2 of 1 and the even number.
That is, in data obtained by combining the transmission data 121 and the parity bit 122, the parity bit 122 is added so that the number of existing 1s is always an even number. The parity check circuit 49 of the master station on the receiving side determines that there is no transmission error if the number of 1s in the data of each of the time slots 12a, 12b to 12n is an even number. If the number of 1s in the data of the time slot is an odd number, it is determined that there is an error in the data, a polling signal is transmitted to the corresponding slave station, and a retransmission request is made, so that the correct data is transmitted to the master station. Can be received. According to the present embodiment, since retransmission is requested only for the wrong slave station, the reduction in transmission efficiency is small.

Next, a case in which the monitoring and control device 22 monitors and controls devices will be described. Now, monitoring
The control device 22 controls the lamp 24, the sensor 25, and the display board 26.
When monitoring for failures at regular intervals, information on failures is 1-bit data, and it is necessary to collect data from all slave stations. Is good. Therefore, a time slot request signal may be transmitted from the master station 1 and each slave station may transmit information on whether a failure such as a lamp has occurred in a predetermined time slot. The monitoring / control device 22 turns on / off each lamp.
When controlling OFF, only specific lamps are ON / OF
F, ON / OFF from master station 1 to a specific slave station
The OFF information may be transmitted by a packet method. Also, when all the lamps are switched ON / OFF at the same time, it is more efficient to transmit by the packet method. In this case, the address signal 9 having the packet configuration shown in FIG.
Is provided with identification information for receiving all the slave stations to which the lamps are connected, and ON / OFF commands for each lamp are stored in the data section in a predetermined order. Address signal 9 is set to 8
In the case of bits, 255 slave station addresses can be set. Assuming that the number of actually existing slave stations is 200, 5
Five addresses are available, and one of the addresses may be used as identification information for receiving all the slave stations to which the lamp is connected. If a plurality of slave stations are grouped in this way, a group address is set, and the master station transmits the packet by the packet method, the transmission efficiency is higher than when individual packets are transmitted. It should be noted that, even when the transmission is received from the slave station by the time slot method, the transmission may be performed using the group address. When displaying character information on the display board 26 connected to the slave station N, the character information is stored in the data part of the packet from the master station 1 and transmitted to the slave station N. In this case, since the packet method can be used, the character information can be transmitted efficiently even if the data length of the character information is different for each transmission.

As described above, according to the present embodiment, it is possible to efficiently perform transmission and reception with respect to each slave station at a fixed period and transmission and reception with respect to a specific slave station between a master station and a slave station using a power line as a transmission line. Can be. Further, a system in which a lamp, a sensor, and a display panel are connected as shown in FIG.
For example, this is a configuration found in a system for displaying lighting on roads and airports, and displaying traffic information. By transmitting a power line between them, it is not necessary to lay a dedicated transmission line, and the system can be constructed at low cost.

FIG. 5 illustrates another embodiment of the present invention. This embodiment is characterized in that a constant current source 27 is used instead of the constant voltage source 17 in FIG. The constant current source 27 supplies power to the lamp 24, the sensor 25, and the display panel 26, and transmits the power to the central transmission device 29 via the power line 18 and the current transformer 28.
And the terminal transmission device 30 for transmission and monitoring and control. The central transmission device 29 is composed of the master station 1 and the monitoring / control device 22 shown in FIG.
Is composed of the slave station 3 and the control device 23 shown in FIG. In this embodiment, since the brightness of the lamp is proportional to the current, the current output from the constant current source 27 is controlled, and the brightness of all the lamps is controlled simultaneously. Then, transmission is performed by switching between the time slot and the packet system in the embodiment of FIG. 1 described above, such as the presence or absence of a failure and the transmission of character information to the display panel. By switching between the time slot and the packet system, data transmission can be performed with high transmission efficiency.

As described above, the power line carrier system has been described as an embodiment of the present invention. In general, improvement of transmission efficiency in data transmission is desired for all communication systems, and particularly, transmission capacity (transmission speed). A communication system in which the amount of data to be transmitted is relatively large,
If the present invention is applied to a communication system having some restrictions on increasing the transmission speed, the effect is large.

[0018]

As described above, according to the present invention,
The time slot method with good transmission efficiency when the number of data is small and the number of slave stations is large, and the packet method with good transmission efficiency when changing the data length to a specific slave station are switched according to the form of transmission. Therefore, the transmission efficiency can be significantly improved. In addition, by using the power line as a transmission line, there is no need to lay a dedicated transmission line between the master station and the slave station for transmission / reception to / from each slave station at a fixed period and for transmission / reception to a specific slave station, thereby reducing cost. The system can be constructed with. In addition, the reliability of communication can be improved by repeating transmission data by the time slot method a plurality of times and transmitting the data from the slave station to the master station so that the most frequent data is data without transmission errors. In addition, since a parity check for detecting an error in transmission data is adopted in the time slot method, and retransmission is requested only for an incorrect slave station, a decrease in transmission efficiency can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a power line carrier device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a format of transmission data according to the present invention;

FIG. 3 is a diagram schematically showing a time slot transmission state during time slot transmission according to the present invention.

FIG. 4 is a configuration diagram of a transmission data format of a time slot and a transmission control unit according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of a power line carrier system according to another embodiment of the present invention.

FIG. 6 is a time-wave diagram of each part of the power line carrier of the present invention.

[Explanation of symbols]

1 ... master station, 3 ... slave station, 17 ... constant voltage source, 18 ... power line,
19: Power coupling unit, 20: Modulation / demodulation unit, 21: Transmission control unit, 22: Monitoring / control unit, 23: Control unit, 24: Lamp, 25: Sensor, 26: Display panel, 27: Constant current source,
28 current transformer, 29 central transmission device, 30 terminal transmission device, 34 amplifier, 35 power supply cycle detection circuit, 3
6 modulator, 37 BPF, 38 demodulator, 39 synchronization detector, 40 SOF detector, 41 address discriminator,
42: control information decoder, 43: CRC detector, 44: reception timing controller, 45: transmission timing controller, 4
6 packet data assembler, 47 switch, 48 parity bit addition circuit, 49 parity check circuit

Continued on the front page (72) Inventor Masahiro Yoshioka 5-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Information Control Systems Division, Hitachi, Ltd. F-term (reference) 5K032 AA01 BA02 CA01 CD01 DB01 5K046 AA03 BA00 BB06 PS05 PS13 PS29 PS31 ZZ15 ZZ19 5K048 AA06 BA07 BA27 BA29 CA03 DA02 DC06 EB02 EB04 FA05 FB10 GB08 HA01 HA02 HA21

Claims (6)

[Claims] In a data transmission system for transmitting and receiving data between a master station and a plurality of slave stations connected via a transmission line or a power line, transmission control information and transmission data between the master station and the slave station are provided. A packet system for transmitting and receiving packets as a series of lump, and a time slot system for each slave station to continuously transmit data in a predetermined order after the transmission control information transmitted from the master station, from the master station. A data transmission method, wherein the transmission is switched by the transmission control information to be transmitted. 2. The slave station according to claim 1, wherein information indicating the length of data transmitted from the slave station is added to the transmission control information, and each slave station is arranged in a predetermined order after the transmission control information transmitted from the master station. A data transmission method characterized by transmitting data. 3. The method according to claim 1, wherein after the transmission control information transmitted from the master station, a procedure in which each slave station transmits data in a predetermined order is repeated a plurality of times.
A data transmission method characterized in that transmission data from each slave station received a plurality of times by a master station is compared, and data having the highest frequency is regarded as data without transmission errors. 4. The method according to claim 1, wherein when each slave station transmits data in a predetermined order after the transmission control information transmitted from the master station, an error at the time of transmission is detected in the data. A data transmission method characterized by adding information for performing data transmission. 5. The transmission control information according to claim 1, wherein identification information of a slave station to be transmitted and received is added to the transmission control information, wherein the identification information is one slave station, a plurality of slave stations, and all slave stations. A data transmission method characterized by specifying a station. 6. The power line according to claim 1, wherein a constant voltage source or a constant current source is connected to the power line, and a device including a lamp, a sensor, or a display board is connected to the power line. Is transmitted to the master station, or
A data transmission method, wherein an ON / OFF command of the device is transmitted from a master station, or display information is transmitted from the master station to the display panel.