JPS63290039A - Data transmission system - Google Patents

Abstract

PURPOSE:To ensure a loop system to transmit data even if a line state is a deteriorated state or a line disconnection state by adding the identification flag of a line disconnection to a transmission data frame, and transmitting it, and switching a primary station mode and a secondary station mode according to this transmitted identification flag. CONSTITUTION:The primary station 1 and the secondary stations 2-4 are loop-connected by two data lines of an outer data line 5 and an inner data line 6. Besides, the respective data transmitting devices of the primary station 1 and the secondary stations 2-4 are provided with a means to monitor the line state, the means to transmit a go-ahead flag for starting a transmission at a loop mode, the means to switch the primary station mode to transmit the go-ahead flag and the secondary station mode to execute a loop transmission, and a flag adding means to add the identification flag of the line disconnection, in the transmission data frame. By switching the primary station mode and the secondary station mode according to the transmission identification flag, obtained by this adding means, the loop system to transmit the data can be ensured even if the line state is the deteriorated state of the line disconnection state.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to HDLC (High tev6A Data
This relates to a data transmission method when transferring data using loop mode (LinkControl).

[Conventional technology]

An example of a data transmission system in a conventional data transmission system using the HDLC loop system is shown in FIG. 6 and will be described.

In the figure, 31 is the primary station, 32.33 is the secondary station, and 34
is a data line, and the direction of data transmission is indicated by an arrow.

In this way, each of the primary station 31 and the secondary stations 32, 33 is connected to the transmitting terminal and receiving terminal of another station, forming a so-called tandem connection. The data transmitted through this data line 34 follows the HDLC protocol.

FIG. 7 shows the structure of a data frame transmitted by the primary station 31.

In the figure, 41 is a start φ flag (start flag), which is 8-bit reference data of 01111110.

42 is a transmission data field, which is usually divided into a receive address indicating the number of the receiving station, a control field for controlling the data transfer rate, and an I field that is other actual transmission data. . 43 is a CRC (C
yclic Redundancy Check) code part. At the time of transmission, this transmission data section 42 and C
If there are 5 consecutive "1"s in the data part of the RC code section 43, "0" is inserted, and conversely, when receiving, "1" is inserted into 5 pits.
When the bits are consecutive, the next "0" is removed. 44 is go.
011111 with Go AHEAD flag
11 8-bit data.

The secondary stations 32 and 33 shown in FIG. 6 monitor the received data and transmit it with a one-bit delay.

Here, if six consecutive bits are 1, the beginning and end of the data frame can be detected.

However, if there are 7 consecutive 1 bits, the
It is regarded as an ahead flag, and the last bit is changed to '1rOJ, that is, it is transmitted instead of the data frame start flag or end flag, and the own station data frame is transmitted.

When the secondary stations 32 and 33 have finished transmitting all of their own data, they transmit a go-ahead flag consisting of 7 or more consecutive bits of "1" after bit "0" at the end of the data frame. As a result, when the data returns to the receiving terminal of the primary station 31 once! , 11.1, . . . , the data frames of each device are separated by flags and lined up.

Conventionally, when data is transmitted in HDLC loop mode, one primary station and multiple secondary stations are provided in one loop system, and these secondary stations monitor the reception of the go-ahead flag. At the same time, a copy of the received data is sent to the secondary station. When the go-ahead flag from the primary station is detected, it replaces this flag with the HDLC transmission flag and transmits its own data frame, and after transmitting its own data frame, it attaches the go-ahead flag and sends the next Send to secondary station. Reception and transmission are performed in the same way at the next secondary station, and data frames from each secondary station can be collected in line at the primary station after going around the loop system once.

[Problem that the invention seeks to solve]

In the conventional data transmission system described above, only one primary station is allowed in one loop system. In such a loop-based data transmission system, the primary station normally takes the timing of data transmission and monitors the flow of data frames. For this reason, when the go-ahead flag and data frame from the primary station cannot go around the loop normally due to line deterioration or line disconnection, the secondary station alone cannot start transmission, and the secondary station There was a problem in that data could not be exchanged between stations.

Furthermore, in this conventional data transmission system, only the primary station always initiates data transmission.

Also, when transferring data from the secondary station to another station, 1
This primary station must control the reception and delivery of data via the next station. Here, whether a failure occurs in the primary station or the data I! There was a problem in that if the 21 line deteriorated or was disconnected and the go ahead flag was no longer received, the secondary station would be unable to transmit data even if it was functioning normally.

[Means for solving problems]

The data transmission method of the present invention is a data communication method using HDLC loop mode, and includes means for monitoring line status and means for transmitting a go-ahead flag for starting transmission in loop mode to each data transmission device; means for switching between a primary station mode for transmitting the go-ahead flag and a secondary station mode for loop transmission;
A flag adding means for adding a line disconnection identification flag to the frame is provided, and the line status is determined by switching between the primary station mode and the secondary station mode based on the transmission word identification flag obtained by the flag adding means. The loop system 'f6' is designed to ensure data transmission even when the line is degraded or the line is disconnected.

[For f]

In the present invention, a line disconnection identification flag is added to the transmission data frame and transmitted, and the primary station mode and secondary station mode are switched based on the transmission identification flag.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram of a data transmission system showing an embodiment of the data transmission system according to the present invention.

In the figure, 1 is a primary station, 2, 3.4 are secondary stations, 5 is an outer data line, and 6 is an inner data line. Here, the outer data line and the local data line are names given for convenience to distinguish the data transfer direction.

In the data transmission system according to the present invention, the primary station 1 and the secondary stations 2 to 4 are connected in a loop using two data lines, an outer data line 5 and an inner data line 6, which have different data transfer directions.

Each data transmission device of each primary station 1 and secondary stations 2 to 4 also includes means for monitoring line conditions, means for transmitting a go-ahead flag for starting transmission in loop mode, and means for transmitting a go-ahead flag for starting transmission in loop mode. It is equipped with means for switching between a primary station mode for transmitting an ahead flag and a secondary station mode for loop transmission, and a flag adding means for adding a line disconnection identification flag to the transmission data frame, and the transmission obtained by this flag adding means. By switching between the primary station mode and the secondary station mode based on the identification flag, the system is configured to ensure a loop system for transmitting data even when the line condition is degraded or the line is disconnected.

Normally, the primary station 1 becomes the primary station mode and sends a go-ahead flag to the outer and inner data lines, and the secondary station 2.3.4 receives and transmits data in the loop mode. . At this time, the device number of each device and its own 9. Transmits a data frame that notifies all stations of a line disconnection identification flag indicating the reception status of the line for both directions. Data transmission to all stations is made possible by setting the receive address to a global address.

This data frame is called an idle frame. The structure of this data frame is shown in FIG.

In FIG. 2, 11 is a start flag, which is filled with 8-bit Φ data of 01111110. 1
2 is the receive address, 13 is the line disconnection identification flag,
14 is the CRC code, 15 is the go ahead flag and 0
This is 8-bit data of 111i111.

For example, when transmitting a command from secondary station 2 to secondary station 4 on this data line, secondary station 2 sends a command message following or before sending out its own idle frame. After sending the data frame, send the go-ahead flag. Then, if the receive address is not the local address or the global address, the secondary station 3 does not receive the data frame,
In order to transmit the received data as is, the command frame sent by secondary station 2 passes through secondary station 3 and is sent to secondary station 4.
It will reach .

FIG. 3 is an explanatory diagram showing the structure of a data frame transmitted by the secondary station 2. In FIG. 3, 21 is a start flag, which is 8-bit data of 01111110. 2
2 is data for idle frame of primary station 1, 23 is CR
C code, 24 is the end start flag and 8 bit data of 01111110, 25 is the data for idle frame of secondary station 2, 26 is the CRC' code, 2T is the end start flag and 8 bit data of 01111110, 28 is 2 Next station 2 command frame data, 29 is the CRC code, 30 is the go ahead flag, 8 of 01111111
This is bit data.

Next, the operation of each device when the data line is disconnected will be explained using FIG. 4.

FIG. 4 is a block diagram showing the data transmission system.

In FIG. 4, the same reference numerals as in FIG. 1 indicate corresponding parts, and T is the line disconnection point. Here, in addition to the data transmission system shown in FIG. 1, it is assumed that a line disconnection occurs at position 7. At this time, line disconnection is detected in the inner data line 6 in the secondary station 2 and in the outer data line @5 in the secondary station 3.

The secondary station that detected the line disconnection then
Switch to next station mode. That is, the secondary station 2 becomes the primary station for the inner loop, and the secondary station 3 becomes the primary station for the outer loop, and starts transmitting its own idle frame and go-ahead flag. Furthermore, a line disconnection identification flag is set in the idle frame to indicate that a line disconnection has occurred in each direction. And 1
In response to the idle frame, the next station 1 switches to the secondary station mode in the same direction as the respective line disconnection identification flags.

Therefore, the go-ahead flag is exchanged between the secondary station 2 and the secondary station 3, and data can be received and passed between each device on the data line as a trigger for activating all transmission of this flag.

FIG. 5 is a block diagram showing the data transmission system when a failure occurs in the primary station. In FIG. 5, the same parts as in FIG. 1 are designated by the same reference numerals, and their explanation will be omitted.

Here, the secondary station 2 and the secondary station 4 detect a failure in the data transmission system as an outer line and an inner line disconnection, respectively.
The mode is set to next game.

In this case, the secondary station 2 sends the outer ring υ, and the secondary station 4 sends the idle φ frame and the go meeting ahead flag to the inner ring, allowing data exchange between the secondary stations between both devices.

〔Effect of the invention〕

As explained above, according to the present invention, a line disconnection identification flag is added to the transmission data frame and transmitted, and the primary station mode and the secondary station mode are switched based on this transmission identification flag. As a result, a loop system for transmitting data can be secured even when the line condition is degraded or the line is disconnected, and data can be exchanged between secondary stations.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a data transmission system showing an embodiment of the data transmission method according to the present invention, FIGS. 2 and 3 are explanatory diagrams showing the structure of a data frame to explain the operation of FIG. Figures 4 and 50 are block diagrams showing an example of a data transmission system in a line-broken state, Figure 6 is a block diagram showing an example of a data transmission system using the conventional 1 (DLC loop method 2), and Figure 7 is a block diagram showing an example of a data transmission system using the conventional
FIG. 3 is an explanatory diagram showing the structure of a data frame for explaining the operation of the figure. 1・+1 Goku・1st station, 2~4・Shaken・2nd station, 5◆...
・Outer data line, 6... Inner data line, T
--- Line disconnection point.

Claims (1)

[Claims] In the data communication method using HDLC loop mode,
Each data transmission device includes a means for monitoring line status, a means for transmitting a go-ahead flag for starting transmission in loop mode, a primary station mode for transmitting the go-ahead flag, and a secondary station for loop transmission. It is equipped with a means for switching the station mode, and a flag adding means for adding a line disconnection identification flag to the transmission data frame, and based on the transmission identification flag obtained by the flag adding means, the above-mentioned 1.
By switching between the next station mode and the secondary station mode,
A data transmission method characterized by ensuring a loop system for transmitting data even when the line condition is deteriorated or the line is disconnected.