JPH08172426A - Asynchronous data transmission system - Google Patents

Abstract

PURPOSE: To perform asynchronous data communication without the need for informing a reception side of data transmission speed and the speed conversion of synchronization/asynchronization on the reception side. CONSTITUTION: The asynchronous data of a transmission terminal equipment 1 are speed converted by a FIFO memory 21 and a flow control part 22 on a transmission side, turned to a state matched with the stipulated data transmission speed of a reception terminal equipment 5 and transmitted to the reception side. On the other hand, the speed conversion of the synchronization/ asynchronization is not performed on the reception side and the data are received as they are by the reception terminal equipment 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to transparent relay transmission of asynchronous data when asynchronous data is communicated between asynchronous terminal devices and synchronous data such as a switched line network such as ISDN or a dedicated data line. A transmission device such as a terminal adapter installed for transmission through a transmission path, particularly a data transmission system that realizes a function of converting asynchronous data into synchronous data for transmission and reproducing the asynchronous data from the synchronous data transmitted on the receiving side. It is about.

[0002]

2. Description of the Related Art In order to transmit asynchronous data through a synchronous data transmission line, asynchronous / synchronous conversion is required to match the data rate of asynchronous data with the transmission rate of synchronous data.

As a method for realizing this asynchronous / synchronous conversion, the transmitting side inserts or deletes stuff data into or from an asynchronous data string to perform asynchronous / synchronous speed matching and transmits it as synchronous data to a transmission line. On the receiving side, there is a method in which the stuff data inserted on the transmitting side is deleted from the synchronous data received from the transmission line to perform synchronous / asynchronous speed matching and reproduce only the asynchronous character string.

The conventional technique based on this method is CC
ITT Recommendation V. The method defined in 14 is known.

In this method, stop bits in an asynchronous character are used as the stuff data. On the transmission side, a stop bit is added between characters so that the transmission speed of the input asynchronous character is matched to the data transmission speed of the transmission path, and transmission is performed on the transmission path. On the receiving side, an asynchronous character is detected from the synchronous data string received from the transmission path, unnecessary stop bits are deleted, and the data is transmitted while being matched in speed with the original asynchronous character data transmission speed.

In the case of this method, it is necessary to know the specified data transmission rate of the asynchronous character to be transmitted in advance in order to match the rate on the receiving side. It is also necessary to perform character synchronization in order to determine the position of which of the transmitted data strings is the added stop bit. This is a stop that is added between each character.
This is because it is a bit position. Therefore, it is also necessary to know the character configuration of the asynchronous character that is transmitted in advance in order to synchronize the characters on the receiving side.

[0007]

As described above, according to the conventional method, communication is started every time when it is applied to a service in which the data transmission rate of asynchronous data exchanged between users by terminals may be changed. Before sending, the sender must notify the receiver of the data transmission speed of the asynchronous character to be sent and set it in the speed matching circuit or character synchronization circuit in the transmission device. However, there is a problem in that it is necessary to provide some means for setting the speed matching circuit and the character synchronization circuit.

An object of the present invention is to eliminate the trouble and means for the transmitting side to notify the receiving side of the data transmission rate of the asynchronous character to be transmitted or to set in the transmission device before starting the communication every time, It is to realize asynchronous data communication.

[0009]

On the transmitting side, the above-mentioned object is to write the asynchronous data of the transmitting terminal device to the FIFO memory at the asynchronous data transmission rate, and to write the data by the writing means to the FIFO memory. And a means for performing speed matching by means of a flow control function for temporarily suspending the transmission operation to the transmitting terminal device to make it in an idle state when the overflow occurs, and then restarting the transmitting operation to the transmitting terminal device when the overflow is recovered, And a means for transmitting the data read from the FIFO memory at the specified data transmission rate on the receiving terminal side to the transmission line as it is, and for the receiving side, a means for sending the synchronization data received from the transmission line to the receiving terminal as it is And the specified data transmission rate of the receiving terminal device is the maximum in the service. It is obtained by setting a larger rate than over data transmission rate is achieved by.

[0010]

According to the above means, the transmission rate of the asynchronous data of the transmitting terminal device is converted to the specified data transmission rate of the receiving terminal device on the transmitting side.

That is, the asynchronous data of the transmitting terminal device is
It is written in the FIFO memory according to the data transmission rate. After that, the data is sequentially read out at the specified data transmission rate on the receiving terminal device side and transmitted as synchronization data to the transmission line. At this time, the difference in the data transmission speed between the writing and reading of the FIFO memory is absorbed by the flow control function for the transmitting terminal device.

As described above, since the synchronous data to be transmitted to the transmission line on the transmitting side has already been converted to the specified data transmission rate on the receiving terminal device side, the receiving side directly receives the synchronous data received from the transmission line on the receiving side. Can be passed to. That is, the receiving side does not need to discriminate the stuff data or insert / extract the stuff data for speed matching, and need not know the data transmission rate of asynchronous data to be transmitted in advance.

By doing so, the transmission side notifies the reception side of the data transmission rate of the asynchronous data to be transmitted, and the rate matching circuit in the transmission apparatus on the reception side before starting the communication every time. Asynchronous data communication can be realized without setting in the character synchronization circuit.

[0014]

The present invention will be described below with reference to examples. FIG.
FIG. 1 is a block diagram of a data communication system according to an embodiment of the present invention.

The transmission terminal device 1 relays the transmission device 2, the synchronous data transmission path 3, and the transmission device 4 to perform data communication with the reception terminal device 5 of the other party by an asynchronous character.

Next, the operation of this data communication system when transmitting asynchronous data from the transmitting terminal device 1 to the receiving terminal device 5 will be described.

The asynchronous data sent from the transmission terminal device 1 to the transmission device 2 is temporarily written in the FIFO memory 21 in order to absorb the speed difference between the data transmission speed of the asynchronous data and the data transmission speed of the transmission line 3. It is temporarily stored and then sequentially read.

The asynchronous character stored in the FIFO memory 21 is read at the same data transmission rate as the prescribed data transmission rate of the receiving terminal device 5, but the speed is different due to the difference between the writing and reading data transmission rates of the FIFO memory 21. We are making a match.

The FIFO memory 21 in this speed matching
The flow control function of the flow control unit 22 supplements the transmission data with respect to the difference between the data transmission rates of writing and reading. That is, when the flow control unit 22 detects an overflow of the FIFO memory 21 during writing, the CTS signal is turned off, the transmission operation of the transmitting terminal device 1 is temporarily suspended, and the idle state is set.
A stop bit is written in the memory 21. After that, when it is detected that the overflow of the FIFO memory 21 is recovered, the CTS signal is turned on, the transmission operation of the transmission terminal device 1 is restarted, and the transmission data is written.

The transmission data complemented according to the speed difference by the flow control function in this way is stored in the FIFO memory 21.
Then, the data is sequentially read at the specified data transmission rate of the receiving terminal device 5 and transmitted to the synchronous data transmission line 3 as synchronous data.

In the transmission device 4 on the receiving side, the synchronization data received from the synchronization data transmission line 3 is directly received by the reception terminal device 5
Send to. At this time, the synchronous data received from the synchronous data transmission path 3 has already been speed-matched to the specified data transmission rate of the receiving terminal device 5 on the transmitting side, so that the receiving terminal device 5 can receive it as it is. It is possible. That is, it is possible to realize asynchronous data communication without requiring a speed matching circuit or a character synchronization circuit in the transmission device 4 on the receiving side.

[0022]

As described above, according to the configuration of the present invention, since it is possible to perform transmission after matching the specified data transmission rate of the receiving terminal device on the transmitting side, the receiving side can change the transmission rate. There is no need to rate match the specified data rate of the receiving terminal.

Therefore, it is possible to omit the labor and means for notifying the data transmission rate of the asynchronous character to be transmitted from the transmitting side to the receiving side before starting the communication every time, or receiving the notification and setting it in the transmission device. It is possible to realize asynchronous data communication.

[Brief description of drawings]

FIG. 1 is a block diagram of an example system according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transmission terminal device, 2 ... Transmission device, 3 ... Synchronous data transmission path, 4 ... Transmission device, 5 ... Reception terminal device, 21 ... FIFO
Memory, 22 ... Flow control unit, 23 ... Line termination unit, 41
… Line termination.

Claims (1)

[Claims] 1. A transmission system in which asynchronous data is received from a terminal device and asynchronous / synchronous speed conversion is performed, and synchronous data communication is performed on a transmission path.
A means for writing to the FO memory at the asynchronous data transmission speed, and the above-mentioned FIF at the time of writing by the writing means.
When the O-memory overflows, the transmission operation is temporarily suspended in the transmission terminal device to put it in an idle state, and when the overflow is recovered, the transmission operation is resumed to the transmission terminal device. And means for transmitting the data read from the FIFO memory at the specified data transmission rate of the receiving terminal device side to the transmission line as it is, and at the receiving side, the synchronous data received from the transmission line is sent to the receiving terminal device as it is. An asynchronous data transmission system, comprising: means, wherein the prescribed data transmission rate of the receiving terminal device is set to a rate higher than the maximum data transmission rate in the service.