JPH0364227A - Data communication system using high level data link control procedure - Google Patents

Abstract

PURPOSE:To attain the direct transfer of data to a desired communication station with no intervention of another communication station by enabling each communication state to exchange the functions between the primary and secondary stations as necessary. CONSTITUTION:The communication stations 2a-2c defined as the secondary stations send a function switch request to a primary communication station 1 via a switching request means 6 of a secondary control means 5 when the transfer of data is required to other secondary communication stations. Then the means 5 is switched to a main control means 4 via a switch means 7 in accordance with a response received from the means 4 of the station 1. Then the station 1 is turned into a secondary station after the means 4 is switched to the means 5 by the means 7. Thus each communication station can switch the functions between the primary and secondary stations as necessary and can perform the direct transfer of data to a desired station with no intervention of another station (primary station).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data communication system using a high-level data link controller J@ (hereinafter referred to as HDLC) having a multi-point configuration.

[Conventional technology]

FIG. 5 is a block diagram showing a data communication system using a conventional HD LC as shown in, for example, Japanese Industrial Standard (JIS) X5106. In the figure, reference numeral 1 denotes a primary station as a communication station that controls data links and has full responsibility for error control and recovery at the link level. 2
Secondary stations a to 2c are communication stations that execute data link control functions according to instructions from the primary station 1. Further, 3 is a communication line connecting these primary stations 1 and each secondary station 2 (general term for 2a to 2c, the same applies hereinafter). 4 is the above l
A main control means 5 is disposed in each of the secondary stations 2 and is disposed in the next station 1 and has a built-in transmission counter and a reception counter (not shown) to realize the function of the primary station, Similarly, it is a sub-control means that incorporates a transmission counter and a reception counter (not shown) and realizes the function of the secondary station.

Further, FIG. 4 is an explanatory diagram showing the structure of a frame transmitted in such a data communication system using HDLCt. In the figure, 11 is an 8-bit flag section that transmits a flag indicating a frame break, 12 is an 8-bit address section that transmits address information, 13 is an 8-bit control section that transmits control information, and 14 15 is an arbitrary bit information section for transmitting communication data, and 15 is a 16-bit Fe2 (7 frame check sequence) section for transmitting information for error control. This frame is the control unit 13
(hereinafter, P when it is on; P when it is off)
) and final bit (hereinafter referred to as F when on)
, when off, it is written as F) to request a response/
A distinction is made between non-requests and response completion/non-completion.

Next, the operation will be explained. Here, FIG. 6 is a sequence diagram showing the communication state in this data communication system,
FIG. 7 is a sequence diagram showing the exchange of data between secondary stations. The primary station 1 polls each secondary station 2 at a predetermined period determined by the system to confirm the normality of the data link. That is,
As shown in FIG. 6, the primary station 1 sequentially transmits the P command p that turns on the ball bit to the target secondary station 2, and the final bit is sent from the corresponding secondary station 2. When it receives the turned-on F-Renbonsr, it is determined that the data link is normal. However, if the F response r to the sent P command p is not returned within a predetermined time, the P
If the command p is retransmitted and the F response r is not returned even after repeating the retransmission of the P command p a predetermined number of times, it is determined that the link is broken and a recovery process is executed.

At this time, if there is data to be sent from primary station 1 to secondary station 2,
It is placed on the information part 14 of the frame shown in FIG. 4 and transmitted together with the P command p, or it is transmitted in a P frame before the P command p. Similarly, the data from the secondary station 2 to the primary station 1 is transferred to the information section 14, and the F response r
Sent with However, this data is transmitted by the primary station 1 to P.
It is also possible to transmit and receive P frames or F frames between the time when the command p is transmitted and the time when the secondary station 2 transmits the F response r.

Here, for example, if the secondary station 2c wants to transmit data to the secondary stations 2b> and 2a, the data will be transmitted via the primary station 1.

That is, as shown by Sr2 in FIG. 7, the secondary station 2c first
When it receives the P command p sent from the primary station 1 during polling of its own station, it sends the data addressed to the secondary station 2b to the primary station 1 along with the F response r returned in response. The primary station 1 that has received this data sends the data to the secondary station 2b together with the P command p during the next polling of the secondary station 2b. In this way, data from the secondary station 2C is transmitted via the primary station 1 to the secondary station 2b. Similarly, data addressed to the secondary station 2a is transmitted to the secondary station 2a via the primary station 1, as shown by Sr1 in FIG.

[Problem to be solved by the invention]

Since the conventional data communication system using HDLC is configured as described above, when the secondary stations 2 exchange data with each other, it must go through the primary station 1, and the 2 There has been a problem in that the use efficiency of the communication line 3 decreases when communication is performed between the next stations.

This invention was made to solve the above-mentioned problems, and provides a data communication system using HDLC that can directly transmit and receive data between secondary stations without going through a primary station. The purpose is to

[Means for Solving the Problems] A data communication system using HDLC according to the present invention performs data link control on each communication station connected in a multi-point configuration to function as a primary station. A main control means for realizing the function, a sub-control means for realizing the function as a secondary station by executing control functions according to instructions from the communication station which has become the primary station, and a sub-control means disposed within the sub-control means for requesting switching of functions. It is provided with a switching requesting means and a switching means for switching between the main control means and the sub-control means.

[Effect]

When a communication station that has become a secondary station according to this invention needs to send data to another communication station that is also a secondary station,
The switching request means in the sub-control means sends a request for switching functions to the communication station that has become the primary station, and in accordance with the response from the main control means of the communication station that has received the request, the communication station has become the primary station. When the communication station which had become the 11th station which is the primary station by switching the sub-control means to the main control means by the switching means receives the above-mentioned request, the communication station switches the main control means to the sub-control means by the switching means and becomes the secondary station. By becoming a communication station, each communication station can exchange the functions of the primary station and the function of the secondary station as necessary, and exchange data directly with the target communication station without going through other communication stations. To realize a data communication system using HDLC that can send and receive data.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a primary station as a communication station, 2a to 2c
(2) is a secondary station via the communication station, 3 is a communication line, 4 is a main control means, and 5 is a sub-control means, which are the same or equivalent parts as those in the conventional system with the same reference numerals in FIG. Therefore, detailed explanation will be omitted.

Here, the main control means 4 is provided not only in the primary station 1 but also in all the secondary stations 2, and the sub control means 5 is also provided not only in each secondary station 2 but also in the primary station 1. are also provided. Cabinet,
6 is built in each of the sub-control means 5, and the 1
This is a switching requesting means for requesting the main control means 4 of the next station 1 to switch functions. T is primary station 1 and each secondary station 2
The main control means 4 of the primary station 1, or the switching requesting means 6, which is located within the main station and receiving the request from the switching requesting means 6.
is a switching means for switching between the main control means 4 and the sub-control means 5 in accordance with instructions from the sub-control means 5 of the secondary station 2 which has generated the request.

Next, the operation will be explained. Here, FIG. 2 is a sequence diagram showing the communication state in this embodiment. Now, for example, when the secondary station 2c transmits data to the secondary stations 2a and 2b, the secondary station 2C will, when polling its own station,
As shown by STI in FIG. 2, the switching requesting means 6 requests the primary station 1 to switch between the j21 and secondary station functions. FIG. 3 shows the procedure for exchanging the primary station function and secondary station function. In other words, when polling your own station, primary station 1
P command without data sent by someone (RR-P)
Upon receiving the request, the sub-control means 5 of the secondary station 2c sends back to the primary station 1 a request command (UI-F) indicating that it wants to change to the primary station, in accordance with the request generated by the switching request means 6.

Upon receiving this request command (UI-F), the main control means 4 of the primary station 1 issues a current mode termination/disconnection command (DISC-P).
) is transmitted to the secondary station 2c, and upon receiving it, the sub-control means 5 of the secondary station 2c sends an acknowledgment response (UA-F) back to the primary station 1. Upon receiving this reception confirmation response (UI-F), the main control means 4 of the primary station 1 issues a permission command (UI-P
) and at the same time instructs the switching means 7 to perform a switching operation.

By this switching operation of the switching means T, the primary station 1 switches the main control means 4 to the sub control means 5. Further, the sub-control means 5 of the secondary station 2C which has received the permission command (UI-P) instructs the switching means T to perform a switching operation, and also sends reception confirmation and response completion (RR-F) to the primary station 1. Send it back. In the secondary station 2c, the sub control means 5 is switched to the main control means 4 by the operation of the switching means 7. In this way, the functions of the primary station 1 and the secondary station 2c are exchanged with the secondary station function and the primary station function, respectively.

Thereafter, the secondary station 2c starts polling the primary station 1 and the secondary stations 2a*2b at a period determined by the system. Then, when transmitting data to the secondary station 2a,
As shown at ST2 in FIG. 2, data addressed to the secondary station 2a is transmitted together with the P command p when polling the secondary station 2a. As a result, data from the secondary station 2c is directly transmitted to the secondary station 2a. Further, data addressed to the secondary station 2b is similarly transmitted directly to the secondary station 2b (by the secondary station 2C, as indicated by ST3 in FIG. 2).

In order for primary station 1 to return to the primary station function, primary station 1 must
Perform the same steps as above when polling for
The main control means 4 and the sub-control means 5 are switched between the primary station 1 and the secondary station 2c.

〔Effect of the invention〕

As described above, according to the present invention, the function of the primary station and the function of the secondary station can be exchanged as needed in response to a request from the communication station serving as the secondary station. The advantage of a data communication system using HDLC is that it is possible to send and receive data directly to and from the target communication station without going through other communication stations, and the communication line is not wasted. There is.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a data communication system using HDLC according to an embodiment of the present invention, Fig. 2 is a sequence diagram showing its communication status, and Fig. 3 shows its primary station function and two.
Sequence diagram showing the procedure for replacing the next station function, Figure 4 is for HD
An explanatory diagram showing the structure of a frame transmitted in a communication system using LC, FIG. 5 is a block diagram showing a conventional data communication system using HDLC, FIG. 6 is a sequence diagram showing the communication state, and FIG. FIG. 7 is a sequence diagram showing the exchange of data between the secondary stations. 1 is a communication station (primary station), 2a to 2C are communication stations (secondary station)
, 3 is a communication line, 4 is a main control means, 5 is a sub-control means, 6
7 is a switching request means, and 7 is a switching means. In the figures, the same symbols indicate the same or equivalent parts.

Claims (1)

[Claims] One of the plurality of communication stations connected in a multi-point configuration is designated as the primary station that controls the data link, and the others are designated as the primary station that controls the data link.
In a data communication system using a high-level data link control procedure in which a secondary station executes a control function according to instructions from a communication station that has become a next station, each of the communication stations controls the data link, a main control means for realizing the function as the primary station; a sub-control means for realizing the function as the secondary station by executing a control function according to instructions from the communication station which has become the primary station; a switching requesting means disposed in the sub-controlling means and requesting the main control means of the communication station which has become the primary station to switch functions; and the main control means receiving a request from the switching requesting means; Alternatively, the high-level data link control procedure is characterized by comprising a switching means for switching between the main control means and the sub-control means in accordance with an instruction from the sub-control means which has issued a request from the switching request means. Data communication system used.