JPS6253043A - Data communication control method - Google Patents

Abstract

PURPOSE:To control a data link even a primary station is at fault by allowing each primary station on a data link to set in internal timer every time a data from an opposed primary station is received and establishing the synchronization with respect to the data transmission by the said resetting. CONSTITUTION:The primary stations 1, 2 exist on the data link 8 and >=1 secondary station 3 is connected to them. Further, timers 6, 7 and CPUs 4, 5 controlling the timers and data transmission exist in the stations 1, 2. When the timer 6 in the station 1 applies triggering to the CPU 4, the CPU 4 resets Tsec to the timer 6 and starts transmitting a synchronizing data to the data link 8. When the station 2 confirms the data from the station 1, the timer 7 is set to T/2sec. Thus, since the sending of the station 2 is started after T/2sec from the point of time, the station 1 applied transfer control as the primary station during the time.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a control method for controlling transfer of one or more secondary stations on the same data link by two primary stations. .

[Conventional technology]

Conventionally, when a primary station having means for activating transfer control and one or more secondary stations controlled by this primary station are set on one common data link, Only one primary station was allowed.

[Problem that the invention seeks to solve]

In conventional data communication control methods, if two primary stations are set up on one common data link, if both primary stations send transfer control data at the same time, a data collision will occur and normal data transmission will not be possible. Therefore, only one primary station is allowed on the same data link.

However, this case has the disadvantage that if a failure occurs in the primary station, data from each station on the data link cannot be collected from anywhere, and control is no longer possible.

[Means for solving problems]

In order to eliminate such drawbacks, the present invention provides a data communications system comprising two primaries with activation means and time management means and one or more secondary stations controlled by this primary. In a communication control method, each primary station on a data link resets an internal timer each time it receives data from the opposing next station, and by resetting the internal timer, synchronization regarding data transmission between both primary stations is achieved. is established, and based on this established synchronization, control matters are exchanged in a time-sharing manner, and transfer control is performed from both of the two primary sides.

[Effect]

In the present invention, even if two primary stations are set up on a data link, synchronization regarding data transmission can be easily established between both primary stations, and data can be transferred from the two primary stations by exchanging control items in a time-sharing manner. can be controlled.

[Embodiment] A data communication system for explaining an embodiment of the data communication control method according to the present invention is shown in the figure.

In the figure, 1 and 2 are primary sides, 3 is a secondary station, 4.5 is a CPLI as a starting means, 6.7 is a timer as a time management means, and 8 is one common data link.

There are primary stations 1 and 2 at each end of one data link 8, and one or more secondary stations 3 are connected to this data link 8, although only one is shown in the figure. In addition, on both primary sides 1.2, there is a timer 6.7 used for control time management and a CPU that controls the timer and data transfer.
There are 4 and 5.

Here, the timer has a function of triggering the CPU after a predetermined time of 1 second when a predetermined time is set by the CPU.

When the timer 6 in the primary station 1 triggers the CPU 4, the CPU 4 resets the timer 6 to 1 second and starts transmitting synchronization data to the data link 8. When the primary side 2 receives the synchronization data link from the primary station 1 and confirms that the data is from the primary side 1, it sets the timer 7 in its own station to T/2 seconds. Therefore, since the primary station 2 starts transmitting T/2 seconds after this point, the primary station 1 can perform transfer control as the only primary side on this data link during that time.

The above operation is the same in the opposite direction. That is, even when the primary station 2 sends synchronization data, the primary station 1 receives the synchronization data from the primary side 2 and starts the timer 6 in its own station.
Set to T/2 seconds.

In this way, the primary stations 1 and 2 divide the fixed time period T seconds into two, and use the data link 8 in a time-sharing manner.

Therefore, even if a failure occurs in one of the primary sides, for example, primary side 2, and transmission cannot be performed, the primary station 1 can maintain a data link because the timer 6 continues to trigger the CPU 4 every T seconds for a certain period of time. The transfer control will be repeated for 8.

〔Effect of the invention〕

As explained above, the present invention provides a data communication control method in a data communication system comprising two primary sides having a starting means and a time management means and one or more secondary stations controlled by the primary side. , each primary station on the data link re-centres its internal timer each time it receives data from the opposing primary side, and by re-centring the internal timer, synchronization regarding data transmission between both primary stations is established. By exchanging control items in a time-sharing manner through established synchronization and controlling transfer from both primary sides, even if a failure occurs on one primary side, the data link can be maintained by the remaining primary side. It has the effect of controlling the

[Brief explanation of drawings]

The figure is a system diagram showing an embodiment of the data communication control method according to the present invention. 1.2...Primary station, 3...Secondary station, 4.5...
...CPU, 6.7...Timer, 8...Data link.

Claims (1)

[Claims] Two primary stations having activation means for activating transfer control 1 on one data link and time management means for time management of control 1, and one or more secondary stations controlled by the primary station. In the data communication control method in a data communication system with A data communication control method, characterized in that synchronization regarding data transmission between stations is established, and based on the established synchronization, control items are exchanged in a time-sharing manner, and transfer control is performed from both of the two primary stations.