JPH0447840A - Flow control system for transmitted data - Google Patents

Abstract

PURPOSE:To reduce the load of a common line control part by defining the AND of a transmission restart enable announce signal from a data line terminal equipment and of a transmitting character request signal from a transmission circuit as a transmitting character request signal to the common line control part. CONSTITUTION:A line connection part 12 is equipped with an AND circuit 121 in addition to a transmission circuit 120. The transmitting character request signal of the transmission circuit 120 becomes one input of this AND circuit 121 and as the other input of the AND circuit 121, a transmission restart enable announce signal 41 is applied from a data line terminal equipment 2. The output of this AND circuit 121 becomes a transmitting character request signal 13 to a common line control part 11. When the common line control part 11 receives the ON of the transmitting character request signal 13 from the line connection part 12, a data (character) is transferred through a transmission data line 15 to the transmission circuit 120, and a transmitting character, is set to the transmission circuit 120.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data communication system, and particularly to a flow control method for transmission data in a communication control device connected to a data communication line via a data line termination device.

[Conventional technology]

The basic configuration of the data communication system is shown in FIG.

Although not shown in FIG. 5, the communication control devices 1a and 1b are each connected to a central processing unit (CPU), and control data communication with a partner device independently of the central processing unit. The communication control device la consists of a plurality of line connection units 12a having various logical/physical/electrical interfaces corresponding to data line termination devices, and a line control unit 11a that commonly controls these line connection units 12a. , each line connection section 1!2a is connected to a corresponding data line termination device 2a by a cable 4a, respectively.

The configuration of the communication control device 1b is also the same, and each line connecting section 1
2b is connected to the corresponding data line termination device 2b by a cable 4b. A high-speed data communication line 3 connects the data line termination devices 2a and 2b.

Data communication between the communication control devices 1a and 1b is carried out through a line common control section 11a - line connection section 12a - cable 4a - data line termination device 2a - data communication line 3 - data line termination device [2b - cable 4b - line connection This is performed along the route from section 12b to line common control section 11b.

By the way, in recent years, in such data communication systems, data line terminating devices have appeared whose transfer capacity between the data line terminating devices dynamically changes depending on the characteristics of the transferred data, the quality of the data communication line, etc. . In order to utilize such a data line termination device and make effective use of its constant transfer capacity, the transfer speed between the communication control device and the data line termination device must be equal to or higher than the average transfer capacity between the data line termination devices, and It is necessary to absorb the difference in transfer speed by providing a transmission data buffer within the data line termination device and performing flow control with the communication control device.

Conventionally, flow control of transmission data between the data line termination device and the communication control device has been realized by a configuration as shown in FIG. In FIG. 3, 1 is a communication control device, 2
3 is a data line termination device, and 3 is a data communication line. The communication control device 1 is divided into a line common control unit 11 and a line connection unit 12, and the line connection unit 12 has a transmission circuit 120.

Although there are a plurality of line connection units 12, only one is shown here. 13 from the transmission circuit 120 to the line common control unit 1
1 is a transmission character request signal, 14 is a transmission resumption notification signal sent from the line connection unit 12 to the line common control unit 11, and 15 is a transmission data line between the line common control unit 11 and the transmission circuit 120. 41 is the line connection part 1 from the data line termination equipment N2
2, and 42 is a transmission data line between the transmission circuit 120 and the data line termination equipment WL2.

FIG. 4 shows the processing flow of FIG. 3. The data line termination device w2 turns on the transmission resumption possible notification signal 41 when data transmission to the data communication line 3 becomes possible, and turns off the transmission resumption possible notification signal 41 when data transmission is temporarily stopped. The connection unit 12 receives the transmission resumable notification signal 41
is directly transmitted to the line common control unit 11 as a transmission resumption possible notification signal 14. On the other hand, the transmission circuit 1 of the 1-line connection section 12
20 turns on the transmission character request signal 13 when data is needed, regardless of whether the transmission resumable notification signal 14 (41) is on or off. Upon receiving signal 13 on,
The state of the transmission resumable notification signal 14 from the line connection unit 12 is determined, and if the transmission resumable en route signal 14 is on, the data is transferred to the transmission circuit 120 via the transmission data line 15, and the signal 14 is If it is off, the data transfer is suspended. When the transmission circuit 120 receives the data from the line common control unit 11, it transfers it to the data line termination device 2 via the transmission data line 42, and sends the transmission character request signal 13 again.
Turn on. In the data line termination equipment w2, the transmitting circuit 1
The data received from the data communication line 20 is sent to the data communication line 3 in accordance with the quality of the data communication line 3.

[Problem to be solved by the invention]

As mentioned above, in the conventional transmission data flow control method, in the communication control device, the notification signal that transmission can be resumed from the data line termination device to the line connection unit is transmitted directly from the line connection unit to the line common control unit. This is communicated as a possibility notification signal. Therefore, when the line common control unit receives the transmission character request signal from the transmission circuit of the line connection unit,
The line common control unit determines whether the transmission resumption notification signal from the line connection unit is on or off, and if the transmission resumption notification signal is OFF, data transmission is performed without setting transmission characters to the transmission circuit. If the transmission is paused and the notification signal that transmission can be resumed is on, set the transmission character to the transmission circuit,
The process of restarting data transmission is required for each transmission character request, and there is a problem in that the load on the line common control section that commonly controls a plurality of line connection sections increases. moreover,
There is also the problem that the connection between the line connection unit and the line common control unit becomes complicated, and the number of connection bins in the line common control unit increases.

An object of the present invention is to reduce the load on a line common control unit in a communication control device, simplify the connection between a plurality of line connection units and the line common control unit, and connect the line common control unit to a transmission resumable notification signal. An object of the present invention is to provide a flow control method for transmission data that allows the number of pins to be reduced.

[Means to solve the problem]

In order to achieve the above object, in the present invention, in the line connection section, the transmission resumable notification signal from the data line termination device and the transmission character request signal from the transmission circuit are ANDed,
The output is now used as a transmission character request signal to the line common control unit.

[For production]

When the transmission resumable notification signal from the data line termination device is off, the transmission character request signal from the line connection unit to the line common control unit is turned off, regardless of whether there is a transmission character request in the transmission circuit, and the data line termination device When the transmission resumable notification signal from the line is on, if there is a transmission character request in the transmission circuit, the transmission character request signal from the line connection section to the line common control section is turned on. The line common control unit pays attention only to the transmission character request signal from this line connection unit, and transfers the transmission data to the line connection unit when the transmission character request signal is on.

This eliminates the need for the line common control unit to determine whether there is a notification that transmission can be resumed, and the line common control unit only needs to process transmission character requests from the line connection unit, reducing the load on the line common control unit. I can do it. Also, since the transmission resumable notification signal from the line connection unit to the line common control unit can be omitted, the connection between the line connection unit and the line common control unit can be simplified, and the connection for the transmission resumption notification signal in the line common control unit can be omitted. The number of pins can be reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, 1 is a communication control device, 2 is a data line termination device, and 3 is a communication control device.
is a data communication line. The communication control device 1 is divided into a line common control section 11 and a line connection section 12. As shown in FIG. 5, there are actually a plurality of line connection sections 12, but only one is shown here. The line connection section 12 includes a transmission circuit 120. 13 is a transmission character request signal from the line connection unit 12 to the line common control unit 11; 15 is a transmission data line between the line common control unit 11 and the transmission circuit 120; Further, 41 is a transmission resumption notification signal from the data line termination device 2 to the line connection unit 12, and 42 is a transmission data line between the transmission circuit 120 and the data line termination device 12.

Now, in FIG. 1, the line connection section 12 includes an AND circuit 121 in addition to the transmission circuit 120. The transmission character request signal of the transmission circuit 120 becomes one input of this AND circuit 121, and the other input of the AND circuit 121 is
Transmission resumption notification signal 41 from data line terminal device 2
is given.

The output of this AND circuit 121 becomes the transmission character request signal 13 to the line common control section 11.

The processing flow in the case of FIG. 1 is shown in FIG. When the transmission resumable notification signal 41 from the data line terminating device 2 is on, if there is a transmission character request in the transmission circuit 120, A
The output of the ND circuit 121 is on, and the transmission character request signal 13 from the line connection section 12 to the line common control section 11 is turned on. When the line common control unit 11 receives the turn-on of the transmission character request signal 13 from the line connection unit 12, the line common control unit 11 controls the transmission data line 15.
The data (characters) are transferred to the transmitting circuit 120 via the transmitting circuit 120, and transmission character settings for the transmitting circuit 120 are performed. Upon receiving the data from the line common control unit 11, the transmitting circuit 120 converts it into transmission data, i! 42 to the data line termination device 2. The data line termination device 2 transmits the data received from the transmission circuit 120 to the data communication line 3 according to the quality of the data communication line 3 and the like. After transmitting the data to the data line terminal device 2, the transmitting circuit 120 turns on the transmission character request again. At this time, if the transmission resumption notification signal 41 from the data line termination device 2 is still on, the AND circuit 121 sends the transmission character request signal 13 from the 1-line connection section 12 to the line common control section 11.
is turned on again. In this way, one line common control unit 1
1 to the next data is transferred to the transmitting circuit 12 via the transmitting data line 15.

On the other hand, when the transmission resumable notification signal 41 from the data line termination device 2 is off, the output of the AND circuit 121 is off, regardless of the transmission character request in the transmission circuit 120, and the output from the line connection unit 12 to the line common control unit 11 is The transmission character request signal 13 to is turned off. In this case, the line common control unit 11
Now, setting the transmission character to the transmission circuit 120 is pending.
Therefore, data transmission is temporarily stopped. Thereafter, the transmission resumption notification signal 41 from the data line termination device 2 is turned on again, and if the transmission character request in the transmission circuit 120 of the line connection section 12 is turned on, data transfer is resumed.

As described above, by adopting the configuration shown in FIG. 1, it becomes unnecessary for the line common control unit 11 to perform processing for determining whether or not there is a notification that transmission can be resumed, and the line common control unit 11 only responds to transmission character requests from the line connection unit 12. It is only necessary to pay attention to this and process it, and the transmission resumption notification signal sent from the line connection unit 12 to the line common control unit 11 can be omitted.

〔Effect of the invention〕

As described above, according to the present invention, a plurality of line connection units having various logical/physical/electrical interfaces corresponding to data line termination devices and a line common unit that commonly controls the plurality of line connection units are provided. In a communication control device having a control unit, when controlling the flow of transmission data, the line common control unit does not need transmission-time stop processing and transmission restart processing, and the processing is reduced compared to conventional methods. This has the advantage that the load on the common control unit can be reduced.

Furthermore, according to the present invention, the transmission resumption notification signal from the line connection unit to the line common control unit can be omitted, which simplifies the connection between a plurality of line connection units and the line common control unit, and the line common control unit Another advantage is that the number of connection pins for transmission resumption notification signals can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a processing flow diagram of FIG. 1, FIG. 3 is a block diagram showing the configuration of a conventional transmission data flow control system, and FIG. This figure is a processing flow diagram of FIG. 3, and FIG. 5 is a block diagram showing the basic configuration of a data communication system targeted by the present invention. 1... Communication control device, 11... Line common control unit,
12... Line connection part, 13... Transmission character request signal, 15... Transmission data line, 120... Transmission circuit,
121...AND circuit, 2...Data line termination device, 3...Data communication line, 41...Transmission resumption notification signal, 42...Transmission data line.

Claims (1)

[Claims] (1) In a communication control device that is connected to a data communication line via a data line termination device and has a plurality of line connection units compatible with the data line termination unit and a line common control unit that commonly controls the plurality of line connection units. In the transmission data flow control method, when the transmission resumable notification signal from the data line terminating device is off, the line common control unit controls the transmission data regardless of whether there is a transmission character request in the line connection. When the transmission character request signal to the line common control unit is turned off and the transmission resumable notification signal from the data line termination device is on, if there is a transmission character request at the line connection unit, the transmission character request signal to the line common control unit is turned on. . The transmission data flow control system, wherein the line common control unit transfers data to the line connection unit when a transmission character request signal from the line connection unit is on.