JPH0317261B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a communication control method for a communication system comprising a plurality of communication stations connected by a bidirectional broadcast transmission path.

Line access control methods for n:n communication on a broadcast transmission path include (a) interrupt method, (b) polling method, and (c) baton (token) pass method.

Each of the above methods (a) and (b) requires a control station in the system, and since this part becomes a centralized part of the system, there are problems in maintaining reliability and the length of the transmission path. There are problems such as being affected by the noise, and the transmission efficiency is not very good.

On the other hand, the method (c) has been improved and is now being widely adopted for process data ways.

This baton pass method uses the following line access method.

In other words, the control authority (called a baton or token) that allows master operations to be performed on a line is sequentially transmitted to each communication station by a command frame (baton pass command) in a predetermined order. When each communication station receives the baton, it sends a command if there is a transmission request at that time, receives a response if necessary, and passes the baton to the next station. If there is no transmission request, the baton is immediately sent to the next one.

In the baton passing sequence, if there is a communication station that does not receive the baton, it is determined to be an abnormal communication station, is automatically excluded from the normal baton passing sequence, and the baton is passed to the next communication station. That is, a normal baton passing sequence occurs between communication stations that are in a normal state. You can know which communication station is in a normal state by observing the source address of the baton pass frame on the line (in the case of an abnormal state, no baton pass frame is sent on the line). ).

In such baton-pass type communication control, the communication station to which the baton is bypassed is repaired, for example, from an abnormal state, and is able to operate normally at any time.

Here, it is necessary to perform recovery communication control for a communication station that has recovered from an abnormal state at any time to participate in the normal baton sequence.

Such recovery communication control is attempted periodically or as needed for communication stations that are removed from the normal baton sequence, and must be performed at all communication stations that receive the normal baton. You have to become familiar with it.

For this purpose, each communication station has the latest information on which communication stations are normal and which stations have recovered from a failure, that is, a data list representing the normality/abnormality of each communication station (this list is called a station live list). ) is required.

The contents of this station live list must be consistent and always updated to the latest information at each communication station.

<Conventional Example> Conventionally, the list of each communication station was updated in the following manner. In other words, all communication stations monitored the baton pass command sent to the transmission path, recognized the station that sent the baton pass command based on the source address contained in it, and sent the baton pass command. The station is recorded as normal in the list. Then, the source address of the current baton pass command is compared with the source address of the previous baton pass command to determine whether they are in a predetermined order. If the order is correct, there is no abnormality because the station that was supposed to issue the baton pass command this time sent out the baton pass command correctly. However, if the order is out of order, the station that was supposed to issue the baton pass command this time did not send the baton pass command, and the next station or the station after that sent the baton pass command, which is abnormal. be. Therefore, in this case, communication stations having addresses between the previous address and the current address are recorded as being abnormal in the list.

Updating such a list results in communication overhead at each communication station. Although it is desirable that the communication overhead be as small as possible, the list updating method described above involves a large communication overhead because the procedure is complicated and time consuming.

<Objective> An object of the present invention is to provide a communication control method that allows updating of a list of data representing normality/abnormality of all communication stations in a simple procedure with a short processing time.

<Main points> The present invention consists of a plurality of communication stations connected by a broadcast transmission line, and allows one of the plurality of communication stations to perform a master operation, and its status is determined by a baton pass. The baton pass is a communication control method including an address of a source station, an address of a destination station, and a baton pass command, and the baton pass command of the baton pass is transmitted to a normal communication station. Two types of baton pass commands are specified: an in-ring baton pass command that instructs a group of communication stations to circulate, and an out-of-ring baton pass command that instructs a group of communication stations other than that to circulate, and performs a master operation on all communication stations. Getting normal/ about all communication stations
A station live list consisting of bit patterns that indicate abnormalities is set up, and when a station performing master operation performs a baton pass to a communication station that is displayed as normal in its own station live list, it must pass the baton in the ring. When using the pass command to perform a baton pass to a communication station that is displayed as abnormal in the station live list, use the outside-ring baton pass command to pass the baton to all communication stations other than the one that is performing the master operation. The communication stations constantly monitor the batons circulating on the transmission path, and when receiving an intra-ring baton pass command, each communication station corresponds to the source address of the communication station that sent the baton in its own station live list. Set the bit to a value that means normal, and when receiving an outside-ring baton pass command, set the bit corresponding to the destination address of the baton in your own station live list to a value that means abnormal. The above object has been achieved by a communication control method characterized by the following.

<Examples> The present invention will be explained in detail below using Examples. Figure 1 is a conceptual diagram of a communication system to which the present invention is applied, Figure 2 is a conceptual diagram of a communication station, Figure 3 is an example of a list configuration, Figure 4 is a frame configuration diagram of a baton pass command, and Figure 5. 1 is a flow diagram showing the configuration of a program according to an embodiment of the present invention.

<Configuration> In FIG. 1, S1 to Sn are communication stations, and L is a bidirectional broadcast type transmission line connecting these communication stations. Terminators are provided at both ends of the transmission line L.

The configuration of communication station Si (i=1 to n) is as follows:
As shown in Figure 2, the processor CPU and memory
MM, I/O control unit IOC, and communication control unit COM
are connected by an internal bus BS. The communication control unit COM is connected to the transmission line L via a modem device MDM. The communication control unit COM has
It includes a microprocessor, etc., and its data processing function performs communication control.

The communication control unit COM is provided with a list as shown in FIG. This list is called Station Live List SLL. Station live list
The SLL consists of a predetermined number of bit patterns, each bit being associated with a particular communication station. The bit value 1/0 represents the normality/abnormality of the corresponding communication station. The baton pass is performed in the order of the bit arrangement in the station live list SLL, and is repeated from the beginning every time it goes around.

The communication control unit COM uses a baton pass command with a frame structure as shown in FIG. In Figure 4, PRA is briamble, F is flag, and S
is the destination address, M is the source address, C is the control information, CRC is the check code, and POA is the postamble.

The control information C is information representing the type of baton pass command and control information for information transmission. Two types of baton pass commands are defined: an inside-ring baton pass command and an outside-ring baton pass command, one of which is specified by the control information C.

A ring is a baton-pass circle made up of a group of normal communication stations. Therefore, inside the ring means inside the normal station group, and outside the ring means outside the normal station group. Communication stations within the ring are recorded as normal in the station live list SLL, and stations outside the ring are recorded as abnormal. The in-ring baton pass command is used when attempting to pass the baton to a communication station that is recorded as normal, and the out-of-ring baton pass command is used when attempting to pass the baton to a communication station that is recorded as abnormal. .

Here, the station live list SLL possessed by each communication station is created by observing the baton pass frame on the transmission path L at each communication station, but in order to keep the contents up to date. The update operation is automatically performed under communication control as described below.

The communication control unit COM has a program as shown in FIG. 5, and performs communication control using this program.

In FIG. 5, stage 1 is a carrier detect, which determines the presence or absence of a communication frame on the transmission path. When there is no communication frame,
Looping is performed at this stage, and if there is a communication frame, the process branches to stage 2. In step 2, a communication frame reception process is performed, and in step 3, it is determined whether or not there is an error. If there is an error, the process returns to step 1, and if there is no error, the process branches to step 4. Step 4 determines whether the received frame is a baton pass command.

If it is not a baton pass command, branch to step 16 to determine whether the communication is addressed to your own station, and if it is not addressed to your own station, return to step 1, but if it is addressed to your own station, proceed to step 17. process commands,
A response is sent in step 18, and the process returns to step 1.

If it is a baton pass command, the process branches from step 4 to step 5 to determine whether it is an intra-ring baton pass command. If it is an intra-ring baton pass command, branch to step 6 and set the corresponding bit in the live station list SLL to 1 according to the command source address; if it is an out-ring baton pass command,
Branching to step 7, based on the destination address of the command, zeros the corresponding bit in the station live list SLL.

After each of these processes, it is determined in step 8 whether the baton pass command is addressed to the own station, and if it is not addressed to the own station, the process returns to step 1, and if it is addressed to the own station, the process proceeds to step 9. branch to.

In step 9, it is determined whether or not there is a request to send a command to the own station. If there is a request, the command is sent in step 10, and a response is received in step 11. If there is no command sending request, these steps are skipped.

In step 12, it is determined whether the station to which the baton is passed is abnormal based on the station live list SLL. If it is abnormal, the process branches to step 13 and sends an outside-ring baton pass command. In step 14, it is determined whether the opponent's station has successfully received the baton. If it is successful, the process returns to step 1. , if unsuccessful, branch to step 15. Note that these steps are skipped if it is determined in step 12 that the other party to whom the baton is passed is normal.

In step 15, an intra-ring baton pass command is sent to the normal station on the station live list SLL after the local station, and the process returns to step 1.

Furthermore, even if there are multiple abnormal stations between your own station and the station that is normal on the station live list SLL next to your own station, the outside-ring baton pass command can be used to execute any one of the multiple abnormal stations. When the baton is sent to the local station, the baton is sent to a different destination than the previous out-of-ring baton pass command, and the out-of-ring baton is sent to the abnormal station. The transmission of pass commands is controlled equally.

<Operation> The operation of the embodiment of the present invention configured as described above is as follows.

Communication control unit of each communication station S1 to Sn
COM is connected to the transmission line L by the program shown in Figure 5.
each communication frame is processed.

Therefore, when a station sends a baton pass command, this command is observed by all other stations, and if it is an intra-link baton pass command, the station live list corresponding to the station that sent it
Set the SLL bit to 1 to record that it is normal, and if it is a baton pass command outside the ring,
The bit in the station live list SLL corresponding to the destination address is set to 0 and an abnormality is recorded.
That is, the normality/abnormality of the station is recorded only by the baton pass command received this time.

When this baton pass command is received by the destination station, that station will eventually send out the baton pass command, so
Observing that baton pass command at all other stations updates the value of the next bit of the SLL in the station live list. In this way, each time one station sends a baton pass command, the station live list SLL is updated at the other stations, so when the baton bus goes around, the station live list SLL is updated at all stations.
The contents of SLL will be standardized.

In this way, the method of updating the station live list SLL using only the currently received baton pass command is to update the station live list by comparing the current baton pass command with the previous baton bus command, as in the conventional method. It is a much simpler procedure and requires less processing time than the previous method.

<Effects> As described above, according to the present invention, it is possible to realize a communication control method in which a list of data representing the normality/abnormality of all communication stations can be updated in a simple procedure with a short processing time.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a communication system to which the present invention is applied;
FIG. 2 is a conceptual diagram of a communication station, FIG. 3 is an example of the structure of a list, FIG. 4 is a frame structure diagram of a baton pass command, and FIG. 5 is a flow diagram showing the structure of a program according to an embodiment of the present invention. S1~Sn...Communication station, L...Transmission line, CPU...Processor, MM...Memory, IOC
...I/O control section, COM...Communication control section,
MDM...modulator/demodulator, BS...internal bus.

Claims (1)

[Claims] 1. Consisting of a plurality of communication stations connected by a broadcast transmission line, one of the plurality of communication stations can perform master operation, and its status is determined by a baton pass. The baton pass is configured to include an address of a source station, an address of a destination station, and a baton pass command, and the baton pass command of the baton pass is , two types of baton pass commands are defined: an in-ring baton pass command that instructs to circulate to a group of normal communication stations, and an outside ring baton pass command that instructs to circulate to other communication stations, and the command is applied to all communication stations. , normal/normal status for all communication stations capable of master operation.
A station live list consisting of bit patterns that indicate abnormalities is set up, and when a station performing master operation performs a baton pass to a communication station that is displayed as normal in its own station live list, it must pass the baton in the ring. When using the pass command to perform a baton pass to a communication station that is displayed as abnormal in the station live list, use the outside-ring baton pass command to pass the baton to all communication stations other than the one that is performing the master operation. The communication stations constantly monitor the batons circulating on the transmission path, and when receiving an intra-ring baton pass command, each communication station corresponds to the source address of the communication station that sent the baton in its own station live list. Set the bit to a value that means normal, and when receiving an outside-ring baton pass command, set the bit corresponding to the destination address of the baton in your own station live list to a value that means abnormal. A communication control method characterized by: