JPH05108848A - Data transmission system - Google Patents

Abstract

PURPOSE:To continuously receive data from a lower rank device by transmitting the data in a long cycle without temporarily stopping the data transmission of the lower ranke device even when a processing load ratio at a host device side is large. CONSTITUTION:When the change of state is generated at a lower rank device 2, and it is necessary to transmit the change of state transmission data to a host device 10, the change of state transmission data are transmitted from the lower rank device 2 to the host device 10. When the load ratio of the CPU of the host device 10 is beyond a normal value by the data processing, the host device 10 issues the long cycle command of the normal transmission data to the entire lower rank devices. After receiving the information, a lower rank device 1 updates the transmission cycle of the normal transmission data from T1 to T1', and the lower ranke device 2 updates that from T2 to T2', in order to operate the transmission of the normal transmission data. When the CPU load ratio of the host device 10 is less than the normal value, the host device 10 generates the information of releasing the long cycle command of the normal transmission data to the entire lower rank devices. As the result, the lower device 2 is returns to the cycle T2 in the same way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission system, and more particularly to a data transmission system in the case of performing communication between a single upper device and a plurality of lower devices.

[0002]

2. Description of the Related Art Steady transmission data composed of a single upper device and a plurality of lower devices, which are constantly transmitted at a constant cycle, and state transmission data which is not transmitted when there is no state change and is transmitted when there is a state change There is an information transmission system that transmits the above two types from a lower device to a higher device.

In such a system, if state change transmission data is generated in the lower device and the CPU load factor of the upper device exceeds a specified value due to an increase in reception processing, the upper device is busy with the lower device. When the busy state of the self-device is released, the sub-device is notified to that effect to prompt the resumption of data transmission.

Conventionally, in such a data transmission system, when state change transmission data is generated in a lower device and the CPU load factor of the upper device exceeds a specified value due to an increase in reception processing, the upper device automatically sends data to the lower device. Since the device notifies that the device is busy and temporarily stops the data transmission of the lower device, there is a disadvantage that the upper device cannot collect necessary data during this period.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a data transmission system capable of collecting necessary data from a lower device even if the CPU load factor of the upper device is large.

[0006]

According to the present invention, a plurality of lower devices and an upper device common to these lower devices are provided, and steady data is constantly transmitted from the lower device to the upper device at a constant cycle,
A data transmission system configured to transmit state change data to the higher-level device when a state change occurs in the lower-level device, wherein the higher-level device when the processing load factor in the higher-level device exceeds a specified value. Has means for notifying the lower-level device of this excess state, and the lower-level device has means for changing the transmission cycle of the stationary data to a value larger than the fixed cycle in response to the notification. A data transmission system is provided.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram of a data transmission system to which an embodiment of the present invention is applied. A plurality of lower-level devices 1 to 3 and a single higher-level device 10 common to these lower-level devices
And are provided.

Each of the lower devices 1 to 3 constantly transmits steady data to the upper device in a constant cycle, and when a change occurs in the lower device, the lower device responds to this by transmitting the lower device to the upper device. The state change data is transmitted.

FIG. 2 is a diagram showing an operation sequence example of the embodiment of the present invention. First, when there is no state change data, the lower devices 1 and 2 transmit the steady transmission data to the upper device 10 in the normal transmission periods T1 and T2, respectively.

For example, when a change occurs in the lower device 2 and it becomes necessary to transmit the change transmission data to the higher device 10, the lower device 2 transmits the change transmission data to the higher device 10. By this state change transmission data processing, the host device 10
When the CPU load factor of 1 exceeds the specified value, the upper device 10 notifies all lower devices of the instruction to lengthen the regular transmission data.

In response to this, the lower device 1 changes the transmission cycle of the steady transmission data from T1 to T1 '(T1 <T1'), and the lower device 2 changes the transmission cycle of the steady transmission data from T2 to T.
2 '(T2 <T2') is changed, and the steady transmission data is transmitted.

When the CPU load factor of the higher-level device 10 falls below a specified value, the higher-level device 10 issues a notification to all lower-level devices to cancel the instruction to lengthen the regular transmission data period. As a result, the lower device 2 also recovers to T2.

[0014]

As described above, according to the present invention, even if the processing load factor on the upper device side becomes large, the data transmission of the lower device is transmitted in a long cycle without being temporarily stopped. Therefore, there is an effect that data can be continuously received from the lower device.

[Brief description of drawings]

FIG. 1 is a block diagram of a data transmission system to which an embodiment of the present invention is applied.

FIG. 2 is a sequence diagram showing an operation of the exemplary embodiment of the present invention.

[Explanation of symbols]

 1-3 Lower device 10 Upper device

Claims (1)

[Claims] 1. A plurality of lower-level devices and an upper-level device common to these lower-level devices, wherein steady data is constantly transmitted from the lower-level device to the upper-level device at a constant cycle, and the lower-level device changes state. A data transmission system configured to transmit state change data to the higher-level device when it occurs, and when the processing load factor in the higher-level device exceeds a specified value, the higher-level device sets the excess state to the lower level. A data transmission system, comprising means for notifying a device, and the lower device having means for changing the transmission cycle of the stationary data to a value larger than the fixed cycle in response to the notification.