JPH01208928A - Communication system - Google Patents

Abstract

PURPOSE:To prolong the distance of a transmission line by calculating the distance and controlling the timewise gap so that the time of transmission/ reception of a 2-way data signal is within a prescribed time when the time of the transmission/reception of a 2-way data signal is brought into a prescribed time based on the distance of the transmission line. CONSTITUTION:When a reception circuit 9 of a master equipment receives a data signal from a slave equipment, whether or not a data signal is transmitted/received between the master equipment and the slave equipment within the time T is judged. When the time exceeds the prescribed time T, a transmission distance calculation circuit 5 calculates the distance of the transmission 11 between both the equipments. Then the data relating to the calculated distance of the transmission line 11 is sent to a slave side guard time data generating circuit 7 to decide an optimum guard time TGB for the slave device. Thus, when the distance of the transmission line 11 is long, the guard time TGB of the slave equipment is set short and the transmission of the data signal between the master equipment and the slave equipment is attained within the prescribed time T.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a communication system using a so-called ping-pong transmission method.

(Prior art) The so-called ping-pong transmission method is a method in which the transmission of signals from a first transmission device (master device) to a second transmission device (slave device) and the transmission of signals from a slave device to the master device are constant. By performing this alternately and repeatedly during time T, a state is established in which the master device and slave device communicate almost simultaneously.

FIG. 5 is a sequence diagram of this method.

As shown in the figure, when the master device transmits, the data signal is received by the slave device after a transmission delay time TD.

On the other hand, the slave device starts transmitting data signals after the guard time TGB has elapsed after all data signals have been received.

This data signal is then received by the master device after a transmission delay time TD.

By the way, in order to prevent such a slave device from mistaking the reflected wave of the signal sent by the slave device itself for the signal sent by the master device, a guard time TGB is provided, similar to the guard time TGA in the master device. After this slave device finishes transmitting, it ignores the signals it receives for a certain period of time.

However, when the guard time TGB is provided in the slave device in this way, there is a time period that is exclusively occupied by the guard time TGB within the fixed time T, so there is a problem that the distance of the transmission path cannot be made very long.

(Problem to be Solved by the Invention) As described above, in the conventional communication system using the ping-pong transmission method, when the slave device is provided with the guard time TGB, there is a time period that is exclusively occupied by the guard time TGB within the fixed time T. There is a problem in that the distance of the transmission path cannot be made very long.

The present invention was made based on such circumstances, and an object of the present invention is to provide a communication system that can lengthen the distance of a transmission path.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention connects a plurality of terminals via a transmission line, and communicates bidirectional communication between these terminals within a predetermined time via the transmission line. It is applied to communication systems that transmit and receive data signals with a time gap after one terminal receives the data signal, and calculates the distance of the transmission path. , when the time for transmitting and receiving a bidirectional data signal exceeds the predetermined time mentioned above, the time for transmitting and receiving a bidirectional data signal is adjusted based on the distance of the transmission path so that the time for transmitting and receiving the bidirectional data signal is within the predetermined time. This is to control the gap.

(Function) In the present invention, when the time for transmitting and receiving bidirectional data signals exceeds a predetermined time set in advance, the distance of the transmission path is calculated and the time for transmitting and receiving bidirectional data signals is calculated based on this distance. Since the time gap inserted between the transmitted and received data signals of one terminal is controlled so that the data signal is within this predetermined time, the distance of the transmission path can be increased.

(Example) Hereinafter, details of an example of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a master device as a first transmission device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a slave device as a second transmission device. be.

As shown in FIG. 1, the master device includes a transmission timing generation circuit 1, a transmission circuit 3, a transmission distance calculation circuit 5, a slave side guard time data generation circuit 7, and a reception circuit 9.

The sending timing generating circuit 1 notifies the sending circuit 3 of the sending timing of the data signal, and the sending circuit 3 sends the data signal to the transmission line 11 based on this timing.

Further, the receiving circuit 9 receives the data signal sent from the slave device via the transmission line 11, and the transmission distance calculating circuit 5 calculates the timing at which the data signal is sent from the sending circuit 3 and the timing at which the data signal is sent from the sending circuit 3. The distance of the transmission line 11 between the master device and the slave device is calculated based on the timing of receiving the data signal corresponding to the transmitted data signal.

Then, the slave side guard time data generation circuit 7 sets the guard time TGB of the slave device to the optimum value according to the distance of the transmission path 11 calculated by the transmission distance calculation circuit 5.

On the other hand, the slave device includes a receiving circuit 13, a guard time control circuit 15, a sending timing generating circuit 17, and a sending circuit 19, as shown in FIG.

The receiving circuit 13 receives a data signal sent from the master device via the transmission line 11, sends a data signal related to guard time out of this data signal to the guard time control circuit 15, and extracts a clock signal from the data signal. Then, this clock signal is sent to the sending timing generation circuit 17.

Further, the guard time control circuit 15 sends out a predetermined timing control and control signal to the sending timing generating circuit 17 based on the guard time data sent from the receiving circuit 13. A sending timing signal is sent to the sending circuit 19 in accordance with the timing control signal sent from the time control circuit 15 and the clock signal sent from the receiving circuit 13.

Then, the sending circuit 19 sends the sending data to the transmission line 11 according to the sending timing signal sent from the sending timing generating circuit 17, that is, with the guard time TGB set on the master side.

Next, the operation of the communication system configured as described above will be explained.

First, in the initial state, the guard time TG on the slave device side
B is set to be equal to the guard time TGA on the master device side.

Therefore, as shown in FIG. 3, when a data signal is sent from the sending circuit 3 of the master device via the transmission path 11, this data signal is received by the receiving circuit 13 of the slave device after the transmission delay time TD. .

Then, after the slave device finishes receiving this data signal and the guard time TGB has elapsed, the data signal is sent from the sending circuit 19 to the master device side via the transmission line 11.

When receiving the data signal from the slave device, the receiving circuit 9 of the master device communicates with the master device and the slave device within a fixed time T shown in FIG. It is determined whether data signals are transmitted and received between the two.

If it is performed within a certain time T, then the guard time set in the initial state, that is, the guard time TGB
Data signals are transmitted and received between the master device and the slave device while the guard time TGA and the guard time TGA remain equal.

On the other hand, if the predetermined time T has been exceeded, the transmission distance calculation circuit 5 of the master device calculates the distance of the transmission path 11 between the master device and the slave device.

That is, the transmission distance calculating circuit 5 calculates the distance based on the timing at which the data signal is sent from the sending circuit 3 and the timing at which the receiving circuit 9 receives a data signal corresponding to this sent data signal.

Then, data regarding the calculated distance of the transmission path 11 is sent to the slave side guard time data generation circuit 7, and the optimum guard time TGB of the slave device is determined.

Thereafter, data regarding this guard time TGB is sent as a data signal from the sending circuit 3 to the slave device via the transmission line 11 and received by the receiving circuit 13 of the slave device.

Thereafter, the data signal regarding the guard time TGB received by the receiving circuit 13 is sent to the guard time control circuit 15, and the guard time control circuit 15 sends a predetermined timing control signal based on this guard time data to the sending timing generation circuit 17. It will be done.

Then, the transmission timing generation circuit 17 sends a sending timing signal to the sending circuit 19 in accordance with the timing control signal sent from the guard time control circuit 15 and the clock signal sent from the receiving circuit 13, and the sending circuit 19 sends the timing signal to the sending circuit 19. A data signal is sent out in accordance with.

Therefore, in this embodiment, when the distance of the transmission path 11 is long, the guard time TGB of the slave device is set short as shown in FIG. It becomes possible to transmit data signals.

[Effects of the Invention] As explained above, according to the communication system of the present invention, a plurality of terminals are connected via a transmission line, and bidirectional data signals are transmitted and received between these terminals within a predetermined time via the transmission line. If the data signal is transmitted with a time interval after one terminal receives the data signal, the signal is inserted between the transmitted and received data signals of one terminal depending on the distance of the transmission path. Since the time interval is controlled, the distance of the transmission path can be increased.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing the configurations of a master device and a slave device of a communication system according to an embodiment of the present invention, and FIGS. 3 and 4 are sequence diagrams of the communication system of this embodiment. FIG. 5 is a sequence diagram of a conventional communication system. 1... Sending timing generation circuit, 3... Sending circuit,
5... Transmission distance calculation circuit, 7... Slave side guard time data generation circuit, 9... Receiving circuit, 11...
Transmission path, 13... Receiving circuit, 15... Guard time control circuit, 17... Sending timing generation circuit, 19.
...Sending circuit. Applicant Toshiba Corporation Patent Attorney Sasa Suyama - Figure 1 Figure 2

Claims (1)

[Claims] (1) Multiple terminals are connected via a transmission path, bidirectional data signals are sent and received between these terminals within a predetermined period of time, and after one terminal receives the data signal, In a communication system in which data signals are transmitted with gaps, the first means calculates the distance of the transmission path, and when the time for transmitting and receiving the bidirectional data signal exceeds the predetermined time, the first means calculates the distance of the transmission path. and second means for controlling the time gap so that the time for transmitting and receiving the bidirectional data signal is within a predetermined time based on the distance of the transmission path calculated in the above.