JPH0454040A - Priority data communication system in multiplex communication - Google Patents

Abstract

PURPOSE:To send information to a prescribed computer urgently when a fault of a microcomputer or a sensor takes place by outputting a voltage signal of a prescribed level from the computer for a prescribed period so as to destroy forcibly a transmission output of other computer when it is required to make communication of information urgently from the computer. CONSTITUTION:An output terminal 7 of computers 1-3 is connected to a communication bus 4 and each computer has an output circuit 6 outputting a data of a relevant computer and a level discrimination circuit 5 comparing an output valve of the said output circuit with an input value from the communication bus 4 in its inside. When a computer requires urgent transmission of information, the said computer outputs a voltage having a prescribed level for a prescribed time to destroy an output data from other computer and to interrupt the transmission function of the other computer thereby opening the communication bus 4, and the required information of the said computer is sent through the said communication bus 4 while taking precedence over the other information and the information is sent to the required computer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a priority data communication system in multiplex communication.

[Conventional technology]

The so-called multiplex communication system, in which information is serially communicated between a plurality of computers connected on a common communication line (bus), is currently commonly used in various industrial fields.

However, in the conventional multiplex communication system via computers, a priority order is determined for communication data within each computer, but a priority order is determined especially for communication data between multiple computers. Therefore, priority is given to communication of information currently being carried out.

Therefore, the data to be sent can only be sent after the current communication has finished, and even if the communication line becomes free, the data from the computer that started communication earlier will have priority. After all, conventionally, there is no priority order for communication data.

Therefore, even if it becomes necessary to send predetermined information to a predetermined computer at a time when information is being transmitted in one data communication system, it is impossible to send it urgently. Ta.

In addition, if an attempt was made to improve this drawback, it would be necessary to prepare another line, which resulted in a drawback in that the communication cost would increase significantly.

[Problems to be Solved by the Invention] The purpose of the present invention is to improve the drawbacks of the related art and to serially communicate information between multiple computers connected on a common communication line (bus). In a so-called multiplex communication system, for example, if a microcomputer malfunction or sensor malfunction occurs, a priority data communication system is provided that can urgently transmit information about the product to a predetermined computer.

(Problems to be Solved by the Invention) In order to achieve the above object, the present invention employs the following technical configuration.

In other words, in a multiplex communication system in which information is communicated between multiple computers connected on a common communication line, if it becomes necessary for each computer to urgently communicate information, the This is a priority data communication system in multiplex communication that outputs a voltage signal at a predetermined level for a predetermined period and has a function of forcibly destroying the transmission output of other computers.

[Function] In the present invention, by adopting the configuration as described above, first, a computer that needs to transmit urgent information is made to destroy output data of computers other than the computer for a predetermined period of time. A voltage signal having a certain level is output, thereby stopping the transmission functions of all computers other than the computer that needs to urgently transmit information, and then outputting the information of the computer onto the communication line. and sends that information to a predetermined computer with priority over other information.

〔Example〕

A specific example of the priority data communication system in multiplex communication according to the present invention will be described in detail with reference to the drawings.

In the priority data communication system in multiplex communication according to the present invention, as an example is shown in FIG.
, and 3 are connected, and each of the computers 1, 2.3, etc. is connected to the multiplex communication system in which information is mutually communicated between them, for example, as shown in FIG. It is possible to take a circuit configuration as shown.

That is, the output terminals 7 of the computers 1 to 3 are connected to the communication bus 4, and each computer has an output circuit 6 that outputs the data of the computer, an output value of the output circuit, and a human power value from the communication bus 4. It has a built-in level judgment circuit 5 for comparing the levels.

The level determination circuit 5 outputs data used by a computer having the circuit and data outputted by another computer,
It has a function of comparing the data on the communication bus 4 to which the computer is connected and, for example, stopping the output of the computer if the two data are different.

Further, each of the computers 1 to 3 in the present invention fixes its output to a predetermined voltage level for a predetermined period when it becomes necessary to urgently transmit specific data in the computer to another computer. It has an emergency transmission instruction circuit 8 that can transmit a signal from the output terminal 7 of the computer to the communication bus 4 when an emergency transmission is necessary. A voltage having a certain level can be applied.

In the present invention, when it is necessary to urgently transmit information from a computer, output data of other computers can be destroyed by causing the computer to output voltage at a predetermined level for a predetermined time as described above. ,
By interrupting the transmission function of the computer, the communication bus 4 is freed up, and the necessary information of the computer can be placed on the communication bus 4 with priority over other information, and the information can be sent to the necessary computers. be.

In this case, the voltage having a predetermined level output from the computer is determined by the characteristics of the computer used, but if any computer used in the present invention is activated at a negative voltage level. If the voltage is easily active, it is preferable that the voltage having the predetermined level be an L level voltage, and conversely, if it is likely to become active at a positive voltage level, it is preferably an H level voltage.

Furthermore, in the present invention, the output time of the output and transmission instruction voltage outputted from the computer is not particularly limited, but the transmission output of all the computers connected to the communication lotus 4 is transmitted from the computer. It is sufficient that the time is sufficient for the device to be destroyed by the output command voltage, and if the basic structure of the data used in the multiplex communication is 8 bits, at least 8 bits of data will be transmitted. You can take as much time as necessary.

To explain the operation of the priority data communication system in multiplex communication according to the present invention, first, when normal transmission is performed in the priority data communication system in multiplex communication having the configuration as shown in FIG. Suppose that it becomes necessary to send data from computer l to computer.

It is assumed that all computers used in the multiplex communication system of FIG. 1 become active with negative input voltages.

Therefore, it is assumed that the computer is configured so that when an L level voltage is applied to the communication bus 4, the transmitted data is destroyed and transmission is stopped.

As shown in FIG. 2, the computer 2 is currently executing a predetermined communication, and the information waveform thereof is shown in FIG. 2B.

Therefore, the output waveform of the computer 2 appears as it is on the communication bus 4, as shown in FIG. 2C.

Therefore, if computer l requires urgent transmission at time TI, as can be seen from the waveform in Figure 2A,
The computer 1 had been outputting an H-level voltage until then, but at time TI it switches to an L-level voltage and maintains the L-level voltage for a predetermined period, that is, from time TI to T3.

On the other hand, the output of computer 2 becomes H level at time TI, but as mentioned above, the voltage level on communication bus 4 is L level, so the transmission output of computer 2 should originally be at L level at time T2. However, since such data will be destroyed, the computer 2 will stop transmitting after time T2. In other words, after time T2, it cannot reach the L level and continues to be at the H level.

Also, at time T3, it can be determined that the transmission output of the computer 2 has already been destroyed, so the output of the computer 1 is returned to the level, but at that time the communication bus 4 has already been cleared for flourishing and transmission. It is in a state of being

Therefore, at time T4 after a predetermined period of time has elapsed, a priority data communication system in multiplex communication can be implemented by outputting the necessary information data from the computer 1 with priority over the communication data from the computer 2.

The waveform for performing such emergency communication is as shown in FIG. 2C.

Flowcharts for executing the priority data communication system in multiplex communication according to the present invention are shown in FIGS. 3A and 3.
Shown in Figure B.

That is, when the computer 1 urgently needs to communicate, it sets its output to L level and maintains the voltage level for a predetermined period, for example, for l clocks, and then ( Step b) Return the output to H level once to create a standby time. Step C) Check the voltage level of the communication bus. (Step d) If the voltage level is H level, execute emergency transmission in Step e. do.

If the voltage level is not at the H level in step d, the process returns to step a and repeats the above routine.

In addition, the computer 2 executes normal data transmission in step f, and in step g, compares the voltage level of the human power, that is, the communication bus, and the output of the computer 2. , return to step f,
If they are not the same, proceed to step h and stop transmitting the data.

Above, an example of a system using two computers has been described as a specific example of the priority data communication system in multiplex communication related to the present invention, but the present invention may also use a plurality of computers as described above. It goes without saying that it is a thing, and even in that case,
It is clear that the method of operation of the system can be implemented simply by developing the example described above.

Further, even if the emergency communication circuit 8 is used also as the output circuit 6, the above contents can be implemented.

〔effect〕

Since the priority data communication system in multiplex communication according to the present invention has the above-mentioned technical configuration, information is serially communicated between multiple computers connected on a common communication line (bus). In this case, if a microcomputer or sensor abnormality occurs, a priority data communication system can be obtained that can easily and urgently transmit the information to a designated computer without complicating the system. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a specific example of a priority data communication system in multiplex communication according to the present invention. FIG. 2 is a timing chart in the priority data communication system shown in FIG. FIGS. 3A and 3B are flowcharts illustrating the operation of the priority data communication system in accordance with the present invention. 1. 4- ・ 6-... Computer 2, 3 Communication bus level judgment circuit Output circuit/output terminal prosperity, transmission instruction circuit Figure 1 In Figure 1? FIG. 2 is a diagram showing a timing chart for implementing the computer 1, computer 2, and FIG. 3 is a flowchart for carrying out the present invention.

Claims (1)

[Claims] In a multiplex communication system in which information is communicated between multiple computers connected on a common communication line, if each computer urgently needs to communicate information, the computer sends a predetermined message to each computer. 1. A priority data communication system for multiplex communication, characterized in that it has a function of outputting a level voltage signal for a predetermined period and forcibly destroying the transmission output of other computers.