JPH0550902B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objectives of the Invention] The present invention relates to a data collection system suitable for a case where the amount of data transmitted per terminal is extremely small.

Figure 7 shows three types of data collection systems, in each figure 1 is a data collection device;
2 is a data transmission terminal, and 3 is a transmission line. The data transmission terminal 2 can turn relay contacts ON and OFF, power switch ON and OFF, fire alarm ON,
It captures digital data such as OFF and sends it to the central data collection device 1 using an appropriate method.
It decodes the signals sent from the terminal, stores or displays the data on the terminal side, and in some cases issues an alarm.

In the system configuration shown in Figure 7A, the central data collection device 1 and each terminal device 2 are individually wired in a 1:1 ratio, and although the configuration is simple, the wiring cost of the transmission line 3 is high. Become.

In the system configuration shown in FIG. Since they are connected by one transmission line 3, the wiring cost is reduced. On the other hand,
In order to avoid a situation in which terminal devices 2 send duplicate signals (hereinafter referred to as "collision"), software consideration is required.

In the system configuration shown in FIG. It also becomes possible to exchange signals between the two. In this system, although the wiring cost of the transmission line 3 is higher than that of the system shown in FIG. 7B, the data transmission function is significantly higher.

FIG. 8 shows a general configuration example of the data transmission terminal 2. As shown in FIG.

microprocessor 4, read-only memory 5,
Random access memory 6, LSI for data transmission and reception
7. A data input/output LSI 8 and the like are connected via a bus line 9.

The microprocessor 4 temporarily stores information that comes in from the outside via the transmission line 10a, and then immediately sends it to the data collection device 1 via the transmission line 10b, and is connected to its own terminal at an appropriate timing. Input information is taken in via the terminal 11 and sent to the data collection device 1 via the transmission line 10b.

FIG. 9 shows the state of the signals entering the central data collection device 1.

Figure 9A shows the case of a rather simple transmission method,
Signals 12 from each terminal 2 arrive at random timing. As a result, the signals 12 and 13 from the two terminals may collide, and in this case, both data become invalid. Although there are such drawbacks, this method is applicable when the data transmission time per terminal is short or when the frequency of data generation is low because the software of the terminal device is simple.

FIG. 9B shows a commonly used method, in which the signals 14 from each terminal 2 arrive without collision. The way to prevent collisions when using a system like the one shown in Figure 7B is to have the terminal receiving a signal wait temporarily without transmitting its own signal, and then transmit its own signal after transmitting the received signal. Such measures are necessary. Furthermore, in a system such as that shown in FIG. 7C, it is common that only designated terminals perform transmission based on commands from the central data collection device 1.

In any case, if we look at the data transmitted from one terminal in more detail, it consists of a header section a, data b, an error check section c, etc. The header section a includes a code indicating the start of data, the sending terminal address, etc., and the error check section c includes a parity check code or CRC code, as well as a code indicating the end of the transmitted information. There is.

Among the configurations of the data transmission system described above, FIG. 7B is the simplest. However, in the case of the configuration shown in FIG. , it has the disadvantage of being troublesome.

The present invention has been made in view of the above, and an object of the present invention is to provide a data collection system that has a simple system configuration and can prevent data transmitted from each terminal from colliding.

[Summary of the Invention] The first feature of the present invention is that data is sequentially transmitted in one direction toward the central device from the terminal located farthest from the central device at an appropriate period, and other terminals are It adds self-data after the data sent from the terminal and transmits it, and if the input signal stops longer than a predetermined time, it is determined that there is a line abnormality,
The terminal device that recognizes the line abnormality immediately becomes the temporary farthest terminal device and transmits its own data signal at a fixed period, and from this terminal device, the above central equipment side prevents the system from going down and recovers from the failure. In this case, when the correct signal arrives at the provisional farthest terminal device a predetermined number of times, at that point, the function is to synchronize the timing with the input signal and add self-data after the input signal and transmit it as in normal times. The point lies in the configuration that each of the above-mentioned terminal devices has. The second feature is that data transmitted from an adjacent terminal is delayed by a predetermined time and self-data is added in front of the data before being transmitted to a terminal other than the terminal located farthest from the central device. The point is that it has the function to do.

[Example] Hereinafter, the present invention will be explained in detail using FIGS. 1 to 6.

FIG. 1 is a time chart showing an example of signal transmission and reception in each part, #2a, #2b,
#2c and #2d mean the numbers of the data terminals,
#1 means central unit. Furthermore, signals with diagonal lines represent outgoing signals, and signals without hatching represent received signals. Note that for convenience of explanation, the number of terminals is assumed to be four, but this can be expanded to any number.

First, from time T ₀ to T ₁ , the previous terminal #2
It is assumed that a to #2d are operating normally. First, data 20d is transmitted from the terminal device #2d that is farthest from the central device #1. This data consists of multiple bits. When terminal #2c next to terminal #2d receives this data 20d,
After that, it adds its own data 20c and sends it out. Similarly, terminals #2b and #2a also receive their own data 20b and 20 after the received data.
A is added and sent.

Therefore, the central device #1 has each terminal device #d~
Data from #a 20d, 20c, 20b, 20
a arrives in sequence.

The terminal #2d furthest from the central device #1 sends its own data 20d every time τ ₀ , and each terminal adds its own data after the data from the adjacent terminal, so in the end, each terminal The data transmission period of the device is τ ₀ .

Next, we will discuss the operation of the system when some kind of failure occurs in a certain terminal and data transmission from that terminal stops.

In FIG. 1, terminal # ₂ at time T1
Assume that a failure occurs in c and the signal transmission stops. Normally, the data reception period (ie, transmission period) in each terminal device is determined to be τ ₀ . Therefore, when each terminal receives data from an adjacent terminal, it can predict at what time the data will arrive next. Therefore, in each terminal device, we set a time τ ₁ that is larger than the data transmission and reception cycle τ ₀ , and if no data is received even after the time τ ₁ has elapsed since the previous data reception, it is determined that a signal interruption has occurred. Then, the terminal device that detected the signal loss occurrence, terminal device #2b in FIG. 1, sends the signal loss detection signal 21b.
, the terminal #2a sends out a signal disconnection detection signal 21a.

In this case, the time interval τ ₁ for determining signal disconnection
Since there are variations depending on each terminal device, the times Ta and Tb (respectively, terminal device #2
a, 2b) are unlikely to match exactly, and are usually slightly off.

Therefore, if a signal loss is detected in a certain terminal device, and it is confirmed that no signal is sent from the adjacent terminal device for a while before and after the signal loss is detected, It is uniquely recognized that the terminal device is adjacent to the failed terminal device.

For example, in FIG. 1, terminal device #2b
A signal loss is detected at Tb, but since no signal arrives from adjacent terminal #2c,
It can be seen that it is adjacent to the failed terminal device. On the other hand, terminal #2a also detects a signal loss at time Ta, but immediately after that, at time Tb, it receives the signal loss detection signal 21b from terminal #2b. It can be seen that it is not adjacent to the vessel.

Here, the time at which the terminal device located closer to the central device #1 than the failed terminal device detects a signal loss is due to variations in the circuit (more specifically, the timer circuit); 1
The variation in τ ₁ in the figure can be roughly predicted in advance.

Therefore, for a while after detecting a signal disconnection,
If you wait for T ₂ and no signal arrives from the adjacent terminal during that time, wait at this time, that is, the first
At time T ₂ in the figure (the time T ₂ has elapsed since the signal interruption was detected), the terminal transmits its own normal data again.

In the example of FIG. 1, the terminal device adjacent to the failed terminal device #2c is the terminal device #2b, and the terminal device #2b confirms that it is adjacent to the failed terminal device #2c for the reason described above. , Terminal #2a also confirms that a failure has occurred in one of the terminals and that it is not a terminal adjacent to the failed terminal. Furthermore, since the terminal device #2d that is farthest from the central device #1 simply sends a signal, there is no way to recognize whether a failure has occurred somewhere in the system.

Therefore, the terminal device #2d mechanically has a period τ ₀
Continue sending data. Also, terminal #2b
knows that it is adjacent to the failed terminal #2c, that is, it is the farthest terminal as seen from the central device #1, so from time T ₂ onwards, _it The data 20b is transmitted (the signal transmission cycle τ ₀ ' when a line disconnection occurs may be the same as or different from the cycle τ ₀ during normal operation).
Further, when terminal device #2a receives data from adjacent terminal device #2b, as it did before time _T1 , it adds its own data to the end of this data and sends it to central device #1.

In the central device #1, terminal devices #2a, #2
Just as in case b, it is known approximately at times Ta and Tb that a failure has occurred in one of the terminals. For central unit #1, the time is determined by the operation described above.
Normal data is sent after T ₂ , but if you count the amount of received data (number of bits, number of words) at this time, you can determine the number of normal terminals from this. Therefore, it is clear that the number of the failed terminal device can also be known.

Of course, if the data sent from these terminals is designed in advance so that the terminal number is included as part of the data, it is also possible to determine the faulty terminal number by decoding the received data. It is possible. This method is effective when the amount of data transmitted from each data terminal is unequal.

Also, what should be noted here is what kind of signal should be used when each terminal detects a signal loss and transmits a signal loss detection signal. In principle, the presence of a faulty terminal can be recognized from the fact that there is no reception signal on each normal terminal after time T ₁ (approximately at times Ta and Tb), so the purpose of this fault detection signal is to , it only determines whether each terminal is adjacent to a faulty terminal, so it can simply be any suitable pulse signal. Of course, the format is clearly different from the data signal,
The content signal may also indicate the source of the detected failure.

Now, suppose that terminal device #2c, which has failed due to some object, returns to normal operation at time _T3 . In this case, terminal device #2b receives data 20d and 20c from terminal devices #2d and #2c at a period of τ ₀ from time T ₃ . Furthermore, by receiving these signals, it can be determined that the operation of the adjacent terminal has returned to normal.

Moreover, at this time, terminal device #2b does not immediately send this input data to central device #1, but for a while (until time T ₄ ).
I threw away the received data and my own data 2
0d at a period of τ ₀ , and after data from terminal #2c is received several times, time T ₄ (T ₄
The timing may be determined to be a certain period of time after T ₃ , or after receiving normal data several times), and the self data is added to the end of the transmitted data and sent. , and then repeat this.

Next, another operation in the case where any terminal device fails in this system will be explained using FIG. 2. Note that FIG. 2 is exactly the same as FIG. 1 up to the times before and after time _T1 .

Now, at time T ₁ , terminal #2c breaks down,
As a result, it is assumed that not only the data of the terminal #2c but also the data of the normal terminal #2d are stopped. In this case, as explained in Fig. 1, since the previous data reception, each terminal has a preset time τ ₁ (varies from terminal to terminal, and τ ₁ for terminal #2b). However, terminal device #2a determines that the signal is disconnected if no data is received during the period τ ₁ ', and τ ₁ ≈τ ₁ '.

In the example shown in FIG.
The signal disconnection detection signal was once issued at the time when

However, in the method shown in FIG.
#2b transmits its own data, although there is a slight timing difference.

In the example of FIG. 2, terminal #2b is terminal #2a
The self data 20b is sent at a slightly earlier time Tb, and the terminal #2a is sent at a slightly later time than the terminal #2b.
At Ta, the self data 20a is also transmitted.
Since the times of Ta and Tb are slightly different from each other, in terminal #2a, the data from the adjacent terminal #2b overlaps with its own data. Then, these data are received by the central device #1 while being overlapped.

In the central unit #1, as has been stated repeatedly, since the received data does not arrive for a certain period of time, the next data that comes in is essentially overlapping data, and therefore,
Since we can recognize that it is incorrect, we throw away this data.

Next, the terminal device that the system recognizes as having a signal interruption determines whether it is immediately adjacent to the faulty terminal device and closer to the central device #1. This determination is made based on whether data is received from the adjacent terminal at the time before and after the signal interruption is detected.
If no signal is received, it can be determined that the terminal is adjacent to a failed terminal. Also, when data comes in, it can be seen that they are not adjacent.

In this way, only the terminal device (terminal #2b in the example of FIG. 2) that has recognized itself as being adjacent to the failed terminal device will continue to have a cycle τ from time τ ₀ after sending data last time. Continue sending self data with ₀ . Further, the other terminal device #2a adds its own data after the data from the adjacent terminal device #2b and transmits the data.

Also in the case of the method shown in Figure 2, the faulty terminal #2
After c recovers its operation, it performs exactly the same operation as in FIG.

Next, in the present invention, the format of signals transmitted from each terminal will be explained.

There are multiple bits of data transmitted from each terminal, and these include: (1) A combination of the transmitting terminal number and the information to be transmitted.

(2) Combination of calling terminal number, information to be sent, and error detection code.

(3) Simply a combination of information to be disseminated.

(4) Simply a combination of information to be transmitted and error detection codes.

etc. are possible. However, in (1) to (4), it is necessary that a single core or a plurality of pits representing the delimitation of information such as the beginning and end be added to the beginning and end of these pieces of information, respectively.

In addition, in this method, each terminal adds its own information to the information sent from the adjacent terminal and transmits it, so central device #1 can read the information as long as there is a delimiter between the pieces of information. , it is possible to uniquely recognize whether the information is from the original terminal without the calling terminal number.

Figure 3 is a diagram showing a specific example of a waveform. As an example, the case where the data is 10010 is shown, and a is
In the case of the NRZ code, if b corresponds to a wide pulse for data “1” and a narrow pulse for data “0”, then c corresponds to two pulses for data “1”. When one pulse corresponds to data “0”, d is
This is an example of DMI encoding.

In addition, in these examples, except for a in FIG. 3, some kind of signal is output in either case of data "1" or "0", but in case a, a signal is output only when data is "1". is not issued, so 00…0
Such data cannot be transmitted, and consideration must be given in advance to ensure that the data to be sent contains an appropriate amount of "1".

Also, as mentioned earlier, information indicating the beginning and end must be added before and after these data, but it is not absolutely necessary; for example, in the example in Figure 3, these Even if the data does not include information indicating the end or beginning,
If there is a blank part of a predetermined length before and after this data, the beginning and end of the data can be easily recognized by interpreting this blank part as a delimiter.

Next, in the present invention, own terminal data is added to the end of the data that is transmitted one after another and transmitted, but in this case, some care and ingenuity are required. This will be explained with reference to Figure 4.

FIG. 4 is a diagram showing details of data transmission timing, and FIG. 4a shows terminal #2b transmitting own data 30b to data 30d, 30c sequentially transmitted from terminal #2d, #2c. This is a time chart showing how data is added. In this case, it is recognized that the data has ended because there are blank periods τi ₁ and τi ₂ between the data.

By doing this, the data of the own terminal device is immediately additionally transmitted, and for example, on the side of a, terminal device #2
There is a blank period of τi ₁ between the data of d and #2c, and then the terminal #2b similarly transmits its own data 30b after a blank period of τi ₂ . However, due to variations in the manufacturing characteristics of terminal devices, in some cases, as shown in FIG. It may happen that the self-data 30b is transmitted at a time interval of τi ₂ from the previous data. In this case, the immediately preceding terminal #2c
The data 30c sent from the previous data is sent at a time interval of τi ₁ from the previous data, and
Since τi ₂ ≒τi ₁ , both will collide and both data will be destroyed.

To avoid such problems, some ingenuity is required. In other words, the simplest method is to delay the timing of data transmission for terminals closer to central device #1, but this requires changing the characteristics slightly for each terminal.
Not suitable for mass production.

Therefore, the first thing to consider is Figure 4 c and d.
This is the method shown in That is, in the methods described so far, the own data is transmitted after the data arriving from the adjacent terminal, but in Fig. 4c and d,
On the contrary, if the data from the adjacent terminal device is conventionally transmitted as shown in c, the input data 3 is as shown in d.
0c and 30d are delayed for a certain period of time, and the self data 30b is sent out immediately upon arrival of the input data 30c. Of course, in this case, the input data should be delayed sufficiently,
It is necessary to avoid conflicts with self-data.
To do this, the input data delay interval is set to a value equal to or greater than (self-data length) + (inter-data blank time).

Next, FIGS. 4e and 4f show cases in which another measure has been taken. In this method, as in Figure 4a and b, self-data is added after the data arriving from an adjacent terminal, but the timing of sending input data and self-data is uniform for all data. In other words, as shown in Figure 4e, terminal #2
When b receives the input data 30d and 30c, it sends out these data with a delay of τd as shown in f of the same figure, and also measures the time length of the input data blank period, and the blank period length is determined in advance. If the value τ is greater than ₀ , it is determined that the input data has ended, and the self data is transmitted after a time of τd + τi ₂ −τs from the determined time. here,
τi ₂ is the blank time between data.

In this way, input data and self-data are simply transmitted with a timing delay of τd, and at the same time, the blank period length τs is measured and it is determined whether it is greater than or equal to a predetermined value. Since the data transmission has not been completed in , it is sufficient to transmit the own data after a while, and if the value of τs is set to a value larger than the blank period between data τi ₁ , τi ₂ , ... with sufficient margin. , it is possible to reliably confirm the end of input data. Note that τd+
Since τi ₂ −τs > 0, τd is τs−
Needless to say, it must be set to a value even larger than τi ₂ .

Next, the configurations of the data terminal device and the central device will be explained using FIGS. 5 and 6.

FIG. 5 is a block diagram showing one embodiment of the configuration of the data terminal device of the data collection system of the present invention. In FIG. 5, the signal coming in from the transmission line 40 is generally modulated to make it easier to pass through the transmission line 40, as explained in FIG. In the processing circuit 42, the information from the terminal device is added to the tip or tail, and the signal is modulated again by the modulator 43 and output from the transmission line 44. 4
5 and 46 are input and output terminals of the data processing circuit 42.

As explained using FIGS. 1 and 2, this data terminal usually simply relays input signals,
It simply adds self-information to this and transmits it, but if the input signal is interrupted, it generally becomes the farthest terminal from the central equipment's point of view and transmits self-data to predetermined information. It transmits periodically, and when an input signal starts coming in again at a certain point, it returns to the original transmission mode.

Further, as shown in FIG. 5, this data terminal device receives transmission data from the input terminal 45 and transmits it. In some cases, it is also possible to output the input data from the output terminal 46, so that the terminal device can be checked.

The data processing path 42 can be configured using a microprocessor, but since its function is relatively simple, it can be configured using a dedicated circuit and an IC using a gate array.
It would probably be cheaper to use a modified version.

FIG. 6 is a block diagram showing an embodiment of the central device of the data collection system of the present invention. In FIG. 6, a signal coming in from a transmission line 50 is returned to the original information by a demodulator 51, as in the case of a terminal device, and a data processing circuit 52 determines what kind of data is coming from which terminal device. The content is determined, stored, and displayed on the display device 53. 54 is a man-machine interface.

It is generally convenient to use a microprocessor, minicomputer, etc. as the central device. Additionally, an appropriate man-machine interface 54 (for example, a keyboard and CRT display) is required to receive various commands from the person conducting the monitoring.

[Effects of the Invention] As explained above, according to the present invention, the functions of the terminal device are basically simple such as relay transmission and self-data transmission, and even if processing in the case of line disconnection is included, If it is integrated into an IC using a gate array, it becomes simple hardware. Furthermore, even in the event of a line disconnection, the system is designed to prevent the entire system from being disconnected, making it highly reliable. In addition, all terminal devices may have exactly the same circuit, making it suitable for mass production. The terminal farthest from the central device can automatically recognize this on its own. In addition, when expanding the system, the same operation as when recovering from a failure is performed at the moment of expansion. The newly added terminal automatically becomes the farthest terminal, and the terminal that was previously the farthest becomes a general intermediate terminal. Even if the line is disconnected for maintenance reasons, the central unit will continue to operate normally, simplifying the system configuration, and preventing collisions between the sending data from each terminal, improving reliability. There is an effect.

[Brief explanation of the drawing]

Fig. 1 is a time chart showing one embodiment of signal transmission and reception in each part of the data collection system of the present invention, and Fig. 2 is a time chart showing another embodiment when one of the terminals in the system fails. 3 is a diagram showing an example of a signal waveform in the data acquisition system of the present invention, FIG. 4 is a diagram showing details of the timing of data transmission in the data acquisition system of the present invention, and FIG. 5 is a diagram showing the data transmission timing of the data acquisition system of the present invention. A block diagram showing an example of the configuration of a terminal device of the collection system,
FIG. 6 is a block diagram showing one embodiment of the central device of the data collection system of the present invention, FIG. 7 is a diagram showing three types of data collection system, and FIG. 8 is a general diagram of a data transmission terminal. FIG. 9 is a diagram illustrating an example of the configuration, and is a diagram illustrating the state of signals entering the central data collection device. 1: Data collection device, 2: Data transmission terminal,
3: Transmission line, 21a, 21b: Signal disconnection detection signal, 40, 44, 51: Transmission line, 41, 43,
51: Demodulator, 42, 52: Data processing circuit, 5
3: Display device, 54: Man-machine interface.

Claims (1)

[Claims] 1. One central device, a plurality of data terminals,
The terminals are directly connected to each other, and the central device is installed at the final end of the transmission line, and the central device collects information transmitted from the terminals,
In a data collection system for storing and displaying data, the terminal located farthest from the central device sequentially transmits data in one direction toward the central device at an appropriate period, and each of the other terminals transmits data to an adjacent terminal. If the input signal stops for longer than a predetermined time, it is determined that there is a line abnormality, and the terminal device that recognizes the line abnormality immediately switches to the temporary farthest end. It acts as a terminal device and transmits its own data signal at a fixed period, so that the system does not go down on the central device side from the terminal device, and when the failure recovers, the correct signal is transmitted a predetermined number of times to the provisional farthest terminal. Each terminal device is characterized in that each of the terminal devices has a function of adding self-data after the input signal and transmitting it in time with the input signal at that time, as in normal times, when the terminal device arrives at the input signal. system. 2. Each of the above-mentioned terminal devices has a function in which the terminal device that recognizes a line abnormality immediately sends a signal loss detection signal, and the terminal device newly becomes the temporary farthest terminal device and transmits signals at a fixed period. A data collection system according to claim 1, comprising: 3. One central device, multiple data terminal devices,
A data collection system consisting of a transmission path that connects the terminals in a straight line and has the central device installed at the final end, and the central device collects, stores, and displays information transmitted from each of the terminals. The terminal device located farthest from the central device sequentially transmits data in one direction toward the central device at an appropriate period, and each of the other terminal devices transmits data from an adjacent terminal device. The data is delayed for a predetermined period of time, self-data is added in front of the data, and transmitted. If the input signal stops longer than the predetermined period of time, it is determined that there is a line abnormality, and the terminal device that recognizes the line abnormality immediately sends a temporary It acts as the farthest terminal and transmits a signal at a certain period to prevent the system from going down on the central equipment side from the terminal, and when the failure recovers, the correct signal is sent a predetermined number of times to the temporary farthest end. Data characterized in that each of the terminal devices has a function of adding self-data to the front of the input signal and transmitting it in synchronization with the input signal when the terminal device reaches the terminal device at the end, as in normal times. Collection system.