JPS61222343A - Data communication equipment - Google Patents

Abstract

PURPOSE:To prevent reduction in the communication speed by comparing a priority data in a transmission request data desired to be sent with a priority data of a communication data sent already on a transmission line and sending the data only when the priority data of the communication request data is larger. CONSTITUTION:The communication request data are stored in data storage means 1a-1n in a data communication device C. A priority comparison means 2 compares the data stored in the means 1a-1n and the largest priority data among the priority data compared by the means 2 is stored in a priority storage means 3. A priority comparison means 4 compares the data sent already on a transmission line L with the priority data stored in the means 3, and when the priority data stored in the means 3 is larger, a switch 5 is thrown to the position P2 to send the data with high priority.

Description

Detailed Description of the Invention [Technical Field of the Invention 1] The present invention relates to a data communication device that is connected to, for example, a slotted ring type transmission line and that sends communication request data to which priority data indicating processing priority is added. Regarding.

[Technical background of the invention and its problems] In general, communication systems for local areas can be roughly divided into bus network systems and loop network systems, and the slotted ring system is one of the loop network systems. There is.

The slotted ring system is configured such that time slots of a certain fixed length are moved at high speed in a certain direction on the ring, communication request data is placed in these time slots by a data communication device, and the data is retrieved at the destination. Furthermore, the slotted ring method includes a method in which each communication request data is allocated to a time slot in a fixed manner;
There is a method in which multiple pieces of communication request data occupy a single time slot without fixing the allocation, but in the former method, if there is a large amount of communication request data with low communication frequency, unused time slots increase and the transmission path There is a problem that the usage efficiency of the system decreases.

Therefore, a method has been proposed in which priority data indicating processing priority is given to each communication request data, so that a request with a high priority has the right to use a time slot, but according to this method, one communication request data Once the right to use one of the time slots is obtained, the allocated time slot will be monopolized until the communication is completed. There was an inconvenience that the communication request data was forced to wait.

A delayed insertion method was proposed to solve this problem.

In this method, each data communication device that sends communication request data has a shift register that bypasses the communication request data, and when the data communication device wants to send communication request data, the communication data that has already been sent out on the transmission path is In this method, the shift register is bypassed in synchronization with the communication speed, and the communication request data to be sent is placed on the transmission path during that time.

After the communication request data is placed on the transmission path, the shift register is regarded as a part of the original transmission path, and the bypassed communication request data is returned to the transmission path.

However, according to this method, if the shift register that bypasses the communication request data is empty or available, the data communication device can send the communication request data at any time, but if the shift register is not empty, the transmission It is no longer possible to extend the road, and as with the method described above,
A problem arises in that communication request data with a higher priority is forced to wait. In addition, if the length of the bypass shift register is increased each time the need arises, the transmission path will become longer one after another, resulting in a problem of lowering the overall communication speed.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional circumstances. For example, in a data communication device connected to a slotted ring type transmission path, communication request data with a high priority is prevented from unnecessary waiting. The object of the present invention is to provide a data communication device that performs processing without being forced to do so and does not reduce communication speed.

[Summary of the Invention] That is, a data communication device of the present invention is a data communication device that is connected to a predetermined transmission path and sends out communication request data to which priority data indicating processing priority is added. a storage means for storing communication request data; a comparison means for comparing priority data of the communication request data to be sent with priority data of already sent communication data already sent out on the transmission path; If the priority data of any of the stored communication request data has a higher processing priority than the priority data of the already sent communication data, the already sent communication data is taken into the storage means, and the storage means The apparatus is characterized by comprising an input/output means for transmitting communication request data having a high processing priority stored in the transmission line onto the transmission path.

[Embodiments of the invention] DESCRIPTION OF THE PREFERRED EMBODIMENTS Details of embodiments of the present invention will be described below with reference to the drawings.

The drawing is a block diagram showing the configuration of an embodiment of a data communication device of the present invention.

In the figure, L is a slotted ring type transmission path in which a plurality of time slots move cyclically at high speed, and C is a data communication device of this embodiment.

The data communication device C of this embodiment includes data storage means 18 to 1n for storing a plurality of pieces of communication request data to be sent, a priority storage means 2 for comparing priority data of these communication request data to be sent, and Priority storage means 3 that stores priority data with the highest processing priority among priority data of communication request data to be sent, and priority data stored in priority storage means 3 and other data communication devices A device consisting of a priority comparison means 4 for comparing priority data of communication data sent from a source onto a transmission path, and switches 5 to 7 to be described later.Next, the operation of the data communication device of this embodiment will be explained. explain.

First, each time slot on the transmission path contains already transmitted communication data that has already been transmitted from another data communication device.

On the other hand, communication request data to be sent by the data communication device flc is stored in data storage means 1a to 1n.

Furthermore, the priority comparison means 2 compares the priority data of each of the communication request data stored in the data storage means 18 to 1n, and the priority data compared in the priority comparison means 2 is stored in the priority storage means 3. Among them, the priority data with the highest processing priority is saved.

The priority comparing means 4 then compares the already sent communication data already in the time slot on the transmission path with the priority data stored in the priority storage means 3, and determines the processing priority of the already sent communication data. is large, the control signal S1
The switch 5 is connected to the R1 side, and the already sent communication data is passed through as is.

On the contrary, if the priority data of the already sent communication data is smaller than the priority data stored in the priority storage means 3, the switch 5 is connected to the Pz side. Prior to this, the priority comparison means 2 compares the priority data of the communication request data stored in the data storage means 1a to 1n and stores the priority data with the highest processing priority into the priority storage means 3. At this time, the control signal S2 causes the switch 6 to be moved to the data storage means 1 in which the communication request data to which the priority data with the highest processing priority is stored is stored.
Connect to any one of a to 1n (terminal QI=03).

Therefore, the priority comparing means 4 connects the switch 5 to R2 by means of the control signal S1, and connects the switch 5 to R2 by means of the control signal S3.
When connected to R1, the communication request data with the highest processing priority among the communication request data to be sent in the data communication device IC is sent out onto the transmission path, while the communication data that has already been sent out on the transmission path is added to the string of communication request data to be sent inputted from the system connected to the data communication device C, and written to any one of the data storage means 1a to 1n.

In other words, the previously sent communication data is intercepted from the time slot on the transmission path, and the communication request data with the highest processing priority is placed in the empty time slot.

According to the data communication device C of this embodiment, even if communication data has already been placed in a time slot on the transmission path by another data communication device, the communication request data to be sent is the same as the already sent communication data. If the processing priority is higher than that, the data can be sent in a time slot-preempted form, and the already-sent communication data that has been preempted from the time slot is treated the same as the communication request data to be sent from the data communication device IC. Therefore, there is no risk of damaging the contents of communication data that has already been sent out.

Note that if the communication request data is written to the data storage means 1a to 1n every predetermined unit time, the hold time of already sent communication data will not exceed the predetermined unit time, so that other data communication devices can be There is no risk of any major hindrance to the request.

In the embodiment described above, the priority comparison means 2 compares the priority data of the communication request data stored in the data storage means 18 to 1n in advance, and the highest priority data is stored in the priority storage means 3. The priority comparison means 4 compares the stored priority data with the priority data of the already transmitted communication data. However, in the case of a system where the time slot circulation speed is relatively slow, for example, the As shown in FIG. 2, the two priority comparison means 2.4 are combined into one priority comparison means 8, and this priority comparison means 8 compares the communication request data stored in the data storage means 1a to 1n. It is also possible to sequentially compare the priority data of the communication data and the priority data of the already sent communication data.

[Effects of the Invention] As explained above, according to the data communication device of the present invention,
If the priority data of the communication request data to be sent is higher than the priority of communication data already sent from another data communication device, the time slot can be intercepted and sent, so the priority data of the entire system is Data with a high communication request is processed preferentially, and the communication speed does not decrease.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the structure of one embodiment of the invention, and FIG. 2 is a block diagram showing the structure of another embodiment of the invention.

Claims (1)

[Claims] (1) In a data communication device that is connected to a predetermined transmission path and sends communication request data to which priority data indicating processing priority is added, a storage means for storing a plurality of pieces of communication request data to be sent; Comparing means for comparing priority data of communication request data to be transmitted with priority data of already transmitted communication data already transmitted on the transmission path; If the priority data has a higher processing priority than the priority data of the already sent communication data, the already sent communication data is taken into the storage means and the communication stored in the storage means has a higher processing priority. A data communication device comprising: input/output means for sending request data onto the transmission path.