JPH0773281B2 - Data transmission method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a data transmission method for transferring data using a loop mode based on a high level data link control (HDLC) procedure.

[Conventional technology]

Figure 2 shows the basic configuration of a standard data transmission system using the HDLC loop method. Here, 21 is a primary station, 22, 23 and 24 are secondary stations, and 25 is a data line. Data transmission directions are indicated by arrows. The primary station and the secondary station are so-called daisy-chain connections in which the transmission terminal and the reception terminal of different stations are connected to each other. The data frame transmitted through this data line has the same structure as the HDLC data frame.

FIG. 3 shows the structure of the data frame transmitted by the primary station 21. 31 and 32 are synchronization flags, which are bits of "01111110".
The data. The device which receives the data detects the start or end of the data frame by this synchronization flag.

33 is a transmission data portion, which is normally a receive address A indicating the number of the receiving station and a control field C for controlling the data transfer procedure.
And the I-field which is the actual transmission data.

A unique address is set to each station, and each station has a so-called HDLC address search function that does not capture a data frame when the receive address A does not match this unique address.

However, if the receive address is FF ₍₁₆₎ (hexadecimal notation), it is called specially global addressing, and a data frame is received regardless of the unique address setting of the station.

Reference numeral 34 is a CRC code portion for identifying an error in the transmission data portion 33. Further, 35 is a transmission start flag for starting the transmission of the secondary station.

At the time of transmission, if the transmission data part 33 and the data part of the CRC code part 34 have five consecutive "1" s, a "0" is inserted. , And 0 bit insertion and removal. Therefore, the data in the transmission data section 2 does not have the same shape as the start flag.

When each station is monitoring the received data and transmitting with a 1-bit delay, and if the bit "1" continues for 6 bits, the data
The beginning and end of a frame can be detected, and the CRC of the preceding 2 bytes and the CRC created when receiving data are compared to detect whether an error has occurred in the data frame.

Further, in the transmission start flag 35, if seven bits "1" continue, it is regarded as a transmission start flag and the last one bit is replaced with "0", that is, the data frame start flag or end flag is transmitted. , Start transmitting local data frame.

When the secondary station finishes transmitting its own data, at the end of the data frame, it transmits a transmission start flag in which “0” is followed by “1” for 7 bits or more. As a result, when the data returns to the receiving terminal of the primary station 1 in one cycle, in FIG.
The data frames of the respective devices are lined up in the order of the primary station 21, the secondary stations 22, 23, 24, separated by flags.

The flow of this data frame is shown in FIG.

In this system, only the primary station 21 always triggers data transmission. Further, for example, when transferring data from the secondary station 24 to the secondary station 22 in FIG. 2, the primary station 21 needs to control the delivery of data via the primary station 21. Therefore, the primary station intervenes and manages the delivery of data between the data transmission devices on the loop line.

However, if the primary station 21 fails, the data line 25
If the transmission start flag is not passed due to deterioration or disconnection of the line, data transmission cannot be performed even if the secondary stations 22, 23, 24 are functioning normally.

To compensate for this drawback, Fig. 5 shows a data transmission system for switching between the primary station mode and the secondary station mode.

In the figure, 51, 52, 53, and 54 are data transmission stations, which are primary stations or secondary stations depending on the line status. 55 is a clockwise data line, and 56 is a counterclockwise data line. In this data transmission system, the primary station and the secondary station are connected in a ring by two clockwise and counterclockwise data lines whose data transfer directions are different from each other.

Here, the data transmission station 51 is set to the primary station mode, the transmission start flag is transmitted in the clockwise and counterclockwise directions, and the data transmission stations (secondary stations) 52, 53, and 54 are in the loop mode in each direction. Is being received and transmitted. At this time, the device number of each station on the ring line and a line disconnection identification flag indicating the receiving state of the line for clockwise and counterclockwise bidirectional for each device are added to the data frame to notify all stations. The transmission state identification flag of this data frame enables all stations on the ring line to know the line state.

Here, as indicated by numeral 61 in FIG. 6, when a failure occurs in the line, the data transmission device that has detected the failure, that is, the sixth
In the figure, the secondary stations 52 and 53 respectively transmit a line disconnection identification flag counterclockwise until the line is restored clockwise and a data frame is received, and the primary station mode is entered to activate the data transmission timing. Hang

On the other hand, in this state, when each station issues a command request for a data frame between arbitrary stations, it searches the data string received from each of the clockwise and counterclockwise directions to determine at which position the line is disconnected, By confirming in which direction the data frame should be transmitted and transferring the data frame, a data frame can be transmitted between arbitrary stations as long as the line is connected without a fixed primary station. It becomes possible to hand over.

[Problems to be solved by the invention]

However, in the above-described conventional transmission method, each secondary station on the line receives all data frames including data that is not necessary for itself, resulting in waste of processing. is there.

In addition, it is necessary to guarantee data transfer at the application level, such as whether the data is normally transmitted to the partner station and whether the sequence of the data frame sequence is correct. This requires a complicated procedure. There is.

[Means for solving problems]

According to the present invention, a data transmission device having a data communication function according to a loop mode of an HDLC communication procedure is connected by two ring lines that transmit data in opposite directions, and each data transmission device has means for monitoring the line state. , Means for transmitting a transmission start flag for starting transmission in loop mode, loop transmission of the signal received from the primary station mode for transmitting the transmission notation flag and the upstream station of the loop line, and transmission When a startup flag is detected, it is replaced with an HDLC flag, and then there is a secondary station mode in which a local station data frame is transmitted and then a transmission startup flag is sent, and these primary station mode and secondary station mode are switched. Switching means and means for transmitting a line disconnection identification flag in the transmission data frame are provided, and the primary station mode and the secondary station are set based on the line disconnection identification flag. In a data transmission system in which data communication is performed between data transmission devices by switching modes, a data frame called a carrier frame indicating the state of each station is periodically transmitted to a transmission line in each direction, and the carrier frame is continued. This is a data transmission method characterized in that an inter-station communication data frame is added and transmitted, and a frame transfer procedure is managed for each data frame between communicating stations.

〔Example〕

 Next, the present invention will be described with reference to examples.

FIG. 1 shows the configuration of a data transmission device according to the present invention. 11
Is a data transmission device, 12 and 13 are a reception side and a transmission side of a clockwise data line, and 14 and 15 are a reception side and a transmission side of a counterclockwise data line. Reference numerals 11a and 11b are HDLC loop data communication means, which have a function of performing loop communication in the secondary station mode, and have a function of separately performing reception and transmission in the primary station mode.

Reference numerals 11c and 11d are clockwise and counterclockwise receive buffers, respectively, and 11e and 11f are clockwise and counterclockwise transmit buffers, respectively. 11g is a management means for managing the transmission / reception procedure, 11h
Is a transmission data distribution means for controlling whether the transmission data is sent clockwise or counterclockwise, 11i is a memory for storing management data when managing transmission / reception procedures, and 11j is an application module .

In this method, the entire system configuration uses a dual ring line connection, and the system configuration follows that shown in FIG.

FIG. 7 shows the structure of a data frame transmitted by each data transmission device.

In the figure, 7a, 7b and 7c are synchronization flags, 71 is the data part of the carrier frame, and 71d is the CRC code of this data frame. Global address 71 for carrier frame 71
a, an I-field 71c including a control field 71b and a line disconnection identification flag. Incidentally, here, a special code without a number is added to the control field 71b because the carrier frame 71 uses a so-called non-stop data transfer method in which the transmission procedure is not managed and the retransmission request is not performed.

In the figure, 72 is the data portion of the data frame with procedure.
The procedure-provided data frame 72 is provided with a reception address 72a indicating a transfer destination station, a control field 72b, an I-field 72c which is transfer data, and a CRC code 72d for checking these errors. Where control field 72b of procedural data frame 72
In order to perform the HDLC communication procedure by the data frame with procedure 72, manage the order of the data frames, request retransmission, and set the communication mode, a normal HDLC control character is set. Normally, the procedural data frame 72 uses a numbered communication procedure in asynchronous balanced mode.

In the present invention, in order to maintain the connection of the loop line,
A frame is always transmitted and received by each data transmission device, but a procedural data frame is not transmitted unless each data transmission device has data to be transmitted.

FIG. 8 shows the hierarchical structure of the control means for establishing the data communication system according to the present invention.

As shown in FIG. 8, the data communication according to the present invention is managed and operated by a hierarchical structure of some functions. First, the first layer 81 is hardware for performing data communication, which has a function of transmitting and receiving HDLC data frames in clockwise and counterclockwise directions, respectively, and independently performs loop communication mode and normal transmission / reception. It is performed by switching the normal communication mode that is performed separately.

The 1.5th layer 82 uses a firmware to identify the type of transmitted / received data frame by a carrier frame and a procedural data frame. The procedure-provided data frame among the received data frames is handed over to the second layer 83. In addition, the transmission data with procedure of its own station passed from the second layer 83
The frame is delivered to the first layer 81 after the carrier frame is transmitted at the transmission timing of its own station, and control is performed to activate the transmission.

On the other hand, the 1.5th layer 82 stores line disconnection information for managing the line connection state from the received carrier frame in the line connection management memory 85, and based on this information, the primary station mode / secondary station is stored. Switch hardware between modes,
Data is sent to either the clockwise or counterclockwise line during transmission.
It has a function of deciding whether to transmit a frame and distributing the data frame. Also, the line information by the line disconnection detecting means of the own station is set in the carrier frame of the own station and transmitted in both directions of the ring line.

The second layer 83 manages only the procedure of transmitting and receiving the data frame with the procedure. This transmission / reception procedure performs the same operation as the normal HDLC communication procedure for the second layer and above.

The third layer 84 is the application module firmware and software. Generally, a layered model such as firmware for establishing a data link on the third layer 84 and software for causing an application to function on the layered layer 84 is used. However, in the present invention, the second layer and above are other general communication. Since the procedure is similar, these functions are collectively described as the third layer application module.

The operation of the firmware of the layer 1.5 will be described with reference to FIGS. 9 and 10.

The data transmission device according to the present invention has the 1.5-layer firmware both clockwise and counterclockwise,
Each works independently. In the data communication system of the present invention, each data transmission device first starts up in the secondary station mode when the device starts up. Figure 9 shows the operation procedure in secondary station mode, 10th
The figure shows the operation procedure in the primary station mode. After starting up the data transmission equipment, after performing various procedures such as self-diagnosis and system startup, the data transmission equipment will enter the communication system of the loop line.

In the transmission of the data frame in the secondary station mode, the hardware of the first layer automatically detects the reception of the transmission start flag and transmits it. For this reason, the firmware of layer 1.5 waits for the completion of data frame transmission once the data frame is set in the transmission buffer and the loop communication mode is set. When a carrier frame or data frame with a procedure is received from the upstream station during this time, only the received data pointer and the status of the reception state are saved in the management memory each time one frame is received. These pointers and statuses are used when the line disconnection flag is extracted from the carrier frame after the transmission start flag is received to create the line state management information, or when the data processing is handed over to the second layer firmware.

When transmission of the carrier frame set in the transmission buffer is completed, layer 1.5 checks whether or not there is a procedure-oriented data frame to be transmitted to the local station. If there is a data frame with a procedure that has not been transmitted, the data frame is set in the transmission buffer and transmission is started. If there are no data frames to send in your station,
Layer 1.5 performs the process of outputting the transmission start flag, performs the process of waiting for the next reception such as switching the receiving buffer and resetting the receiving buffer after the completion of transmission, and further obtains it by the line monitoring means of the own station. Create a carrier frame with the line disconnection identification flag set and set it in the transmission buffer.

In the secondary station mode, there is a transmission completion guard time waiting for the completion of data frame transmission together with the line monitoring means, and if a line disconnection is detected or transmission is not started for a certain period of time or more, the own station is switched to the primary station mode. .

When in the primary station mode, the line disconnection identification flag is set in the carrier frame and transmission is performed. Here again, if there is a data frame with a procedure to be transmitted to the local station after transmitting the carrier frame, this data frame is set in the transmission buffer and transmission is started. When the transmission data frame is exhausted, the transmission start flag is immediately transmitted, the second layer is notified of the release of the transmission buffer, and the standby state for receiving data from the opposite station is established.

Here, if a data frame is received from the game, the pointer and status of the received data are saved for each data frame.

When the transmission start flag is received from the game, a series of data
When the reception of the frame sequence is completed, the analysis and editing process of the received data is started. Here, the management information of the connection state of the line is created based on the received carrier frame, and the process of the data frame with the procedure is handed over to the second layer. After analyzing the received data, it checks whether or not there is a data frame transmitted by the own station in the data frame sequence received from the upstream of the same direction line, and if there is the own station data frame, the loop line is closed. It is assumed that the station is fixed as the primary station mode. If there is no own data frame in the data frame sequence received from the upstream in the same direction at this time, it means that the ring line is disconnected upstream of other than the own station and there is another primary station. Therefore, the same direction data reception counter is incremented.

When the count value n of the counter exceeds a certain guard count N, it is determined that the upstream line is functioning properly and the layer 1.5 of the own station is set to the secondary station mode and the line disconnection flag is cleared. Then, it shifts to the secondary station mode.

In other cases, that is, when no data frame is received from the upstream in the same direction, or when there is transmission data of the own station in the received data frame sequence, the transmission interval
After the wait time by the timer, the next carrier frame is transmitted.

When a series of 1.5 layer firmware operations causes a failure in the ring line in any disconnection mode, the primary station can be generated at both end disconnection points, and the ring line is closed without failure. However, it is possible to fix the primary station and perform data communication between the stations that can be connected.

In addition, the layer-1 firmware manages the connection status of the line so that the layer-2 data communication procedure is
It is possible to divide the functions so that only normal procedures such as the order of frames and a request for resending data are performed.

In the data communication system according to the present invention, the above-described firmware is used to manage the line connection by the carrier frame and establish the data communication procedure between arbitrary stations. For this reason, the firmware modules and software modules of the second layer and above in each data transmission device can communicate without considering the line disconnection state, the direction of data transmission, and the like.

〔The invention's effect〕

As described above, a carrier frame that informs all the data transmission devices on the loop line of the status of each data transmission device is periodically transferred to the clockwise and counterclockwise bidirectional lines, and the (Following) the inter-station communication data frame is added and transmitted, and by managing the frame transfer procedure for each data frame between the communicating stations, data can be efficiently exchanged between arbitrary stations. It becomes possible to do.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a data transmission device used in the present invention, FIG. 2 is a diagram showing an example of a conventional data transmission system, FIG. 3 is a diagram showing the structure of a data frame, and FIG. FIG. 5 is a diagram for explaining the flow of a data frame, FIG. 5 is a diagram showing another example of a conventional data transmission system, and FIG. 6 is a diagram for explaining data transmission when a line failure occurs. , FIG. 7 shows the data transmitted by the data transmission device shown in FIG.
FIG. 8 is a diagram showing the frame structure, FIG. 8 is a diagram for explaining the hierarchical structure of the control means, FIG. 9 is a diagram for explaining the operation procedure in the secondary station mode, and FIG. 10 is an operation in the primary station mode. It is a figure for demonstrating a procedure. 11 …… Data transmission device, 11a, 11b …… HDLC communication device, 11c, 1
1d …… Receive buffer, 11e, 11f …… Send buffer, 11g ……
Transmission / reception procedure management means, 11h ... Transmission data distribution means, 11i ...
… Transmission / reception procedure management memory, 11j …… Application module.

Claims (1)

[Claims] 1. A data transmission device for performing data communication in a loop mode of a high level data link control (HDLC) procedure is connected by two ring lines for transmitting data in opposite directions, and a line is connected to each data transmission device. Monitoring means for monitoring the state, and means for transmitting a transmission start flag for starting transmission in the loop mode,
When the signal received from the primary station mode for transmitting the transmission recording flag and the upstream station of the ring line is loop-transmitted, and the transmission activation flag is detected, the transmission activation flag is changed to the HDLC flag, and then the own data frame A switching means for switching between the primary station mode and the secondary station mode, which has a secondary station mode for transmitting a transmission start flag after transmitting the transmission, and means for transmitting the line disconnection identification flag in the transmission data frame. Is provided, and in a data transmission system for performing data communication between data transmission devices by switching between a primary station mode and a secondary station mode based on the line disconnection identification flag, a carrier frame indicating the state of each station is predetermined. The data is transmitted to the transmission line at regular intervals, the inter-station communication data frame is added after the carrier frame, and the data frame is transmitted between the communication stations. A data transmission method characterized in that it has a means for managing the frame transfer procedure for each frame and exchanges data between predetermined stations.