JPH06291748A - System for reducing collision number of times and preventing inclination for half-duplex communication - Google Patents

Abstract

PURPOSE:To reduce futile collisions and to transmit/receive transmission requests from both systems equally without inclination by informing an opposite side of the information of whether or not transmission data retained on a present system side are present in header information. CONSTITUTION:It is recognized that the side which performed a reception processing in a previous time between both systems 1 and 3 is provided with a transmission right, the header information is added to and deleted from the transmission/reception data in both systems 1 and 3 and the header information is provided with the information of whether or not the transmission data retained on the side of the present system 1 are present and informes the opposite side of it. Then, a transmission processing is executed when the side of the present system 1 is provided with the transmission right and the transmission processing is not executed or the reception processing is actively performed even when the transmission data are present on the side of the present system 1 when the side of the opposite system 3 is provided with the transmission right and it is informed that the retained transmission data are present. In such a manner, the transmission requests of both systems 1 and 3 are transmitted/ received equally without the inclination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a half-duplex communication path such as a channel or a communication line that can recognize a collision, and has a 1: 1 ratio.
In a configuration in which two systems communicate with each other, the present invention relates to a method for reducing unnecessary collisions and for transmitting and receiving transmission requests of both systems evenly and irrespective of the performance difference between both systems.

[0002]

2. Description of the Related Art In the conventional basic transmission control procedure, the mutual activation method does not consider collision prevention or reduction of the number of collisions. Due to the negotiated priority and non-priority station settings, transmission from the priority station is always prioritized.

Similarly, in the polling selection method for controlling the 1-to-n system connection, the main station performs polling and selection for a plurality of partner systems so as to prevent collision. .

The mutual activation method and the polling selection method are described on pages 11 to 14 of Software Course 16 "Online System" (published on June 20, 1987 by Shokoido Co., Ltd.). .

[0005]

In the above mutual activation method, when a collision occurs, the transmission of the system set as the priority station is prioritized, so that uniform transmission / reception cannot be performed and the collision is prevented. Since there is no workaround, there is a problem that the transmissions from both systems collide with each other in a state where transmission requests are accumulated in both systems, resulting in a performance loss due to the collision.

In the polling selection method,
Since the primary station controls all transmission / reception, there is a problem that even if transmission data is generated at the secondary station, transmission operation cannot be performed until polling arrives, and uniform transmission / reception cannot be performed.

[0007]

[Means for Solving the Problems] The above-mentioned problem is that the side that has performed the reception processing last time has the transmission right, and that the header information is added to the transmission / reception data and stays in the own system side in the header information. This is achieved by providing a means for notifying the other party of information as to whether or not there is transmission data present.

[0008]

First, only which system has the transmission right in the case of collision in the first transmission / reception is set between both systems. Further, header information is added to the transmission data before the data so that the other party can be notified whether or not there is the transmission data still remaining after the current transmission data.
Then, the data receiving side deletes the header information in front of the data and recognizes whether or not there is any transmission data remaining in the other side, and when performing transmission / reception, the transmission / reception does not collide. If it can be executed normally, the two systems recognize that the side that has executed the reception this time has the transmission right.

Then, the system having the transmission right executes the transmission, but it is notified that there is transmission data staying at the other party in the header information of the previous reception data in the system having no transmission right. If there is send data on the local side, either the send process is not performed or if the receive operation is positively performed as necessary, the system performance is improved when the send data exists on both systems. Even if there is a difference, it is possible to reduce useless collisions and to uniformly transmit and receive transmission requests from both systems without bias.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
3 and FIG.

FIG. 1 shows a block diagram of an embodiment of the present invention. FIG. 1 shows a configuration in which a local system 1 and a remote system 3 are connected by a half-duplex communication path 2 in which a collision can be recognized, and communication is performed using this half-duplex communication path 2. The local system 1 has, as a configuration related to the present invention, a host program 11, a communication control program 12, and a communication control device 13.
It is equipped with. The communication control program 12 is a program for performing half-duplex communication with a partner system via the half-duplex communication path 2 using the communication control device 13.
Then, the upper program 11 issues a data transmission / reception request to the communication control program 12 in order to perform the business processing of the system.

Further, FIG. 2 shows the communication control program 1
2 shows a flowchart of 2. The processing contents of the communication control pregram 12 will be described with reference to FIG. First, the transmission process and the reception process are repeated until the stop request of the program is instructed, and if the stop request is instructed, the process is stopped (step 101). If the stop request is not instructed, the process is repeated, and it is determined whether there is a transmission data request from the upper program 11 (step 102). If there is transmission data, the transmission process is performed, but if there is no transmission data, the reception process (step 121 and subsequent steps). Then, if the receiving side does not have the transmission right (step 103) and the receiving side is notified of the staying transmission data by the previous reception data (step 104), the reception process (step 1)
21 or later). Since it is confirmed that the transmission process is executed as described above, the header information 210 is added to the user data 220 as shown in FIG. 3 (step 105).
Next, it is determined whether or not there is transmission data that remains after the transmission data that is about to be transmitted this time (step 10
6) Then, if there is transmission data that remains, it is set to that effect in the retention transmission data presence / absence bit 211 in the header information created in step 106 (step 107).
In addition, when there is no transmission data that is staying, the fact is similarly set in the staying transmission data presence / absence bit (step 1).
08). After the header information 210 is completed as described above, the transmission process is executed (step 109). Then, it is determined whether a collision has occurred when the transmission process is executed (step 110). If a collision has occurred and the transmission side does not have the transmission right (step 111), reception processing (step 121 and subsequent steps) is performed to receive data from the communication side. However, if the user has the transmission right, the transmission process is executed again (step 112). Then, when the transmission process is completed normally, the fact that the transmission right has been transferred to the other party is recorded in the table (step 113), the process returns to the beginning again and the transmission / reception process is repeated.

In the receiving process, first, the receiving process is executed (step 121). When the reception process is completed normally, the fact that the transmission right has been transferred to the self side is recorded in the table (step 122). Then, the staying transmission data presence / absence bit 211 in the header information 210 of the reception data is determined (step 123), and if there is transmission data staying on the partner side, that fact is recorded in the table (step 124). Also, when there is no transmission data staying on the other side, that fact is recorded in the table (step 12).
5). In any case, the header information 210 of the received data is deleted and the upper program is notified (step 126).

[0014]

According to the present invention, in a structure in which two systems communicate on a one-to-one basis using a half-duplex communication path that can be recognized as a collision, the load on both systems increases and stays. In a situation where the transmission data is stationary, the number of collisions due to the transmission from both systems is reduced to reduce the performance loss. Even if there is a difference in the time until the transmission / reception processing is started, the transmission from one side can be transmitted / received evenly without being biased.

[Brief description of drawings]

FIG. 1 is a system configuration diagram to which the present invention is applied.

FIG. 2 is a flowchart of a communication control program to which the present invention is applied.

FIG. 3 is a diagram showing a format of transmission / reception data to which the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Self-system, 2 ... Half-duplex communication path, 3 ... Other system, 11 ... Higher-order program, 12 ... Communication control program, 13 ... Communication control apparatus, 101 ... Judgment whether there is a stop request, 102 ... determination as to whether or not there is transmission data on its own side, 103 ... determination as to whether or not it has transmission right on its own side, 104 ... determination as to whether or not there is transmission data retained on the other side, 105 ... transmission data Information processing for inserting header information into 106, determination as to whether or not there is transmission data that has accumulated on its own side, 107 ... processing for setting that there is transmission data that has accumulated in the header information in the transmission data, 108 that has accumulated There is no transmission data that is being set in the header information in the transmission data, 109 ... Execution of transmission processing, 110 ... Judgment of whether or not a collision occurs in the transmission processing, 111 ... Transmission right to the self side Whether there is Whether or not, 112 ... Execution of transmission processing, 113 ... Processing of recording the transmission right transferred to the other side in the table, 121 ... Execution of reception processing, 122 ... Transmission of the transmission right to the own side in the table Processing for recording, 123 ... Judgment of staying transmission data presence / absence bit in header information of received data, 124 ... Processing for setting in the table that there is transmission data staying on the other party, 125 ... Staying on the other party Processing for setting in the table that there is no transmission data that exists, 126 ... Processing for deleting header information in the reception data and passing it to the upper program, 200 ... Format of transmission / reception data, 210 ... Header information, 211 ... Presence / absence of accumulated transmission data Bit, 220 ... User data.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04L 29/12

Claims (1)

[Claims] 1. In a structure in which two systems communicate on a one-to-one basis using a half-duplex communication path capable of recognizing a collision, it is recognized that the side that has previously received processing has a transmission right between both systems. At the same time, both systems add and delete header information to the transmission / reception data, and add information to the other side to indicate whether or not there is transmission data retained in the own system side in the header information. By sending the notification, the transmission process is executed when the local system has the transmission right, but if the remote system is notified that there is transmission data that has the transmission right and remains, Even if there is transmission data on the system side, either the transmission process is not executed or the reception process is actively executed to reduce the performance loss due to unnecessary collision and to reduce the performance difference between both systems. Protection for offset and collisions reduction half-duplex communication, characterized by uniformly receive no deviation of the transmission request of both systems without straw.