JPS62245838A - Data communication system - Google Patents

Abstract

PURPOSE:To send a signal such as fault information from a slave terminal equipment by providing a supervisory and control section for the state of a line and its own station data. CONSTITUTION:When a data is desired to be sent from a slave terminal equipment without awaiting a polling command from a master terminal equipment and a data from a reply side line 51 is not sent, the 3rd selector switch SW 3 is controlled by the control of the supervisory and control section 24 for the state of line and own station data to send the data as it is and when a data is sent, the 1st selector switch SW 1 is controlled, the data is stored once in the 1st memroy 22, and after the data transmission from the reply side line 51 is finished, the data is sent. When a data is inputted from the line 51 during the transmission from its own station, the 2nd selector switch SW 2 is controlled to store the data once in the 2nd memory 23, and the data is sent after the end of transmission. Thus, no data collision takes place even when the data is sent earlier without awaiting the polling command, then the data is sent quickly to the master terminal equipment.

Description

[Detailed Description of the Invention] [Summary] In a data communication system in which multiple slave terminals are connected to a line from a main terminal using a multi-drop method and communicate using a polling method, transmission signals other than polling responses from the slave terminals collide. This is something that can be transmitted quickly.

[Industrial application field]

The present invention enables a data communication system in which a plurality of slave terminals are connected to a line from a main terminal in a multi-drop method and communicates in a polling method to be used as a control system for controlling switching of active and backup lines of the communication system. This relates to a data communication system.

A communication system that performs the switching between the working line and the protection line will be explained with reference to the drawings.

FIG. 5 is a block diagram showing the configuration of an example of a communication system, in which (A) to (C) show the configuration of the working line, (D) shows the configuration of the protection line, and a - d indicate each station. There is.

In the figure, 1 to 16 indicate terminal stations, and 17 to 20 indicate relay devices.

In the working line (A), the channel is temporarily dropped at terminal stations 2 and 3 at station b, and then connected again when the line is extended. In the working line (C), the channel is temporarily dropped at the terminal station 8.9 at station 0, and then connected again when the line is extended. The working line (B) connects stations a and d without dropping the channel. The protection line (D) is configured to be dropped to the channel at terminal stations 12 and 13, 14 and 15 at station c, and for example, if the working line (B) is in trouble, the protection line (D) is dropped. Connect terminal stations 12 and 13, 14 and 15,
Switch to the protection line (D), and if there is a failure between terminal stations 1 and 2 of the working line (A), switch to the protection line (D) terminal stations 11 and 12.
The line between terminal stations 13 and 16 is switched to this, and if terminal stations 3 and 4 have a failure, the line is secured by switching the line between terminal stations 13 and 16 on the protection line (D) to this.

In order to control the switching of each line, a.

Line failure information from the terminal stations of stations b, c, and d is sent to the slave terminals installed at each station, and these terminals send it to the main terminals of the three safeter stations, and the main terminal issues the necessary switching commands. The signal is sent to the slave terminal and the faulty line is switched to the backup line.

It is desirable for the data communication system used for this switching control to have a small number of lines and to be able to send failure information to the main terminal more quickly than to the slave terminal.

[Problems to be solved by the prior art and the invention] The line failure information from the terminal stations of stations A, C, and D shown in Fig. 5 is immediately reported to the main terminals of the three SAFTER stations from the slave terminals installed at each station. A data communication system that can be used is a star type in which transmission lines are provided between the slave terminals of stations b, c, and d and the main terminals of the three safety stations, but this has the problem of increasing the number of transmission lines and making it expensive. There is a point.

Therefore, a data communication system having a multi-drop configuration, in which the number of transmission paths is one tree, as shown in FIG. 6, in which communication is performed using a polling method, is considered.

In this case, the command side line 50. Connected through the response line 51, and from the main terminal 30,
To prevent responses from the slave terminals 31 to 33 from colliding on the responding line 51, the slave terminals 31 to 33 are sent via the command line 50.
33, and sends polling commands to the slave terminals 31~
If the communication processing units 41 to 43 of 33 receive the data sequentially, the switch SWI1, which is normally on the solid line side, SWI 2,
5W13 are sequentially set to the dotted line side, and the response signal of the response side line is sent to the main terminal 30.

However, in this case, when a failure is detected at stations b and d, it is necessary to notify the main terminal 30 earlier than the slave terminals of each station, but this notification is not sent until a polling command is received from the main terminal 30. There is a problem that it is not possible to do this and it becomes slow.

[Means for solving the problem] The above problem occurs in a data communication system in which a plurality of slave terminals are connected to a line from a main terminal using a multi-drop method and communicate using a polling method, as shown in Fig. 1. The slave terminal has a first memory 22 that stores data sent from the own station, a second memory 23 that stores data from the line 51 on the response side, and a memory 22 that stores the data sent from the response side line 51. First selection switch S for selecting whether to memorize or not
WI, a second selection switch SW2 that selects whether to transmit data from the responding line 51 or to store it in the second memory 23; a third selection switch SW3 for selecting data from the memory 23 of the second station or data from the four line 51 on the responding side; and data from the communication processing unit 21 of the own station and data from the line 51 on the responding side monitors the status of the response side, and when transmitting data, if there is no data from the responding line 51,
The third selection switch SW3 selects and transmits the data to be transmitted, and if there is data from the responding line 51, the first selection switch SWL stores it in the first memory 22. Select and memorize the answering line 5.
After the data transmission from 1 is completed, the third selection switch SW3
to select and transmit the data from the first memory 22, and when data is input from the responding line 51 while transmitting data from the local station, the second selection switch SW2 The data to be stored in the second memory 23 is selected and written t0, and after the transmission is completed, the third selection switch SW3 is used to select the data to be stored in the second memory 23 and transmitted. This problem is solved by the data communication system of the present invention, which includes a station data status monitoring and control section 24.

[Effect]

According to the present invention, since it is a multi-drop configuration, only one transmission path is required, and if the slave terminal wants to transmit without waiting for a polling command from the master terminal 30, the state of the data of the line and own station can be monitored. Under the control of the control unit 24, if the data from the response side line 51 is not sent, the third selection switch SW3 is controlled to transmit the data while the data is being sent, and if the data is sent, the first selection switch The SWI is controlled and stored once in the first memory 22, and after the data transmission from the responding line 51 is completed, it is transmitted, and when data is input from the responding line 51 while the own station is transmitting, it is stored in the second memory 22. selection switch S
W2 is controlled to temporarily store this in the second memory 23, and after the transmission is completed, it is transmitted. Therefore, even if data is sent quickly without waiting for a polling command, data collision will not occur, so data can be sent to the main terminal 30 quickly.

〔Example〕

FIG. 2 is a block diagram showing the configuration of a slave terminal according to an embodiment of the present invention, FIG. 3 is a signal frame format, and FIG.
3 is a time chart showing the timing of the input signal from the response side line and the own station transmission signal in the case shown in the figure.

In FIG. 2, 25 is a transmission data status monitoring unit, 26 is a line data status monitoring unit, 27 is a conflict determination and control unit, and 28 to 31
is an 8-bit shift register, 32 to 35 are NAND circuits, 36 and 37 are decoders, and 38 to 45 are NOT circuits, and the same reference numerals indicate the same functions throughout the drawings.

In the case of a polling-based multi-drop configuration, if the slave terminal sends a transmission signal such as failure information that must be sent quickly in addition to a response signal to the polling command, a problem arises when this transmission signal and This is a collision with the data sent through the response line 51, and measures to prevent this must be considered.

This point will be mainly explained below.

In Fig. 2, selection switches SWI, SW2゜SW3
is normally connected to ■, and the frame format of the signal in the polling method is as shown in Figure 3 (in order to clearly indicate the beginning and end of the data, the start signal and end signal are connected after 11;I). have.

The start signal, end signal and data have an 8-bit configuration, and the start signal and end signal are 0°1.1.1.
1. L 1. In the following explanation, it is assumed that the signal is 0, and that a signal having the same configuration as the start signal is repeatedly transmitted in an idle state in which no data is transmitted.

Transmission data status monitoring unit 25 and line data status monitoring unit 26
Since they have the same configuration, the line data status monitoring unit 26 will be explained as an example.

The shift registers 31 and 30 are 8-bit ones, and from the positions at both ends, the signals are input via knot circuits 42 to 45.
From the middle, it is input to NAND circuits 34 and 35. Further, the outputs of the NAND circuits 34 and 35 are input to the decoder 37.

Therefore, when a signal is input from the response side line 51 and a start signal comes to the shift register 30, the output of the NAND circuit 34 becomes 0 and the output of the NAND circuit 35 becomes 1. Next, when the data is in the middle, the output of the NAND circuit 34.35 becomes 1, and when the end signal comes to the shift register 31, the output of the NAND circuit 34.35 becomes 1.0, and no data is transmitted again. In the idle state, the output of the NAND circuits 34 and 35 becomes 0.0. Note that there is no idle state on the transmitting side from the own station.

Therefore, in the decoder 37, the output Yo is set to 1 when the start signal is detected, the output Y1 is set to 1 during the data, and the output Y2 is set to 1 when the end signal is detected, using the outputs of the NAND circuits 34 and 35. Y in idle state
By setting 3 to 1, the state of the line data is input to the conflict determination and control unit 27.

The conflict determination and control unit 27 inputs the information from the outputs Y0 to Y of the decoders 36 and 37 into a ROM, for example, so as to prevent the data from the own station from colliding with the data from the responding line 51 in advance. Each selection switch S written
WI, SW2. It is designed to output a control signal for SW3.

That is, when data is being sent from the responding line 51 as shown in FIG. 4(A) and the output Y1 of the decoder 37 is 1, when the own station's transmission signal is output as shown in FIG. 4(B). ,
Since the output Y0 of the start signal detection of the decoder 36 of the transmission data state monitoring section 25 becomes 1, the selection switch SWI is turned to the ■ side as shown in (D) until the output Yt of the end signal detection from the decoder 36 becomes 1. The transmission data is stored in the memory 22, and when the end signal detection output v2 from the decoder 37 becomes 1, the selection switch S
The W3 is set to the ■ side, and the transmission signal is sent out after the signal on the line side as shown in (C).

Further, as shown in FIG. 4(E), when the own station is transmitting a signal and the output Y1 of the decoder 36 is 1, (
When data is input as shown in F) and a signal with the start signal detection output Y0 of 1 is input from the decoder 37, the selection switch SW2 is pressed until the end signal detection output Y2 becomes 1 as shown in (H). When the end signal detection output Y2 becomes 1 from the input 36, the selection switch SW3 is set to the ■ side as shown in (H), and the transmission signal is stored in the memory 23 as shown in (G). Next, the signal from the line is sent out.

Of course, when transmitting a signal from the own station, if the data from the responding line 51 is idle and the output Y of the decoder 37 is 1, the selection switch SW3 is set to the ■ side and the signal is transmitted in the meantime.

By doing so, the transmission signal from the local station can be transmitted quickly without collision without waiting for a polling command.

Therefore, signals such as failure information can be quickly transmitted from slave terminals of a plurality of stations through one transmission path.

〔Effect of the invention〕

As explained in detail above, according to the present invention, a data communication system is used in which a plurality of slave terminals are connected to a line from a main terminal in a multi-drop manner and communicate in a polling manner,
This has the effect of making it possible to transmit signals such as failure information faster than the slave terminal.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram showing the configuration of a slave terminal according to an embodiment of the present invention, Fig. 3 is a signal frame format, and Fig. 4 is the case of Fig. 2. Figure 5 is a block diagram showing the configuration of an example of a communication system. Figure 6 shows communication using the conventional polling method. FIG. 1 is a block diagram of a data communication system with a multi-drop configuration. In the figure, 21 is a communication processing unit, 22, 23 is a memory, 24 is a line and own station data status monitoring and control unit, 25 is a transmission data status monitoring unit, 26 is a line data status monitoring unit, and 27 is a contention unit. Judgment and control section, 28 to 31 are shift registers, 32 to 35 are NAND circuits, 36 and 37 are decoders, 38 to 45 are NOT circuits, and SWI to SW3 are selection switches. 4-The principle of the bald head 2 (a) Broom 1 Spear 3 ni) Mekomaji 4 $ 3 Giant 2222 = Yo 1000 4 ni

Claims (1)

[Scope of Claims] In a data communication system in which a plurality of slave terminals are connected to a line from a main terminal in a multi-drop manner and communicate in a polling manner, a first slave terminal that stores transmission data from its own station is provided. a second memory (23) for storing data from the responding line (51), and a second memory (23) for selecting whether to transmit the transmitted data or to store it in the first memory (22). 1
a second selection switch (SW2) that selects whether to transmit data from the responding line (51) or store it in the second memory (23); Data from the first memory (22) or data from the second memory (23) or the responding line (
51), a third selection switch (S
W3) and the state of the data from the communication processing unit (21) of its own station and the data from the responding line (51), and when transmitting data from its own station, the status of the data from the responding line (51) is monitored. If there is no data from (51), the third selection switch (SW3)
to select and transmit data to be transmitted, and if there is data from the responding line (51), use the first selection switch (SW1) to store it in the first memory (22). is selected and memorized, and after data transmission from the responding line (51) is completed, data from the first memory (22) is selected and transmitted using the third selection switch (SW3). , When data is input from the responding line (51) while data is being transmitted from the own station, the second selection switch (SW2)
to select and store the data to be stored in the second memory (23), and after the transmission is completed, select the data from the second memory (23) with the third selection switch (SW3). 1. A data communication system comprising a monitoring and controlling section (24) for monitoring and controlling the state of data of a line and its own station.