JP2656048B2 - Data communication device - Google Patents

Description

The present invention has a low-speed mode for modulating and demodulating a signal at a low speed and a high-speed mode for modulating and demodulating a signal at a low speed. And performing data communication by switching to the high-speed mode in accordance with the setting by communication of the procedure signal.

[Conventional technology]

Conventionally, in the G3 procedure of this type of apparatus, for example, a facsimile apparatus, when detecting a low-speed signal and a high-speed signal, it is realized by having two independent modems and receiving whichever signal is transmitted. Was. However, in recent years, modems having two modulation and demodulation modes of low speed and high speed have been increasing in one model. These models can only receive one modulated signal at a time,
High / low speed judgment is made in the modem with or without the training sequence.

[Problems to be solved by the invention]

As described above, when a modem having two demodulation modes of low speed or high speed is used in one modem, particularly when monitoring only the training sequence, there is a possibility that the noise at the head of the signal may make a mistake in distinguishing between high speed and low speed. Is high.

[Means and actions for solving the problems]

According to the present invention, when switching from communication of a procedural signal in the low-speed mode to communication of data in the high-speed mode, detection means for detecting a specific code unique to high-speed data from demodulated data in the high-speed mode; If the specific code is detected before the predetermined time elapses, the data communication in the high-speed mode is continued.If the specific code is not detected before the predetermined time elapses, the high-speed mode is used. By providing control means for switching to the low-speed mode and retransmitting the procedure signal,
Priority is given to data communication in the high-speed mode, and it is possible to return from data communication in the high-speed mode to communication of procedure signals in the low-speed mode again.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the facsimile apparatus of the present embodiment.

In FIG. 1, reference numeral 1 denotes an NCU for controlling circuit switching. Reference numeral 2 denotes a model that modulates serial data from the sub CPU 3 and demodulates a signal received from a line via the NCU 1. When the signal from NUC1 is demodulated, the data is transmitted to sub CPU3. The sub CPU 3 controls the model by a command from the main CPU 4 and performs serial / parallel conversion of signal data. The main CPU 4 controls not only the sub CPU 3 and the model 2 but also the entire facsimile machine. Main CPU4,
The sub CPU 3 is composed of a micro computer, and is connected to peripheral devices of the micro computer such as a read only memory (ROM) storing a control program by a bus line and a random access memory (RAM) for temporarily storing data. .

First, when the facsimile apparatus starts operating as a receiver, the control NCU 1 from the main CPU 4 switches the line to the facsimile side. Next, the main CPU 4 sets the modem 2 to the low-speed mode, and the main CPU 4 outputs to the sub CPU 3 data of a digital identification signal (DIS) indicating a function of the apparatus. The sub CPU 3 serially outputs the data from the main CPU 4 to the modem 2 sequentially, and the modem 2 modulates the data at a low speed (FSK) and sends it out to the line via the NCU 1 (DIS sending).

On the other hand, when receiving the DIS, the transmitting side identifies the function of the receiving side according to the facsimile communication procedure of the CCITT recommendation, and if the receiving side has the error correction mode, the error correcting mode (ECM) is designated by the transmitting side. The ECM selection information is set in the digital command signal DCS for setting the communication mode, and the training and training check signal (TCF) is transmitted in the command and high-speed mode.

The receiving side sets the mode (error correction, high-speed mode, etc.) specified by the transmitting side according to the DCS, and receives the TCF. If there is no error in the TCF, a reception preparation confirmation signal CFR indicating that reception preparation has been completed is transmitted.

After transmitting the CFR, two signals, that is, a high-speed image signal of HDLC format and a procedure signal of DCS and TCF may be transmitted.

One is when the transmitting side can normally receive the CFR transmitted from the receiving side (FIG. 3 (a)).

The second case is when the transmitting side cannot correctly receive the CFR transmitted from the receiving side due to noise or the like (FIG. 5 (a)).

In the former, a high-speed image signal (HDLC format) is transmitted. In the latter, the low-speed procedure signal (DCS + TCF) is transmitted again.

Therefore, it is necessary for the receiving side to distinguish between a high-speed signal and a low-speed signal.

The determination of the former, high-speed image signal will be described below with reference to the flowchart of FIG.

First, in steps S1 and S2, the timer is set and the high-speed mode is set for the modem. Next, steps S3 and S
4. Wait for the signal until a carrier (high speed and low speed) arrives at 4 (here, the timer ends and an error is terminated because the signal does not come).

Here, when the high-speed image signal data is received, the main CPU 4 detects that there is a carrier, clears the flag counter (COUNT) in steps S5 and S6, and sets the timer. Then, in the loop of steps S7 and S8, the main CPU 4
Waits within the time until the flag pattern is received by accessing the sub CPU3.

When a flag pattern is found in the demodulated data of the modem 2, the sub CPU 3 outputs 1 to a predetermined bit in its own register to inform the main CPU 4 that the high speed flag has been found.

When the main CPU 4 detects the flag detection by accessing the sub CPU 3, it starts counting up in step S9. This count up repeats S7, S8, S9, and S10 of the loop, ends when the number of times of flag detection is 10, and proceeds to the high-speed reception routine. Since the minimum transmission time of the flag pattern from the transmission side is determined, the number of times of detection is set in accordance with the minimum. FIG. 4 shows the timing for the image signal of the bit to be set when the sub CPU detects the flag pattern. In the high-speed data reception routine, the demodulated data from the modem is converted serially and transmitted to the main CPU4.

 The above is the reception of the high-speed image signal.

 Next, a case where a low-speed procedure signal is received will be described.

As in the previous case, in steps S1 and S2, the timer is set and the high-speed mode is set for the modem. In steps S3 and S4, wait until a signal carrier arrives. Here, upon receiving the low-speed procedure signal, the main CPU 4 detects that there is a carrier, clears the flag counter in steps S5 and S6, and sets a timer. In the loop of S7 and S8, the main CPU 4 accesses the sub CPU 3 and waits for a time until a flag pattern can be received. But,
The modem 2 starts demodulation, but cannot detect a normal flag pattern due to the low-speed signal, and the time is over in the loop of steps S7 and S8. Step S1 after time over
At 1, the modem 2 is reset to low speed, and low speed reception is started. Since the low-speed procedure signal has a flag transmitted for about 1 second, it can be normally received even if it is received after resetting.

Since the convergence of the modem may be delayed during high-speed reception, if the timer value in step S6 is made slightly longer, the reliability to the high-speed reception determination side is improved. This makes it difficult to receive the low-speed procedure signal, but there is no problem on the low-speed side because command retransmission is specified.

In the above-described embodiment, the facsimile apparatus has been described as an example. However, the present invention can be applied to any data communication apparatus having a plurality of demodulation units.

〔The invention's effect〕

As described above, according to the present invention, when switching from communication of a procedural signal in low-speed mode to communication of data in high-speed mode, detection for detecting a specific code specific to high-speed data from demodulated data in high-speed mode Means, when the specific code is detected by a predetermined time by the detection means, continue the data communication in the high-speed mode,
If the specific code is not detected before the predetermined time elapses, by providing control means for switching from the high-speed mode to the low-speed mode and communicating the procedure signal again, priority is given to data communication in the high-speed mode. In addition, the data communication in the high-speed mode can be returned to the communication of the procedure signal in the low-speed mode again.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present embodiment, FIG. 2 is a flowchart showing a control operation of the present embodiment, FIG. 3 is a diagram showing an image data format in an error correction mode. Fig. 4 shows the image signal reception and the
Fig. 5 shows the detection timing of the CPU.
FIG. 9 is a diagram showing detection timing of U. 1 is an NCU, 2 is a modem, 3 is a sub CPU, and 4 is a main CPU.

Claims (1)

(57) [Claims] 1. A low-speed mode for modulating and demodulating a signal at a low speed, and a high-speed mode for modulating and demodulating a signal at a high speed. Communication of a procedure signal is performed in the low-speed mode. In the data communication device for performing data communication by switching to the high-speed mode, when switching from communication of procedure signals in the low-speed mode to communication of data in the high-speed mode, the high-speed mode Detecting means for detecting a specific code specific to the data, if the detecting means detects the specific code by a predetermined time, communication of the data in the high-speed mode is continued, while the specific code is If not detected by the elapse of a predetermined time, the mode is switched from the high-speed mode to the low-speed mode, and the procedure signal communication is performed again. Data communication apparatus, characterized in that it comprises a control means.