JPH03177133A - Data communication control system - Google Patents

Abstract

PURPOSE:To restart communication in a short time by transmitting a C frame through the line of an opposite direction when a data frame does not arrive from the upper stream, and setting a new condition that a node receiving the C frame is inhibited from becoming a primary station. CONSTITUTION:When the line of the direction opposite to a sending direction is in a disconnected state, a control flag C is erected, and in this case, the primary station 11 and secondary stations 13, 15 are in a C flag ON state. The primary station 16 of a clockwise direction and the secondary stations 17, 19 of a counterclockwise direction do not become the primary station in the case the C flag in the last data frame received by the station of the direction opposite to its own station (the primary station 11 in the case of the primary station 16, the secondary station 12 in the case of the secondary station 17, the secondary station 14 in the case of the secondary station 19) is ON, and this is made to be the condition 4 next time. Namely, the condition 4 inhibits the station from becoming the primary station in the case the C flag in the last data frame received by the station of the direction opposite to its own station is ON. Thus, even in the case the disconnection of the line occurs, the communication restarted in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for data communication control. The present invention relates to a data communication control system for a data transmission system that transfers data in a ring type communication system. In particular, it relates to a primary station resetting method.

〔overview〕

The present invention relates to a data communication control method in a ring communication system in which a large number of nodes are connected in a ring shape by clockwise and counterclockwise double lines, and a primary station (master station) is automatically set for each line. , by setting a new condition that when a data frame does not arrive from upstream, a C frame is sent to the opposite line, and a node receiving this C frame is prohibited from becoming a primary station, the data line Even when a data frame cannot normally travel around the ring due to an abnormality, the primary station can be correctly set in a short time and communication can be resumed.

[Conventional technology]

Conventionally, when transmitting data using a ring-type communication system, the first
As shown in the figure, one primary station (
A master station) and multiple secondary stations (slave stations) are installed, and the secondary station copies the received data while monitoring the reception of control flags, then adds its own data to the next secondary station. is being sent to.

In addition, in the case of line deterioration or line disconnection, it is necessary to set not only one but a plurality of primary stations, and a method for automatically performing this setting is known. The conditions for this are (Condition 1) No data frame arrives from the upstream station (
timeout), the secondary station becomes the primary station. However, the timeout period differs depending on each node (priority order).

(Condition 2) When the upstream station receives a data frame transmitted by another station, the primary station becomes a secondary station.

(Condition 3) The primary station in either the clockwise or counterclockwise direction has a control flag for the opposite direction (R flag (flag that turns ON when the ring is formed normally)
) is ON and the control flag (P flag (flag that turns OFF for data frames that have not been relayed even once)) when the primary station is in the opposite direction to the transmission direction is OFF. It serves as a primary station in both clockwise and counterclockwise directions.

is taken. Under these conditions, the primary and secondary stations were reconfigured to enable data collection.

[Problem to be solved by the invention]

In such conventional ring-type communication systems, when data frames from the primary station cannot circulate normally on the ring due to line deterioration or line disconnection, there is a procedure to switch to an accurate data transmission system. There was a problem that required unnecessary operations. In other words, if there is only the above-mentioned three-way property, nodes are set as primary stations one after another according to their priorities, and then the right of the primary station is transferred to the station with the next priority. It will take time to set the primary station appropriately.

The purpose of the present invention is to solve this problem, and to provide a method that allows only the secondary station to resume communication in a short time even when the data frame from the next station cannot normally circulate on the ring. do.

[Means to solve the problem]

In the present invention, a large number of nodes are connected in a ring shape by clockwise and counterclockwise lines, and each node has a
A transmitting/receiving station is provided for each clockwise and counterclockwise line, and each transmitting/receiving station operates in two modes: a primary station mode in which data frames are generated and transmitted, and a secondary station mode in which received data frames are relayed and transmitted. The secondary station becomes the primary station when a data frame does not arrive from the upstream station within a predetermined time (condition 1) as a condition for either of these two modes. However, this predetermined time is different depending on the priority of each node. (Condition 2) When the upstream station receives a data frame transmitted by another station, the primary station becomes the secondary station. (Condition 3) Clockwise rotation And for a node that is a primary station only on one counterclockwise side, it is confirmed that a ring is established by the R flag on the line opposite to the line that is the primary station, and In a data communication control system in which the following three conditions are set, each node has the following conditions: When the upstream neighbor station of the local station is recognized as the primary side by the P flag, both lines become the primary side. When no data frame arrives from upstream, C is sent to the opposite line.
A means for transmitting a flag is provided, and the conditions for being in either of the two modes are (Condition 4) When a station in the opposite direction of the own node receives the C flag, that node becomes the primary side. It is characterized by the addition of a condition that prohibits.

[Effect]

Add resetting control flags (R flag, P flag, C flag) for the primary and secondary stations to the transmitted data frame, copy the received data while monitoring the reception of these control flags, and then copy the received data. The data is attached and transmitted to the next secondary station.

Here, the R flag is a flag that is ON when the data frame has made one round. The P flag is OFF when the data frame has never been relayed, and the flag is ON when the data frame is relayed. The C flag is a flag that is ON when the data frame is relayed. This flag is turned ON when no data frame arrives from upstream.

When the secondary station does not receive a data frame, it switches from secondary station mode to primary side mode, and when the primary station receives a data frame from another station, it switches from primary side mode to secondary station mode. Also, if the R flag is ON in either the clockwise or counterclockwise direction, the primary side in one direction is in the opposite direction.
By detecting that the P flag is OFF, it switches to the bidirectional primary side mode, and by detecting that the C flag in the direction opposite to the local station is ON, it switches to the secondary station mode.

That is, if possible, the same node moves to become the primary side for the bidirectional line, or the first station of the disconnected line is set as the primary side without going through the operation of sequentially moving up the nodes according to the priority order.

Thereby, it is possible to set up a communication system that transmits data in a short time even if the line condition deteriorates or becomes disconnected.

〔Example〕 Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing the overall configuration of an embodiment of the present invention.

In the embodiment of the present invention, a large number of nodes A-E are connected in a ring shape by clockwise and counterclockwise lines 21 to 25 and 26 to 30, and each node A to E has clockwise and counterclockwise lines. Each line 21-25 and 26
~30 are provided with transmitting/receiving stations 11-15 and 16-20, and each transmitting/receiving station 11-15 and 16-20 is
A means for setting one of two modes: a primary station mode that generates and transmits a data frame and a secondary station mode that relays and transmits a received data frame, and the conditions for being in either of these two modes. As, (condition 1
) When a data frame does not arrive from the upstream station within a predetermined time, the secondary station becomes the primary side. However, this predetermined time is different depending on the priority of each node. (Condition 2) When the upstream station receives a data frame transmitted by another station, the primary station becomes the secondary station. (Condition 3) Clockwise rotation For nodes that are primary on only one side in the counterclockwise direction, it is confirmed that a ring is established by the R flag on the line opposite to the line that is the primary station, and the P
When it is recognized by the flag that the station adjacent to the upstream side of the own station is the primary side, both lines become the primary side.

In the data communication control system in which the three conditions described above are set, each node A to E is provided with a means for transmitting a C flag to the opposite line when no data frame arrives from upstream, and the above two modes are set. As a condition for either of these, (Condition 4) a condition is added that prohibits that node from becoming the primary side when the C flag is received at a station in the opposite direction of the own node.

FIG. 2 is a block diagram showing a specific configuration example for realizing the embodiment of the present invention. According to this, each node A-E
The transmitting/receiving stations 11-15 and 16-20 include data transmission connection means 1 for connecting data transmission with data lines 21-25 and 26-30, and lines 21-25 and 2.
6 to 30 to detect deterioration or disconnection, and a control flag (R
flag, P flag, C flag) and receives r-
a data transmitting means 8 for adding own station data to the evening copy and transmitting it to the next secondary station; a timing monitoring means 7 for determining the timing of data transmission and monitoring the flow of data frames; and transmitting/receiving stations 11 to 15. and a secondary station/primary station mode switching means 4 that switches from secondary station mode to primary station mode when the transmitting/receiving stations 11-15 and 16-20 do not receive data frames of other stations. It is equipped with a primary station/secondary station mode switching means 5 that switches from the primary station mode to the secondary station mode when receiving the data, and further includes control flags (R flag, R flag, A control flag switching means 3 for adding a P flag, a C flag, and a transmitting/receiving station 11 for either clockwise or counterclockwise direction.
A primary station mode switching means 6 is provided for switching to a bidirectional primary station mode when the data transmitting means 8 of I5 and 16 to 20 detects a control flag.

Next, for comparison, the conventional method described above will be explained using FIG. 1. That is, the state without condition 4 will be explained first. In the figure, 11 is a clockwise primary station, and 12 to 15 are clockwise secondary stations.

16 is a counterclockwise primary station, and 17 to 20 are counterclockwise secondary stations. These primary and secondary stations are connected by clockwise and counterclockwise data lines. Here, the clockwise data line and counterclockwise data line are names given for convenience to distinguish the data transfer direction.

In such conventional data transmission systems, the primary station and the secondary station are connected in a ring with two data lines, one clockwise and one counterclockwise, with different data transfer directions.
Each primary station and secondary station has a function of monitoring the data line and switching between the primary station mode and the secondary station mode when detecting that the line has deteriorated or is disconnected.

Assume now that lines are disconnected at three locations as shown in FIG. Timeout priority is A-4B-+
C-) The order is D-+E. At this time, the secondary station 17 is switched to the primary station mode according to the condition l (priority order) for resetting the primary station and secondary station. Thereafter, the secondary station 18 is switched to the primary station mode again according to condition 1 (priority order) for resetting the primary station and secondary station. Then, under condition 2, primary station 17 switches to secondary station mode, and under condition 3, stations 18 and 13 become primary stations in both directions.

Further, the secondary station 19 is switched to the primary station mode according to the condition l (priority order) for resetting the primary station and secondary station.

Thereafter, the secondary station 20 is switched to the primary station mode again according to the condition l (priority order) for resetting the primary station and secondary station. Then, according to condition 2, primary station 19 switches to the secondary station mode, and according to condition 3, stations 20 and 5 become primary stations in both directions.

When the line in the data transmission system is disconnected in this way, many steps are required to restart communication, resulting in wasted time.

On the other hand, in the embodiment of the present invention, the operation of switching the counterclockwise secondary stations 17 and 19 to the primary station mode in the conventional method is not necessary because the counterclockwise data lines from both stations are disconnected.

To solve this problem, a control flag C flag is set when the line in the opposite direction to the sending direction is disconnected. In this case, the C flag is ON for the primary station 11 and the secondary stations 13 and 15. Clockwise primary station 16 and counterclockwise secondary station 17.1
9 is the direction opposite to the own station (if the primary station is 16, then the primary station is 11)
, if the C flag in the last data frame received by the secondary station 17, the secondary station 12, or the secondary station 19, the secondary station 14) is ON, the station does not become the primary station. This is referred to as condition 4 shown below.

(Condition 4) If the C flag in the last data frame received in the direction opposite to the local station is ON, the station is prohibited from becoming the primary station.

Even if a line disconnection as shown in FIG. 3 occurs due to condition 4, the secondary station 18 is switched to the primary station mode according to condition 1 (priority order) for resetting the primary station and secondary station. Also, according to condition 3, the secondary stations 18 and 13 become primary stations in both directions. Then, the secondary station 20 switches to the primary station mode according to condition 1 (priority order).

In this way, the steps are shortened and communication can be restarted in a short time.

〔Effect of the invention〕

As explained above, according to the present invention, in a ring-type data transmission system, even when the data frame from the primary station cannot normally circulate around the ring due to line deterioration or line disconnection, it can be set to the secondary station in a short time. Since the appropriate station among the stations that were previously set is automatically set as the primary station, communication can be restarted.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of a conventional example and an embodiment. FIG. 2 is a block diagram showing the configuration of a transmitting/receiving station according to an embodiment of the present invention. FIG. 3 is a diagram showing a state when a line disconnection occurs in the conventional example and the embodiment. DESCRIPTION OF SYMBOLS 1...Data transmission connection means, 2...Data frame monitoring means, 3...Control flag switching means, 4...Secondary station/primary station mode switching means, 5...Primary station/secondary station Station mode switching means, 6... Primary station mode switching means, 7...
- Timing monitoring means, 8... data transmission means, AS
B. C, DS E... Node. Figure Example 2

Claims (1)

[Claims] 1. A large number of nodes are connected in a ring shape by clockwise and counterclockwise lines, and each node is provided with a transmitting and receiving station for each clockwise and counterclockwise line, and each transmitting and receiving station is provided for each of the clockwise and counterclockwise lines. The station includes means for setting one of two modes: a primary station mode in which data frames are generated and transmitted, and a secondary station mode in which received data frames are relayed and transmitted; (Condition 1) When a data frame does not arrive from the upstream station within a predetermined time, the secondary station becomes the primary station. However, this predetermined time is set differently depending on each node. (Condition 2) When the upstream station receives a data frame transmitted by another station, the primary station becomes the secondary station. (Condition 3) For a node that is a primary station only on either the clockwise or counterclockwise side, it is confirmed that a ring is established by the R flag on the line that is the primary station and the line that is opposite to the line that is the primary station. If the station next to the station on the upstream side is recognized as the primary station by the P flag, both lines become the primary station. In a data communication control system in which the following three conditions are set, each node is provided with a means for transmitting a C flag to the opposite line when no data frame arrives from upstream, and either of the above two modes is set. (Condition 4) A data communication control method characterized by adding a condition that prohibits a node from becoming a primary station when the C flag is received by a station in the opposite direction of the own node. .