JP4497248B2 - Data transmission method and data transmission apparatus - Google Patents

Description

The present invention relates to a data transmission method, and more particularly, to a data transmission method and a data transmission apparatus for transmitting data using a transmission path through which a transmission signal represented by a train of pulse waveforms having a substantially rectangular shape on a time axis is transmitted. Is.

  2. Description of the Related Art Conventionally, there has been provided a remote monitoring and control system for remotely monitoring and controlling a load using a transmission signal represented by a pulse waveform sequence that is substantially rectangular on a time axis.

  As such a remote monitoring control system, for example, as shown in FIG. 9, an input terminal 22 and a control terminal 23 are connected to the transmission unit 21 via a two-wire signal line Ls and attached to the input terminal 22. There is one in which a load L attached to the control terminal 23 is controlled in accordance with a monitoring input from a switch or a sensor (see Patent Document 1). An address is set for each of the input terminal 22 and the control terminal 23. When a monitoring input is input to the input terminal 22, monitoring data corresponding to the monitoring input is transmitted to the transmission unit 21, and the transmission unit 21 When the monitoring data is received, the control data corresponding to the monitoring data is transmitted to the control terminal 23 whose correspondence with the input terminal 22 is set by the address, and the load L is controlled via the control terminal 23. It is. The means for giving the monitoring input to the input terminal 22 is not limited to the switch, but may be a sensor that can be handled equivalently to the switch, but in the following, the monitoring input is given to the input terminal 22 by the operation of the switch. It will be explained as a thing. That is, since the monitoring input is generated in response to the operation of the switch, the monitoring input is referred to as an operation input.

  The transmission unit 21 sends a transmission signal Vs having a format as shown in FIGS. 10A and 10B to the signal line Ls. That is, the transmission signal Vs controls the start pulse SY indicating the start of signal transmission, the mode data MD indicating the mode of the transmission signal Vs, the address data AD for individually calling the input terminal 22 and the control terminal 23, and the load. Control signal CD, checksum data CS for detecting a transmission error, a double pole (± 24V) including a signal return period WT which is a time slot for receiving a return signal from the input terminal 22 or the control terminal 23 ), And data is transmitted by performing pulse width modulation on a pulse waveform sequence that is substantially rectangular on the time axis.

  In each input terminal 22 and each control terminal 23, when the address data of the transmission signal Vs received via the signal line Ls matches the address data set in each, the control data is fetched from the transmission signal Vs, In synchronization with the signal return period WT of the transmission signal Vs, the monitoring data is returned as a current mode signal (a signal transmitted by short-circuiting the signal line Ls through an appropriate low impedance).

  The transmission unit 21 constantly performs polling for sequentially accessing the input terminal 22 and the control terminal 23 by cyclically changing the address data included in the transmission signal Vs. In the case of constant polling, the input terminal 22 or the control terminal 23 in which the address data included in the transmission signal Vs is identical operates if the control data is included in the transmission signal Vs, and the input terminal 22 operates. The operating state of the device 22 or the control terminal device 23 is returned to the transmission unit 21 as monitoring data.

  On the other hand, the transmission unit 21 generates an interrupt signal when any one of the input terminals 22 receives the interrupt signal Vi as shown in FIG. 10C corresponding to the operation input from the switch. After detecting the input terminal 22, interrupt polling is performed to access the input terminal 22 and return monitoring data corresponding to the operation input.

  In other words, the transmission unit 21 always performs polling to send the transmission signal Vs whose address data is cyclically changed to the signal line Ls, and starts the transmission signal Vs with the interrupt signal Vi generated from the input terminal 22. When detected in synchronization with the pulse SY, the transmission signal Vs in which the mode data MD is set to the interrupt polling mode is sent out. When the high-order bits of the address data of the transmission signal Vs in the interrupt polling mode match, the input terminal 22 that has generated the interrupt signal Vi is synchronized with the signal return period WT of the transmission signal Vs. The lower bits of the address data set in 22 are returned as reply data. In this way, the transmission unit 21 acquires the address of the input terminal 22 that has generated the interrupt signal Vi.

  In this way, when the transmission unit 21 acquires the address of the input terminal 22 that has generated the interrupt signal Vi, the transmission unit 21 sends the transmission signal Vs requesting the input terminal 22 to return the monitoring data. The input terminal 22 returns monitoring data corresponding to the operation input to the transmission unit 21. When receiving the monitoring data, the transmission unit 21 gives an instruction to clear the operation input of the corresponding input terminal device 22, and the input terminal device 22 returns the operation input clear. That is, the transmission unit 21 receives the operation input by the four transmission signals Vs including the transmission signal Vs for detecting the interrupt signal Vi.

  The transmission unit 21 that has received the monitoring data generates control data for the control terminal 23 that is associated in advance with the input terminal 22 according to the address correspondence, and transmits the transmission signal Vs including this control data to the signal line Ls. The load L sent out and attached to the control terminal 23 is controlled.

  By the way, in the remote monitoring control system as described above, the input terminal device 22 and the control terminal device 23 communicate with each other via the transmission unit 21 by a polling / selecting method. For this reason, the communication speed is relatively low. For example, it is not suitable for transmission of data whose communication volume is much larger than monitoring data and control data, such as a measured value of electric energy and voice for calls. is there.

  Thus, a data transmission method has been proposed in which high-speed communication is performed while sharing the signal line Ls with the remote monitoring control system by modulating and superimposing the audio signal on the transmission signal Vs (see, for example, Patent Document 2). In the conventional example described in Patent Document 2, the pulse waveform of the transmission signal Vs is set to the high level and the low level in order to avoid the influence of noise (harmonic noise) generated at the rising and falling of the transmission signal Vs. The audio signal is superimposed only during a stable period.

JP 2005-73075 A JP-A-8-274742

  However, in the above conventional example, the length of the transmittable frame (frame length) is defined by the minimum value of the pulse width of the transmission signal Vs, so the frame length cannot be increased so much and the transmission efficiency is not good. There was a problem.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a data transmission method and a data transmission device capable of improving the transmission efficiency of data transmission while sharing a signal line with other data transmission methods. There is.

In order to achieve the above object, the invention according to claim 1 is a data transmission method for transmitting data using a transmission path through which a transmission signal represented by a train of pulse waveforms having a substantially rectangular shape on a time axis is transmitted. The frame including the data is transmitted by being superimposed on the pulse waveform, and is synchronized with the rise and fall of the pulse waveform at the same time interval as the shortest time interval of the rise and fall of the pulse waveform. In the period, invalid data is inserted into the frame and transmitted.

  According to the first aspect of the present invention, since invalid data is inserted and transmitted in the frame at the same time interval as the shortest time interval of the rise and fall of the pulse waveform, the rise and fall intervals of the pulse waveform The frame length can be transmitted compared to the case where the frame is superimposed only on the section not including the harmonic noise as in the conventional example. As a result, the transmission efficiency of data transmission can be improved while sharing the transmission path with other data transmission methods.

  The invention of claim 2 is characterized in that, in the invention of claim 1, the synchronization symbol of the frame is composed of a preamble and a frame start section.

  According to the invention of claim 2, since the synchronization symbol of the frame is constituted by the preamble and the frame start portion, a transmission error occurs in a part of the preamble due to the harmonic noise generated at the rise or fall of the pulse waveform. Can also establish synchronization.

  The invention of claim 3 is characterized in that, in the invention of claim 2, a plurality of the synchronization symbols are continuously transmitted.

  According to the invention of claim 3, since a plurality of the synchronization symbols are continuously transmitted, the probability that the synchronization cannot be achieved due to the harmonic noise generated at the rise or fall of the pulse waveform is further reduced.

  The invention of claim 4 is characterized in that, in the invention of claim 3, in each synchronization symbol transmitted continuously, information on the number of bits of the remaining synchronization symbols is included in each frame start portion.

  According to the fourth aspect of the present invention, since information on the number of bits of the remaining synchronization symbols is included in each frame start portion in each synchronization symbol transmitted continuously, the synchronization symbols after synchronization is established are ignored. Therefore, processing of received data can be simplified.

  The invention of claim 5 is characterized in that, in the invention of claim 1, the synchronization symbol of the frame is composed of a preamble and a plurality of frame start sections.

  According to the invention of claim 5, since the synchronization symbol of the frame is composed of a preamble and a plurality of frame start parts, a transmission error occurs in a part of the preamble due to harmonic noise generated at the rise or fall of the pulse waveform. However, synchronization can be established and transmission efficiency can be improved.

  According to a sixth aspect of the present invention, in the invention of any one of the third to fifth aspects, the preamble and the frame start part constituting a plurality of synchronization symbols to be transmitted continuously are intersymbol-coded for each synchronization symbol. It consists of different codes with long distances.

According to the invention of claim 6, since the preamble and the frame start part constituting a plurality of synchronization symbols to be continuously transmitted are composed of different codes having a long inter-code distance for each synchronization symbol, The probability of misreading decreases.
The invention of claim 7 is a data transmission device for transmitting data using a transmission path through which a transmission signal represented by a train of pulse waveforms having a substantially rectangular shape on the time axis is transmitted. 6. Data is transmitted by the data transmission method according to any one of the sixth aspect.

  According to the present invention, it is possible to improve the transmission efficiency of data transmission while sharing the transmission path with other data transmission methods.

(A) is a system configuration | structure figure of the data transmission system for implementing the data transmission method based on this invention, (b) is a block diagram of the data transmission apparatus same as the above. (A), (b) is a data structure diagram of a frame and a synchronization symbol in Embodiment 1 of the present invention. (A) is a principal part circuit block diagram of the receiving part of a data transmission apparatus, (b) is a wave form diagram of the signal which passed through the diode bridge which a receiving part comprises. FIG. 10 is a data structure diagram in which a part of a frame and a synchronization symbol are omitted in Embodiment 2 of the present invention. It is a data structure figure which a part of a frame and a synchronization symbol were omitted in Embodiment 3 of the present invention. FIG. 10 is a data structure diagram in which a part of a frame and a synchronization symbol is omitted in Embodiment 4 of the present invention. It is a data structure figure which a part of a frame and a synchronization symbol were omitted in Embodiment 5 of the present invention. It is explanatory drawing of the flame | frame and synchronous symbol in Embodiment 6 of this invention. It is a system block diagram of the conventional remote monitoring control system. It is a signal format of the transmission signal in the same as the above.

  Hereinafter, an embodiment in which the technical idea of the present invention is applied to the data transmission method of the remote monitoring control system described in the conventional example and the data transmission method sharing the signal line Ls will be described. However, other data transmission methods in which the data transmission method according to the present invention can share a signal line are not limited to those of the embodiment (time division multiplex transmission by pulse width modulation).

  First, a data transmission system that implements a data transmission method according to the present invention will be described with reference to FIG.

  The data transmission system of this embodiment shares the signal line Ls with the remote monitoring and control system described in the prior art. In the remote monitoring control system, an input terminal 22 and a control terminal 23 are connected in parallel to the transmission unit 21 by a two-wire signal line Ls, and the pulse train is subjected to pulse width modulation as described in the prior art. The transmission signal Vs is time-division multiplexed and transmitted between the transmission unit 21, the input terminal 22, and the control terminal 23.

  As shown in FIG. 1A, the data transmission system according to the present embodiment includes a plurality (two in the illustrated example) of data transmission apparatuses 1 and 1 connected in parallel to the signal line Ls. As shown in FIG. 1B, the data transmission device 1 includes a transmission signal monitoring unit 10 that monitors a transmission signal Vs transmitted between the transmission unit 21 and the terminals 22 and 23 via the signal line Ls, A transmission unit 11 that modulates a frame including data to be transmitted to another data transmission apparatus 1 and transmits it to the signal line Ls while being superimposed on the transmission signal Vs, and a frame transmitted via the signal line Ls as a transmission signal A receiving unit 12 that receives and demodulates the signal separately from Vs; a transmission process in which internally generated data or externally input data is stored in a frame and transmitted from the transmitting unit 11; And a transmission control unit 13 that executes a reception process of taking in the demodulated frame and taking out data stored in the frame.

  The receiver 12 separates the frame from the transmission signal Vs having a relatively low frequency by performing balanced / unbalanced conversion by the diode bridge DB as shown in FIG. Here, as shown in FIG. 3B, since the harmonic noise N generated at the rise and fall of the transmission signal Vs is superimposed on the signal voltage that has passed through the diode bridge DB, at the rise and fall. There is a possibility that an excessive instantaneous voltage is applied between the output terminals of the diode bridge DB and the subsequent amplifier A or the like is destroyed. Therefore, in the present embodiment, a clamp circuit including a pair of diodes D1 and D2 connected in series is provided at a connection point between the output on the high potential side of the diode bridge DB and the input end of the amplifier A, and the excessive instantaneous voltage is increased. It is prevented from being applied to the amplifier A. However, a DC cut capacitor Cc is inserted between the diode bridge DB and the clamp circuit so that the line voltage of the signal line Ls is not limited by the clamp circuit. Furthermore, in this embodiment, the power supply for operation of the data transmission device 1 is created by making the output voltage of the diode bridge DB constant by the constant voltage circuit REG.

  In the data transmission apparatus 1, the transmission signal monitoring unit 10 monitors the pulse waveform of the transmission signal Vs via the signal line Ls, and outputs a monitoring signal synchronized with the rising and falling of the pulse waveform to the transmission control unit 13. . Then, the transmission control unit 13 adjusts the timing of sending a frame from the transmission unit 11 and superimposing it on the transmission signal Vs after the pulse waveform rises or falls based on the monitoring signal output from the transmission signal reception unit 10. .

(Embodiment 1)
FIG. 2 shows a data structure of frames and synchronization symbols in the data transmission method of this embodiment. In general data transmission, a synchronization symbol is transmitted prior to a frame to establish synchronization. In this embodiment, a preamble is used as a synchronization symbol. A frame transmitted following the synchronization symbol is usually composed of a control bit, a destination address, a source address, data, and a frame check sequence (FCS) (see FIG. 2A).

  The present embodiment is characterized in that invalid data (dummy bits) Dmb is inserted into a frame at the same time interval as the shortest time interval of the rising and falling edges of the transmission signal Vs as shown in FIG. There is.

  As described above, since the harmonic noise N generated when the transmission signal Vs rises and falls is superimposed on the signal voltage that has passed through the diode bridge DB of the receiving unit 12, the frame is partially crushed at this portion. Transmission errors are likely to occur. Therefore, in this embodiment, the amount of data (valid data) that can be transmitted in a single frame can be increased by transmitting the dummy bit Dmb in a period synchronized with the rising and falling edges of the transmission signal Vs. . In addition, the transmission efficiency can be improved by reducing the number of frames required for data transmission as compared with the case where data is divided and transmitted in a large number of frames. In other words, since the transmission efficiency is reduced by the parts (control bits, destination address, source address, FCS) other than the data included in the frame, the transmission efficiency is improved by the amount other than the data by reducing the number of frames. .

(Embodiment 2)
FIG. 4 shows the data structure of frames and synchronization symbols in the data transmission method of this embodiment. The present embodiment is characterized in that a synchronization symbol transmitted prior to a frame is composed of a preamble and a frame start unit (frame start delimiter) SFD. However, since the structure of the frame is the same as that of the first embodiment, the description thereof is omitted.

  Thus, if the synchronization symbol composed of the preamble and the frame start unit SFD is transmitted prior to the frame, synchronization can be established even if a transmission error occurs in a part of the preamble due to harmonic noise, The accuracy of establishment of synchronization can be further increased.

(Embodiment 3)
FIG. 5 shows a data structure of frames and synchronization symbols in the data transmission method of the present embodiment. The present embodiment is characterized in that a plurality (three in the illustrated example) of synchronization symbols configured by a preamble and a frame start unit SFD are transmitted prior to the frame. However, since the structure of each synchronization symbol and frame is the same as that of the second embodiment, the description thereof is omitted.

  As described above, if a plurality of synchronization symbols composed of the preamble and the frame start unit SFD are transmitted prior to the frame, even if synchronization cannot be established with any synchronization symbol due to harmonic noise, The probability that synchronization cannot be established because synchronization can be established with this synchronization symbol becomes low.

(Embodiment 4)
FIG. 6 shows the data structure of frames and synchronization symbols in the data transmission method of this embodiment. In the present embodiment, as in the third embodiment, a plurality of (three in the illustrated example) synchronization symbols configured by the preamble and the frame start unit SFD are transmitted prior to the frame, and the number of bits of the subsequent synchronization symbols A characteristic is that a value (total number of bits) obtained by summing is included in the frame start part SFD. However, since the structure of each synchronization symbol and frame is the same as that of the second embodiment, the description thereof is omitted.

  In the third embodiment, for example, even if synchronization can be established with the first synchronization symbol, it is not possible to know the synchronization symbol that is the synchronization symbol, in other words, where the frame starts. It becomes complicated.

  In contrast, in the present embodiment, the frame start portion SFD of the first synchronization symbol includes the total number of bits obtained by adding the number of bits of the second and third synchronization symbols, and the frame start of the second synchronization symbol. Since the number of bits of the third synchronization symbol is included in the unit SFD, the transmission control unit 13 in the data transmission apparatus 1 on the receiving side has a frame start unit of the synchronization symbol after synchronization is established with any synchronization symbol. Since the received data for the total number of bits included in the SFD may be ignored, the processing of the received data can be simplified.

(Embodiment 5)
FIG. 7 shows the data structure of frames and synchronization symbols in the data transmission method of this embodiment. The present embodiment is characterized in that a synchronization symbol transmitted prior to a frame is composed of a preamble and a plurality (three in the illustrated example) of frame start units SFD. However, since the structure of the frame is the same as that of the first embodiment, the description thereof is omitted.

  As described above, if a synchronization symbol composed of a preamble and a plurality of frame start sections SFD is transmitted prior to the frame, even if synchronization cannot be established between the preamble and any of the frame start sections SFD due to harmonic noise. The probability that synchronization can be established by any other frame start unit SFD is reduced, and the probability that synchronization cannot be achieved is reduced.

  Here, for example, when three frame start parts SFD are transmitted continuously as described above, when the frame start part SFD is a bit pattern of “0000_1010_0111”, the frame start is started when the bit pattern coincides with 8 bits continuously. The part SFD may be detected. That is, even if a transmission error occurs in consecutive 4 bits of any frame start part SFD due to a burst error due to harmonic noise, it can be detected between the frame start part SFD before or after that.

(Embodiment 6)
In the present embodiment, as in the third to fifth embodiments, a plurality of preambles and a frame start unit SFD that are continuously transmitted are configured with different codes having a long inter-code distance for each synchronization symbol or each frame start unit SFD. There is a feature in that.

  For example, as shown in FIG. 8, if each preamble and frame start unit SFD are configured with (001), (010), and (100) if they are 3 bits, the transmission control unit 13 reduces the probability of misreading a synchronization symbol. be able to.

DESCRIPTION OF SYMBOLS 1 Data transmission apparatus 10 Transmission signal monitoring part 11 Transmission part 12 Reception part 13 Transmission control part

Claims (7)

A data transmission method for transmitting data using a transmission path through which a transmission signal represented by a train of pulse waveforms having a substantially rectangular shape on a time axis is transmitted,
A frame including the data is transmitted by being superimposed on the pulse waveform, and in a period synchronized with the rise and fall of the pulse waveform at the same time interval as the shortest time interval of the rise and fall of the pulse waveform. A data transmission method characterized by inserting invalid data into a frame for transmission.   2. The data transmission method according to claim 1, wherein the synchronization symbol of the frame is composed of a preamble and a frame start unit.   3. The data transmission method according to claim 2, wherein a plurality of the synchronization symbols are continuously transmitted.   4. The data transmission method according to claim 3, wherein in each synchronization symbol transmitted continuously, information on the number of bits of the remaining synchronization symbols is included in each frame start portion.   2. The data transmission method according to claim 1, wherein the synchronization symbol of the frame is composed of a preamble and a plurality of frame start sections.   6. The preamble and the frame start part constituting a plurality of synchronization symbols to be continuously transmitted are composed of different codes having a long inter-code distance for each synchronization symbol. The data transmission method according to item. A data transmission device for transmitting data using a transmission path through which a transmission signal represented by a train of pulse waveforms having a substantially rectangular shape on a time axis is transmitted. A data transmission apparatus for transmitting data by the data transmission method according to the invention.

Images