JPH09238201A - Modulation/demodulation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely shift data demodulation state even if the line fault of hit and the like occur by shifting a system to the data demodulation state of a control channel for procedure signal when a frame showing a shift to the communication of a procedure signal is detected. SOLUTION: At the time of an ECM mode (error correction communication mode), the partial page control restoration of a final part in primary channel data is constituted of three partial page control restoration instruction (RCP) frames. Since it is considered as the termination of a picture signal when the RCP frame is detected, the system shifts to a state 101 when MODEM detects the RCP frame in a primary channel data demodulation state 100 and it holds the control channel data demodulation state. When the RCP frame is not detected in the state 100, the same state (primary channel data demodulation state) is held.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modulator / demodulator (modem) for performing data communication via a communication line.

[0002]

2. Description of the Related Art When transmitting digital signal data via a general public line (analog line), a modulator / demodulator (modem) for converting the digital signal into a desired analog signal and vice versa is required. Among the modulation / demodulation devices, the ITU-T V series recommendation V.3 has a transmission rate of 2.4 kbps to 33.6 kbps. 34 has been recommended as a full-duplex / half-duplex modem for transmitting digital data via an analog line as a modem realizing the highest transmission speed. Regarding half-duplex modems used in facsimile machines, V. 27ter (2400bp
s-4800 bps), V.I. 29 (5800bps-9
600 bps), V. 17 (7200bps-1440)
In order to be applicable to a facsimile machine as a modem exceeding a transmission rate of 0 bps), ITU-T Recommendation V.3 34 half duplex version (2400bps ~ 33600kbp
A revision to s) is in progress. This modem is a transmission control procedure T. It comprises a control channel for transmitting 30 and a primary channel for transmitting an image signal, and is for automatically transiting between the primary channel and the control channel in response to an incoming signal from the line. Sequence control function is needed.

In FIG. 5, V34 half-duplex (2400 bps-
33600 kbps) shows an outline of an operation procedure between the primary and control channels.

In the figure, 5-1 is a sequence of a transmitting modem (image transmitting side) and 5-2 is a receiving modem (image receiving side).
Shows the sequence of.

Initially, the transmitting modem as well as the receiving modem are 8 procedures exchange and V.8. At 34, perform line probing and training. Here, the modulation modes and functions applicable between the two are determined, and at the same time, by performing line equalization, the parameters (carrier frequency, symbol rate, pre-emphasis coefficient) necessary for transmitting the subsequent primary channel are determined. Etc.). Subsequently, the transmitting modem is (70 ± 5 mse
c) After sending silence, by transmitting and receiving PPh, ALT, MPh, and E signals, line equalization and synchronization with the receiving modem are established to complete preparation for receiving control channel data sent from the receiving modem. To do. When the receiving modem receives the PPh signal from the transmitting modem,
As a response, after sending the PPh signal, ALT, MP
By transmitting and receiving the h and E signals, line equalization and synchronization with the transmitting modem are established as in the transmitting modem, and the preparation for receiving the control channel data sent from the transmitting modem is completed. Here, the exchange of the MPh signal is performed in order to determine the optimum transmission speed between the transmitting and receiving modems. The signals PPh, ALT, MPh, and E are V.V. 3
This is the same signal as described in 4.

When the preparation for transmission / reception of control channel data is completed by exchanging the PPh-E signals, the transmission control procedure using the control channel is started. In a facsimile apparatus, the T.T.
In general, a communication system based on a half-duplex communication system defined in T.30 is used. 30 and revised to V.30. Considerations have been made to accommodate 34 control channels.
When a series of transmission control procedure exchanges (pre-procedures) are completed prior to transmission / reception of image signals, the transmission / reception modem releases scrambled “1” (turn off) when the transmission request of the control channel from the facsimile apparatus is released. Send for a predetermined period. Subsequently, the transmitting modem will
0 ± 5 msec) Send out silence. After the silence is sent, the sending modem uses S, S , P to resynchronize with the receiving modem.
A resynchronization signal composed of P and B1 is transmitted. The receiving modem sends the scrambled "1" (turn off),
The receiving modem is resynchronized with the transmitting modem by using S, S , PP and B1, and the preparation for receiving the primary channel data (image signal) transmitted from the transmitting modem is completed. still,
The signals S, S , PP, and B1 are V.S. 34 is the same signal as described in FIG.

When the resynchronization is established and the preparation for the transmission / reception of the primary channel data is completed, the transmission / reception of the image signal using the primary channel is started. In the conventional facsimile apparatus, a mode in which the binary coded image signal is transmitted as it is (NON-ECM mode) and a mode in which the image signal using the error correction function is transmitted in the HDLC format (ECM mode) There are two types. If the V. Regarding the image signal format in the case of applying H.34, the study is being advanced mainly in the ECM mode. When the transmission of the image signal is completed, the transmitting modem transmits the scrambled "1" (turn-off) for a predetermined period, and then transmits the silence during the period (70 ± 5 msec). The receiving modem is set so that a silent signal (70 ± 5 msec) can be detected at the same time while receiving the image signal. Upon detecting silence, the receiving modem makes a state transition to control channel data reception.

After the silence is sent by the sending modem, if the previous primary channel data is the last page of the transmitted document, the post-procedure, otherwise, the inter-page procedure is exchanged with the control channel for exchanging the control channel. Restart. The preparation for receiving the control channel data sent from the receiving modem is completed by establishing the synchronization with the receiving modem by transmitting / receiving the Sh, Sh , ALT, E signals. The receiving modem uses the S from the transmitting modem.
When the h signal is received, as a response, the Sh signal is transmitted, and then the Sh , ALT, and E signals are transmitted and received to establish synchronization with the transmission modem and to be transmitted from the transmission modem, similarly to the transmission modem. Complete preparations for receiving control channel data. Here, in the inter-page procedure,
When there is a mode change such as transmission speed, the PPh and MPh signals are also used in the same manner as in the previous procedure. In addition, Sh, S
h , ALT, and E signals are V.h. 34 is the same signal as described in FIG.

Similar to the above-mentioned pre-procedure, when preparation for transmission / reception of control channel data is completed by exchanging Sh to E signals, a transmission control procedure using the control channel is started, and T. Post-procedure or inter-page procedure based on 30 is exchanged. When a series of transmission control procedure exchanges (inter-page procedure or post-procedure) is completed, the transmission / reception modem releases the control channel transmission request from the facsimile apparatus, and then scrambles "1" (turn-off) for a predetermined period. Send out. After that, in the case after the inter-page procedure, the silent signal (70 ± 5 mse
c) After transmission, data transmission by the primary channel and control channel is repeated, and after the post-procedure, the line is disconnected.

FIG. 6 shows the T.S.T. series recommended by the ITU-T. 4 shows details of the HDLC format defined in No. 4. In the figure, 6-1 shows an outline of the frame structure of the primary channel data, which is composed of a synchronization signal, a partial page, and partial page control return. The sync signal is sent prior to the binary coded information, and has a training sequence, a nominal value of 200 msec, and an allowable value of +100 mse.
c continuous flag sequence. However,
V. When applied to H.34, it is considered to omit the training sequence because of the resynchronization signals S, S , PP, B1 for the primary channel before the synchronization signal. The file data means a partial page in the ECM mode, the image signal is HDLC formatted, and the frame number is added. The maximum number of frames is 256. Partial page control return is shown in 6-
As shown in 2, it consists of 3 consecutive RCP frames. Further, in each RCP frame, as shown by 6-3 in the figure, the facsimile control field of the HDLC frame is RCP. still,
The facsimile control field of the HDLC format of the partial page including the image signal is FCD.

FIG. 7 shows a state transition diagram of a conventional data demodulation system. The sequence control of the conventional data demodulation system will be described with reference to FIG. First, in the figure, it is assumed that the data demodulation system of the modem is in the primary channel. This state represents the state of the receiving modem during the period from to in FIG. During this period, the sending modem is S, S, P
Since the resynchronization signals P, B1 and the image signal and the turn-off sequence are transmitted, the energy of these signals exists in the line. When energy is present in the line after receiving the resynchronization signal, the receiving modem holds the state of primary channel data demodulation according to 7-1 in FIG. continue,
The transmitting modem has a silent signal (70 ± 5 mse
After c), the control channel data is sent following Sh, Sh , ALT, E. When the receiving modem receives the silent signal transmitted when the transmitting modem transits from the primary channel of the transmitting modem to the control channel, and when it judges that there is no energy in the line, the data demodulation system operates as shown in FIG.
According to 2, the transition from the primary channel to the control channel is made. Thereafter, the state of data demodulation of the control channel is maintained until the line runs out of energy.

The above is the V. It is a method of sequence control from the primary channel to the control channel in the 34 modem.

[0013]

However, in the above-mentioned one, during the reception of the primary channel data, the line energy detector causes a line failure such as a momentary interruption between the silent signal units (7).
(0 ± 5 msec), it is erroneously determined that there is no line energy. As a result, even though the primary channel data is being received, the state of the receiving modem transits to demodulation of control channel data. There is a disadvantage that data cannot be demodulated correctly.

[0014]

According to the present invention, in the error correction communication mode, when the first detecting means detects the frame indicating the transition of the procedure signal to the communication, the control means causes the data demodulation state of the primary channel for data. To the data demodulation state of the control signal for the procedure signal.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments 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 modem of this embodiment.

In FIG. 1, 4 is a modem, and 40
Reference numeral 0 denotes a facsimile control system (a personal computer having a facsimile communication function, or a main control unit for facsimile communication in a facsimile device) that performs data communication via the modem 4, and 405 denotes a telephone line 4.
This is a network control unit (NCU) that captures the 09 line and the like.

Further, the modem 4 includes a facsimile control system 40.
0 interface circuit (I / F circuit) 401, a digital signal processor (DSP) 402 for controlling various processes of the modem 4 according to a program, a digital-analog converter (D / A converter) 403, a communication band low-pass Filter (LPF), amplifier 406,
It is composed of a bandpass filter 407 and an analog-digital converter (A / D converter).

The I / F circuit 401, which is an interface portion with the facsimile control system 400, is one of the features of this embodiment.
Includes a mode register. This mode register determines whether to set RCP (partial page control return instruction) frame detection as a judgment criterion at the time of state transition from primary channel data demodulation to control channel data demodulation, and ECM mode (error correction). When the communication mode) is set, RCP frame detection is used as a criterion, and when the ECM mode is not set, the presence or absence of simple line energy is used as a criterion. The DSP 402 is a device that realizes the sequence control shown in FIG. 2, FIG. 3, or FIG. 4 and the modulation / demodulation processing of the modem device. The image data generated by the facsimile control system 400 is the I / F circuit 4
After being sent to the DSP 402 via 01, the baseband signal is converted into a digital modulation signal. The digital modulation signal is converted into an analog signal by the D / A converter 403, and unnecessary components are removed by the LPF 404, and then N
It is sent to the telephone line 409 via the CU 405. Also, the analog modulated signal coming from the telephone line 409 is N
After being amplified by the required amount by the amplifier 406 via the CU 405, the BPF 407 removes the out-of-band component and A / D
It is converted into a digital signal by the converter 408, further sent to the DSP 402, and digitally demodulated and converted into a baseband signal. In the figure, DSP 402 to A / D
Feedback paths to the converter 408 and the BPF 407 perform AD conversion timing adjustment and BPF bandwidth adjustment, respectively. The image signal converted into the baseband is transmitted through the I / F circuit 401 to the facsimile control system 40.
Sent to 0.

As described above, by providing the I / F circuit including the mode register inside the modem, the sequence control method can be selected from the outside of the device, so that the primary channel data is not HDLC formatted. It is possible to cope with the case, and further, it is possible to easily cope with the case where the sequence control of the conventional method is desired to be used.

Next, the sequence control in the present embodiment will be described with reference to FIGS.

In FIG. 1, a state 100
Indicates that the modem 4 is in the demodulation state of the primary channel data, and the state (state) 101 is the modem 4
Indicates that the control channel data is in the demodulation state.

When the modem 4 is receiving the primary channel data shown in FIG.
In the inside state 100, the primary channel data demodulation state is held. In the ECM mode, the primary channel data consists of the sync signal, the facsimile coded data, and the partial page control return as described above, and particularly the final portion of the partial page control return consists of three RCP frames. Therefore, in the ECM mode, if the RCP frame is detected from the demodulation result of the primary channel data, this can be regarded as the end of the image signal. When the modem 4 detects the RCP frame as a result of the RCP detection processing shown in FIG. 3 in the primary channel data demodulation state state 100, it transits to the state 101 by 1-2 in FIG. In state 101,
The modem 4 holds the control channel data demodulation state. On the contrary, when the RCP is not detected in the state 100, the same state (primary channel data demodulation) is held by 1-1 in the figure.

Detailed RCP detection processing will be described with reference to FIG. FIG. 3 is a flow showing the RCP detection process executed by the DSP.

In step S201, the recommended V. 34
Data demodulation processing of the primary channel based on The demodulation result is subjected to HDLC deframing processing in step S202. When it is discovered that the HDLC frame has an error as a result of the HDLC deframing process, an FCS error occurs. If there is an FCS error in step S203, the process proceeds to step S206 to end the RCP detection process. If there is no FCS error, the process proceeds to step S204, and it is determined whether the currently deframed HDLC frame is an RCP frame. S206 if it is not an RCP frame
Then, the RCP detection process ends. If the frame is an RCP frame, the process proceeds to step S205, where RCPFLAG is first set, and RCP frame detection is determined. It is assumed that RCPFLAG has been reset before starting the RCP detection process. Therefore, the sequence control program for controlling the state transition of FIG. 2 monitors RCPFLAG in the data demodulation state of the primary channel, and if this flag is set, it is regarded as RCP detection and transits to control channel data recovery and is reset. If it is present, the RCP is not detected and the primary channel state is maintained.

In the sequence control described above, the transition from the data demodulation state of the primary channel to the data demodulation state of the control channel is made by the detection of the RCP frame indicating the transition to the procedure in the ECM mode, but the detection of the RCP frame is performed. In addition to this, a transition may be made to data demodulation of the control channel by detecting the presence or absence of energy on the line.

FIG. 4 is a diagram showing a state transition in the case of transition from the data demodulation state of the primary channel to the data demodulation state of the control channel by detection of no line energy in addition to detection of the RCP frame.

The RCP detection processing is the same as the flow shown in FIG.

When the modem 4 is receiving the primary channel data shown in FIG.
In the inside state 300, the primary channel data demodulation state is held. In the ECM mode, the primary channel data consists of the sync signal, the facsimile coded data, and the partial page control return as described above, and particularly the final portion of the partial page control return consists of three RCP frames. Therefore, in the ECM mode, if the RCP frame is detected from the demodulation result of the primary channel data, this can be regarded as the end of the image signal. When the modem 4 detects RCP and subsequently detects no line energy in the primary channel data demodulation state state 300 as a result of the RCP detection processing shown in FIG.
Transitions to. In the state 301, the modem 4 holds the data demodulation state of the control channel. On the contrary, if the RCP is not detected in the state 300, the same state (primary channel data demodulation) is held by 3-1 in the figure.

As described above, in FIG. 4, not only the RCP detection but also the presence / absence of line energy is used as a criterion for judging the state transition of the receiving modem, so that the line energy after the RCP detection can be detected more reliably. Disappears (when there is no line failure such as a momentary interruption in the middle, a silent signal period sent by the modem on the transmitting side) at the same timing.

Further, the NCU 405 in FIG.
The dialing function may be provided in the modem 4 or in the modem 4.

Further, the modem 4, the NCU 405 and the facsimile control system 400 may be integrated into a facsimile device or a data communication device.

Further, the present invention is not limited to the above-mentioned embodiment, but various modifications can be made.

[0034]

As described above, according to the present invention, in the error correction communication mode, by detecting the frame indicating the transition of the procedure signal to the communication, the data demodulation state of the primary channel for data is changed from the data demodulation state to the procedure signal. Since the transition to the data demodulation state of the control channel is made, the state transition of the data demodulation can be surely performed even when a line failure such as a momentary interruption occurs.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a modem according to the present embodiment.

FIG. 2 is a diagram showing a state transition of the modem according to the present embodiment.

FIG. 3 is a flowchart showing an RCP frame detection process.

FIG. 4 is a diagram showing a state transition of a modem according to another embodiment.

FIG. 5: It is the figure which showed the operation procedure between the primary / control channels in 34 half duplex communication.

FIG. 6 is a diagram showing an HDLC format.

FIG. 7 is a diagram showing a state transition of data demodulation.

[Explanation of symbols]

 400 Facsimile control system 401 I / F circuit 402 DSP 403 D / A converter 404 LPF 405 NCU 406 Amplifier 407 BPF 408 A / D converter 409 Telephone line

Claims (6)

[Claims] 1. A modulator / demodulator having a data demodulation state of a primary channel for data and a data demodulation state of a control channel for a procedure signal, wherein a frame indicating a transition of the procedure signal to communication is detected in an error correction communication mode. A modulation / demodulation device comprising: a first detection unit; and a control unit that transitions from a data demodulation state of the primary channel to a data demodulation state of the control channel according to the detection by the first detection unit. 2. The method according to claim 1, further comprising second detecting means for detecting the presence / absence of energy on the line, wherein the control means detects the primary channel of the primary channel according to the detection by the first and second detecting means. A modulator / demodulator characterized by making a transition from a data demodulation state to a data demodulation state of the control channel. 3. The control means according to claim 2, wherein the control channel changes from the primary channel data demodulation state based on the detection by the first detection means in accordance with whether or not the error correction communication mode is selected. A modulation / demodulation device characterized by switching between a transition process to a data demodulation state and a transition process from the primary channel data demodulation state to the control channel data demodulation state based on detection by the second detection means. 4. The control means according to claim 2, wherein the control means changes from the primary channel data demodulation state based on the detection by the first and second detection means according to whether or not the error correction communication mode is selected. A modulation / demodulation device characterized by switching between a transition process to the control channel data demodulation state and a transition process from the primary channel data demodulation state to the control channel data demodulation state based on detection by the second detection means. 5. The interface according to claim 3, further comprising a mode register in an interface portion with an external device, wherein the mode register can set mode information from the external device, and the control means includes the mode register. A modulation / demodulation device characterized by selecting communication in a mode according to the mode information of. 6. A data communication device comprising the modulation / demodulation device according to claim 1, 2, 3, 4 or 5.