JPS6120181B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synchronous control method that can be used when branching and expanding DC data. (referred to as modem)
The present invention relates to a method for performing data communication with a terminal device or a communication control device at a remote location via a remote terminal device or a communication control device.

The conventional DC branching method performs data communication between, for example, a communication control device and a selected one of a plurality of data transfer devices, such as a terminal device, connected to a DC branching circuit, and in this case, The transmission data SD sent from the terminal device to one side of the modem via the DC branch circuit must be synchronized with the transmission timing information ST ₂ sent from the modem, and therefore the transmission data SD sent from the terminal device to the modem must be synchronized with the transmission timing information ST 2 sent from the modem. Timing information ST ₁ was prohibited. By doing this, the modem uses the same frequency transmission timing information for the transmitted data SD from any terminal device.
It can be input in synchronization with ST ₂ , and the modem operation will be stable.

However, if at least one of the plurality of terminal devices to be branched from the DC branch circuit is located in a remote location, a pair of modems is required between the DC branch circuit and the terminal device. Depending on the method, it has been impossible to unify the frequency of timing information associated with data transmission and reception. That is, in the case of a DC branch system using a conventional modem as shown in FIG. 3, the following problems arise.
Conventionally, when the terminal device 5-2 is remote and requires two pairs of modems 2, 3 and 6, 7 between it and the communication control device 1, when data is transmitted between each modem, each Even though it was necessary to transfer data with the modems synchronized, the modems could not be synchronized.

The problem will be explained in detail with reference to FIG.

In the figure, in data transmission from the terminal device 5-2 to the communication control device 1, the terminal device 5-2 sends out data in synchronization with the clock signal ST2 of the modem 7.

Even if the buffer 41 is prepared in the DC branching device 40, the frequencies of the clock signal ST2 of the modem 3 and the clock signal ST2 of the modem 7 do not match, and data errors occur due to frequency deviation. For this reason, conventionally, unless an asynchronous modem with a speed of 1200 bits/second or less was used, it was impossible to add a modem to the DC branch circuit to perform data communication with a terminal device in a remote location. .

The purpose of the present invention is to adopt a DC branch expansion method in which an expansion modem is added to the DC branch circuit, based on the idea that the modem has a timing signal return function and the DC branch circuit has a timing signal phase synchronization function. The purpose is to enable synchronization even in the case of transmission and reception, and to synchronize the frequency and phase of timing information associated with transmission and reception.

The system provided in the present invention includes a branching device 40 that branches and outputs data and reception timing signals received from a data transmission device 30 to a plurality of data transfer devices 5 and 6, In a data transmission system that transmits and receives data to and from a transfer device, the data transmission device 30 is provided with means for supplying a transmission timing signal ST ₂ having the same frequency as the reception timing signal to the branching device 40, and The transfer device 6 is configured to send data using a transmission timing signal ST ₁ having the same frequency as the reception timing signal outputted from the branching device 40 , and the branching device 40 uses the transmission timing signal ST 1 outputted from the data transfer device 6 to transmit data. ST ₁ receives data based on ST 1 and transmits the received data to the data transmission device 30 at a timing synchronized with the transmission timing signal ST ₂ supplied from the data transmission device 30, and includes phase synchronization control means. This is a synchronous control method characterized by the following:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A DC branch expansion system according to an embodiment of the present invention will be described below in comparison with a conventional example based on the accompanying drawings.

FIG. 1 is a block diagram showing an example of a conventional DC branching system. In FIG. 1, the DC branch system includes a communication control device 1, a pair of data transmission devices 2 and 3 connected to this, modems 2 and 3 in this embodiment, and a DC branch circuit 4 connected to modem 3. Five data transfer devices, terminal devices 5-1, 5-2, .
..., 5-5. DC transmission data sent from communication control device 1 to modem 2
SD is sent in synchronization with the transmission clock signal of either transmission external timing information _ST1 or transmission timing information _ST2 . Here, the transmission external timing information ST ₁ is given to the modem from a device external to the modem, and the transmission timing information ST ₂ is information given from the modem to a device external to the modem. Therefore, the transmission data is synchronized with the transmission external timing ST ₁ .
The transmission clock frequency ₁ when SD is sent is equal to the oscillation frequency of the modem interface (not shown) included in the communication control device 1, and when the transmission data SD is sent in synchronization with the transmission timing information ST ₂ . Clock frequency ₂ is equal to the oscillation frequency of a modem interface (not shown) included in modem 2. The DC transmission data SD and transmission clock signal input to the modem 2 are each converted into AC signals and transmitted to the modem 3. In the modem 3, the AC signal is regenerated into a DC signal and becomes reception data RD and reception timing information RT.
It is input to the DC branch circuit 4. The DC branch circuit 4 receives DC reception data RD and reception timing information RT.
is input into five terminal devices 5-1 to 5-5. Now, according to the received data RD, the terminal device 5-1
shall respond. In this case, the terminal device 5-
Transmission data sent from 1 to modem 3
The SD timing information is limited to the transmission timing information ST ₂ given from the modem 3. The reason for this is that if the transmission external timing information ST ₁ is allowed, the transmission clock frequency is generally different for each terminal device, so the input clock frequency from the terminal device to the modem 3 is changed every time one terminal device is switched to another. This is because the synchronization frequency of the transmitted data SD will be different, and the stability of the operation of the modem 3 will be impaired.
Transmission data SD input from the terminal device 5-1 to the modem 3 in synchronization with the transmission timing information _ST2 is converted into an AC signal and transmitted to the modem 2 together with a transmission clock signal. The AC signal received by the modem 2 is converted into DC reception timing information RT and reception data RD, and is input to the communication control device 1. Data communication is thus performed between the communication control device 1 and one of the terminal devices.

However, if at least one of the terminal devices is located in a remote location and an additional pair of modems is required between the DC branch circuit and the terminal device, it has conventionally been impossible to unify the frequency of the timing information as described above. Ta.

FIG. 2 is a block diagram showing a DC branch system employing the synchronous control method of the present invention. In Fig. 2, the difference from Fig. 1 is that instead of the modem 3 in Fig. 1, reception timing information is provided internally.
Modem 3 with added function to use RT as transmission timing information ST ₂ for return data
0, in place of the DC branch circuit 4 shown in FIG. A pair of modems 6 and 7 are provided between the DC branch circuit 40 and the DC branch circuit 40.
The DC branch circuit 40 is a received data output device that outputs received data RD and a reception timing signal RT generated in accordance with the unit of this data.
Each of the modems 6 receives data RD in accordance with the reception timing signal RT, and transfers the transmission data SD to the DC branch circuit 40 in synchronization with a predetermined transmission timing signal. Similarly to the modem 30, the modem 7 connected to the terminal device in a DC manner also receives the reception timing information RT and the transmission timing information RT ₂
It also has a function that can be used as a.

The operation of the system shown in FIG. 2 will first be described with respect to the case where data is sent from the communication control device 1 to each terminal device. The flow of data and timing information from the communication control device 1 to the modem 30 is exactly the same as in the case of FIG. Frequency from communication control device 1
When the transmission data SD is transmitted in synchronization with the transmission external timing information ST ₁ of ST ₁ , the reception timing information RT of frequency ₁ output from the modem 30 is input to the DC branch circuit 40 and the transmission external timing information ST 1 of the modem 30
Internally the same frequency ₁ transmission timing information ST ₂
It is given to the DC branch circuit 40 as follows. The reception timing signal RT and reception data RD inputted from the modem 30 to the DC branch circuit 40 are sent to the terminal device 5 - which is connected to the DC branch circuit 40 in a DC manner.
1, the terminal device 5- is used as before.
1, but for the terminal devices 5-2 to 5-5 connected via the pair of added modems 6 and 7, first, the transmitter S of the modem 6 is input.
Transmission external timing information of the same frequency ₁ ST ₁
and transmission data SD, and are converted into AC signals by the modem 6. This AC signal is received by the receiving section R of the modem 7, and the reception timing information RT and reception data RD of frequency ₁ are reproduced and given to the terminal device _5-2 . It is also used as transmission timing information ST ₂ , and this transmission timing information ST ₂ is given to the terminal device 5-2. Reception timing information RT similarly reproduced for other terminal devices 5-3, 5-4, and 5-5;
Reception data RD and folded transmission timing information ST ₂ are given.

Next, a case will be described in which data is sent from one of the terminal devices, for example, the terminal device 5-2, to the communication control device 1. Frequency obtained from reception timing information RT
The transmission data SD synchronized with the transmission timing information ST _{1 and 2} is sent from the terminal device 5-2 and received by the transmission unit S of the modem 7, and the transmission timing information ST
Together with ST ₂ , it is converted into an AC signal and received by the receiving section R of the modem 6. Reception timing information RT and reception data RD from the AC signal received by modem 6
are played, but each of these signals has a frequency
The _{data is input to the DC branching device 40 as transmission external timing information ST 1 and} transmission data SD. The frequency of the transmission external timing information ST ₁ sent out from the modem 6 and input to the DC branch circuit 40, and the frequency of the transmission timing information ST ₂ obtained within the modem 30, which is input from the modem 30 to the DC branch circuit 40. The frequency is equal, and both communication control device 1
The frequency of transmission external timing information ST ₁ given to modem 2 from modem 2 or communication control device 1 from modem 2
Transmission timing information given to ST ₂ frequency
Equal to ₂ . However, the modem 3 uses the received data RD sent from the modem 6 as the transmitted data SD.
In order to input 0, it is necessary to perform not only frequency synchronization of the clock signal but also phase synchronization. Therefore, in this embodiment, the DC branch circuit 40
A phase synchronization buffer 41 is provided in the phase synchronization buffer 41, and transmission data SD is taken into the phase synchronization buffer 41 based on transmission external timing information ST ₁ from the modem 6, and transmission data SD is taken into the phase synchronization buffer 41 based on transmission timing information ST ₂ from the modem 30. SD is phase synchronization buffer 4
It is now taken out from 1. In this way, the transmission data SD is received without causing a phase shift in the transmission section S within the modem 30. The transmission data SD and transmission timing information ST ₂ are converted into AC signals and received by the receiving section R of the modem 2, and the reception timing information RT and the reception data RD are received in the modem 2.
and is input to the communication control device 1.

The phase synchronization buffer 41 is, for example, a FIFO.
This is realized by a (first-in, first-out) register.

In the above-described embodiments of the present invention, a case has been described in which data communication is performed between a communication control device and a DC-branched terminal device, but a communication control device may be used in place of the terminal device. , a terminal device may be used instead of the communication control device. Furthermore,
The number of terminal devices is not limited to five.

As is clear from the above description, the present invention makes it possible to synchronize the frequency and phase of timing information associated with data transmission even in a DC branch system in which an expansion modem is added to a DC branch circuit.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a conventional DC branch system, Fig. 2 is a block diagram showing an example of the present invention applied to a DC branch system, and Fig. 3 is a block diagram showing an example of a conventional DC branch system. FIG. 3 is a block diagram for explaining the problem. 1... Communication control device, 2, 3, 30... Modulation/demodulation device, 4, 40... DC branch circuit, 5-1, 5-
2,..., 5-5...terminal device, 6,7...pair of extended modulation/recovery devices, ST ₁ ...transmission external timing information, ST ₂ ...transmission timing information, RT
... Reception timing information, SD ... Transmission data,
RD...Received data.

Claims (1)

[Claims] 1. Data RD received from the data transmission device 30
and a DC branching device 4 that branches and outputs the reception timing signal RT to a plurality of data transfer devices 5 and 6.
0, the data transmission system transmits and receives data between the data transmission device and the plurality of data transfer devices, wherein the data transmission device 30 is provided with a transmission timing signal having the same frequency as the reception timing signal RT.
A means for supplying ST ₂ to the branching device 40 is provided, and the data transfer device 6 is connected to the DC branching device 40.
The DC branching device 40 is configured to send data using a transmission timing signal ST ₁ having the same frequency as the reception timing signal ST outputted from the data transfer device 6, and the DC branching device 40 transmits data based on the transmission timing signal ST ₁ outputted from the data transfer device 6. The device receives data and sends the received data to the data transmission device 30 at a timing synchronized with the transmission timing signal ST ₂ supplied from the data transmission device 30, and further comprises phase synchronization control means. Synchronous control method.