JPH05268292A - Data communication equipment - Google Patents

Abstract

PURPOSE:To prevent the impossibility of subsequent transmission when a transmitting side can not receive an XON signal by providing a timer which is stopped when data is received after the sending of the XON, and outputs and instructs the transmission of the XON when the data is not received for a period longer than definite time. CONSTITUTION:Data circuit terminating equipment (DCE) 2 can receive the data when it detects the ON of a data terminal ready DTR signal from data terminal equipment (DTE) 1. When stored quantity in a receiving buffer exceeds a first threshold by the received data, an XOFF signal is outputted to the equipment DTE 1. When the data in the buffer is processed by a control part 22, and the stored quantity in the receiving buffer decreases down to a second threshold, the equipment 2 outputs the XON to the equipment DTE 1 so as to enable the transmission of the data from the equipment DTE 1. At that time, it starts the timer 221, and stops the timer 221 when it receives the data, and when a period of time longer than the definite time elapses, the equipment DCE 2 outputs again the XON to the equipment DTE 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication device, and more particularly to data transmission control.

[0002]

2. Description of the Related Art In a conventional data communication device, an XON signal is output to a partner device only once when the amount of data stored in a reception buffer on the data receiving side becomes less than a second threshold value.

[0003]

However, in this conventional data communication apparatus, since the transmission of the XON signal is performed to the partner apparatus only once when it becomes less than the second threshold value, this XON signal causes a transmission line error. Alternatively, when reception cannot be performed due to a reception overrun error in the serial communication controller of the partner device, it is considered that the XOFF state continues, and there is a problem that data transmission is permanently disabled.

The present invention has been made in view of the above conventional circumstances, and therefore, an object of the present invention is to provide a novel data communication apparatus capable of solving the above problems inherent in the conventional technology. Especially.

[0005]

In order to achieve the above object, a data communication apparatus according to the present invention provides a partner apparatus when the amount of data stored in a reception buffer decreases to a second threshold after sending an XOFF signal. The timer is activated after sending the XON signal, and is stopped if data is received during the activation, and is again provided with a timer for instructing the transmission of the XON signal when a certain set time is exceeded without data reception.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the accompanying drawings with reference to the accompanying drawings.

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

Referring to FIG. 1, a data terminal device (DT
E) 1 and the data circuit terminating device (DCE) 2 are connected by a serial interface, and each receive serial data and convert it into parallel data, and vice versa, convert parallel data into serial data. It has serial controllers 11 and 21 for transmission, and control units 12 and 22 for generating transmission data and analyzing received data.
The control units 12 and 22 are provided with timers 121 and 221 respectively.

FIG. 2 shows an operation flow for explaining the operation of the present invention.
Shown in. In FIG. 2, the data line termination device (DC
The operation in E) is shown, and the data circuit terminating device (DCE) enables data reception when it detects that the DTR signal transmitted from the data terminal device (DTE) is "ON". The first threshold TH which has the amount accumulated in the reception buffer according to the received data
XOFF for data terminal equipment (DTE)
Is output.

The data processing in the buffer is performed by the control unit 22, and there is an amount accumulated in the reception buffer.
When the data line terminal equipment (DCE) is reduced to the threshold value TH of
To enable data transmission from the data terminal equipment (DTE).

At this time, the timer 221 is activated, and if data is received during activation, this timer 221 is stopped. If the timer 221 has exceeded a certain time Tth,
The data circuit terminating equipment (DCE) again outputs XON to the data terminal equipment (DTE).

[0012]

As described above, according to the present invention,
A timer that is activated after the amount of data in the receive buffer is reduced to less than the second threshold and the XON signal is sent to the transmitting side, and when the timer exceeds a certain time, the XON signal is sent to the transmitting side again. By sending the data, even if an error occurs in the first XON signal on the transmission line and the transmission side cannot receive the signal, the retransmission function has an effect that the transmission side can restart data transmission.

[Brief description of drawings]

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

FIG. 2 is an operation flow chart of an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Data terminal equipment (DTE) 11 ... Serial communication controller 12 ... Control part 121 ... Timer 2 ... Data line terminal (DCE) 21 ... Serial communication controller 22 ... Control part 221 ... Timer

Claims (1)

[Claims] 1. When the amount of data in the receiving buffer on the data receiving side between the data terminal device and the data circuit terminating device exceeds the first threshold value, an XOFF signal is output to the transmitting side so that Stop data transmission, second
In the serial communication in which the data transmission is restarted by outputting the XON signal to the transmission side when the data processing is completed up to the threshold value, the data transmission is stopped after the XON transmission, and is stopped at a certain level. A data communication device comprising a timer for instructing a partner device to output XON transmission when no data is received for a time or more.