JPH0744566B2 - Data communication controller - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for controlling data communication between a plurality of lines and a plurality of partner stations in which the plurality of lines are multiplexed. The present invention relates to a data communication control device capable of improving efficiency when a plurality of lines and a plurality of partner stations in which the plurality of lines are multiplexed communicate with each other.

[0002]

2. Description of the Related Art Conventionally, in this type of data communication control device, a buffer pool inside the device is managed and buffer control is performed. Transmission data from the host device is temporarily stored in the transmission buffer acquired from the buffer pool. Also, the received data from the physical line is temporarily stored in the receiving buffer acquired from the buffer pool.

When performing a transmission operation in a communication protocol for controlling data communication of a large number of partner stations per line, it is possible to acquire a transmission buffer from a buffer pool when the transmission data is passed from a host device. For example, the transmission buffer is acquired and the transmission data is stored. If data can be transmitted to the communication partner, the transmission data is fetched from the transmission buffer and transmitted to the physical line. When the transmission is completed, the transmission buffer is released and returned to the buffer pool.

Whether or not the transmission buffer can be acquired is determined by managing the number of transmission buffers retained inside the device for each line.
To prevent the buffer from being occupied by one line, define the maximum number of transmit buffers that can be acquired as the transmit buffer busy occurrence value, and include this acquisition when acquiring the transmit buffer from the buffer pool. When it is compared with the already acquired number and becomes equal to the transmission buffer busy occurrence value, the upper device is notified that the transmission buffer busy state has occurred. At this time, it is displayed to the upper device that the transmission data cannot be received.

When the communication partner cannot receive the transmission data, the transmission buffer retained in the device due to the stop of the transmission operation is returned to the buffer pool by the release of the transmission buffer when the transmission operation is started, and the transmission buffer is acquired again. The transmit buffer busy state is defined as the transmit buffer busy state release value, and compared with the number of transmit buffers already acquired when releasing the transmit buffer, and when the transmit buffer busy state becomes equal to the transmit buffer busy state release value. The higher-level device is notified of the cancellation. In this way, the flow control is performed by managing the number of transmission buffers storing transmission data for each line. At this time, it is displayed to the host device that the transmission data can be received.

As described above, the conventional device controls the number of transmission buffers storing transmission data on a line-by-line basis to control the flow of data transmission.

On the other hand, when performing the receiving operation, when the reception data is sent from the communication partner via the physical circuit, if the reception buffer can be acquired from the buffer pool, the reception buffer is acquired and the reception data is stored. . If data can be received from the communication partner, the received data is extracted from the reception buffer and received on the physical line. When reception is completed, the receive buffer is released and returned to the buffer pool.

Whether the reception buffer can be acquired or not is managed by managing the number of reception buffers retained in the device for each line, and the reception buffer can be acquired so that one line does not occupy the buffer. When the maximum value of the number of receive buffers is defined as the receive buffer busy occurrence value, and when the receive buffer is acquired from the buffer pool, it is compared with the already acquired number including this acquisition, and when it becomes equal to the receive buffer busy occurrence value In addition, the upper device is notified that the reception buffer busy state has occurred. At this time, it is displayed to the communication partner that the received data cannot be received.

Further, when the host device cannot receive the received data from the communication partner, the reception buffer retained in the device due to the stop of the reception operation is returned to the buffer pool by the start of the reception operation by releasing the reception buffer, and the reception buffer is again received. Is defined as the receive buffer busy state release value, compared with the number of receive buffers already acquired when releasing the receive buffer, and when it becomes equal to the receive buffer busy release value, Notify the higher-level device that the buffer busy state has been released. At this time, it is displayed to the communication partner that the reception data can be received.

As described above, the conventional apparatus manages the number of reception buffers storing the reception data for each line to control the flow of data reception.

[0011]

In the above-mentioned conventional data communication control device, a large amount of transmission buffers are allocated to each line by the transmission data of a certain partner station among the multiplexed lines. In addition, since a large amount of receive buffer allocated to each line is occupied by the received data of a certain partner station in the line where the line is multiplexed to the other station, data transmission and reception to and from all the other stations should be equalized. There was an uncontrollable drawback.

The present invention solves such a problem, and an object of the present invention is to provide a data communication control device capable of uniformly controlling the data transmission / reception with all the partner stations and improving the efficiency of data communication. And

[0013]

A first aspect of the present invention comprises a data transmitting means and a data receiving means, wherein the data transmitting means includes a transmission buffer for temporarily storing transmission data, and the data receiving means includes Manages the number of the above-mentioned transmission buffers storing the transmission data accumulated in each line in the data communication control device including the reception buffer for temporarily storing the reception data, and the number of the transmission buffers is preset for each line. In the case of performing a line unit transmission buffer busy state according to the established threshold value and a line unit transmission buffer control means for releasing the line unit transmission buffer busy state and performing data communication with a plurality of partner stations by multiplexing the line, It manages the number of transmission buffers that store the transmission data accumulated in the partner station, and Dimethyl occurrence of other station units transmit buffer busy state according to a threshold set for each other station,
And a partner station unit transmit buffer control means for releasing the busy state of the partner station unit transmit buffer, and manages the number of the receive buffers storing the receive data accumulated in the line unit, A line-unit receive buffer control means for generating a line-unit receive buffer busy state and releasing the line-unit receive buffer busy state according to a threshold number of which is set in advance for each line, and a line multiplex with a plurality of partner stations When performing data communication, it manages the number of receive buffers that store the received data accumulated in each partner station, and the number of receive buffers Generates a receive buffer busy status and cancels the receive buffer busy status of the partner station. Characterized in that the § control means is juxtaposed.

A second aspect of the present invention comprises a data transmission means,
In this data transmission means, in the data transmission control device including the transmission buffer for temporarily storing the transmission data, the number of the transmission buffers storing the transmission data accumulated in the line unit is managed, and the number of the transmission buffers is controlled. Line-unit transmission buffer control means for generating a line-unit transmission buffer busy state and releasing the line-unit transmission buffer busy state according to a threshold preset for each line, and data communication with a plurality of partner stations by multiplexing the line In this case, the number of the transmission buffers storing the transmission data accumulated in the partner station is managed, and the number of the transmission buffers is adjusted in accordance with the threshold value set in advance for each partner station. Transmission buffer for the partner station that generates a busy status and cancels the transmission buffer of the partner station Wherein the control and were juxtaposed.

A third aspect of the present invention comprises data receiving means,
In the data reception control device including a reception buffer for temporarily accumulating the reception data in the data reception means, the number of the reception buffers storing the reception data accumulated in the line unit is managed, and the number of the reception buffers is controlled. A line-unit receive buffer control means for generating a line-unit receive buffer busy state and releasing the line-unit receive buffer busy state according to a threshold preset for each line, and data communication with a plurality of partner stations by multiplexing the line In this case, the number of reception buffers storing the reception data accumulated in the partner station is managed, and the number of the reception buffers is adjusted in accordance with the threshold set in advance for each partner station. Remote station reception buffer that generates busy status and remote station unit reception buffer busy status Characterized in that the control means is juxtaposed.

As the threshold value, another value can be set for setting and releasing the busy state.

[0017]

The line-unit transmission buffer control means manages the number of transmission buffers in which transmission data accumulated in line units is stored, and the number of transmission buffers is set in advance for each line to generate a transmission buffer busy state. Line-by-line transmit buffer busy occurrence value becomes equal to the line-by-line transmit buffer busy occurrence value, or the number of transmit buffers is preset for each line. When it becomes equal to the buffer busy cancellation value and it is detected whether the transmission buffer busy condition for each line is canceled, it is reported to the host device. On the other hand, the partner station unit transmission buffer control means manages the number of transmission buffers storing the transmission data accumulated in the partner station, and the number of transmission buffers is set in advance for each partner station. The transmission buffer busy occurrence value becomes equal to the remote station unit transmit buffer busy occurrence value, or the remote station unit transmit buffer busy state has occurred, or the number of transmit buffers set in advance for each remote station is released. When it becomes equal to the remote station unit transmission buffer busy cancellation value to be detected and it is detected whether the remote station unit transmission buffer busy status is released, it is reported to the higher-level device.

Further, the line unit reception buffer control means is
It manages the number of receive buffers that store the receive data that is accumulated in each line, and the number of receive buffers is set in advance for each line. Equal to the line-by-line receive buffer busy state, or the number of receive buffers becomes equal to the line-by-line receive buffer busy release value that detects the release of the receive buffer busy state preset for each line. When it detects whether the busy state has been released, it reports to the host device. On the other hand, the reception buffer control means for each partner station manages the number of reception buffers storing the reception data accumulated in each partner station, and the number of reception buffers is set in advance for each partner station. When the reception buffer busy status of the remote station is detected and the reception buffer busy status of the remote station has occurred, or
When the number of receive buffers is equal to the remote station unit receive buffer busy release value that detects the release of the receive buffer busy state set for each remote station in advance, the higher rank is detected when the remote station unit receive buffer busy state is released. Report to the device.

As a result, the transmission buffer and the reception buffer are managed for each line and each partner station to control the busy state, and the efficiency of data communication can be improved.

[0020]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention.

The embodiment of the present invention comprises a data transmitting means 14,
The data receiving means 24 and the host device communication means 11 are provided, the data transmitting means 14 includes a transmission buffer 14a for temporarily storing the transmission data, and the data receiving means 24 includes a reception buffer 24a for temporarily storing the reception data. Further, as a feature of the present invention, the number of transmission buffers 14a storing the transmission data accumulated in each line is managed, and the number of the transmission buffers 14a is set in accordance with a threshold value set in advance for each line. A line unit transmission buffer control means 12 for generating a transmission buffer busy state and releasing the line unit transmission buffer busy state;
When the lines are multiplexed and data communication is performed with a plurality of partner stations, the number of the send buffers 14a storing transmission data accumulated in the partner stations is managed, and the number of the send buffers 14a is preset in advance. Occurrence of a transmission buffer busy state for each partner station according to the threshold set for each
And a partner station unit transmit buffer control unit 13 for releasing the busy state of the partner station unit, and manages the number of the receive buffers 24a storing the received data accumulated in the line unit, and the receive buffers The line-unit receive buffer control means 22 for generating a line-unit receive buffer busy state and releasing the line-unit receive buffer busy state according to a threshold value set in advance for each line, and a plurality of partners by multiplexing the line When performing data communication with a station, the number of reception buffers 24a storing the reception data accumulated in the partner station is managed,
The number of the receiving buffers 24a is provided together with the receiving buffer control means for the receiving station, which generates the receiving buffer busy state for the receiving station according to the threshold value set in advance for the receiving station and releases the receiving buffer busy state for the receiving station. To be done. The threshold is set to another value for setting and releasing the busy state.

In the case of the transmission buffer control in data transmission, the host device communication means 11 receives the control information and the transmission data from the host device, stores it in the transmission buffer, passes the control information to the host device, and controls the transmission buffer for each line. The means 12 manages the number of transmission buffers storing the transmission data accumulated inside the communication control device for each line, and when detecting the occurrence or cancellation of the line unit transmission buffer busy state, the host device communication means 11 Report to.

The partner station unit transmission buffer control means 13
Manages the number of transmission buffers storing the transmission data accumulated in the communication control device for each partner station, detects the occurrence or cancellation of the partner-unit-unit transmit buffer busy state, and reports it to the host device communication means 11. Data transmission means 14
Transmits the transmission data stored in the transmission buffer transmitted from the host device communication means 11 to the physical line, and the control means 15 follows the procedure of the transmission buffer control and the host device communication means 11 and the line unit transmission buffer control means 12 , The partner station unit transmission buffer means 13 and the data transmission means 14 are sequentially controlled.

In the case of receiving buffer control in data reception, the host device communication means 11 receives control information from the host device and passes the received data and control information to the host device,
The line-by-line receive buffer control means 22 manages the number of receive buffers storing the received data accumulated inside the communication control unit on a line-by-line basis, and detects the occurrence or cancellation of the line-by-line receive buffer busy state. It reports to the host device communication means 11.

Also, the receiving buffer control means 23 for each partner station
Manages the number of transmission buffers storing the reception data accumulated in the communication control device for each partner station, and when the occurrence or cancellation of the partner-unit-unit reception buffer busy state is detected, the host device communication means 11 The data receiving means 24 stores the received data received from the physical line in the receive buffer 24a and detects the presence or absence of the received data, and the control means 15 follows the procedure of the receive buffer control and the upper device communication means 11 and the line. Unit reception buffer control means 22,
The receiving station unit reception buffer control means 23 and the data reception means 24 are sequentially controlled.

FIG. 2 is a flow chart showing the flow of the preprocessing operation of data transmission in the embodiment of the present invention, and FIG. 3 is a flow chart showing the flow of the control operation of data transmission in the embodiment of the present invention.

When data is transmitted to the physical lines of a plurality of partner stations via a plurality of multiplexed lines, the number of transmission buffers that can be acquired from the transmission buffer pool is determined for each line and used as the transmission L busy occurrence value. Furthermore, the number of transmission buffers that can be acquired from the transmission buffer pool is determined for each partner station and set as the transmission T busy occurrence value. The transmission L busy occurrence value can be set to a different value for each line.
The transmission T busy occurrence value can be set to a different value for each partner station.

On the other hand, the number of transmission buffers stored in the communication control device capable of canceling the transmission L busy state is set as the transmission L busy release value, and the communication control device capable of releasing the transmission T busy state. The number of transmission buffers retained inside is set as the transmission T busy release value. A different transmission L busy release value can be set for each line, and a different transmission T busy release value can be set for each partner station.

Here, the number of transmission buffers ≧ transmission L busy occurrence value ≧ transmission L busy release value, transmission L busy occurrence value ≦ transmission T busy occurrence value T1 + ... + T
By setting n, it is possible to control the transmission buffer corresponding to the state of data communication and the communication protocol.

The pre-processing operation for transmitting data to the line will be described in detail with reference to FIG.

When the host device transmits data to the host device communication means 11, the host device communication means 11 reports the start of data transmission to the control means 15 according to the control information (step A).
1) Obtain one transmission buffer from the transmission buffer pool (step A2), and read the transmission data into the transmission buffer (step A3).

The line-by-line transmission buffer control means 12 checks to which line of the plurality of lines the transmission data is sent (step A4), and when the transmission L busy counter is incremented by 1, the transmission L busy counter is stored in the communication control unit. The number of transmission buffers storing the transmission data staying in is counted (step A5). Next, the transmission L busy counter is compared with the transmission L busy occurrence value. The transmission L busy occurrence value is a boundary value at which a transmission L busy occurs which is predetermined for each partner station (step A6). If the transmission L busy counter and the transmission L busy occurrence value are equal by this comparison, the transmission L busy occurrence is notified to the host device communication means 11 via the control means 15. Upon receiving this notification, the host device communication means 11 notifies the host device of the occurrence of transmission L busy (step A7).

Next, in order to control the transmission buffer of the partner station, the partner station unit transmission buffer control means 13 investigates to which partner station among the plurality of partner stations the transmission data is sent (step A8). The transmission T busy counter stored for each station is incremented by 1. The transmission T busy counter counts, for each partner station, the number of transmission buffers storing transmission data accumulated in the communication control device (step A9). Subsequently, the partner station unit transmission buffer control means 13 compares the transmission T busy counter with the transmission T busy occurrence value. The transmission T busy occurrence value is a boundary value at which a transmission T busy occurs that is predetermined for each partner station (step A10). If the transmission T busy counter and the transmission T busy occurrence value are equal by this comparison, the higher-level device communication means 11 is notified via the control means 15 that the transmission T busy has occurred. The host device communication means 11 notifies the host device of the occurrence of transmission T busy (step A11).
At this time, the data transmission means 14 puts the transmission buffer in the data transmission queue for transmission to the physical line (step A12).

Next, the control operation of data transmission to the physical line will be described in detail with reference to FIG.

If the data transmission to the physical line is possible, the data transmission means 14 starts the data transmission to the physical line under the control of the control means 15 (step B1), and the data transmission queue transmission. The buffer is taken out and the data in the transmission buffer is transmitted to the physical line (step B2), the transmission buffer is released and returned to the transmission buffer pool (step B3).

The line-by-line transmission buffer control means 12 investigates to which line of the plurality of lines the transmission data is transmitted (step B4), subtracts 1 from the transmission L busy counter (step B5), and the transmission L busy counter. And the transmission L busy release value are compared. The transmission L busy cancellation value is a boundary value for canceling the transmission L busy predetermined for each partner station (step B6). If the transmission L busy counter and the transmission L busy cancellation value are equal by this comparison, the transmission L busy cancellation is notified to the host device communication means 11 via the control means 15. The host device communication means 11 notifies the host device of the transmission L busy cancellation (step B7).

Next, in order to control the transmission buffer of the partner station, the partner station unit transmission buffer control means 13 investigates to which partner station among the plurality of partner stations the transmission data is sent (step B8). The transmission T busy counter stored for each partner station is decremented by 1 (step B9). Then, the transmission T busy counter is compared with the transmission T busy release value. The transmission T busy release value is a boundary value for releasing the transmission T busy predetermined for each partner station (step B1).
0). If the transmission T busy counter and the transmission T busy cancellation value are equal, the higher-level device communication means 11 is notified of the transmission T busy cancellation via the control means 15. The upper device communication means 11 notifies the upper device of the transmission T busy cancellation (step B11). The control means 15 ends the data transmission to the physical line (step B12).

Next, the control of the reception buffer in data reception will be described. FIG. 4 is a flow chart showing the flow of pre-processing operation for data reception, and FIG. 5 is a flow chart showing the flow of control operation for data reception.

When performing data communication with a plurality of partner stations through a plurality of multiplexed lines, the number of reception buffers that can be acquired from the transmission buffer pool is determined for each line and the reception L
Set as the busy occurrence value. Further, the number of reception buffers that can be acquired from the reception buffer pool is determined for each partner station and set as the reception T busy occurrence value. As the reception L busy occurrence value, different values can be set for each line. Further, the reception T busy occurrence value can be set to a different value for each partner station.

On the other hand, the number of reception buffers retained in the communication control device capable of canceling the reception L busy state is set as the reception L busy release value, and the communication control device capable of releasing the reception T busy state. The number of reception buffers retained inside is set as the reception T busy release value. As the reception L busy cancellation value, different values can be set for each line. Further, the reception T busy cancellation value can be set to a different value for each partner station.

Here, the number of reception buffers ≧ reception L busy occurrence value ≧ reception L busy release value, and reception L busy occurrence value ≦ reception T busy occurrence value T1 + ... + T
By setting n, the reception buffer control corresponding to the state of data communication and the communication protocol can be performed.

The pre-processing operation for receiving data will be described in detail with reference to FIG.

The data for the host device is the data receiving means 24.
When the data is received from the physical line,
The start of data reception is reported to the control means 15 by the control information (step C1), one reception buffer is acquired from the reception buffer pool (step C2), and the reception data is stored in the reception buffer (step C3).

The line-by-line receive buffer control means 22 checks which of the plurality of lines the received data is from (step C4), and increments the receive L busy counter by 1 (step C5). The reception L busy counter counts the number of reception buffers storing the reception data accumulated in the communication control device. Next, the reception L busy counter is compared with the reception L busy occurrence value. Receive L
The busy occurrence value is the reception L that is predetermined for each partner station.
This is a boundary value at which busy occurs (step C6). If the reception L busy counter and the reception L busy occurrence value are equal to each other by this comparison, the reception L busy occurrence is notified to the host device communication means 11 via the control means 15. The host device communication means 11 notifies the host device of the reception L busy occurrence (step C7).

Next, in order to control the reception buffer of the partner station, the partner station unit reception buffer control means 23 investigates which partner station among the plurality of partner stations the received data is (step C8), The reception T busy counter stored for each partner station is incremented by 1. The reception T busy counter counts the number of reception buffers storing the reception data accumulated in the communication control device for each partner station (step C9). Further, the partner station unit reception buffer control means 23 compares the reception T busy counter with the reception T busy occurrence value. The reception T busy occurrence value is a boundary value at which reception T busy occurs which is predetermined for each partner station (step C10). If the reception T busy counter and the reception T busy occurrence value are equal by this comparison, the reception T busy occurrence is notified to the host device communication means 11 via the control means 15. The host device communication means 11 notifies the host device of the occurrence of reception T busy (step C11). The data receiving means 24 stores the reception buffer in the reception data transfer queue for transferring to the host device (step C12).

Next, the control for transferring the received data to the host device will be described with reference to FIG.

If the received data can be transferred to the host device, the host device communication means 11 controls the control means 1.
According to the control of 5, the reception data transfer to the host device is started (step D1), the reception buffer in the reception data transfer queue is taken out, the reception data in the reception buffer is transferred to the host device (step D2), and the reception buffer Is released and returned to the reception buffer pool (step D3).

The line-by-line receive buffer control means 22 checks which line of the plurality of lines the received data is from (step D4), subtracts 1 from the received L busy counter (step D5), and receives the received L busy counter. And the received L busy release value are compared. The reception L busy cancellation value is a boundary value for canceling the reception L busy predetermined for each partner station (step D6). Next, if the reception L busy counter and the reception L busy cancellation value are equal, the upper apparatus communication means 11 is notified of the reception L busy cancellation via the control means 15. The host device communication means 11 notifies the host device of the reception L busy cancellation (step D7).

Next, in order to perform the receiving buffer control device of the partner station, the partner station unit receive buffer control means 23 investigates to which partner station among the plurality of partner stations the received data is received (step D8). , The reception T busy counter stored for each partner station is decremented by 1 (step D9). continue,
The reception T busy counter and the reception T busy release value are compared. The reception T busy cancellation value is a boundary value for canceling the reception T busy predetermined for each partner station (step D10). If the reception T busy counter and the reception T busy cancellation value are equal by this comparison, the host device communication means 11
Is notified of the reception T busy cancellation via the control means 15.
The upper device communication means 11 notifies the upper device of the reception T busy cancellation (step D11). The control means 15 terminates the data reception to the physical line (step D12).

[0050]

As described above, according to the present invention, a large amount of transmission buffer is not occupied by the transmission data of one partner station, and the data transmission of all the partner stations can be equally controlled. it can. Further, it is possible to prevent the reception buffer from being occupied in a large amount by the reception data of a certain one partner station, and to equally control the data reception of all the partner stations. Therefore, there is an effect that data communication can be efficiently performed in a communication path configured by logical multiplexing in which there are a plurality of partner stations per line.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing a flow of a preprocessing operation of data transmission in the embodiment of the present invention.

FIG. 3 is a flowchart showing a flow of control operation of data transmission in the embodiment of the present invention.

FIG. 4 is a flowchart showing a flow of a pre-processing operation for data reception in the embodiment of the present invention.

FIG. 5 is a flowchart showing a flow of control operation of data reception in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 host device communication means 12 line unit transmission buffer control means 13 partner station unit transmission buffer control means 14 data transmission means 14a transmission buffer 15 control means 22 line unit reception buffer control means 23 partner station unit reception buffer control means 24 data reception means 24a Receive buffer

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Claims (4)

[Claims] 1. A data transmission unit and a data reception unit, wherein the data transmission unit includes a transmission buffer for temporarily storing the transmission data, and the data reception unit includes a reception buffer for temporarily storing the reception data. The data communication control device manages the number of the above-mentioned transmission buffers storing the transmission data accumulated in each line, and the number of the transmission buffers is in the line unit transmission buffer busy state according to the threshold value set in advance for each line. Error occurs, and the line unit transmission buffer control means for releasing the line unit transmission buffer busy state, and when the line is multiplexed and data communication is performed with multiple other stations, The number of stored transmission buffers is managed, and the number of transmission buffers is set in advance for each partner station. According to the above, the partner station unit transmit buffer busy state is generated and the partner station unit transmit buffer busy state is released together with the partner station unit transmit buffer control means, and the received data accumulated in the line unit is stored. A line-unit receive buffer control means for managing the number of receive buffers, generating a line-unit receive buffer busy state and canceling the line-unit receive buffer busy state according to a threshold value set beforehand for each line. When multiple lines are used for data communication with other stations, the number of receive buffers that store the received data that is accumulated in each station is managed, and the number of receive buffers is adjusted in advance. Depending on the threshold set for each station, the reception buffer busy status of the partner station may occur and That the other station unit receiving buffer control means to release the receive buffer busy state is annexed data communication control device according to claim. 2. A data transmission control device comprising a data transmission means, wherein the data transmission means includes a transmission buffer for temporarily accumulating the transmission data, wherein the transmission buffer storing the transmission data staying on a line basis. A line-unit transmission buffer control unit that manages the number of transmission buffers, generates a line-unit transmission buffer busy state according to a threshold value set in advance for each line, and releases the line-unit transmission buffer busy state. When performing data communication with a plurality of partner stations by multiplexing, the number of the above-mentioned send buffers in which the send data staying in each partner station is stored is managed, and the number of the send buffers is preset for each partner station. Occurrence of a transmission buffer busy state for each partner station according to the set threshold, and transmission buffer busy for each partner station Data transmission control apparatus characterized by the other station units transmit buffer control means for releasing the status has been juxtaposed. 3. A data reception control device comprising data reception means, wherein the data reception means includes a reception buffer for temporarily accumulating the reception data, wherein the reception buffer of the reception buffer storing the reception data stored in line units is stored. A line-unit receive buffer control means for managing the number of receive buffers and for releasing the line-unit receive buffer busy state according to a threshold value preset for each line When performing data communication with a plurality of partner stations by multiplexing, the number of receive buffers that store the received data accumulated in each partner station is managed, and the number of receive buffers is previously set for each partner station. Occurrence of a receive buffer busy condition for the partner station according to the set threshold, and receive buffer busy for the partner station Data reception control apparatus characterized by the other station unit receiving buffer control means for releasing the status has been juxtaposed. 4. The data communication control device according to claim 1, wherein the threshold value is set to a different value for setting and releasing the busy state.