JPH0544860B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a transmission right control system that can improve the efficiency of data transmission in a plurality of end devices connected in a multipoint format to a host device.

(b) Technical Background With the development of information processing technology, many systems for transmitting data through communication lines have come into practical use, and various methods have been studied and implemented.
Further, as a form of such communication, a method that is classified according to the direction of data flow and the method of controlling time has been put into practical use.

Furthermore, the basic functions of the data transmission control procedure to efficiently and reliably transfer data from the sending side to the receiving side via the communication line are as follows: The purpose of this system is to establish and dissolve a data link between a device (called a transmitting station) and a receiving station (the device on the side that receives data is also called a receiving station), and to ensure the integrity of the data being transferred.

The data communication connection that is logically established after the physical data transmission path, that is, the communication line connection is completed, is called a data link.Actual data transmission is performed through the established data link, and any data that occurs during this time is Recovery from abnormal conditions is guaranteed by the transmission control procedure.

There are various methods for determining which of the two opposing stations has control responsibility regarding the establishment and release of data links and recovery from abnormal conditions. One of these is high-level data link control. A procedure (hereinafter referred to as the HDLC procedure) was developed and standardized.

The HDLC procedure was developed in response to the development of data communication systems into network-like configurations via communication control processing devices, which required a hierarchical configuration of the communication control system. Among the hierarchical communication control functions, It is a part dedicated only to data transfer between two stations facing each other via a line, and is independent of functions related to applications and relay retransmission.

As information processing technology develops and more complex and sophisticated data communication systems are put into practical use,
In a system that uses HDLC procedures for a multi-point line system, which is one of the system methods,
Furthermore, there was a demand for the development of a more efficient data transfer method.

(c) Prior art and problems Next, as a conventional technology, we will discuss the conventional method of controlling transmission rights when data transfer is controlled using the HDLC procedure in a multi-point connected system.
This will be explained with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a multi-point connected system, and FIG. 2 shows a data transfer control situation.

In the figure, 1 is the upper station (controller), 2
indicates each line. Also, a to n are data terminal stations, are general polling signals (hereinafter referred to as GP signals), , are data signals, are receive ready signals (hereinafter referred to as RR signals), and 1 are control signals on the upper station (controller) 1 side. Output status, 2
indicates the signal output status of the data terminal stations a to n, symbol indicates the output signal from the intermediate station (data terminal station a to n-1), and F indicates the signal output from the final terminal n, respectively. In addition, the data shown in Figure 2
F" indicates data transmission from the intermediate stations (data terminal stations a to n-1), and "RR.F" indicates a response signal to the GP signal from the final station n, respectively.

As shown in FIG. 1, when data terminal stations a to n are multi-point connected to an upper station (controller) 1 via a line 2, the data terminal station n becomes the final station of this line 2. When this connection is established, when a GP signal (a signal that inquires all data terminal stations a to n connected to line 2 and prompts them to send data) is issued from the upper station (controller) 1, the final The data terminal station n must always send back a response signal (if there is no data to be transmitted from the final station n, it outputs "RR signal F", and if there is data to be transmitted, it outputs it as "data F"). There is.

For example, as shown in FIG.
Even if there is data to be transmitted only in terminal b and there is no data in the final data terminal station n, the data terminal station n always returns the "RR signal F" which is a response signal to the GP signal. In this way, "RR" issued when there is no data to be transmitted at the final data terminal station n
There was a problem in that the "signal F" caused a drop in data transmission efficiency and was undesirable in terms of data communication control procedures.

(d) Purpose of the invention The present invention provides a new transmitter control method that solves the above problems, and in particular realizes a transmission right control method that can further improve the data transmission efficiency of the system. The purpose is to

(e) Structure of the Invention According to the present invention, in a system in which a plurality of terminal devices are connected to a host device in a multipoint format, and each terminal device transfers data to the host device, A transfer data presence/absence read from a downstream terminal device to a preceding terminal device in the data transmission order of each terminal device in response to general polling from a host device is provided, as well as a transfer data presence/absence read from the own terminal device and the carrier data presence/absence read. Each of the terminal devices is provided with a final station determining means for determining that the terminal device is the final station based on the presence or absence of transfer data from the downstream terminal device notified via the terminal device, If the final station determining means determines that there is data to be transferred and there is no data to be transferred from the subsequent terminal device, the terminal device transmits its own data along with data indicating that the terminal device is the final responding terminal device. This is achieved by a transmission right control device characterized by transmitting data.

(f) Examples of the invention The present invention will be explained below with reference to the drawings.

FIG. 3 shows an embodiment of the transmission right control system according to the present invention, and FIG. 4 shows a data transmission situation according to the present invention.

In the figure, 3 and 6 are NOT circuits, 4 and 7 are NAND circuits (hereinafter referred to as NAND circuits), and 5 and 8 are NAND circuits.
indicate the final game decision section, respectively. In addition, Figures 1 and 2
The same symbols as in the figure indicate the same contents, or the transmission data presence/absence signal output from the subsequent station to the previous station, the transmission data presence/absence signal at the own station, and the data terminal station c
The output data and "data F" respectively indicate the final station data. Note that "0" is a symbol indicating that data is present, and "1" is a symbol indicating that there is no data.

This embodiment provides data terminal stations a to n with a function (final station determination unit 5,
8), in which the NAND circuits 3, 6, and 6 invert the states of the output signals from the NAND circuits 4, 7.
A NAND circuit 4 that outputs “0” only when the data presence/absence signal is “1” and the data presence/absence signal is “1”;
7. Final station determination units 5 and 8 that determine whether the local station is the final station based on the output states of the negative circuits 3 and 6
It consists of

Note that in the data terminal station a in the system shown in FIG. 1, the lee that sends the data presence/absence signal is not connected because there is no previous station. Furthermore, since there is no subsequent station at data terminal station n, the data presence/absence signal is always set to "1".

Next, the operation of this embodiment will be explained based on FIG. 4. In this embodiment, there is data to be transmitted to data terminal stations b and c, and data terminal station n, which is the final station,
The operation when there is no data to be sent will be explained.

A GP signal command is issued from a host device (controller) 1 to data terminal stations a to n via a line 2. This GP signal causes data terminal stations with data to be moved to the upstream side, that is, station a, station b, ... n
Responses are returned in the order of the stations.

In this embodiment, first, data terminal station b determines that its own data presence/absence signal is "0" and the data presence/absence signal of the subsequent station is "0", so that the final station determining unit 5 determines that the data terminal station b is an intermediate station. , and sends the “data” signal to the upper station (controller) 1 using HDLC.
Output through the steps.

Next, the data terminal station c determines that the data terminal station c is the final station by the final station determination unit 8, since the data presence/absence signal of the own station is "0" and the data presence/absence signal of the downstream station is "1". Then, the "data F" signal is output through the HDLC procedure with the upper station (controller) 1, the operation in response to the GP signal command from the upper station (controller) 1 is completed, and the process moves to the next job.

(g) Effects of the Invention According to the present invention as described above, it is possible to provide a transmission right control method that can further improve the data transmission efficiency of the system.

[Brief explanation of the drawing]

Fig. 1 is a system configuration diagram with multi-point connections, Fig. 2 is a data transfer control situation, Fig. 3 is an embodiment of the transmission right control method according to the present invention, and Fig. 4 is a data transmission situation according to the present invention. are shown respectively. In the figure, 1 is the upper station (controller), 2
3 and 6 are inverting circuits, 4 and 7 are NAND circuits, and 5 and 8 are final station determination units, respectively.

Claims (1)

[Scope of Claims] 1. In a system in which a plurality of terminal devices are connected to a host device in a multipoint format, and each terminal device transfers data to the host device, each of the above-mentioned terminal devices in response to general polling from the host device A transfer data presence/absence read from a downstream terminal device to a preceding terminal device in the data transmission order of the terminal device is provided, and a transfer data presence/absence read from the own terminal device and the downstream information notified via the transfer data presence/absence read are provided. Each of the terminal devices is provided with a final station determining means for determining whether the terminal device is the final station based on the presence or absence of data transferred from the terminal device, and the terminal device has data to be transferred and the downstream station If the final station determining means determines that there is no data to be transferred from the terminal device, the terminal device transmits its own transmission data together with data indicating that the terminal device is the final responding terminal device. Transmission right control device.