JPH073972B2 - Data communication device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a data communication device, and more particularly to a data communication device having an error resending function.

[Conventional technology]

Conventionally, as a device of this type, for example, a facsimile device having an error resending function for converting image information into an HDLC format and transmitting the same, the transmitter side divides the encoded image information into a predetermined length, Formatting and transmitting multiple frames at once (for example,
It transmits up to 256 frames). On the receiver side, after receiving a plurality of frames (for example, up to 256 frames), the number of the errored frame is transmitted to the transmitter side. The transmitter side retransmits the erroneous frame.
On the receiver side, when there is no error frame, the information is transmitted to the transmitter, and the transmitter proceeds to the transmission of the next block. Also, even after the transmitter has retransmitted n times (n is 1, 2, 3 ...) If there is still an error frame, the transmitter continues to retransmit the frame or interrupts the retransmission of the frame. , It can be decided whether to proceed to the transmission of the next block.

FIG. 3 is a diagram showing a procedure of ECM (Error Correction Mode).

FIG. 3 (1) is a procedure example without an error frame, FIG. 3 (2) is a procedure example with an error frame, FIG. 3 (3)
Retransmitted one block multiple times, but there are still error frames, example procedure to continue retransmitting that frame,
In Fig. 3 (4), one block was retransmitted multiple times,
This is an example of a procedure in which there is still an error frame, the retransmission of the frame is interrupted, and the transmission of the next block is started.

In Figure 3, PPS-Q, PPR, EOR-Q, ERR, CTC, CTR is 3
This is a 00b / s signal.

First, PPS (Partial page signal) -Q, which is the end of a partial page or one page, indicates that when MCF is received, it returns to phase B or phase C. Where Q is NULL, M
There are PS, EOM, EOP and PRI-Q. MPS, EOM, EOP, PRI-Q are
It has the same concept as the conventional T30. Then, it indicates that it is the last partial page of one page. NULL is a signal used when a one-page original is divided into a plurality of partial pages. That is, it represents a non-final partial page of one page.

PPR (Partial page request) is a signal indicating that the previously received message was incomplete. 256
It has a bit FIF, and requests the retransmission of the frame of the specified number by this FIF.

EOR (End of retransmission) -Q is a signal indicating that the transmitting side terminates the retransmission of the error frame of the partial page transmitted last time and transmits the next block after receiving the ERR signal. Q is the same as that of PPS.

ERR (Response for end of retransmission) is E
It is a response signal to the OR signal.

CTC (Continue to correct) is a signal indicating that the sender wants to continue correcting the previously sent message. The CTC has a FIF and can change the transmission speed.

CTR (Response for continue to correct) is CTC
It is a response signal to the signal, and indicates that the receiving side accepts the content included in the CTC signal.

In FIG. 3 (2), the receiver side sends PPR to the transmitter side when an error frame is detected. PPR on the transmitter side
Retransmission of designated frame by signal (high-speed data)
I do.

On the other hand, in FIGS. 3 (3) and 3 (4), the receiver side sends the PPR to the transmitter side when an error frame is detected. The transmitter side retransmits the specified frame (high-speed data) by the PPR signal, and continues the retransmission of this block (CTC), or interrupts the retransmission of this block and transmits the next block. A procedure signal (EOR) (300 b / s low-speed data) may be transmitted. That is, the receiver needs to be able to receive high speed data and low speed data after transmitting the PPR.

[Problems that the invention is trying to solve]

However, there is a big drawback that the low speed data and the high speed data may be erroneously recognized when the line condition is bad and the probability of communication failure increases.

[Means and Actions for Solving Problems]

According to the present invention, in a data communication device having an error resending function, transmitting data at high speed and transmitting a communication procedure signal at low speed, the error resending by the second sending means is continued or the next data is sent. Since the notification means notifies the reception side in advance of the timing of transmitting a signal indicating whether to transmit, it is possible for the reception side to appropriately perform high-speed data reception and low-speed communication procedure signal switching. You can reduce errors in the procedure.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

First, the method of error retransmission in the facsimile apparatus of this embodiment will be described.

First, on the receiver side, the EOR for the number of PPR
Alternatively, the transmitter side is informed of whether or not it has the function of identifying the CTC transmission by setting it in the NSF signal.
For example, the information is assigned to the 48th bit of the FIF of the NSF signal (signal indicating a non-standard function). When the 48th bit of the FIF of the NSF signal is 0, it does not have the above function, and when the 48th bit of the FIF of the NSF signal is 1, it has the above function.

On the transmitter side, the FIF of the received NSF signal is analyzed to determine whether or not the receiver has the above-mentioned function. When the receiver does not have the above-mentioned function, the communication in the ECM mode described above is performed. In this case, the transmitter sends the NSS signal with the FIF 48 bits of the NSS signal (the signal for setting the non-standard function) set to 0,
Declares to the receiver that communication based on the above functions will not be performed. On the other hand, when the receiver has the above-mentioned function, it performs communication based on the above-mentioned function. Specifically, the transmitter transmits an NSS signal in which the FIF 48 bits of the NSS signal is set to 1, and declares to the receiver that communication based on the above-mentioned function is performed. Then, the number of times the PPR is received at 48 bits to 56 bits of the FIF of the NSS signal before transmitting the EOR or CTC is set.

When the transmitter receives the same block, that is, the number of circuits PPR declared from the 49th bit to the 56th bit of the FIF of the NSS signal in the transmission of the same partial page, the CTC
Alternatively, the EOR is sent.

On the other hand, when receiving the same block, that is, the same partial page, at the 49th to 56th bits of the FIF of the NSS signal, when the PPR less than the declared number of times is transmitted, low-speed data (300b / s only) to receive only.
Here, when sending PPR less than the declared number of times, it was said that high-speed data reception was weighted, but this is because the transmitter could not receive PPR and could retransmit PPS-Q. Because there is.

Hereinafter, the present embodiment will be described in detail based on the embodiment shown in the drawings.

FIG. 1 is a block diagram showing the configuration of the facsimile machine of this embodiment.

In FIG. 1, reference numeral 2 is used for data communication and the like. Therefore, by connecting to the terminal of the line, connection control of the telephone switching network, switching to the data communication path, and loop maintenance are performed. Network control unit NCU (Network Control Uni
t). The signal line 2a is a telephone line. The NCU 2 inputs the signal on the signal line 36a, and if this signal level is "0", the telephone line is on the telephone side, that is, the signal line 2a is the signal line.
Connect to 2b. If the signal on the signal line 36a is input and the signal level is "1", the telephone line is connected to the facsimile machine side, that is, the signal line 2a is connected to the signal line 2c. In a normal state, the telephone line is connected to the telephone side.

Reference numeral 4 is a telephone.

Reference numeral 6 is a hybrid circuit that separates a transmission system signal and a reception system signal. That is, the transmission signal of the signal line 20a passes through the signal line 2c and is sent to the telephone line through the NCU2.
Further, the signal sent from the other party is output to the signal line 6a after passing through the NCU2, the signal line 2c.

Reference numeral 8 denotes a reading circuit, which sequentially reads image signals for one line in the main scanning direction from a transmission document and creates a signal string representing binary values of white and black. It is composed of an imaging device such as CCD (charge coupled device) and an optical system. The binarized signal sequence of white and black is output to the signal line 8a.

10 inputs the data output to the signal line 8a, and encodes it (MH (Modify Eyed Huffman) encoding or MR
(Modulated read) coded) signal line
It is a circuit that outputs to 10a.

Reference numeral 12 is a memory circuit that stores the data output to the signal line 10a. Since this facsimile device transmits a plurality of frames as one block at a time and then retransmits a frame having an error, it is necessary to have at least one block of memory. The memory circuit 12 has a signal line 36c.
When the frame number to be transmitted to the terminal is output, the information of the frame is output to the signal line 12a.

14 is an address field, a control field, an FCF before the encoded data output to the signal line 12a.
This is a circuit that adds a field and a FIF field (where the frame number currently being transmitted is stored), and outputs the information obtained by HDLC formatting to the signal line 14a. HDL
The C framing circuit 14 also outputs a flag for flow control on the transmitter side to the signal line 14a when the signal of the signal level "1" is output to the signal line 36d.

Reference numeral 16 is a modulator that performs modulation based on the well-known CCITT recommendation V27ter (differential phase modulation) or V29 (quadrature modulation). The modulator 16 receives the signal on the signal line 14a, modulates the signal, and outputs the modulated data to the signal line 16a.

Reference numeral 18 is a modulator that performs modulation based on the well-known CCITT recommendation V21. The modulator 18 inputs the procedure signal of the signal line 36b,
Modulation is performed and the modulated data is output to the signal line 18a.

Reference numeral 20 inputs the signals of the signal line 16a and the signal line 18a and outputs the addition result to the signal line 20a.

22 is a demodulator that performs demodulation based on the well-known CCITT recommendation V21. The demodulator 22 receives the signal on the signal line 6a, performs V21 demodulation, and outputs the demodulated data to the signal line 22a.

A demodulator 24 performs demodulation based on the well-known CCITT recommendation V27ter (differential phase modulation) or V29 (quadrature modulation). The demodulator 24 receives the signal on the signal line 6a, demodulates it, and outputs the demodulated data to the signal line 24a.

26 inputs the demodulated data output to the signal line 24a,
This is an HDLC deframing circuit that performs 0 delicate of the data converted into C and outputs the data before being converted into the HDLC format to the signal line 26a.

Reference numeral 28 denotes a temporary memory circuit that temporarily stores the encoded image information output to the signal line 26a in frame units. The data correctly received in frame units is output to the signal line 28a.

Reference numeral 30 is an image memory circuit for storing the frame data output to the signal line 28a in the corresponding image memory space, and a memory space for storing at least one block of data is required. The data up to the frame in which no error has occurred is sequentially output to the signal line 30a.

32 inputs the demodulated data output to the signal line 30a,
This is a circuit for outputting the decoded data (MH (Modified Eye Huffman) decoding or MR (Modified Eye Read) decoding) to the signal line 32a.

34 inputs the signal output to the signal line 32a, sequentially,
This is a recording circuit that performs recording for each line.

Reference numeral 36 is a control circuit that mainly performs the control described in the first section of the embodiment. The control circuit 36 is composed of a peripheral device of a microcomputer such as a read only memory (ROM) storing a microcomputer and a control program and a random access memory (RAM) temporarily storing data.

FIG. 2 is a flow chart showing the control operation of the control circuit 36 shown in FIG.

In FIG. 2, step S40 represents the beginning.

In step S42, the signal level "0" is applied to the signal line 36a.
The signal of is output and CML is turned on.

Then, in step S44, it is determined whether or not facsimile transmission is selected. If facsimile transmission is selected, the process proceeds to step S92, and if it is not selected, the process proceeds to step S46.

Next, in step S46, it is determined whether or not facsimile reception is selected, and if facsimile reception is selected, the process proceeds to step S50. If facsimile reception is not selected, other processing operations (eg, copy processing, etc.) are performed in step S48. ) Is executed.

In step S46, it is judged that the fax is received, and in step S50
In step 1, the signal of the signal level "1" is first output to the signal line 36a and the CML is turned off.

Then, in step S52, the pre-procedure of the facsimile communication procedure is performed. Here, the transmitter is declared to have a function of setting 1 at the 48th bit of the FIF of the MSF signal, that is, having the function of identifying the maximum number of retransmissions.

Next, in step S54, the 48th bit of the FIF of the NSS signal is 1, that is, the transmitter determines whether or not the communication by the above-mentioned identification function is selected, and the FSS of the NSS signal is determined.
If the 48th bit of the IF is 1, the process proceeds to step S62, and if it is 0, the process proceeds to step S56.

In step S56, step S58, step S60, the above-mentioned identification function is not selected, the pre-procedure, the reception of the image signal,
Perform post-procedures.

On the other hand, in step S54, if it is determined that the communication is selected by the above-mentioned identification function, and if the process proceeds to step S62, the information of the 49th to 56th bits of the FIF of the NSS signal, that is, CTC after transmitting the PPR, or, Information about whether EOR is sent
Store in COUNTER.

Then, in step S64, the remaining procedures in the facsimile communication procedure are executed.

Next, at step S66, a counter CHKCOUNT for counting the number of times PPR has been transmitted is set to 0, then at step S68, an image signal is received, and at step S70, 1 is set.
Image signals are received until it is determined that the block data reception is completed.

When it is determined in step S70 that one block of data has been received, the process proceeds to step S72 and step S72
In step S80, it is determined whether or not there is an error frame in the block currently received. If there is an error frame, the process proceeds to step S80, and if there is no error frame, the process proceeds to step S74. At step S74, the MCF is transmitted, and at step S76, it is judged whether or not there is the next block data to be received. Then, if there is the next block data, the process proceeds to step S78, and if there is no next block data, the process proceeds to step S66.

When the process proceeds from step S76 to step S78, it is determined whether or not there is a mode change. If there is a mode change, the process proceeds to step S52, and if there is no mode change, the process proceeds to step S66.

In step S72, it is determined that there is an error frame and step S
At step 80, the PPR is sent at step S80.

Then, in step S82, since PPR was sent in the previous step, CHKCOUNT is incremented by one.

Next, in step S84, the number of times PPR is sent (CHKCOUN
T) is less than the number of times (COUNTER) declared by the transmitter, and if the retransmission forward is less than the designated number, the process proceeds to step S86, and a mode set is performed to receive high-speed data, that is, to receive the retransmission data. . On the other hand, if the number of retransmissions is greater than or equal to the specified number in step S84 (usually equal), step S8
Proceed to step 8 to receive EOR or CTC, and set the mode to receive low-speed data. When EOR or CTC is received, an intermediate procedure of facsimile communication procedure is performed in step S90.

On the other hand, if it is determined in step S44 that the transmission is facsimile transmission and the process proceeds to step S92, the signal of the signal level "1" is output to the signal line 36a in step S92, the CML is turned on, and the step S92 is performed.
At 94, the pre-procedure of the facsimile communication procedure is performed.

Then, in step S96, the FIF 4 of the NSF signal received in the previous procedure
Whether the 8th bit is 1 or not, that is, the receiver has the above-mentioned discrimination function, is determined. If the 48th bit of the FIF of the NSF signal is 1, the process proceeds to step S104, and if it is 0, the step proceeds to step S104. Proceed to S98.

In step S98, step S100, step S102, the above-mentioned identification function is not selected, the pre-procedure, image signal transmission,
Perform post-procedures.

In step S104, 1 is set at the 48th bit of the FIF of the NSS signal (declaring to the receiver that transmission in the above-mentioned identification function mode is performed), and n times from the 49th bit to the 56th bit. , PPR is received, the number of retransmissions of whether to send CTC, EOR is stored. In addition, the number of retransmissions is set to step S108.
Store in COUNTER at. Then, the remaining procedure is performed in step S106.

Next, in step S110, a counter CHKCOUNT for counting the number of times the PPR is received is set to 0, and in step S112
The image signal is transmitted at step S114, and the image signal is transmitted at step S114 until it is determined that the data transmission for one block is completed.

If it is determined in step S114 that the transmission of one block of data has been completed, the process proceeds to step S116 and step S116.
The PPS-Q is transmitted at.

Then, it is determined whether the PPR is received in step S118 or the MCF is received in step S120. When the PPR is received, the process proceeds from step S118 to step S134, and when the MCF is received, the process proceeds from step S120 to step S130.

If PPR or MFC is not received, the process proceeds from step S130 to step S122, determines whether flow control is necessary in step S122, and if flow control is necessary, in step S124, perform flow control as necessary. To do.

If flow control is not required in step S122, it is determined in step S126 whether PPS-Q has been transmitted three times. If it has transmitted three times, the process proceeds to step S128 to send DCN and transmit three times. If not transmitted, the process proceeds to step S116.

On the other hand, if it is determined in step S120 that the MCF is received and the process proceeds to step S130, in step S130 it is determined whether or not the next block is transmitted. If the next block is transmitted, the process proceeds to step S132 and the next block is transmitted. If not, the process returns to step S42.

When the process proceeds from step S130 to step S132, it is determined in step S132 whether or not there is a mode change. If there is a mode change, the process proceeds to step S94, and if not, the process proceeds to step S110.

On the other hand, when it is determined that the PPR signal is received in step S118 and the process proceeds to step S130, since the PPR signal is received in step S134, CHKCOUNT is incremented by 1 and the process proceeds to step S136.

Then, when the process proceeds to step S136, PP is applied to one block.
If the number of resends that received R (the count value of CHKCOUNT) is the above-mentioned identification function and the PPR is received several times, EOR
Alternatively, it is determined whether it is less than the specified number of retransmissions (value of COUNTER) of sending CTC. If the number of retransmissions is less than the specified number of retransmissions, the process proceeds from step S136 to step S112 to retransmit high speed data. If the number of retransmissions is equal to or greater than the designated number of retransmissions (normally equal), the process proceeds to CTC transmission or EOR transmission after step S138. When it proceeds to step S138, it is determined whether or not the current block needs to be retransmitted. If it needs to be retransmitted, it proceeds to step S140 to transmit the CTC, and if it does not need to be retransmitted, step S144 is performed. Proceed to and send the EOR.

After transmitting the CTC or EOR, the intermediate procedure of facsimile communication procedure is performed in step S142 and step S146, respectively, and the process returns to step S110.

In the above-described embodiment, when the error is not terminated no matter how many times a block is retransmitted, the transmitter continues to retransmit this block or, if there is a next block, shifts to the transmission of that block. The control signal (identification signal) is transmitted.

However, this number may be changed depending on the analysis result of the past line status.

That is, it corresponds to a telephone number such as One Touch, analyzes the past communication result, and determines the number of times based on the result.

As described above, according to the present embodiment, the receiver detects the error blame, and after transmitting the PPR signal, it is possible to identify whether the high-speed data for retransmission or the low-speed procedure signal comes next. . Therefore, it is not necessary to receive high-speed data and low-speed data at the same time as in the conventional case, which has a great effect that the error in the procedure is drastically reduced.

Further, although the facsimile apparatus is described as an example in the above-described embodiment, the present invention is not limited to the facsimile apparatus, and any data communication apparatus such as a teletex having an error resending function can be implemented.

[Effect]

As described above, according to the present invention, it is possible to reduce the error in the procedure in error retransmission and increase the data transmission efficiency.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the facsimile machine of this embodiment, FIG. 2 is a flow chart showing the control operation of the control circuit 36 of FIG. 1, and FIG. 3 is a procedure in the ECM mode. It is the figure which showed an example. 2 is NCU, 4 is telephone, 6 is hybrid circuit, 8 is reading circuit, 10 is encoding circuit, 12 is memory circuit, 14 is HDLC framing circuit, 16 is V27ter or V29 modulator, 18 is V21 modulator, 20 is an adder circuit, 22 is a V21 demodulator, 24 is a V27ter or V29 demodulator, 26 is an HDLC deframing circuit, 28 is a temporary memory circuit, 30 is an image memory circuit, 32 is a decoding circuit, 34 is a recording circuit, 36 is a control circuit.

Claims (2)

[Claims] 1. A data communication apparatus for transmitting data at a first transmission rate and transmitting a communication procedure signal at a second transmission rate lower than the first transmission rate, wherein the data is transmitted at the first transmission rate. First transmitting means for transmitting, receiving means for receiving a retransmission request signal of the data transmitted by the first transmitting means sent from the receiving side, and data at the first transmission rate according to the retransmission request signal Retransmitting means for retransmitting, a counting means for counting the number of retransmissions by the retransmitting means, and after performing a predetermined number of retransmissions by the retransmission means,
Second transmitting means for transmitting a signal indicating whether to continue the retransmission or to transmit the next data at the second transmission rate when the retransmission request signal from the receiving side is received; A data communication apparatus comprising means for notifying the receiving side in advance of information indicating the timing of signal transmission by the second transmitting means. 2. The data communication device according to claim 1, wherein the communication means notifies the predetermined number of times of information.