JPS61198846A - Data service unit - Google Patents

Abstract

PURPOSE:To release unefficiency that other data transmission is hindered because of a communication line having no data transmission/reception by opening automatically an invalid communication line having no data transmission/ reception for a prescribed time. CONSTITUTION:A supervisory circuit 14, a counter circuit 15 and a clear signal line for the counter circuit 15 and provided. When the supervisory circuit 14 uses a central processing unit 6 to detect the forming of a communication line by a data highway 13 through a control bus 12, the circuit 14 starts supervising operation representing the presence of a transmission/reception data at the communication line of the channel. When the transmission/reception of the data is started between DTE1A and 1B, and count of the channel in the counter circuit 15 is cleared to zero via a clear signal line 16. The zero clearing is executed at every presence of transmission/reception data. When the count reaches a prescribed value, that is, the time without transmission/reception data reaches a prescribed time, the counter circuit 15 sets the timeout signal of the channel.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention provides communication path forming means for transmitting and receiving control signals between a data terminal and an exchange, and forming a communication path with a partner data terminal via the exchange. The invention relates to a data service unit equipped with a data service unit.

[Technical Background of the Invention] As is well known, in a DDX line-switched data communication network, a data service unit (data service unit) is installed on the data terminal side to convert signal levels and form a communication path between the exchange and the data terminal. Data transmission between two data terminals is performed via a DSU provided corresponding to each data terminal.

FIG. 3 is a block diagram showing the configuration of such a data communication network, where IA and 1B are data terminals, 2A and 2B are D
StJ, 3 represents a switch.

Figure 4 shows data terminals (hereinafter referred to as DTE) 1A, 1
B has a V,24 interface, and DSU2A,
DS when data is transmitted by two-wire burst transmission method (ping-pong transmission method) between 2B and switch 3
It is a block diagram showing the internal configuration of U2A, and is a block diagram showing the internal configuration of U2A.
In addition to interface circuits 4 and 5 for transmitting and receiving signals between the switch 3 and the switch 3, the unit includes a central processing unit 6 that controls the entire unit.

Here, the operation of the DSLJ 2A shown in FIG. 4 will be explained with reference to the sequence diagram shown in FIG.

First, a description will be given of the procedure from when the DSU 2A makes a call to when it is communicating with the DSU 2B.

However, it is assumed that the DTEIA is in a terminal ready state in which the control signal ER is turned on and operation preparations are completed.

First, a call key provided on the various feature keys 10 installed in the DSU 2A is operated. This operation information is read into the central processing unit 6 via the control bus 12 when a key monitoring program stored in the storage circuit 7 is periodically activated by the timer circuit 8. When the central processing bag @6 detects the call key operation information,
A predetermined control signal is transmitted via the control bus 12 and the interface circuit 4 to a central processing unit (not shown) within the exchange 3. Then, the central processing unit in the exchange 3 retrieves the status information corresponding to the corresponding communication channel from "empty" to "empty".
The content is changed to "Waiting for dialing" and a control signal indicating "Dialable" is sent back to the corresponding communication channel. This control signal is read into the central processing unit 6 via the interface circuit 4 and control bus 12 within the DSU 2A. Then, the central processing unit 6 turns on the status display LED (
Light up the “dialable” LED in the light emitting indicator 11. Therefore, the user confirms that the corresponding LED is lit, and
Using dial pad 9 installed in SU2A,
Dial the number of DSU2B.

Then, between DSU2B and DTElB, DSU2A
Control signals CI and DSt indicating that there was a call from
A control signal DR indicating that the J2B is ready to perform data transmission with the DTElB is sent and received, and the DSU
Control signals for incoming call responses are transmitted and received between 2B and the exchange 3. In addition, in response to the "incoming call response", a control signal for the "communication tube" is sent and received between the exchange 3 and the DSU 2A, and then a control signal DR indicating that data transmission is ready from the DSU 2A to the DTE1A is sent and received. is sent and received. As a result, the DSU 2A and DSU 2B enter a state of communication. At this time, data transmission between DTElA and DTElB is performed by interface circuit 5. Data Highway 13.
Interface circuit 4. Time switch in exchange 3 (
(not shown) is performed via the DSU2B.

Next, the process from communication to recovery will be explained. If any DTE becomes terminal not ready, the DSU will
Alternatively, recovery occurs when the RLS (recovery) key in the feature keys 10 is pressed.

When DSLJ2A and DSU2B are communicating, DSU
When the DTE'lA on the 2A side enters the terminal not ready state or when the RLS key of the DSLJ2A is pressed, the information representing the former state is sent to the interface circuit 5.2A. control bus 1
2, and information representing the latter state is read into the central processing unit 6 via the control bus 12 by starting the aforementioned key monitoring program. Then, the central processing unit 6 sends a control signal representing a "recovery request" to the control bus 12.
It is sent via the interface circuit 4 to a central processing unit (not shown) in the exchange 3. When the central processing unit in the exchange 3 receives this signal, it sends control signals to the DSU 28 to allow disconnection and to the DSU 2B to instruct disconnection to the central processing unit via the respective interface circuits 4 and control bus 12. 6. When the central processing unit 6 of the DSLJ2B receives the processed signal, it sends the control signal "LDAI".
control bus 12. It is transmitted via the interface circuit 4 to a central processing unit (not shown) in the exchange 3. Switchboard 3
When the central processing unit (not shown) within the DSU 2A receives this control signal, it restores each corresponding transmission channel to an "empty" state.Thereby, the communication path between the DSU 2A and the DSU 2B is restored.

[Problems in the Background Art] However, in the conventional data service unit described above, the DTE is put in a not-ready state, or the RL is artificially set.
Since the communication channel will not be restored unless the S key is pressed, there is a problem in that if this operation is neglected, the communication channel will remain formed even when no data is being transmitted.

[Object of the Invention] It is an object of the present invention to provide a data service unit that can eliminate the above-mentioned drawbacks and automatically open an invalid communication channel where no data is actually transmitted or received.

[Summary of the Invention] In the present invention, a communication channel is formed by providing a monitoring means for monitoring the presence or absence of transmitted/received data in a data service unit, and a timer means for measuring the time during which data transmission is not performed based on the previous monitoring result. Despite this, the above objective is achieved by automatically opening the communication channel if no data is being sent or received for a certain period of time.

[Embodiments of the invention] The present invention will be explained below based on Examples.

FIG. 1 is a block diagram of a DSU showing an embodiment of the present invention. In addition to the conventional configuration shown in FIG. 4, a monitoring circuit 14, a counter circuit 15, and a clear signal line 16 for the counter circuit 15 are provided. are different. In addition, in FIG. 1, the memory circuit 7° dial pad 9. Feature key 10. The status display LEDI 1 is not shown.

In this configuration, when the monitoring circuit 14 detects via the control bus 12 that the central processing unit 6 has formed a communication path on the data highway 13, it starts monitoring the presence or absence of transmitted and received data on the communication path of the corresponding channel. Then, when transmission and reception of data is started between DTEL A and DTEL 1B, the count value of the corresponding channel in the counter circuit 15 is cleared to zero via the clear signal line 16. This zero clearing operation is executed every time there is transmitted/received data.

However, when there is no transmitted or received data, counter circuit 1
The count value of the corresponding channel in 5 is updated every time the basic clock signal is generated 6. Then, when the count value reaches a certain value, that is, when the time with no transmitted or received data reaches a certain period of time, the counter circuit 15 updates the count value of the corresponding channel. Turn on the timeout signal.

Then, this timeout signal is read into the central processing unit 6 via the control bus 12 by a timeout monitoring program that is periodically activated by the timer circuit 8.

The central processing unit 6 that has received the timeout signal sends a "recovery request" to the central processing unit (not shown) in the exchange 3 via the control bus 12 and the interface circuit 4, as shown in the sequence diagram of FIG. Then, in the same way as when the RLS key is operated, the DSU 2A and 2B that were in communication are sent and received control signals such as "'Disconnect possible", "Disconnect instruction", and "Ready". The communication path between them is opened.

As a result, an invalid communication channel on which data has not been transmitted or received for a certain period of time is automatically disconnected.

[Effects of the Invention] As explained above, in the present invention, an invalid communication channel where no data is sent or received for a certain period of time is automatically opened. This has the effect of eliminating an inefficient situation in which data transmission cannot be performed.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a data service unit showing an embodiment of the present invention, Fig. 2 is a sequence diagram when opening an invalid communication channel, and Fig. 3 is a general diagram of a data communication network using the data service unit. FIG. 4 is a block diagram showing the configuration of a conventional data service unit, and FIG. 5 is a sequence diagram of control signals from call origination to communication path opening in the conventional data service unit. 1A, 1B... Data terminal, 2A, 2B... Data service unit, 3... Exchange, 4° 5... Interface circuit, 6... Central processing unit, 13... Data highway, 14 ...Monitoring circuit, 15...Counter circuit, 16...Clear signal line.

Claims (1)

[Scope of Claims] A data service unit comprising communication path forming means for transmitting and receiving control signals between a data terminal and an exchange and forming a communication path between the data terminal and the exchange, A communication path is formed between the data terminal and the exchange and timer means that measures the time during which no data is being sent or received and requests the communication path formation means to open the communication path when the measured time reaches a predetermined value. and communication channel monitoring means for operating the timer means when there is no transmitted/received data on the communication channel and initializing the clock value of the timer means when there is transmitted/received data. service unit.