JPH0376617B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to network access control technology in loop networks.

Conventional configuration and its problems FIG. 1 shows the configuration of a loop network system with four nodes. 1 is a loop transmission path, 2 to 5 are nodes that manage the transmission interface between the terminal and the loop transmission path, and 6 to 9 are terminals.

Figure 2 shows the structure of a data frame when data is packetized and transmitted over a network.
The start delimiter (SDEL), which indicates the beginning of the data frame and serves as a delimiter, the destination address (DA),
A header section consisting of the source address (SA) and control field C, a data section (DATA) that carries data from the terminal, an FCS that is a CRC check of the data section, and an end delimiter (EDEL) that indicates the end of the data frame. ) The tail section consists of three parts.

FIG. 3 shows the configuration of a normally used delimiter. The delimiter is configured to be distinguishable from other data, and in FIG. 3, as a means of doing so, a code rule violation (CRV) of the transmission path is provided at the beginning of the delimiter to indicate the beginning of the delimiter. A delimiter identification code (PAT) is used to separate multiple delimiters such as a start delimiter and an end delimiter after a violation of the above code rule.

Figure 4 shows the configuration of a delimiter in which the circumferential status of the delimiter is monitored using the center method.
The delimiter configuration shown in FIG. 3 is provided with a monitor bit (MN; 1 bit) for checking the circulation.

Below, the second delimiter configuration shown in Figures 3 and 4 will be used.
1 shows a conventional loop access method for transmitting and receiving the data frame shown in the figure.

The way a node accesses a loop is as follows:
There are various methods, but here we will focus on an access method using multi-frame tokens, which is a type of token method and achieves highly efficient throughput.

Normally, a token indicating loop access rights circulates in a loop, and a node that captures this token sends out data in the frame structure shown in FIG.

In the multi-frame token method, the token is released immediately after sending the data frame. Therefore, nodes below the loop can immediately capture the token, and data frames are transmitted on the loop in a concatenated form.

When the node that sent the data frame goes through the data frames that it sent out, if the source address (SD) of the frame header matches its own node address, it sets the start delimiter and end delimiter of the frame. Eliminate the delimitation nature of That is, the data frame is erased by erasing the code violation (CRV).

However, with this data frame erasing method, if an error occurs in the source address of a transmitted data frame while it is going through a loop, the frame cannot be erased, and unnecessary data frames and delimiters will continue to remain in the loop. It had the disadvantage of having to keep on patrolling.

As a countermeasure to the above method, there is a method in which a monitor bit (MN) is provided in the delimiter as shown in FIG. In this method, when transmitting the data frame shown in Fig. 2, the monitor bit is set to logic 'O' and transmitted.One node on the loop (center node, etc.) monitors the delimiter, and the monitor bit MN of the delimiter is If the monitor bit MN is logic "O", it is set to logic "1", and if the monitor bit MN is logic "1", the delimiter is erased to prevent unnecessary delimiters from circulating.However, in this method, the node that monitors the monitor bit is Although it is effective for a predetermined center control method, it has the disadvantage that it cannot be applied to a system that completely decentralizes control of a loop network.

OBJECTS OF THE INVENTION An object of the present invention is to perform highly reliable and highly stable loop network control by removing unnecessary data frames in a completely distributed manner in a loop network.

Structure of the Invention The present invention provides a loop network in which each node monitors data frames transmitted by other nodes and has a function to delete unnecessary data frames that have circulated more than once. This is a loop network control method that increases loop transmission efficiency by removing unnecessary data frames early.

DESCRIPTION OF THE EMBODIMENTS The present invention uses a field in a data frame for a node other than the transmitting node to check the circulation of the data frame. In the data frame shown in FIG. 2, there are two methods: one method has the check field inside the delimiter, and the other method has the check field inside the control field C. In this embodiment, the check field is placed inside the delimiter SDEL.
I will explain the case where it is included in or EDEL. Figures 5 to 7
The figure is a diagram for explaining the method of the present invention. FIG. 5 shows a delimiter according to the present invention, in which a delimiter control section (CNT) is added to the conventional format shown in FIG. FIG. 6 is a flowchart of the delimiter reception process, and FIG. 7 is the delimiter control circuit.

The loop access and deletion of unnecessary data frames according to the present invention will be explained below. As in the conventional system, the data frame has a structure in which the data section is sandwiched between a start delimiter and an end delimiter, as shown in FIG. 2, and the delimiters have the format shown in FIG. 5.

By capturing the token, the data
In the data frame shown in the figure, the delimiter control sections (CNT) of the start delimiter (SDEL) and end delimiter (EDEL) are cleared (logically all "O") and sent.

Each node monitors the delimiter, and the sixth
Perform delimiter reception processing as shown in the figure. The node that receives the delimiter compares whether the delimiter control unit (CNT) is cleared (logic "O") or whether it is the same as its own node address (NA). If the delimiter control unit (CNT) is cleared, the own node address (NA)
Insert into the delimiter control part (CNT) above,
The mode is set to monitor the data frame (monitoring mode).

Since data propagates sequentially downstream of the loop, the node that first detects the clear state of the delimiter control unit (CNT) corresponds to the first node downstream from the transmitting node, that is, the adjacent node. In the monitoring mode, if the delimiter control unit (CNT) matches the self-node address (NA), the delimiter is determined to be an unnecessary delimiter that has completed one cycle of the loop,
Delete the delimiter. Under normal conditions, the node that sent the data frame erases the data frame including the delimiter, so as mentioned above, the data frame will not be erased by anyone other than the sending node. The monitoring mode is reset after one cycle delay time of the loop plus some time. When the delimiter control unit is not at logic "O" and is not at its own node address, the delimiter is passed through as is.

FIG. 7 is a block diagram of a delimiter control circuit related to the present invention.

Reference numerals 10 and 11 denote loop transmission lines made of optical fibers, etc., and transmitted signals use transmission line codes such as CMI encoding. Reference numeral 12 denotes a receiving circuit that receives the transmission path encoded signal, decodes the data, and detects violation of coding rules. Reference numeral 13 denotes an output signal of the receiving circuit, which includes decoded data and information about violation of coding rules. 14 is a serial/parallel conversion circuit that temporarily stores data and code rule violation information, and is a register that can insert its own node address into the delimiter control section (CNT) of the delimiter shown in FIG. 5 by a preset function. Reference numeral 15 denotes an insertion control circuit that controls the insertion of a node address as described above using the preset function of the register 14. 16 is a bidirectional bus for carrying data, coding rule violation information, and various control signals; 17 is a delimiter identification circuit including a decoder that determines whether or not it is a delimiter based on the output of the register 14; and 18 is a delimiter. A control circuit that controls the entire transmission and reception process, 19 is a CPU
20 is the node address, 21 is an erasing circuit for erasing the delimiter from the loop, and 22 is a sending circuit to the loop transmission line, which includes a transmission line encoding circuit and the like. 23 is an erase command signal from the control circuit 18.

The operation of the delimiter control circuit shown in FIG. 7 will be described below. The reception signal from the loop transmission path 10 undergoes decoding of the transmission path code in the reception circuit 12, and the decoded data and code rule violation information become the output signal of the reception circuit. It is input to the register 14, converted into serial and parallel data, and output to the bidirectional bus 16. The delimiter identification circuit 17 determines whether or not it is a delimiter based on the code rule information and data pattern on the bidirectional bus, and if it is a delimiter, the control circuit 18
to notify. As a result, the control circuit 18 takes in the inside of the delimiter directly from the bidirectional bus 16, and
The processing shown in FIG. 6 is performed.

If the delimiter control unit (FIG. 5) is at logic “O”, the delimiter control unit presets and inserts its own node address (NA) into the register 14 via the insertion control circuit 15, and enters the monitoring mode. to move to. The control circuit 18 is in a monitoring mode, and
Delimiter control unit CNT (fifth
If the node address (in the figure) matches its own node address, an erase command is output to the signal line 23. This erase command activates the erase circuit 21, masks the output of the register 14, and erases the delimiter from the loop. When the delimiter control unit CNT is neither logic "O" nor its own node address, the insertion control circuit 15 and the erase circuit 21 do not operate, and the output of the register 22 is sent to the loop 11 as is. Also, the monitoring mode is reset after a delay time of one round of the loop plus a certain amount of time. The above-mentioned time setting timer is located in the control circuit 18.

Effects of the Invention When a multi-frame token system or the like is used as an access means for a loop network, data frames are erased based on the source address of the received data frame that has been completed by the sending node. However, if a transmission error occurs in the above source address, the data frame cannot be erased at the sending node.
The drawback is that unnecessary data frames or delimiters keep going around the loop. In the present invention, a check area is provided in the delimiter or control field of the data frame shown in the figure for nodes other than the own node to check the circulation of the data frame. , data frames can be deleted by nodes that have reserved monitoring, and unnecessary delimiters and unnecessary data frames can be prevented from circulating, making it possible to construct a highly stable and efficient completely distributed loop network.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a loop network, Figure 2 is a configuration diagram of a data frame, Figures 3 and 4 are configuration diagrams of a conventional delimiter, and Figure 5 is a loop network according to an embodiment of the present invention. FIG. 6 is a block diagram of the delimiter in the control system, FIG. 6 is a flowchart of the delimiter reception process, and FIG. 7 is a delimiter control circuit diagram in the same system. 10, 11... Loop transmission path, 12... Receiving circuit, 13... Output of receiving circuit, 14... Register, 15... Insertion control circuit, 16... Bidirectional bus, 17... Delimiter identification circuit, 18 ...Control circuit, 19...Delimiter sending command signal, 20...
...Node address, 21... Erasing circuit, 22...
... Sending circuit, 13... Erase command signal.

Claims (1)

[Claims] 1. A data frame that connects a plurality of nodes in a loop and includes transmission data, a control field, a destination address, a source address, and a delimiter for distinguishing from data. In a loop network in which the nodes transmit and receive data to each other, a check field is provided in the control field or delimiter, and the node sending data clears the check field and sends a data frame, and the node that sends the data frame Any node that detects a cleared check field in a data frame acquires the right to monitor the data frame by writing its own node address in the check field, and acquires the right to monitor the data frame. A loop network control method characterized in that a node monitors a check field of a data frame on a loop, and deletes the delimiter of a data frame whose own node address is detected in the check field, assuming that the node has completed one cycle of the loop. 2 The sending node sends out a check field that is cleared by writing a logic "O" in the check field, and the node that has acquired monitoring rights calculates its own node address by adding a certain amount of time to the one-round delay time of the loop. 2. The loop network control system according to claim 1, wherein the loop network control method is reset at .