JPH043702B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a data communication system using data packets.

Conventional configurations and their problems In recent years, the demand for communication between computing devices has been increasing, especially in data communication systems using microcomputers.
Particular attention will be focused on the advantages of distributed control for optimizing the computational processing power of these systems and reducing the impact of computer failures on the entire data communication equipment, and for packet switching technology as a means of improving data transmission efficiency. There is a need for an inexpensive and reliable communication system that utilizes these technologies.

FIG. 1 shows a block diagram of a conventional data communication system, where 1 is a communication medium consisting of any one or a combination of coaxial cable, optical fiber, twisted wire cable, or the like. It is. 2 is a terminator that matches the impedance of the communication medium 1, 101, 102, 10
3 is a data transmitting device that transmits a signal via the communication medium 1; 201, 202, 203 is a data receiving device that receives the signal communicated through the communication medium 1; 30
1 is a data delay device having a delay equal to the transmission delay time until the signal transmitted by the data transmitting device 101 to the communication medium 1 is received by the data receiving device 201; similarly, 302 is the data transmitting device 102 and the data receiving device 202. 303 is a data delay device having a delay equal to the transmission delay time between the data transmitting device 103 and the data receiving device 203; 401 is the data delay device 301 that is input via the data delay device 301; When a mismatch occurs between the signal from the data transmitting device 101 and the signal input from the data receiving device 201, the collision detecting device generates a collision signal, similarly to the collision detecting device 4.
02 is a data delay device 302 and a data receiving device 2
Collision detection device based on input signals from 02, 40
3 is a data delay device 303 and a data receiving device 20
Collision detection device based on input signals from 3 and 50
1, 502, 503 are collision detection devices 40, respectively.
601, 602, and 603 are data transmitting devices, respectively, for interrupting the transmission of signals to the communication medium 1 by each data transmitting device 101, 102, and 103 in response to the presence of a collision signal from 1,402, and 403; 101, 102, 103 and a utilization device that is connected to the data receiving devices 201, 202, 203 and uses signals transmitted via the communication medium 1; 901 includes the data transmitting device 101;
data receiving device 201, data delay device 301,
Stations with collision detection device 401, transmission interruption device 501, and utilization device 601, 902, 903
is also a station consisting of similar components.

The operation of the conventional data communication system configured as described above will be explained below.

First, the data transmitting device 101 detecting the communication medium 1 as a suspended cable starts transmitting information prepared by the device 601 to the communication medium 1 in response to a request from the device 601. At the same time as this transmission starts, information is also sent to the data delay device 301. Information transmitted to the communication medium 1 propagates on the communication medium 1 and arrives at the data receiving device 201 . At this time, one other station 903 may have started transmitting onto communication medium 1 due to propagation delays. In order to adjust for this special coincidence, the collision detection device 401 compares the signal transmitted by the data transmitting device 101 and the signal received by the data receiving device 201, which are input via the data delay device 301. is detected, a collision signal is generated, and the transmission interrupting device 501 responds to the existence of this collision signal to interrupt the transmission of the signal by the data transmitting device 101 to the communication medium 1. During this series of operations, the collision detection device 403 also operates on the station 903 side, and the transmission of the signal from the data transmitting device 103 to the communication medium 1 is interrupted due to the transmission interruption 503.

However, in the above configuration, the propagation delay time between the data transmitting device 101 and the data receiving device 201 of the station 901 and the propagation delay time between the data transmitting device 103 and the data receiving device 203 of the station 903 are different. , similarly, the delay times of the data delay devices 301, 302, and 303 are different from those of the station 902, so the delay times of the data delay devices 301, 302, and 303 must be set individually, and if the connection point with the communication medium 1 is changed, the settings must be reset. It has the disadvantage that it does not.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a data communication system that does not require delay time management for each station.

Structure of the Invention The data communication system of the present invention is provided with a plurality of stations each having a data transmitting device and a data receiving device for transmitting and receiving data, and each station is connected to a common communication medium, and each station has its own station. a recognition signal transmitter that transmits to the communication medium a recognition signal obtained by modulating the same carrier frequency as that of another station with a modulation signal unique to that station, and the recognition signal received from the communication medium is that of the own station; The present invention is characterized in that it is further provided with collision transmission interrupting means for interrupting data transmission by the data transmitting device to its own station if the data transmitting device does not transmit data to its own station.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 2, 1 is a communication medium composed of any one or a combination of coaxial cables, optical fibers, stranded wire cables, or the like as in FIG. 1, and 2 is also a first A terminator for impedance matching of the communication medium 1 as shown in the figure,
104, 105, 106 are data transmitting devices that transmit data signals via the communication medium 1; 204, 2;
05, 206 are data receiving devices that receive data signals communicated on the communication medium 1, 304, 305,
Reference numeral 306 denotes a recognition signal transmitting device 40 which transmits, via the communication medium 1, a collision confirmation signal having a carrier frequency common to all stations, which will be described later, and modulated with a unique frequency for each station.
4, 405, and 406 are recognition signal receiving devices that receive collision confirmation signals, and 504, 505, and 506 are recognition signal transmitting devices 30 for the signals received by the recognition signal receiving devices 404, 405, and 406, respectively.
A collision detection device that immediately generates a collision signal when a modulated signal other than 4,305,306 is detected;6
04, 605, and 606 are collision detection devices 5, respectively.
04, 505, and 506, respectively.
Transmission interrupting devices 704, 705, and 706 for interrupting signal transmission to the communication medium 1 by 106 are data transmitting devices 104, 105, and 106, recognition signal transmitting devices 304, 305, and 306, and data receiving devices 204, 205, and recognition signal transmitting devices 304, 305, 30 using data signals connected to 206 and transmitted via communication medium 1;
A utilization device 904 instructs activation/stop of 6, and 904 includes a data transmission device 104, a data reception device 204, a recognition signal transmission device 304, a recognition signal reception device 404, a collision detection device 504, a transmission interruption device 604, and a utilization device. Station with 704, 9
05,906 is also a station made of similar components.

The operation of the data communication system of this embodiment configured as described above will be explained below.

First, the data transmitting device 104 detecting the communication medium 1 as a suspended cable starts transmitting information prepared by the utilizing device 704 to the communication medium 1 in response to a request from the utilizing device 704 . At the same time as this transmission starts, the utilization device 704 permits the recognition signal transmission device 304 to operate. The recognition signal transmitting device 304 that is permitted to operate starts transmitting a collision confirmation signal having a carrier frequency f ₀ and a modulation frequency f ₄ to the communication medium 1 . Furthermore, the recognition signal receiving device 404 also starts receiving at the same time. At this time, one other station 906 may have started transmitting onto communication medium 1 due to propagation delays. That is, the data transmitting device 106
transmits the information prepared by the utilization device 706 to the communication medium 1, and the recognition signal transmitter 306 transmits the information prepared by the utilization device 706 to the recognition signal transmitter 304 whose carrier frequency is the station 904.
The modulation frequency is the same as f ₀ and the recognition signal transmitter 304
The transmission of a collision confirmation signal to the communication medium 1 of f ₆ may be different from that of f 6 . At this time, in order to adjust for other coincidences, the collision detection device 504 generates a collision signal when the recognition signal receiving device 404 detects a frequency component other than the modulation frequency f ₄ of its own station in the signal received at the carrier frequency _{f 0} . However, in response to the presence of this collision signal, the transmission interrupting device 604 interrupts the transmission of the signal to the communication medium 1 by the data transmitting device 104. During this series of operations, the collision detection device 506 also operates on the station 906 side, and the transmission of the signal from the data transmitting device 106 to the communication medium 1 is interrupted by the transmission interrupting device 606.

As described above, according to this embodiment, the recognition signal transmitter 30 has a modulation frequency specific to each station.
4,305,306 and recognition signal receiving device 404,
405, 406, collision detection device 504, 505,
506, by providing transmission interrupting devices 604, 605, 606 separately from data transmitting devices 104, 105, 106 and data receiving devices 204, 205, 206, each station 904, 905, 9
06 data delay time management can be eliminated.

Effects of the Invention As explained above, according to the data communication system of the present invention, the carrier frequency for each station is common to all stations, the modulation frequency is unique to each station, and a recognition signal is transmitted together with data transmission, Since the station is configured to interrupt its own transmission when it confirms the existence of a collision, collisions can be detected without having to manage data delay time for each station, which has a great practical effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional data communication system, and FIG. 2 is a block diagram of a data communication system according to an embodiment of the present invention. 1...Communication medium, 2...Terminator, 104, 10
5,106...data transmitting device, 204,20
5,206...data receiving device, 304,30
5,306...Recognition signal transmitting device, 404,40
5,406...Recognition signal receiving device, 501,50
2,503...Transmission interrupting device, 504,505,
506... Collision detection device, 604, 605, 60
6...Transmission interrupting device, 704, 705, 706...
... Utilizing device, 904, 905, 906... Station.

Claims (1)

[Claims] 1. A plurality of stations each having a data transmitting device and a data receiving device for transmitting and receiving data are provided, each station is connected to a common communication medium, and each station is provided with the same carrier wave as other stations when transmitting data. a recognition signal transmitter that transmits a recognition signal whose frequency is modulated with a modulation signal specific to that station to the communication medium; A data communication system comprising collision transmission interrupting means for interrupting data transmission from a station.