JPH09319681A - Data modem - Google Patents

Abstract

(57) Abstract: It is possible to receive data without discarding the received data even when the terminating terminal is not connected to the modulation and demodulation device. SOLUTION: When the unconnected state of the terminating terminal 2 is detected in the terminating terminal connection detecting section 16, the control section 12 compresses the received data by the data compressing section 17 and the memory section 15 is provided.
Accumulation control to. After that, when the connection state is detected, the data in the memory unit 15 is decompressed by the data decompression unit 18 and sent to the terminal terminal 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data modulator / demodulator for monitoring data, and in particular for exchanging data between a terminal terminal device such as a personal computer and a communication network.

[0002]

2. Description of the Related Art In a conventional data modulator / demodulator of this type, when a message from a communication network is received when a terminal is not connected to the modulator / demodulator, the message is discarded. The message from the communication network is sent to the terminating terminal only when the terminating terminal is connected.

[0003]

As described above, in the conventional modulator / demodulator, when the terminating terminal is not connected,
Even if a message is received, this message is discarded, so that there is a drawback that it is necessary to retransmit the message and check the status of the other party.

An object of the present invention is to provide a data modulation / demodulation device which protects a received message by storing the received message without discarding the received message when the terminal is connected.

Another object of the present invention is to provide a data modulation / demodulation device which makes good use efficiency of a storage memory when storing received messages when a termination terminal is not connected.

[0006]

According to the present invention, there is provided a data modulation / demodulation device for exchanging data between a terminating terminal device and a communication network, which detects a connection state with the terminating terminal device. Detecting means for accumulating received data, and controlling the accumulation of data received from the communication network when the unconnected state is detected by the detecting means to the accumulating means, and connecting by the detecting means. A data modulation / demodulation device is provided which includes control means for controlling transmission of the accumulated data of the accumulating means to the terminal device in response to the detection of the state.

The control means has a compression means for compressing the received data and outputting it to the storage means, and a decompression means for decompressing the storage data of the storage means and outputting it. There is.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention will be described. The received message is stored in the memory even if the terminal is not connected to the terminal, and the stored message is read from the memory and sent out when the connection to the terminal is confirmed.

In this case, in order to effectively use the memory,
Received messages (data) are compressed and stored in memory,
When it is read, it is expanded and sent to the terminal terminal. Incidentally, when the termination terminal is connected, the received message is sent to the termination terminal as it is without being stored in the memory, as in the conventional case.

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

FIG. 1 is a system block diagram showing an embodiment of the present invention. Referring to FIG. 1, a data modulator / demodulator 1
Is connected between the terminating terminal 2 such as a personal computer and the communication network 3, and serves as an interface for exchanging data between the terminating terminal 2 and the communication network 3.

The data input / output unit 11 of the data modulator / demodulator 1
Performs data communication with the terminating terminal 2 via the RS-232C cable 4, for example. The network input / output unit 14 performs data communication with the network 3, and the modulation / demodulation unit 13 performs modulation / demodulation processing of transmission / reception data.

The data compression unit 17 compresses the received data (message) from the network 3 and stores it in the memory unit 15. The data expansion unit 18 stores the data in the memory unit 15.
The stored data is expanded and sent to the terminal terminal via the data input / output unit 11.

The terminating terminal connection detecting section 16 has a function of detecting whether or not the terminating terminal 2 is connected to the data modulation / demodulation device 1, and the cable 4 is the RC-232C described above.
If it is a cable, E provided in this cable
The R signal (terminal ready signal; indicating that terminal transmission / reception is possible when active) is detected to detect the connected / unconnected state of the terminal terminal 2.

The control unit 12 controls the operation of each of these units.

FIG. 2 shows an operation flowchart of the embodiment of the present invention. Referring to FIG. 2, data from the network 3 is received by the network input / output unit 14 (step S1). This received data is sent to the modulator / demodulator 13
Is demodulated (step S2), and the terminal terminal connection detection unit 1
If it is detected at 6 that the terminal 2 is connected (step S3), the received data is sent to the terminal 2 via the data input / output unit 11.

On the contrary, when the terminal terminal 2 is detected to be in the unconnected state (step S3), the data compression section 17 compresses the data (step S4), and the memory section 15 is executed.
Is stored in (step S5).

Thereafter, when it is detected that the terminal terminal 2 is in the connected state (step S6), the compressed data stored in the memory unit 15 is expanded by the data expansion unit 18 (step S7), and the data is expanded. It is sent to the terminal 2 via the input / output unit 11.

As an example of the compression of the data compression unit 17, a common dictionary is used, and while acquiring the data in the received data, it is searched whether or not the character or character string already exists in the dictionary. It is a method of compressing characters or character strings by replacing them with numbers in the dictionary.

If the character or character string does not exist in the dictionary, the character or character string is newly registered in the dictionary.
On the contrary, in decompressing the data, the compressed data is sequentially decompressed using the common dictionary.

For registration in the dictionary, a character string consisting of the previous matching character string and the current matching character string is registered, and when the dictionary is full, the unused items for a long time are discarded.
The dictionary is managed by a queue for each item, and each time an item is used, the item is placed at the end of the queue. In the initial state, it is assumed that nothing is registered in the dictionary.

FIG. 3 is a flow chart of the data compression operation described above. First, it is detected whether or not there is uncompressed received data (step S9), and if there is, the character or character string is acquired ( Step S10). A case where the character string of the received data in this case is "ABAB" and is compressed will be described.

It is detected whether or not the first character "A" is registered in the dictionary (step S11), but since it is not registered yet, it is registered in the dictionary (step S13), and the registration is performed. "1" which is the number in the created dictionary
"No." is output (step S12). The next character "B" is similarly registered in "No. 2" of the dictionary and "2" is output.
No. ”is output. At this point, the two letters“ A ”,
The character "AB" including "B" is also registered in "3" of the dictionary.

Since the next character string "AB" is already registered in the dictionary (step S11), the number "3" is output (step S12). Where the previous letter "B"
And the character string "AB" that matched this time with the character string "BA
"B" and "BA" are registered in "4" and "5" of the dictionary, respectively.

By repeating the above processing until there is no uncompressed received data, the received data can be compressed.

FIG. 4 is a flow chart of the data decompression operation. First, it is detected whether or not undecompressed data exists (step S14), and if it exists, the dictionary number of the undecompressed data is acquired (step S15). The registered 8-bit character string is indexed by this dictionary number (step S16), and this character string is output (step S17).

By repeating the above processing until there is no unexpanded data, the data can be expanded.

Regarding the data compression / decompression method,
Obviously, various known techniques other than the examples shown in FIGS. 3 and 4 can be used.

As a mode of detecting the connected / unconnected state in the terminal terminal connection detecting section 16, the signal state of the predetermined control line in the cable 4 (the signal line which becomes active at the time of connection) can be detected. It ’s good.

[0030]

As described above, according to the present invention, the received data is compressed and stored in the memory, and after confirming the connection with the terminating terminal, the stored compressed data is expanded and terminated. By sending the message to the terminal, the received message is not discarded, and there is an effect that it is not necessary to retransmit the data and confirm the state of the other party. In addition, since the data received when the terminal is not connected is compressed and stored in the memory, the memory usage efficiency is high.

[Brief description of drawings]

FIG. 1 is a block diagram of a data modulation / demodulation device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation procedure at the time of receiving data.

FIG. 3 is an operation flowchart at the time of data compression.

FIG. 4 is an operation flowchart when decompressing data.

[Explanation of symbols]

 1 Data Modulation / Demodulation Device 2 Termination Terminal Device 3 Communication Network 4 Cable 11 Data Input / Output Section 12 Control Section 13 Modulation / Demodulation Section 14 Network Input / Output Section 15 Memory Section 16 Termination Terminal Connection Detection Section 17 Data Compression Section 18 Data Expansion Section

Claims (5)

[Claims] 1. A data modulator / demodulator for exchanging data between a terminating terminal device and a communication network, comprising: detecting means for detecting a connection state with the terminating terminal device; and storing received data. And a storage unit that controls the storage unit to store the data received from the communication network when the connection state is detected by the detection unit, and the storage unit in response to the detection of the connection state by the detection unit. And a control means for controlling transmission of the stored data of the above to the terminal device. 2. The data modulation / demodulation device according to claim 1, wherein the control means has a compression means for compressing the received data and outputting the compressed data to the storage means. 3. The data modulation / demodulation apparatus according to claim 2, wherein the control means has a decompression means for decompressing and outputting the accumulated data of the accumulating means. 4. The detecting means is adapted to detect a connected / unconnected state according to a state of a connection detection signal line in a cable connecting to the terminal device. 3. A data modulator / demodulator according to any one of 3). 5. The terminal device is a personal computer device, the cable is an RS-232C cable, and the detecting means is adapted to detect the state of a terminal ready signal of the RS-232C cable. The data modulator / demodulator according to claim 4, wherein