JP2536656B2 - Terminal interface device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention accumulates packet information received from one of at least one data terminal to be stored in a transmission buffer memory, and stores the packet information in an electronic exchange via a data line. The present invention relates to a terminal interface device to be connected.

[Conventional technology]

The exchange apparatus accommodates a telephone terminal as a subscriber terminal and a data terminal for exchanging high-speed data by a computer or the like to process an exchange service.

Generally, even if a coaxial cable is used as a transmission medium for high-speed data, the rate of occurrence of packet information for communication is low, so a high-speed data line can be created by multiplexing communication channels with various types of subscriber terminals with a switching device. use. In the case of burst type packet communication in which the unit amount is indefinite and the maximum handling data amount is defined, the packet information transmitted from the data terminal has an opportunity to wait for transmission at the terminal interface device due to the multiplexing of the packet information.

On the other hand, since the distributed data terminals handle data at a speed of 10 Mbps, for example, they are connected to the switching device by a coaxial cable. In this case, since the usage rate of the line is low, the terminal interface device converts the speed and, for example, almost all the distance can be connected to the switching device by a telephone cable capable of transmitting data at a speed of 4 Mbps. Also in this case, as in the case of multiplexing, there is an opportunity for the packet information transmitted from the data terminal and stored in the transmission buffer memory to wait for transmission at the terminal interface device.

Conventionally, this kind of terminal interface device can store all the packet information sent from the data terminal in consideration of the data transmission / reception data rate of the data terminal, the packet information generation rate, the transmission / reception data rate with the switching device, and the like. To
The storage capacity of the buffer memory was set according to the conditions of the maximum traffic of the data terminal.

Even under this condition, there is a chance that the storage area of the transmission buffer memory of the terminal interface device is full and the packet information to be transmitted subsequently is lost. In this case, since the data terminal does not receive the reception confirmation from the destination, the data is transmitted by the upper layer retransmission means.

[Problems to be Solved by the Invention]

In the conventional terminal interface device described above, when the storage capacity of the internal buffer memory is determined according to the maximum traffic handled by the data terminal while avoiding the loss of packet information, the storage capacity becomes larger than that during normal communication traffic. Therefore, there is a problem in that there is a lot of waste in the size and cost of the device, but when the storage capacity of the buffer memory is insufficient, the retransmission procedure due to the loss of packet information takes time, which deteriorates the efficiency of use of the line. Give rise to points.

An object of the present invention is to provide a terminal interface device which solves the above problems by transmitting a transmission suppression signal instructing a data terminal to stop transmission of transmission data when a predetermined amount of packet information is stored in a transmission buffer memory. Especially.

[Means for solving the problem]

The basic configuration of the terminal interface device according to the present invention is that the packet information from one of the accommodated data terminals is accumulated in the transmission buffer memory and transmitted to the electronic exchange through the data line, and at the same time, the transmission buffer memory (12) stores In a terminal interface device for transmitting a suppression signal for stopping the transmission of packet information to the data terminal when the packet storage amount matches the storage capacity; a carrier signal transmitted when the line is in use as the suppression signal Suppressing signal transmitting means for transmitting to the data terminal a pseudo carrier signal in which a predetermined code is continuously inserted;

In addition, the suppression signal transmission means detects a storage number of packets in a capacity of the transmission buffer memory and outputs a suppression instruction signal for instructing transmission of the suppression signal, and a storage amount detection unit. A suppression signal generator that generates the suppression signal at least while receiving the suppression instruction signal; packet information received via the data line is input from a reception buffer memory, and the suppression signal generator outputs the suppression signal. And a selection unit for transmitting the suppression signal to the data terminal while receiving the suppression instruction signal.

A collision state detection unit that outputs a collision detection signal when packet information is newly received from the data terminal while the suppression instruction signal is being generated; and the newly received packet that receives the collision detection signal. A collision signal transmitting unit for transmitting a collision signal for prompting the retransmission of information to the data terminal;

Further, the selecting unit receives the packet information from the reception packet memory when the reception buffer memory receives the packet information via the data line while the suppression signal in which the code “0” continues is being input from the suppression signal generation unit. It is a logical sum circuit for transmitting packet information to the data terminal.

〔Example〕

Next, the terminal interface device of the present invention will be described with reference to the drawings.

 FIG. 1 is a block diagram showing one embodiment of the present invention.

As shown in FIG. 1, a terminal interface device 10 for accommodating and connecting a data terminal 1 on one side and connecting to a speech path of an electronic exchange (not shown) on the other side via a data line 2
Includes a reception detection unit 11, a transmission buffer memory 12, a reception buffer memory 13, a collision state detection unit 14, a collision signal transmission unit 15, and a suppression signal transmission unit 16, and the suppression signal transmission unit 16 includes a storage amount detection unit 17 It also has a suppression signal generator 18 and a selector 19.

The reception detection unit 11 notifies the collision state detection unit 14 that a transmission packet has been received from the transmission path of the data terminal 1. The transmission buffer memory 12 temporarily stores the packet information received from the data terminal 1 via the reception detection unit 11, and transmits it to the data line 2 under the control of a control unit (not shown).

The reception buffer memory 13 temporarily stores the packet information received from the data line 2, and transmits it to the data terminal 1 under the control of a control unit (not shown).

When the collision detection section 14 receives the reception detection signal of the packet information from the reception detection section 11 while receiving the suppression instruction signal from the suppression signal transmission means 16, it determines that it is in the collision state and detects it. The collision signal transmission unit 15 transmits a collision signal to the data terminal 1 when receiving the collision state detection signal from the collision state detection unit 14.

The storage amount detection unit 17 of the suppression signal sending means 16 checks the storage state of the transmission buffer memory 12 as the storage amount, and outputs a suppression instruction signal when the maximum storage amount stored in advance is reached.
The suppression instruction signal is transmitted to the collision state detection unit 14 and the selection unit 19. The suppression signal generator 18 generates a predetermined suppression signal. The suppression signal is generated by the selection unit 19
Since there is a selection control of
The suppression instruction signal may be received only from. Selector 19
Sends the suppression instruction signal to the data terminal while receiving the suppression instruction signal.

The buffer memory normally has a capacity for storing at least two pieces of packet information because other packet information is received while transmitting accumulated packet information. Since the maximum amount of each packet information is usually defined by the system, the buffer memory has a capacity to store two pieces of maximum packet information. Therefore, according to this example, when two pieces of packet information are accumulated, a suppression signal for stopping the start of transmission of the next packet information is transmitted to the data terminal. That is, the period from the end of reception of the packet information to the end of transmission and empty becomes the use period, and the suppression instruction signal is sent from the suppression signal sending means when both are in the use period. Therefore, the data terminal starts transmitting the next packet information when at least one becomes available.

In addition, the medium access method of the data terminal is IEEE 802.3
When compliant with CSMA / CD (ISO IS8802-3), the data terminal stops sending packet information when it is not in the "idle state", that is, while receiving the carrier signal sent while using the data line. For example, a pseudo carrier signal such as a continuous signal of code “0” can be used as the suppression signal. When packet information arrives from the data line and is written to the receive buffer memory during sending of the suppress signal by this pseudo carrier signal, it becomes possible to write to the transmit buffer memory and the suppress instruction signal disappears, as in the case where the suppress instruction signal disappears The transmission to the data terminal is stopped, and the original packet information is transmitted and received. The pseudo carrier signal having the continuous code “0” can be a logical sum circuit with the packet information transmitted from the reception buffer memory as the selection unit.

This IEEE 802.3 data terminal is a bus LAN
It is used in the (local area network) system and detects the collision of packet information on the bus by receiving a collision signal. The data terminal that has received the collision signal executes a re-transmission procedure in which the packet information being transmitted is transmitted from the beginning. The above-mentioned collision state detection unit detects that the next packet information has started to be received, even though the transmission buffer memory is full and the suppression instruction signal is generated. In other words, if the next packet information is transmitted from the data terminal before the data terminal receives the suppression signal sent via the selection unit when the transmission buffer memory is full, this packet information is transmitted to the transmission buffer. A collision signal indicating that the memory is full and therefore discarded is transmitted to the data terminal via the collision signal transmission unit. The data terminal receiving this collision signal can rescue the discarded packet information by knowing that the transmission buffer memory is full and the packet information has been discarded and executing the re-transmission means by the IEEE802.3 system. it can.

〔The invention's effect〕

As described above, the terminal interface device of the present invention controls the amount of packet information transmitted from the accommodated data terminal by transmitting the suppression signal to the data terminal while the storage capacity of the transmission buffer memory is full. By reducing the storage capacity of the buffer memory to the required minimum, it is possible to reduce the size of the device and improve the economical efficiency, and to know from the collision signal that the packet information has been discarded because the transmission buffer is full. Therefore, the discarded packet information can be retransmitted. Therefore, the retransmission of the packet information by the upper layer can be minimized, and the effect of improving the usage efficiency of the data line can be obtained. It is possible to obtain the effect of minimizing the retransmission due to loss of data.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the terminal interface device of the present invention. 1 ... data terminal, 2 ... data line, 10 ... terminal interface device, 11 ... reception detection unit, 12 ... transmission buffer memory, 13 ... reception buffer memory, 14 ... collision state detection unit, 15 ...... Collision signal sending unit, 16 ...... Suppression signal sending means, 17 ...... Memory amount detecting unit, 18 ...... Suppression signal generating unit, 19 ...
… Selector.

Claims (4)

(57) [Claims] 1. When packet information from one of the accommodated data terminals is accumulated in a transmission buffer memory and transmitted to an electronic exchange via a data line, and the packet storage amount of the transmission buffer memory matches the storage capacity. A terminal interface device for transmitting a suppression signal for stopping transmission of packet information to the data terminal; a pseudo carrier signal in which a predetermined code is continuously inserted as the suppression signal in a carrier signal transmitted when the line is in use. And a suppression signal transmitting means for transmitting to the data terminal. 2. A storage amount for outputting the suppression instruction signal for instructing the transmission of the suppression signal when the suppression signal transmission means detects that the transmission buffer memory is storing the number of packets of the capacity. A detection unit; a suppression signal generation unit that generates the suppression signal at least while receiving the suppression instruction signal; a packet information received via the data line from a reception buffer memory and from the suppression signal generation unit; The terminal interface device according to claim 1, further comprising: a selector that inputs the suppression signal and sends the suppression signal to the data terminal while receiving the suppression instruction signal. 3. A collision state detection unit that outputs a collision detection signal when packet information is newly received from the data terminal while the suppression instruction signal is being generated; 3. The terminal interface device according to claim 2, further comprising: a collision signal transmission unit that transmits a collision signal for prompting retransmission of the received packet information to the data terminal. 4. The reception packet when the reception buffer memory receives packet information via the data line while the suppression signal in which the code “0” continues is being input from the suppression signal generation unit. 3. The terminal interface device according to claim 2, wherein the terminal interface device is a logical sum circuit for sending packet information from a memory to the data terminal.