JP3440046B2 - Modulation / demodulation device, image communication device, and image communication method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modulation / demodulation device (hereinafter referred to as a modem) for communicating data between data terminal devices (hereinafter referred to as DTE) such as a computer and a facsimile device through a telephone line or the like, and particularly, The present invention relates to a modem that operates by appropriately selecting a plurality of types of modulation schemes.

[0002]

2. Description of the Related Art As is well known, there are "frequency modulation", "four-phase differential phase modulation", "quadrature amplitude modulation", "phase amplitude modulation", etc. as a modulation method of a modem (modulator / demodulator). Different modulation schemes are used depending on the speed. Many modern modems, for example, a modem incorporated in a FAX (facsimile device which is a DTE) is configured to switch the modulation / demodulation mode and speed depending on the protocol, and the timing of the mode switching is synchronized between transmission and reception. Is extremely important in terms of communication reliability. Conventionally, the DTE (data terminal device) which is the host device of the modem selects the operation mode of the modem, and the modem is configured to switch the operation mode according to the instruction. [Configuration of Prior Art Illustrated in FIG. 24] A typical conventional technique will be described with reference to the drawings. FIG. 24 shows a prior art D
It is a block diagram which shows the interface of TE and a modem. FIG. 25 shows the ITU-T Recommendation V.3 using this interface. It is an example of a modem control sequence before the 34 standard,
FIG. 26 shows V.3 using this interface. It is an example of a sequence for controlling a 34 standard modem. ITU-T is the International Telecommunication Union-Telecommunication Standardization Division,
It is ITT.

In FIG. 24, a DTE (data terminal equipment) 011 is a modem (modulation / demodulation equipment) 013 and a bus 019.
Are connected through. CPU012 inside DTE
Knows the contents of transmitted / received data by READ / WRITE the transmission data register 016 and the reception data register 017 inside the modem. Further, the CPU 012
By reading the state display register 015, the operation state of the modem is recognized, and the mode switching of the modem is performed by writing the mode number to the mode register 014. The modulation / demodulation unit 018, which executes the modulation / demodulation operation inside the modem, uses the mode register 014.
, And transmits the sequential operating state to the DTE through the state display register 015. [Operation of Prior Art Illustrated in FIG. 24] FAX before 34 standard
The operation of the mobile modem will be described with reference to the timing chart of FIG. V. All fax modems before 34 are modems used in half-duplex communication, and there is no timing at which waveforms are simultaneously transmitted from both the transmitting and receiving sides, and only one of them can transmit the waveform. Therefore, T. The order of signal transmission is defined by a protocol such as the 30 standard.

FIG. 25 shows the timing when the previous mode is reception and the content of the received data is judged and the next mode is switched to transmission. At that time, the DTE judges the received data and instructs the mode switching instruction to the modem. However, the software processing time of the DTE causes a delay factor, and an inter-signal gap occurs between the end of the received signal and the beginning of the transmitted signal. Occur. However, in the case of half-duplex communication, no matter how long the gap between signals becomes, it does not cause communication failure.

However, V. In the case of the 34 standard, data is exchanged in the full-duplex mode in which signals are simultaneously sent from both sides only during control channel communication. FIG. 34 shows an example of mode switching timing in the 34 standard. This is the case where the previous mode ends with reception of the control channel in full-duplex mode and the next mode becomes reception of the main channel. In this case as well, the DTE determines the data of the control channel and then issues the mode switching instruction.

[0006]

In the configuration of the above-mentioned prior art, since the timing of mode switching in FIG. 26 depends on the instruction from the DTE side, when the transmission / reception data processing on the DTE side consumes time. However, there was a problem that the signal reception in the next mode was delayed and could not be received normally. Especially when the speed of the modem improves,
The amount of processing per hour increases, and this problem becomes more likely to occur.

In addition, V. In the case of a half-duplex modem of 34 standard, one-way communication of the main channel and two-way simultaneous communication of the control channel are alternately switched. in this case,
When the inter-signal gap exceeds a certain period (0.1 seconds), the echo suppressor recovers, so that bidirectional simultaneous communication of the control channel becomes impossible, which causes a problem that communication cannot be recovered. Therefore, V. In the 34 standard, the inter-signal gap is limited to the range of 70 mS ± 5 mS.

Therefore, regarding the interface between the DTE and the modem, a mechanism for shortening the processing time on the DTE side is required. However, even if the processing speed on the DTE side is improved and the mode switching timing can be processed in a short time in proportion to the inter-signal gap, the time monitoring of the inter-signal gap requires an accuracy of about ± 5 mS. . Therefore, the software for monitoring the modem status on the DTE side is required to have the highest priority, which causes a problem that the system design of the DTE becomes difficult.

The present invention has been made in view of the above-mentioned problems of the prior art. The interface processing time between the DTE and the modem is shortened, and the mode switching of the modem is performed by the DT.
An object of the present invention is to provide a modulation / demodulation device capable of reliable communication without depending on E software.

[0010]

In order to achieve the above object, the present invention provides an operation mode for performing sequence control.
The operation mode setting is received from the DTE
Execution means for executing the set operation mode and this execution
The end of the operation mode by means is received from the external line.
Judgment means for judging by detecting RCP frame
Then, it is determined that the RCP frame is detected by this determination means.
Set to the main channel reception mode.
From the control channel mode to the control channel mode
It is a gift. The present invention also performs sequence control.
To set the operating mode to operate from the DTE
Is executed and the operation mode that is set is executed.
The end of the operation mode by the execution means and the execution means
Detects signals with a specified pattern that are received from the local line
By the determination means to determine by
When it is determined that the operation mode has ended, it controls its own operation mode.
Switch from main channel mode to main channel receive mode
And a control means for changing over.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Arrangement of the Embodiment Shown in FIG. 1] FIG. 1 is a block diagram schematically showing a modem according to an embodiment of the present invention. In FIG. 1, reference numeral 11 is a modem for performing data modulation / demodulation processing, and 12 is a facsimile control apparatus as a host DTE for processing such as data expansion and recording. The modem 11 includes a line control unit 111 that controls the line L, an analog FEP (FEP: front end processor) 112,
DSP (digital signal processing unit) 113 for digitally performing processing such as modulation / demodulation, dual port RAM 114 having two write / read access ports, interrupt control unit 11
5 are provided.

The facsimile control device 12 includes an image reading / recording unit 123, an image data compression / expansion unit 122,
A console 121 such as an operation panel, a working RAM 124 for temporarily storing image data, and a CPU (central processing unit) 125 for controlling the operation of the entire apparatus are provided.

Here, the dual port RAM 114 is used.
Is arranged between the modem 11 and the facsimile controller 12, and one access port is the bus B1 in the modem 11.
And the other access port is the facsimile controller 12
It is connected to the internal bus B2 so that reading / writing of data from the modem 11 side and reading / writing from the facsimile control device 12 side can be performed simultaneously.

FIG. 2 shows the dual port RAM shown in FIG.
3 is a memory configuration diagram showing the memory configuration of FIG. In FIG. 2, an A channel block corresponding to a main channel, a B channel block corresponding to a transmission control channel,
A communication buffer is provided separately for each mode, such as a C channel block corresponding to a reception control channel, and each communication buffer has a plurality of banks 0-3. Further, a channel area pointer (CH area pointer) and a channel area (CH area) are provided corresponding to each channel block. Information for accessing the channel area is written in the channel area pointer.

FIG. 3 is a memory block diagram showing an example of a channel area required to access a channel block. In FIG. 3, the channel command is an area for storing a command for switching the corresponding channel between the transmission mode and the reception mode, and the channel status displays information about transmission and reception errors of the corresponding channel. The area. FIG. 4 shows an example of detailed bit allocation of the channel command shown in FIG. FIG. 5 shows an example of detailed bit allocation of the channel status shown in FIG.

Regarding the modem 11 configured as described above, the V. The operation will be described by taking communication in the 34 half-duplex mode as an example. [Data Storage Processing for Each Mode] First, an embodiment in which received data from the DTE is managed for each mode will be described. V. When communicating in the 34 half-duplex mode, there are a main channel and a control channel as communication channels.
The main channel is used for communication of image information in so-called facsimile communication, and the control channel is ITU-T.
T. It is used for communication of phase B control information recommended in 30. Here, the main channel uses the A channel block, and the transmission of the control channel is the B channel.
The channel block and the C channel block are used for receiving the control channel.

First, the control channel transmission process will be described. T. In 30 phase B, the modem 11 sets the channel mode setting bit of the B channel command to "1" in order to transmit the control channel. Write data to bank 0 of B channel block. Also, the modem 11 has a Data Full / Em status 0.
Recognize pty bit "1", confirm write completion,
The data in bank 0 is read, signal processing such as modulation is performed, and the data is sent to the line. After transmitting the data of bank 0, Data Full / Em of status 0
The pty display bit is set to "0".

On the other hand, the facsimile control device 12 uses the Data Full / E of status 1 corresponding to bank 1.
If the mpty indicator bit is "0", the next data frame is written to bank 1 while the modem is transmitting data for bank 0. When writing is completed, set the Data Full / Empty display bit of status 1 to "
When the transmission of bank 0 is completed, the modem checks status 1 and if the Data Full / Empty display bit is "1" (when writing of the next data frame is completed), it is the same as bank 0 , The data of bank 1 is transmitted in the same manner for each data frame in the order of bank 2, bank 3, and bank 0. Here, although the modem is executing the control channel transmission command, all the data are transmitted. In the bank, the Data Full / Empty display bit of the bank status is "
When it is 0 "and there is no data frame to be sent, the transmission error display bit of the B channel status is set to" 1 ",
Notify the facsimile controller of the B channel block transmission error.

Next, the control channel reception process will be described. The modem 11 receives the control channel,
The channel mode setting bit of the C channel command is set to "0". The modem 11 also receives and demodulates data, confirms that the Data Full / Empty display bit of status 0 corresponding to bank 0 of the C channel block is "0", and writes one data frame to bank 0. . When writing is completed, set the Data Full / Empty display bit of status 0 to "
1 ”(writing completion = reading is possible). The facsimile controller 12 displays the Data Full with status 0.
When the / Empty display bit is confirmed to be "1", the data is read from the bank 0. The modem is Dat in bank 1
If the a Full / Empty display bit is "0", the next received data frame is written in bank 1 even while the data in bank 0 is being read by the facsimile controller. After the writing is completed, it is read by the facsimile control device as in the bank 0. Similarly, reception processing is performed for each data frame in the order of bank 2, bank 3, and bank 0. At this time, the modem is in the bank status Data Full / Empt in all banks even though the control channel reception command is being executed.
If the y indication bit is "1" and the received data frame cannot be written to the empty bank of the C channel block, C
Receive error indication bit of channel status is "1"
Then, the C-channel block reception error is notified to the facsimile controller.

As described above, the control channel transmission / reception processing is performed using the B channel block and the C channel block, respectively. Even if full-duplex simultaneous operation of control channel transmission / reception is performed in the 34 half-duplex mode, the facsimile controller and the modem do not need to perform complicated processing, and control channel transmission data and control channel reception data are transferred. You can do it safely.

The main channel of the A channel block has the same structure as the transmission / reception of the control channel, and the transmission mode and the channel mode bit are set to "0" by setting the channel command and the channel mode bit to "1". By setting to, it is possible to switch to the reception mode and perform the transmission and reception operations of the main channel.

Further, V. In 34 half-duplex mode,
It is also possible to execute a mode switching for switching from the transmission / reception operation of the control channel to the transmission / reception operation of the main channel, and conversely, the transmission / reception operation of the main channel to the transmission / reception operation of the control channel. [Data Transmission Stop Processing] Next, the processing will be described with reference to FIGS. FIG. 6 is a diagram showing the relationship between the command area, status area, and bank on the dual port RAM 114. In FIG. 6, the command area stores operation instructions from the DTE regarding channel termination,
The buffer status (Data Full / Empty
Information indicating display, presence / absence of abort, presence / absence of error) is stored. These command area and status area are provided corresponding to each bank. This is to strictly manage which bank the data has been sent to when the processing is terminated.

Here, data is stored in each bank in units of a data frame which is an error detection unit.
FIG. 7 is a memory block diagram showing an example of detailed bit allocation to the command area, and FIG. 8 is a memory block diagram showing an example of detailed bit allocation to the status area. Although the command area and status area corresponding to bank 0 are shown here, the same applies to banks 1 to 3. FIG. 9 is a memory block diagram showing a transmission interrupt status, and FIG. 10 is a memory block diagram showing a reception interrupt status. [Data Transmission Processing] The operation / action of the above configuration will be described. First, the data transmission process will be described (for example, A channel is used among the plurality of channels). The facsimile controller 12 confirms that the Data Full / Empty display bit of status 0 is "0" (read completion = write enabled), and writes one frame of transmission data to bank 0. When writing is completed, set the channel end instruction bit of command 0 to "0" (do not end) and set the status 0 Data Fu
ll / Empty display bit is '1' (write completed = read possible)
To

When the modem 11 recognizes that the channel end instruction bit of the command 0 is "0" and the Data Full / Empty display bit of the status 0 is "1", it reads the data of the bank 0 and outputs a signal for modulation or the like. Process and send data to line L. When the data of the bank 0 is completely transmitted, the Data Full / Empty display bit of the status 0 is set to "0", and at the same time, the interrupt control unit 115 causes the facsimile control unit 1 to operate.
An interrupt occurs in 2.

By checking the transmission interrupt status shown in FIG. 4, the facsimile controller 12 can know that the data in the bank 0 has been read by the modem 11. Facsimile controller 12 is bank 1
If the Data Full / Empty display bit of status 1 corresponding to is 0, the next data frame is written to bank 1 while the modem 11 is transmitting data of bank 0, and the channel of command 1 Set the end instruction bit to "0"
And the Data Full / Empty display bit of status 1 is set to "1".
To

When the transmission of the bank 0 is completed, the modem 11 checks the command 1 and the status 1, and checks the Data Full / Empt
If the y indicator bit is '1' (when the writing of the next data frame is completed), the data of bank 1 is transmitted in the same manner as bank 0, and if there is no channel end instruction, it proceeds to the next bank. Similarly, the data is transmitted for each data frame such as bank 2, bank 3, bank 0, .... To end data transmission (A channel), for example, bank 3
Write a data frame to DataStatus / DataFull / E
At the same time that the mpty display bit is set to "1", the channel end instruction bit of the command 3 is set to "1" to instruct the modem 11 to end. The modem 11 checks not only the status 3 but also the command 3 to recognize that the Data Full / Empty display bit is "1" and the channel end instruction, and after transmitting the data of the bank 3, the data transmission processing (A
Channel). [Data Reception Processing] Next, the data reception processing will be described. When the modem 11 receives the data, it demodulates it, and the status 0 Data Full / Empt
y Confirm that the display bit is '0' and write one data frame to bank 0. When writing is completed, set the Data Full / Empty display bit of status "0" to "1" (writing completed = read enabled). Further, the interrupt control unit 115 interrupts the facsimile control unit 12.

The facsimile controller 12 checks the reception interrupt status and recognizes that the data has been written in the bank 0. When receiving one data frame, the modem 11
Checks the presence or absence of an abort and the error detection signal (frame check sequence) added at the end of the frame to determine whether there is an error, and displays the result in the reception interrupt status. The facsimile controller 12 reads the data from the bank 0 after confirming that the reception interrupt status has not occurred and the data frame has no error.
If the Data Full / Empty display bit of bank 1 is “0”, the modem 11 writes the next received data frame in bank 1 even while the data of bank 0 is being read by the facsimile controller 2. After the writing is completed, it is read by the facsimile controller 12 as in the bank 0. Similarly, reception processing is performed for each data frame in the order of bank 2, bank 3, and bank 0. [Error frame discard processing] Due to a line failure during data reception,
A case where an error occurs in a data frame and a case where an abort is detected will be described with reference to FIGS. 11 to 14. FIG. 11 is a diagram showing a state in which an error frame is detected when a frame check of received data is performed.
FIG. 12A is a memory diagram showing a conventional state in which a frame is stored even when it is determined to be an error frame,
(B) is a memory diagram showing a state of the present invention in which the frame is discarded when it is determined that the frame is an error frame.
FIG. 13 is a diagram showing a state in which the occurrence of an abort is detected in the received data. FIG. 14A is a memory diagram showing a conventional state in which a frame is stored even when it is determined to be an error frame, and FIG. 14B shows a state of the present invention in which the frame is discarded when it is determined to be an error frame. It is the memory diagram shown.

First, when an error is detected by the error detection signal (frame check sequence error),
As shown in FIG. 1, the frame n (error frame) is written in the bank 1, and the interrupt controller 115 causes the facsimile controller 12 to generate an interrupt. Facsimile controller 12 checks the reception interrupt status and finds that data has been written to bank 1 and that a frame check sequence error has occurred in bank 1. Since the data in bank 1 is incorrect, the facsimile control unit 12 does not perform the reading process and waits for the reception of the next data frame.

When receiving the next data frame n + 1 as shown in FIG. 12A, the modem 11 does not write it in the bank 2 but writes it again in the bank 1 as shown in FIG. 12B. When the writing is completed, the interrupt control unit 115 interrupts the facsimile control unit 12. When receiving the interrupt, the facsimile control unit 12 checks the reception interrupt status, knows that the next data frame n + 1 has been written in the bank 1, and performs the reception process. The same is true when an abort occurs. [Mode switching process]
Next, the process in which the modem 11 itself executes the mode will be described with reference to FIGS. FIG. 15 is a control flow chart showing an embodiment of the mode switching processing of the present invention. FIG. 15 shows the DTE mode switching shown in FIG.
FIG. 7 is a control flow diagram shown from the side of the (facsimile controller 12).

First, the DTE 12 sets a comprehensive mode capable of sequence control of the previous mode and the next mode shown in FIG. 26 (S401). Next, the modem 11 receives the instruction (S402) to execute the general mode from the DTE 12.
Executes the set general mode and starts the processing of the previous mode. After that, the DTE 12 waits for the previous mode end notification from the modem 11 (S403). When the processing in the previous mode is completed, the modem 11 notifies the DTE 12 that the previous mode is completed, sets a timer by itself, and monitors the time until the next mode is started. When the DTE 12 receives the notification of the end of the previous mode, it selects one of the modes to be executed in the next mode and instructs the modem 11 (S40
4) Wait for the next mode end notification from the modem 11 (S405). The modem 11 sets the next mode state transition setting (S40) due to the timeout of the timer set above.
The next mode set in 4) is executed, the state is monitored, and when the state is such that the next mode is ended, the DTE 12 is notified of the end of the next mode. DTE receiving notification of next mode end
12 terminates the overall mode sequence.

As described above, according to the present invention, the DTE 12
Since the above process is automatically executed only by receiving the mode setting instruction from the DTE and without waiting for the mode switching instruction and the processing start instruction from the DTE, the accuracy of the signal gap monitoring time of about ± 5 ms is required. Even in the processing procedure that is performed, it is possible to prevent delay in the correspondence to the next mode without making the DTE system design difficult. [Comparison with Prior Art] Here, the features of the present embodiment will be described in detail with reference to FIG. FIG. 16 shows FIG.
It is a flow diagram of the conventional mode switching process which showed the mode switching shown by 6 from the DTE side.

Conventionally, the DET instructs the modem to set the previous mode (S411), gives an instruction to execute the previous mode (S412), and then monitors the end timing of the previous mode processing (S413). . In this case, according to the present invention, it is only necessary to set and execute the general mode from the DTE.
Automatically end the previous mode. Such processing is possible because the modem stores the communication sequence in advance. That is, since the communication sequence is a preset procedure, if the process to be executed is specified, the modem executes the process by managing the state transition based on the stored communication sequence. You will be able to do it. [Timer-based monitoring process] Next, when the DTE determines to end the pre-mode process of the modem, it sets a timer and monitors the time until the next mode is started (S415). In this way, since the DTE is used to monitor the timing, in the case of a processing procedure that requires an accuracy of about ± 5 ms for monitoring the inter-signal gap, switching to the next mode processing is delayed and the modem Although a problem that cannot be normally processed has occurred, the present invention can avoid this problem by the timing monitoring by the modem.

Next, when the DTE detects the time-out of the timer, it sets the next mode (S416) and executes the next mode (S417). Upon receiving the instruction to execute the next mode, the modem starts the next mode processing. The DTE monitors this next mode processing (S418), and when it is in the state of ending the next mode processing, ends this sequence.

As described above, according to the present invention, as shown in FIG. 15, when the processing of the previous mode is completed in S403, the state transition to the next mode is managed by the modem 11 itself, and the next mode in S404 is managed. Since the next mode is set in the state transition setting to, it is possible to ensure the timing of mode switching and ensure communication safety. Furthermore, D
By providing the modem 11 with the timing monitoring performed by the TE 12, the load on the DTE 12 can be reduced. [Various mode switching by the modem itself] Furthermore, the modem 11
However, the significance of having several operation modes and one operation mode having a sequence for controlling this operation mode will be described with reference to FIG. FIG. 17 shows ITU Recommendation V.34.
34 is a flow diagram of a FAX sequence using the H.34 half-duplex mode, including phase 1 (S431) and phase 2 (S4).
32), phase 3 (S433), control channel (S
434) and the main channel (S435) indicate the mode in the sequence. Modem 11 sets these modes to 1
V. It has 34 half-duplex mode.

First, after the line is closed, the modem mode is set to V. Three
When set to 4 half-duplex mode and operated, step S4
It starts from Phase 1 of 31. Here, terminal capability data is exchanged. When this is completed, the modem 11 makes a state transition to phase 2 in step S432, learns the line characteristics, and determines the modem symbol rate. Next, in step S433, the process of phase 3 is started, and the equalizer training of the modem 11 is performed. After the end of phase 3, the modem enters the control channel of step S434. Here, the data rate is determined, and T. 30 pieces of terminal information are exchanged.

When the control channel ends, step S
Enter 435 main channels. Here, FAX image data is transferred. When the main channel is ended, whether to proceed to the control channel in which the data rate is reset in step S437 or to the control channel in which the data rate is not reset in step S438 is determined in step S436.
Determined by the instruction of E12. Therefore, in step S435
By the end of the main channel of DTE 12, the DTE 12 gives an instruction to the modem 11 to determine the state transition.

After proceeding to either step S437 or step S438, the modem 11 returns to the state of the main channel of step S436 if the operation is not finished, and stops the operation if it is finished. The silent section between Phase 1 and Phase 2 is 75 ± 5 msec, and the silent section between each subsequent mode is 70 ± 5 msec, which is the DTE.
It is a very heavy load for the modem 12 to control this, but the modem 11 can improve this load. [Mode End Detection Process] The process in which the modem 11 itself switches the mode (main channel, control channel transmission, control channel reception) has been described above. Next, the control in which the modem 11 itself detects the mode end shown in S403 and S405 of FIG. 15 will be described in detail with reference to FIGS. 18 and 19. FIG. 18 is an explanatory diagram showing modem mode switching by RCP detection.

This is V. This is an example of FAX or data communication at 34, and shows the timing when the main channel ends and the mode changes to the control channel.
V. Since FAX / data communication in the 34 mode is carried out in ECM (error correction mode) which is premised on error retransmission, the end of the main channel must end with the end signal of the partial page called the RCP frame. There is. In the present invention, if the RCP frame is judged inside the modem and the mode of the modem is switched to the control channel mode by itself, the control channel signal that arrives within 75 mS after the end of the main channel is not missed. RC
The internal structure of the P frame is framed by the HDLC method, and the modem 11 needs to be able to execute the deframing operation. If, after deframing, the data is determined to be correct, it is easy to determine the RCP byte and is fully executable inside the modem.

Another embodiment in which the modem 11 itself switches the mode will be described with reference to FIG. FIG. 19 also shows V.I. This is an example of the timing when FAX / data communication is performed in the 34 mode, and particularly shows the timing when the mode is switched to the main channel reception after the end of the control channel.

The end of the control channel is defined by a protocol end rule as a channel end signal. In this case also, the channel end is determined by the DTE 12 rather than the
The modem 11 itself can judge and change the mode to the main channel reception. The channel end signal is specifically a pattern that does not occur during data transfer 40
It is the same as receiving a '1' that is consecutive bits or more, and can be detected inside the modem.

As described above, when the modem 11 itself analyzes the content of the received data, and when a predetermined signal is detected as a result of the analysis, the mode is switched based on the detection result. It is possible to guarantee reliable communication without losing the timing. [Embodiment of FIG. 20 and Retraining Instruction Processing] Next, the processing for the modem 11 itself to instruct the DTE 12 to perform retraining will be described with reference to FIG.
~ It demonstrates using FIG. FIG. 20 is a circuit configuration diagram of the modem 11 showing an embodiment of the present invention. In FIG. 20, reference numeral 617 denotes a DTE-interface unit, which controls exchange of transmission / reception data between the DTE-modem and data such as mode / operation designation of the modem. Reference numeral 613a is transmission data transmitted from the DTE to the communication partner via the DTE-interface unit 617, and 616a is reception data transmitted from the communication partner, which is transferred to the DTE via the DTE-interface unit 617. 620b is an EQM threshold signal, which is set from the DTE via the DTE-interface unit 617 as a set value of the judgment criterion of the retraining control of the modem. Reference numeral 613 is an encoding unit that converts the transmission data 613a from the DTE-interface unit 617 into two-dimensional signals 612R and 612I based on the well-known ITU-T recommendation V.34. Reference numeral 612 is a QAM modulator that performs quadrature amplitude modulation on a two-dimensional signal based on the well-known ITU-T Recommendation V.34.

Depending on the state of the control signal 620c, the QAM modulating section 612 determines if 620c = 0, no signal 620c = 1, quadrature amplitude modulation signal 620c = 2 of the two-dimensional signals 612R and 612I, and training signal 620c. = 3, retraining signal 620c = 4
In this case, the retraining response signal is controlled to be output as the modulated signal 612a.

Reference numeral 611 is a hybrid circuit for separating a transmission system signal and a reception system signal. With this hybrid circuit, the transmission signal 612a is transmitted to the telephone line 611a, and the signal transmitted from the communication partner is output to the reception signal 614a.

The QAM demodulation section 614 has a function of performing quadrature amplitude demodulation on the reception signal 614a and outputting two-dimensional signals 614R and 614I based on the well-known ITU-T recommendation V.34, and discrimination of the reception signal 614a. Is output to the determination signal 620a. This QAM demodulation unit 614 outputs 62 when there is no received signal 614a, when 620a = 0 data received signal, and when 620a = 1 training signal.
In the case of 0a = 2 retraining signal, 620a = 3 is output in the case of 620a = 3 retraining response signal.

The decision unit 615 makes a signal decision on the two-dimensional signals 614R and 614I based on the well-known ITU-T Recommendation V.34. The determination unit 615 outputs the determined two-dimensional signals 615R and 615I.

The decoding unit 616 receives the two-dimensional data 615R and 615I determined based on the well-known ITU-T Recommendation V.34 as the received data 616a.
Convert to. The error calculation unit 618 subtracts the output signals 614R and 614I of the QAM demodulation unit 614 and the output signals 615R and 615I of the determination unit 615, respectively, and outputs two-dimensional error signals 618R and 618I. EQM
The calculator 619 calculates the power of the two-dimensional error signals 618R and 618I, and uses that signal as an EQM signal 619a that represents the quality of received data.
Output as. The control unit 620 receives three signals of an EQM signal 619a representing the quality of the received data, an EQM threshold 620b which is a set value of the retraining judgment criterion, and a discrimination signal 620a representing the discrimination of the received signal, The control signal 620c for the QAM modulator 612 is output.

FIG. 21 is an internal block diagram of the EQM calculating unit 619. Multipliers 621 and 622 are two-dimensional error signals 618R and 61
Square 8I each. The adder 623 adds the signals squared by the multipliers 621 and 622 and outputs a two-dimensional error power signal 632a. The integrator 624 is a two-dimensional error power signal 632a.
Is smoothed and an EQM signal 619a representing the quality of the received data is output. [Operation of the Embodiment of FIG. 20] FIG. 22 is a flowchart to be executed by the control unit 620a shown in FIG. 20 in the data reception mode. In step S601, the modem is set to the training signal detection waiting state, and the signal 620c is set to "0".
Then, the QAM modulation section 612 transmits a silent signal. Step
In S602, it is determined whether or not the training signal from the communication partner modem is detected. If it is detected, the process proceeds to step S603, and if not detected, step S602 is repeated. The determination as to whether or not the training signal is detected is determined as the case where the signal 620a becomes “2” is detected. Step S6
In 03, the modem is set to the training signal reception state. In step S604, it is determined whether or not the training reception is completed. If the training reception is completed, the process proceeds to S605, and if it is not completed, step S602 is repeated. To judge whether or not the training reception has been completed,
When the signal 620a changes from "2" to "1", it is determined that the training reception has ended.

In step S605, the modem is set to the data receiving state. In this state, the received data is sent to the DTE via the QAM demodulation unit 614, the determination unit 615, the decoding unit 616, and the DTE-interface unit. In step S606,
The EQM signal 619a, which represents the quality of the received data, has an EQM threshold 620b.
If the EQM signal 619a is larger, the process proceeds to step S609, and if the EQM threshold 620b is larger, the process proceeds to step S607.

In step S607, it is determined whether or not the data reception is completed. If the data reception is completed, the process proceeds to step S608. If it is not completed, the process returns to step S606. Whether or not the data reception is completed is determined based on, for example, the case where the signal 620a changes from “1” to “0” and the case where the DTE designates the end through the DTE-interface.

In step S608, the modem is set to the data end state, the transmission of the received data to the DTE via the DTE-interface unit is stopped, and the modem goes into the idle mode. In step S609, the modem is set to the retraining signal transmission state, the signal S602c is set to "3" and the retraining signal is transmitted from the QAM modulator 612, and the process proceeds to step S610. At this time, the received data is DTE-
Suspend sending to the DTE via the interface. In step S610, it is determined whether or not a retraining response signal is detected from the communication modem, and if it is detected, the process proceeds to step S601. If not, step S610 is repeated. The determination as to whether or not the retraining signal is detected is determined to be when the case where the signal 620a becomes "4" is detected.

In the embodiments described so far, retraining is controlled based on the EQM threshold value set by the DTE and the EQM value calculated in the modem 11. However, the present invention is not limited to this embodiment,
For example, it is possible to monitor the frame error or the bit error in the modem 11 and control the retraining by the threshold value from the DTE 12 for the frame error or the bit error. In this embodiment, the EQM threshold is DT.
Although the instruction is given from E, the modem may hold it in advance. [Timing Monitoring Process Shown in FIG. 23] A process of timing monitoring performed by the modem 11 itself will be described. FIG. It is a sequence diagram which showed the procedure of the 34 half-duplex mode schematically. First, the T1 timer is operated as follows.
At the called side, the transmission of the ANSam signal is started, and at the same time, the decrement operation of the value of the T1 timer (for example, 35 seconds) provided from the DTE side is started. If the value of the T1 timer reaches 0, this modem 11
Issues an interrupt toward the DTE12 side,
Notify of this abnormal situation. However, if the CM signal from the calling side is detected before the value of the T1 timer reaches 0, the decrement of the value of the T1 timer is stopped.

At the calling side, the reception of the ANSam signal is started, and at the same time, the decrement operation of the value of the T1 timer provided from the DTE 12 side (for example, 35 seconds as well) is started. If the value of the T1 timer reaches 0, this modem notifies this abnormal condition by issuing an interrupt toward the DTE side. However, if the JM signal from the called side is detected before the value of the T1 timer reaches 0, the decrement of the value of the T1 timer is stopped.

As described above, the time T1 from the start of the phase B until the detection of the correct signal is monitored by the D timer.
If it is easier than the TE side, it can be tightened. Also, T
Although it is possible to interpret when the 1 timer should be started, although there are other possibilities, both the calling side and the called side start decrementing the T1 timer value from the moment the terminal connects to the line. The method is of course possible.

The T2 timer is operated as follows. At the called side, the transmission of the NSF / CSI / DIS signal is completed and the TTE provided from the DTE side is completed.
A decrement operation of the value of 2 timers (6 seconds as an example) is started. If the value of the T2 timer reaches 0, the modem 11 issues an interrupt to the DTE 12 side to notify this abnormal situation. However, by the time the value of the T2 timer reaches 0, if the TSI / DCS signal and the bad signal from the calling side are detected up to the address byte and the control byte according to the HDLC format, the value of the T2 timer is decremented. By interrupting and returning it to the initial value, the interruption of occurrence of an abnormal situation is avoided. In this way, only the fact that an abnormal situation has occurred is notified. If it is normal, the DTE 12 does not hinder the progress of the procedure without knowing it. Therefore, the DTE1
The load of 2 is reduced.

At the calling side, the transmission of the TSI / DCS signal is terminated, and at the same time, the decrement operation of the value of the T2 timer provided by the DTE side (this is also 6 seconds, for example) is started. If the value of the T2 timer reaches 0, this modem notifies this abnormal situation by issuing an interrupt toward the DTE side. But T2
By the time the timer value reaches 0, the CF from the called side
According to the HDLC format, if the address signal and the control signal are detected for the R signal and the bad signal, the decrement of the value of the T2 timer is stopped and the value is returned to the initial value.

The above is the handling of the T2 timer immediately after entering the phase A from the phase B.
With respect to the control signal such as the PS signal and the control signal such as the EOP signal and the MCF signal in the phase B after passing through the phase C, it is possible to easily monitor the T2 timer from the DTE side by the same method.

[0057]

As is apparent from the above description, according to the present invention, when the modem itself performs the above control for switching the mode, the modem deframes the data frame received by itself and analyzes the data frame. According to the result of the analysis, it is determined that the frame is an RCP frame, and the control for automatically switching the mode from the main channel reception mode to the control channel mode is performed. It is possible to reliably prevent the channel signal from being missed. Similarly, by analyzing the data signal received by the modem itself, the control channel end signal consisting of a special pattern that cannot occur during data transfer is determined based on the result of the analysis, and the mode is controlled. Since the control for automatically switching from the channel mode to the main channel reception mode is performed, it is possible to reliably prevent the main channel signal arriving within 75 ms after the end of the control channel from being missed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a modem according to an embodiment of the present invention.

FIG. 2 is a memory configuration diagram showing a memory configuration of a dual port RAM in FIG.

FIG. 3 is a memory configuration diagram showing an example of a channel area required to access a channel block.

FIG. 4 is a diagram showing an example of detailed bit allocation of the channel command shown in FIG.

5 is a diagram showing an example of detailed bit allocation of the channel status shown in FIG.

FIG. 6 is a diagram showing the relationship between the command area, status area, and bank on the dual port RAM.

FIG. 7 is a memory configuration diagram showing an example of detailed bit allocation of a command area.

FIG. 8 is a memory configuration diagram showing an example of detailed bit allocation of a status area.

FIG. 9 is a memory configuration diagram showing a transmission interrupt status.

FIG. 10 is a memory configuration diagram showing a reception interrupt status.

FIG. 11 is a diagram showing a state in which an error frame is detected when a frame check of received data is performed.

FIG. 12A is a memory diagram showing a conventional state in which an error frame is stored even when it is determined to be an error frame. FIG. 12B shows a state of the present invention in which the frame is discarded when it is determined to be an error frame. Memory diagram

FIG. 13 is a diagram showing a state in which an occurrence of an abort has been detected in received data.

FIG. 14A is a memory diagram showing a conventional state in which a frame is stored even when it is determined to be an error frame. FIG. 14B shows a state of the present invention in which the frame is discarded when it is determined to be an error frame. Memory diagram shown

FIG. 15 is a control flow chart showing an embodiment of the mode switching processing of the present invention.

FIG. 16 is a flowchart showing conventional mode switching processing.

FIG. 17: V. 34 Receiver flow diagram for fax sequence using half-duplex mode

FIG. 18 is an explanatory diagram showing modem mode switching by RCP detection.

FIG. The figure which showed the example of the timing at the time of FAX / data communication in 34 mode.

FIG. 20 is a circuit configuration diagram of a modem showing an embodiment of the present invention.

FIG. 21 is an internal block diagram of the EQM calculation unit 619.

22 is a flowchart to be executed by the control unit 620a shown in FIG. 20 in the data reception mode.

FIG. 23. 34 Sequence diagram schematically showing the procedure of half-duplex mode

FIG. 24 is a block diagram showing a conventional DTE / modem interface.

FIG. 25 shows V. The figure which showed the example of the modem control sequence before the 34 standard

FIG. 26 is a diagram showing a case where V. The figure which showed the example of a sequence which controls the modem of 34 standards.

[Explanation of symbols]

11 modem 111 Line control unit 112 analog FEP 113 DSP 114 dual port RAM 115 Interrupt control unit 12 Facsimile controller (DTE) 121 console 122 Image data compression / decompression unit 123 Image reading / recording unit 123 124 Working RAM 125 CPU

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eizo Katayama 2-3-8 Shimomeguro, Meguro-ku, Tokyo Matsushita Transmission System Co., Ltd. (72) Inventor Genzo Takagi 2-chome, Shimomeguro, Meguro-ku, Tokyo 3-8 Matsushita Transmission System Co., Ltd. (72) Inventor Yoshihiro Noguchi 2-3-8 Shimomeguro, Meguro-ku, Tokyo Matsushita Transmission System Co., Ltd. (72) Inventor Mitsuhiro Araki Shimogane, Meguro-ku, Tokyo Meguro 2-chome 3-8 Matsushita Electric Transmission Systems Co., Ltd. (56) References JP-A-4-345364 (JP, A) JP-A-61-234154 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 29/00 H04M 11/00 303 H04N 1/32

Claims (12)

(57) [Claims] 1. An operation mode for performing sequence control
The operation mode setting is received from the DTE
Execution means for executing the set operation mode and this execution
The end of the operation mode by means is received from the external line.
Judgment means for judging by detecting RCP frame
Then, it is determined that the RCP frame is detected by this determination means.
Set to the main channel reception mode.
From the control channel mode to the control channel mode
Modulator and demodulator. 2. An operation mode for performing sequence control
The operation mode setting is received from the DTE
Execution means for executing the set operation mode and this execution
The end of the operation mode by means is received from the external line.
Judgment by detecting a signal consisting of a predetermined pattern
And the end of the operation mode by this determination means.
If judged, the self operation mode is controlled channel mode
From the main channel reception mode to the control means
A modulation / demodulation device provided. 3. A signal having the predetermined pattern is a data
It consists of patterns that cannot occur during data transfer.
The modulation / demodulation device according to claim 2. 4. Switching of operation modes in said control means
And a notification means for notifying the DTE side that
The modulation / demodulation device according to any one of claims 1 to 3, wherein 5. An operation mode for performing sequence control
According to the DTE that gives the setting instruction and the instruction from this DTE
Image communication apparatus including a modem that executes a certain operation mode
In the mode, the modem operates in an operation mode instructed by the DTE.
Execution means for executing and the operation mode by this execution means
Detection of RCP frame received from external line
The determination means for determining by
When it is determined that an RCP frame has been detected,
Change the mode from the main channel reception mode to the control channel mode.
Control means for switching to a mode
Image communication device. 6. An operation mode for performing sequence control
According to the DTE that gives the setting instruction and the instruction from this DTE
Image communication apparatus including a modem that executes a certain operation mode
In the above, the modem implements the operation mode according to the instruction from the DTE.
The executing means to execute and the end of the operation mode by this executing means.
Is received from an external line and has a predetermined pattern.
The determination means for determining by detecting
If the stage determines that the operation mode has ended,
From the control channel mode to the main channel reception mode.
A control means for switching to
Image communication device. 7. A signal comprising the predetermined pattern is a data
It consists of patterns that cannot occur during data transfer.
The image communication device according to claim 6. 8. The modem operates in the control means.
To notify the DTE that the mode has been switched.
8. An intelligence means is provided, The said means characterized by the above-mentioned.
Image communication device. 9. An operation mode for performing sequence control
According to the DTE that gives the setting instruction and the instruction from this DTE
The communication method using a modem that executes the
And the modem operates in the operation mode instructed by the DTE.
The execution step that executes the
RCP frame that receives the end of the work mode from the external line
The determination step of determining by detecting the
It is determined that the RCP frame is detected in the determination step.
Then, the self operation mode is changed from the main channel reception mode.
Equipped with a switching step to switch to control channel mode
An image communication method characterized by the following. 10. An operation mode for performing sequence control.
The DTE that gives the instruction to set the mode and the instruction from this DTE.
Image communication method using a modem that executes the operation mode according to
According to the method, the modem implements the operation mode instructed by the DTE.
The execution step to be performed and the operation mode by this execution step
The end of the command from a predetermined pattern received from an external line
Judgment step to judge by detecting the signal
Then, if it is determined that the operation is completed by this determination step,
Control your operating mode from channel mode to main channel
A switching step for switching to a reception mode
Image communication way to said. 11. A signal having the predetermined pattern is a data
Characterized by patterns that cannot occur during data transfer
The image communication method according to claim 10. 12. Mode switching in the control step
A notification step for notifying the DTE that the
The image communication according to claim 9, wherein
Method.