JPH0560704B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a data transmission method in a loop-type data transmission system, and particularly to a data transmission method in a loop-type data transmission system consisting of one central control unit and a plurality of remote terminal devices. The present invention relates to a data transmission method suitable for increasing data transmission efficiency.

[Background of the invention]

Conventional forms of local networks for mutual communication between data terminal devices include bus type and loop type, and access methods include time division multiplexing and token passing. A well-known example of the loop-type data transmission system is Hitachi Review Vol. 65, No. 11 (1983-11), "Integrated optical loop transmission system 'H-8644 loop network.'" In this system, data Communication between terminal devices is realized using a token passing method.
Furthermore, although there are many variations of the token passing method, this transmission system uses the following method. i.e. manage the entire system
LSN (Loop Service Node) sends out special frames and tokens. The token is constantly in a loop, and the FSN where the transmitted data occurred
(Field Service Node) sends a frame when it receives a token, and immediately after that sends a token. In addition to data, the frame includes information such as the sending address and receiving address, and each
The FSN identifies these address information and receives the frame if it is addressed to itself. In other words, each FSN allows you to arbitrarily set the address of the party you want to communicate with, so this system has the advantage of being able to communicate with any party.
Therefore, such a transmission system produces the greatest effect when applied to a system that connects computing engines.

However, in a transmission system in which remote terminal devices that collect process data, etc. within a plant are connected in a loop to a central control device, there is no data communication between the remote terminal devices, and all data is transmitted to the central control device. . The central controller then receives the transmitted data, analyzes it, and transmits control information to the remote terminal device. When the above-mentioned token passing method is adopted for data transmission within such a plant, control information transmitted by the central control unit is transmitted immediately after receiving a token.
Therefore, at the time when the central controller receives the token, no data exists on the loop. However, in plants, process data is transmitted at high speed for control and monitoring, so when there is a time when no data exists, there is a problem that the transmission cycle of control information transmitted from the central control device becomes longer.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a data transmission method that increases data transmission efficiency in a loop data transmission system consisting of a central control unit and a plurality of remote terminals.

[Summary of the invention]

The present invention provides a data transmission system in which one central control device and a plurality of remote terminal devices are connected in a loop through a transmission path, and the present invention provides a data transmission system in which one central control device and a plurality of remote terminal devices are connected in a loop through a transmission path. , by controlling the transmission timing of the data group to be transmitted from the central control device to the remote terminal device in the transmission section of the central control device so that the data group can be received by the reception section of the central control device without any idle time.
This is a data transmission method that shortens the data transmission cycle from the central control unit to the remote terminals and improves data transmission efficiency.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system configuration block diagram showing an embodiment of a data transmission method in a loop type data transmission system according to the present invention. In Figure 1,
1 is one central control unit (hereinafter abbreviated as CCU), 2 is a plurality of remote terminal devices (hereinafter referred to as CCU) that are scattered throughout the plant and collect process data, etc.
(abbreviated as RTU). 3 is a transmission line that connects the CCU and multiple RTUs in a loop. 4 is a CCU transmitting circuit, and 5 is an RTU receiving circuit. 6 is an oscillator of the CCU, 7 is a frequency dividing circuit, and 8 is a counter. 9
10 is a data storage area of the RTU, 10 is a data number table, 11 is a buffer register, 12 is an instruction decoding circuit, 13 is an adder, 14 is a data end signal detection circuit, and 15 is an RTU transmission control circuit. 16
1 is an RTU transmitting circuit, and 17 is a CCU receiving circuit.
18 is the CCU detection circuit, 19 is the latch circuit, 2
0 is a comparator, and 21 is a CCU transmission control circuit. 22 is the CCU data processing device, 23 is the CCU
It is a data creation device.

FIG. 2 is a configuration diagram of transmission data transmitted by the CCU transmitting circuit 4 of FIG. 1. In Figure 2, S is a signal indicating the beginning of a data group, next is the data sending address (in this case, a unique address assigned to the CCU) (area), next is the data receiving address (area), and M is the signal that indicates the beginning of the data group. This is information (area) that specifies the type of data that the CCU transmits to the RTU.
Next, when the RTU specified by the receiving address identifies the type of data specified by the information (area) M and transmits data according to the contents of the information (area) M, the number of data to be sent is stored. This is a data number storage area that can be modified on the RTU side. After the CCU sets the data number storage area to "0" and transmits, if the receiving address is set to multiple devices, each
The RTU sequentially adds the number of data to be transmitted to the data number storage area and transmits the data. e is a signal indicating the end of a series of data transmitted from the CCU, and the signal e
indicates the end of a series of data transmitted not only from the CCU but also from each RTU. E is the signal S sent from the CCU
A signal indicating the end of the data group starting with
When transmitting data, the transmission starts from the time when the signal E is detected, and then a new signal E is transmitted when the data transmission is completed. FIG. 3 is a diagram showing the structure of transmission data transmitted from the RTU signal circuit 16 after the data group of FIG. 2 is received by the RTU receiving circuit 5 of FIG. In FIG. 3, in FIG. 2, a data group starting with signal S is received by the RTU receiving circuit 5, and if the receiving address is addressed to the own station, signal E is erased at the time of detection of signal E, and then After transmitting the transmission address, reception address, data type information M, data, and signal e of the own station's transmission data, a new signal E is transmitted. Also, Figure 4 shows the first
FIG. 4 is a waveform diagram of a clock signal and a bit configuration of transmission data transmitted from the CCU transmitting circuit 4 shown in the figure.
In FIG. 4, data transmitted from the CCU transmitter circuit 4 in FIG. 1 is transmitted as serial data as signal a in FIG. The clock signal b is used. Furthermore, signal a in FIG. 4 is a case in which one data is composed of 8 bits, and the clock signal b of the oscillator 6 is divided by the frequency dividing circuit 7 in FIG. 1 according to the number of bits constituting one data. The signal c shown in FIG. 4 is created, and this signal c is input to the counter 8 to count the number of clocks.

Figure 5 a and b are the CCU and RTU of Figure 1, respectively.
FIG. 3 is a diagram showing a specific example of the transmission data structure of FIGS. 2 and 3 transmitted from the computer; FIG. In Figure 5a, this example is
This is a specific transmission data configuration when issuing a command to "send process data" from the CCU to the RTU 1, and the data number storage area is transmitted as "0". In addition, in FIG. 5b, if the RTU 1 that has received the transmission data in FIG. 5a needs 100 bytes to transmit process data, it changes the data number storage area from "0" to "100" and then
Send 100 bytes of data from signal E,
After that, a new signal E is transmitted. In addition, Figure 6 a, b, and c are each the CCU of Figure 1, and multiple units.
FIG. 4 is another specific example diagram of the transmission data structure of FIGS. 2 and 3 transmitted from the RTU; FIG. In Figure 6a,
This example shows a specific transmission data structure when the CCU issues a command to all RTUs to "send process data." In this case, in Fig. 5b, the transmission data of Fig. 5a is received.
If the RTU1 is to transmit a byte of process data, the data number storage area is changed to "a" and the data is transmitted. Then, for RTU2 or less, each
Sequentially add the number of RTU transmission data and transmit the data. In Fig. 5c, when transmitting data from RTUn, the value of the data number storage area is set as "a+b+...+n", and thus the data transmitted from each RTU is separated by the signal e in order from RTU1. transmitted.

Such operations are performed in the RTU shown in FIG. 1 as follows. First, the process data etc. collected by the RTU are stored in the data storage area 9. And the number of data for each data is data number table 10
Store in. Fig. 2 received by the RTU receiving circuit 5,
The transmission data group shown in FIG. 3 (FIGS. 5 and 6) is put into the buffer register 11, and data groups other than those addressed to the own station are transmitted as they are from the RTU transmission circuit 16 to the transmission line 3. And Figure 2 transmitted from CCU,
When the command decoding circuit 12 identifies the data group addressed to the own station in FIG. The unit 13 adds the data and rewrites the data number storage area. Further, when the signal E is detected by the data end signal detection circuit 14, at that point, the specified process data in the data storage area 9 is transmitted to the RTU transmission circuit 1 by the transmission control circuit 15.
6 to the transmission line 3. Note that the transmission/reception control circuit 24 of the RTU determines the signal (area) M indicating the reception address and data type of the transmission data group transmitted from the CCU, and stores it in the data storage area 9.
It also controls the transmission and reception of the data number table 10 and the like.

Next, FIG. 7 is a block diagram showing a configuration of the loop type transmission system of one CCU and three RTUs shown in FIG. In Figure 7, the number of RTUs is 3.
As a stand, RTU1, RTU2, RTU3 respectively.
It is called. Figure 8 shows the system in Figure 7.
This is a time chart of CCU transmission/reception and each RTU's transmission timing. In FIG. 8, this example shows the data structure and transmission/reception timing when each RTU transmits only process data specified by the CCU. First, a data group A1 corresponding to FIG. 2 (FIG. 6a) is transmitted from the CCU. Note that the numbers or signals shown in parentheses under data group A1 etc. in FIG. 8 indicate the contents of the data number storage area. In other words, the CCU transmits the data number storage area such as data group A1 as "0".
The RTU1 sets the data number storage area of the received data group A1 to "b1", erases the signal E, transmits the data group B1 with the data number "b1" bytes, and then transmits a new signal E. Similarly, RTU
2 sets the data number storage area of the received data group A1 to "b1 + c1", erases the signal E after the data group B1, transmits the data group C1 with the data number "c1" bytes, and then sends a new signal E. Send.
RTU3 sets the data number storage area of received data group A1 to “b1+c1+d1” and then data group B
After erasing the signal E after the data group C1 following 1 and transmitting the data group D1 of data number "d1" bytes, a new signal E is transmitted. Thus RTU3
The data groups transmitted from the RTU transmitting circuit 16 are transmitted to the CCU via the transmission line 3 in the order of data group A1 whose data number storage area contents are "b1 + c1 + d1", data groups B1, C1, D1, and signal E. Ru.
Therefore, the CCU receives the data group sent from RTU3.
When received by the CCU receiving circuit 17, the CCU transmitting circuit 4 detects the content "b1+c1+d1" of the data number storage area in the data group A1 sent and returned,
The timing for transmitting the next data group A2 from the CCU transmitting circuit 4 according to the number of data (number of bytes) "b1 + c1 + d1", that is, the timing from transmitting the signal E after the data group A1 until transmitting the next data group A2 Time t1 is the total number of data “b1” from each RTU
+c1+d1” byte so that it is the same as the time required to transmit it.Next, do the same thing.
Send data group A2 from CCU, RTU1,
RTU2 and RTU3 each have data number “b2”,
“c2”, “d2” byte data group B2, C2, D2
are sequentially transmitted, the CCU receives these data groups, and transmits the next data group A3. In other words, the time from when the CCU transmits the signal E after data group A2 to when it transmits the next data group A3. t2 is the total number of data from each RTU “b2 + c2 +
The control is performed so that the time required to transmit d2" bytes is the same as the time required to transmit d2" bytes. With such transmission timing, data group A is transmitted after data group A1 is transmitted from CCU.
2, A3, etc., the CCU receiving circuit 17 receives the data group using 100% of the transmission capacity as shown in FIG.

This operation is performed in the CCU shown in FIG. 1 as follows. First, from the data group shown in FIG. 8 received by the CCU receiving circuit 17, the second
The latch circuit 19 detects the data group A1 etc. including the data number storage area corresponding to the figure (FIG. 6a) and stores only the rewritten contents of the data number storage area.
Store in. On the other hand, the output signal c (Fig. 4) corresponding to 1 data (1 byte) of the frequency dividing circuit 7 is counted by the counter 8, but the counter 8 is not controlled by the CCU transmitting circuit 4 when the transmitting operation is performed. In other words, the clock starts counting immediately after the CCU transmitting circuit 4 finishes transmitting the data group A1 etc. and the signal E corresponding to FIG. 2 (FIG. 6a). Then, the data group A1 of the latch circuit 19 is set by the comparator 20.
The value of the data number storage area X (“b1+c1+d1”
etc.) and the count value N of counter 8, N≧X
At the point in time (at the elapsed point of time t1, etc.), a transmission start command signal is output to the transmission control circuit 21, and the CCU
The next data group A2 etc. and signal E from the transmitting circuit 4
Send. However, the comparator 20 starts latching the data number M in the latch circuit 19.
It operates during the period until the next data group A2 etc. are transmitted from the CCU transmitting circuit 4. If N>X at the time when the number M of data is stored in the latch circuit 19, a transmission start command signal is immediately output. Note that the process data such as data groups B1, C1, D1, etc. received by the CCU receiving circuit 17 are transmitted to the data processing device 22 and processed. Then, the next data group A2, etc. corresponding to FIG. 2 (FIG. 6a) is constructed by the CCU data creation device 23 according to the processing result or operator's operation, and is transmitted from the above-mentioned CCU transmission circuit 4.

Figure 9 shows the CCU in the system shown in Figure 7.
This is another time chart of the transmission and reception of , and the transmission timing of each RTU. In FIG. 9, this example shows the data structure and transmission/reception timing when each RTU also transmits data other than the process data designated by the CCU. First, CCU
The data group A1 corresponding to Figure 2 (Figure 6a) was sent from the beginning, and a command to "send process data" was issued to all RTUs, but RTU1 and
If there is a request to transmit other information to the CCT in RTU3, RTU1 receives the information M in data group A1 at the time it receives data group A1.
Following the transmission of the data group B1 (number of data "b1" bytes) specified in , the data group B1' (number of data "b2") to be transmitted to the CCT is transmitted. However, the content (value) of the data number storage area in data group A1 is transmitted as "b1+b2". RTU2 transmits only the data group C1 (number of data "c1") specified in data group A1 after changing the contents of the data number storage area of data group A1 to "b1+b2+c1" and subsequently transmitting it to data group B1', but RTU3 is RTU1
Similarly, data group D1 specified by data group A1
(number of data "d1") is subsequently transmitted to the CCU, a group of data D1' (number of data "d2") is sent to the CCU. However, the contents of the data number storage area of data group A1 are set to "b1+b2+c1+d1+d2" and transmitted.
Thus, when the CCU receiving circuit 17 receives the data group A1, the data storage area value (number of data) X detected is "b1+b2+c1+d1+d2", so the CCU transmits the next data group A2 based on this value. timing, that is, data group A
The time t1 from transmitting the signal E of 1 to transmitting the data group A2 is controlled.

Note that FIG. 10 is a data configuration diagram of data groups B1 and B1' transmitted by RTU1 in FIG. 9. 1st
In FIG. 0, the sending addresses and receiving addresses of the data groups B1 and B1' are both RTU1 and CCU, but the information (area) M indicating the type of the next data is different. That is, the information (area) M of the data group B1 specified by the CCU has the same content as the information M of the data group A1 sent from the CCU, but the information (area) M' of the data group B1' is different from the data group A1. The content is different from the information M in the data group B1', and represents the type of data in the data group B1'. Further, the separation between the data groups B1 and B1' can be identified by a signal e indicating the end of the data group B1. FIG. 11 is another data configuration diagram of the data groups A1 and A1' transmitted from the CCU of FIG. In FIG. 11, this example shows a data structure when control information is transmitted to the RTU in addition to transmitting a data transmission command from the CCU to the RTU. In other words, in data group A1
The CCU sends a command to all RTUs to "send process data" of information M, and
In data group A1', control data of information M' is transmitted from the CCU only to a specific RTU3. In this case, the data group A1 is shown in FIGS. 8 and 9 above.
Similar to the case shown in the figure, it corresponds to FIG. 2 (FIG. 6a), but the data group A1' has the reception address RTU3 and is transmitted as information M' indicating the type of data. In each RTU, the information (area) M indicating the reception address and type of data of the data group transmitted from the CCU is mainly stored in the transmission/reception control circuit 24.
The transmission/reception control is performed based on the judgment.

In the transmission system shown in Fig. 1 (Fig. 7), each RTU specifically responds only to the data transmission command from the CCU and sends only data such as data groups B1, C1, D1, etc. designated by the CCU as shown in Fig. 8. and send
Data group B1' other than CCU specification as shown in Fig. 9,
In the case of a special system that does not transmit data such as D1', it is also possible to control the transmission as follows. FIG. 12 is a correspondence table of the RTU in the CCU and the number of data showing another embodiment of the data transmission method in the special transmission system of FIG. 1 in this case. In Figure 12, CCU is connected to each RTU1~
Information M1, M indicating the number of data (number of bytes) of the data group to be sent from RTUn and the type of data
2. Number of data x1, y1, z1~xn, yn, for each M3 etc.
Create it as a table like zn. FIG. 13 is also a data transmission timing chart of the CCU. In FIG. 13, data groups A1, A2,
A3 is a data group transmitted from the CCU. These data groups do not require the above data number storage area, and the data structure in this case is shown in Figure 2 (Figure 6).
This is a configuration in which the data number storage area is removed from Figure a). Here, it is assumed that information (areas) M1 and M2 indicate the types of data specified by data groups A1 and A2. First, the CCU transmits a data group A1 of information M1 indicating the type of data and a signal E. and,
CCU receives the reception address specified in data group A1.
Calculate the total number of data (number of bytes) of the data group corresponding to information M1 in RTU from the correspondence table in Figure 12, and after transmitting the above signal E, transmit the number of bytes of the sum of the data After the required time t1 has elapsed, data group A2 of information M2 indicating the type of next data and signal E are transmitted.
If the transmission timing of the CCU transmission circuit 4 is similarly controlled to transmit the next data group A3 after time t2, it is clear that the reception of the CCU will be similar to that shown in FIG. 8. Furthermore, in this embodiment, since a data number storage area is not required, transmission and reception control is also simplified.

〔Effect of the invention〕

As described above, according to the present invention, data transmission efficiency can be improved because there is no idle time in the receiving operation on the CCU side in a loop data transmission system, and the cycle of transmitting information from the CCU to the RTU can be shortened. In addition to improving the controllability of the RTU, the data transmission cycle from each RTU is also shortened, which improves the CCU's ability to monitor plants, etc., so it is particularly effective when used as a data transmission method within a plant. .

[Brief explanation of the drawing]

Figure 1 is a system configuration block diagram showing an embodiment of a data transmission method in a loop data transmission system according to the present invention, and Figure 2 is a CCU of Figure 1.
Figure 3 is a transmission data configuration diagram of the RTU in Figure 1, Figure 4 is a bit configuration and clock signal waveform diagram of the CCU transmission data in Figure 1, and Figures 5a and b are diagrams of the clock signal waveform. Figures 2 and 3 are diagrams showing one specific example of the transmission data structure, Figures 6a, b, and c are diagrams of other concrete examples of the transmission data configuration in Figures 2 and 3, respectively. Figure 1 shows a block diagram of the transmission system, and Figure 8 shows the CCU and
Figure 9 is a transmission/reception timing chart of one RTU, Figure 9 is a transmission/reception timing chart of another, Figure 10 is a transmission data configuration diagram of RTU1 in Figure 9, Figure 11 is
This figure is another transmission data configuration diagram of the CCU of FIG. 7, and FIG. 12 is a CCU showing another embodiment of the data transmission method in the transmission system of FIG. 1 according to the present invention.
FIG. 13, which is a diagram showing a correspondence table between RTU and the number of data, is also a transmission timing chart of the CCU. 1...Central control unit (CCU), 2...Remote terminal unit (RTU), 3...Transmission line, 4...CCU transmitting circuit, 5...RTU receiving circuit, 16...RTU transmitting circuit, 17... CCU receiver circuit.

Claims (1)

[Scope of Claims] 1. In a data transmission system in which a central control device and a plurality of remote terminal devices are connected in a loop through a transmission path, the central control device transmits commands to each remote terminal device as circular data to the transmission path. An area is provided in which the number of data is written in the circulating data when the data is transmitted to the central controller for one round, and each remote terminal device, when receiving the command for the circulating data, writes the terminal side data to be sent to the central control unit consecutively to the said circulating data. At the same time, a value obtained by adding the number of added data to the number of cyclic data written in the area is written, and the central control unit determines the number of cyclic data written in the area when receiving the cyclic data that has made one round. A data transmission method characterized in that the next command is sent to the transmission path after the reception time of the cyclic data determined based on the value of the number of data. 2. In a data transmission system in which a central controller and multiple remote terminal devices are connected in a loop through a transmission line, the first data group to be transmitted from the central controller to the remote terminal devices is designated as a signal area indicating the beginning of the data group. The first data group is divided by a signal area indicating the end of the data group, and a data number storage area that can be modified on the remote terminal side is provided in the first data group and transmitted from the central controller. When the first data group transmitted by the central control device is received, the number of data of the second data group to be transmitted from the remote terminal device is stored in the data number storage area, and the signal area indicating the end of the first data group is deleted. After transmitting the second data group consecutively to the first data group, a new signal area indicating the end of the data group is added to the end and transmitted, and the next remote terminal device transmits the received data group in the same way. The number of data of the third data group to be transmitted from the remote terminal device is added to the value of the data number storage area inside, and the signal area indicating the end of the data group is erased, and the third data group is transferred to the second data group. After continuously transmitting data, a new signal area indicating the end of the data is added to the end of the data, and the central controller transmits the data group including the data number storage area that was previously transmitted from the central controller. is received after one round of the loop-shaped transmission path, the time required to receive the received data is calculated from the value of the data number storage area, and the transmission timing of the next data group to be sent to the remote terminal device is set after the above-mentioned time has elapsed. Characteristic data transmission method. 3 In a data transmission system in which a central control unit and multiple remote terminal devices are connected in a loop through a transmission path, the central control unit stores in advance the number of data for each type of data group transmitted from each remote terminal device. The command from the central control device to the remote terminal device is passed around the transmission path as circular data,
When the remote terminal device successively adds and transmits the data group to be transmitted in response to the command, it also adds type information indicating the type of the data group and transmits it, and the central control device completes the cycle. When cyclic data is received, the total number of received data is determined from the type information in the cyclic data, and the time required to receive the received data is determined from the number of data, and after the time elapses, the next command is sent to the transmission path. A data transmission method characterized by transmitting data to.