JP2801687B2 - Facsimile machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a data communication device.

[Prior Art] A facsimile apparatus that transmits image information in accordance with an error correction mode (hereinafter abbreviated as ECM) of the G3 standard recommended by CCITT has been put to practical use.

In this ECM, when a transmission-side facsimile apparatus reads a document image, the image information of each line is set in an HDLC frame of a predetermined format by 256 bytes or 64 bytes, and transmitted as one block of image information. Then, the receiving side reports the transmission error of the received image information of one block as 1
Checking every frame and detecting a transmission error,
Request retransmission of the image information of the frame in which the error occurred. Then, the transmitting side retransmits the image information of the requested frame.

By the way, in recent years, facsimile communication using a wireless line like a car telephone has been frequently performed. In such a case, the line condition is deteriorated, and a transmission error is likely to occur. Therefore, when communication is performed by the ECM, the retransmission operation is repeated many times.

In general, in ECM, when this retransmission is performed, if data is transmitted at one data transmission rate, for example, four times, the data transmission rate is shifted down, but the minimum rate of 2400 bps
If you send four times with, you will end the transmission process,
If the transmission is not successful after retransmitting the same frame three times,
The retransmission of the frame is terminated.

Now, for example, the receiving-side facsimile apparatus receives frame numbers No. 1 to No. 8 as image information of one block,
It is assumed that the image data is stored in the image memory as shown in FIG. Then, as shown in FIG. 7B, if there is a transmission error in the received image information of the frame numbers No. 2 and No. 4, the receiving side requests retransmission of the two frames.

At this time, the transmitting side retransmits the image information of the requested frame numbers No. 2 and No. 4, as shown in FIG. Here, suppose that a transmission error occurs in the frame number of the HDLC frame in which the image information is set, and as shown in FIG. It is assumed that the data changes to No. 9 respectively.

The receiving side checks whether the received frame numbers No. 3 and No. 9 are the frames for which retransmission has been requested. In this case, since the frame numbers No. 3 and No. 9 are not the retransmission-requested frames, the received image information is not erroneously stored in the image memory.

On the other hand, the receiving side determines that the frame numbers No. 2 and N
When requesting retransmission of o.4, due to a transmission error, for example,
As shown in FIG. 11 (d), the frame number No. 2 is No. 4
Now, suppose that No. 4 has changed to No. 2 respectively.

In this case, since the frame numbers No. 4 and No. 2 are the frame numbers for which retransmission is requested, the received image information is stored in each area of the image memory corresponding to the frame number. Therefore, the frame number N of the image memory
The image information of frame number No. 2 is erroneously stored in the area of frame number No. 2 in the area of frame number No. 2 in the area of o.4.

In this case, by checking the data of the HDLC frame, it is determined that the data of the two frames just received is an error. Thereby, when retransmission is possible, retransmission processing is repeated, and an error in image information is corrected.

[Problems to be Solved by the Invention] However, in the case of the last retransmission processing immediately before the transmission processing is terminated, the image information of each frame is stored in the wrong area of the image memory as described above. As a result, the reception process of the image information of the one block is stopped.

By the way, even in the image information of the frame in which the data error is detected, the image information of all the lines is not an error, and it is possible to take out the image information without error one by one and record the image. .

However, as described above, when the image processing of the wrong frame number is stored in each area of the image memory and the reception processing is stopped, when the image information is sequentially read from each area of the image memory and the image is recorded, The correct image for one page cannot be obtained.

As described above, conventionally, there has been a problem that the recorded image is disturbed because the received image information of each frame is stored in the wrong area of the image memory.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a data communication apparatus which improves the above-mentioned problem and reduces the possibility that received image information of each frame is stored in an incorrect area of an image memory.

[Means for Solving the Problems] For this purpose, in the first invention, an image memory in which an image information storage area is formed corresponding to each frame number is provided. Is stored in the storage area of the image memory corresponding to the frame number, while it is determined whether or not there is a transmission error in each data frame. If there is no transmission error in one data frame, then the one data Even if image information is received with a frame number equal to or less than the frame number of the frame, the image information is not written to the image memory.

In the second invention, the reception time per one data frame is calculated based on the number of bits of the data frame and the data transmission rate, and for each reception time calculated from the first data frame reception start time, While identifying the frame number to be received next, each time a data frame is received, the frame number indicated by the data frame is compared with the identified frame number, and the two frame numbers match. In such a case, the image information of the received data frame is stored in the storage area of the image memory corresponding to the frame number.

[Operation] According to the first aspect, when one data frame is received without error, even if the frame number of a subsequent data frame indicates an already received frame number due to an error, the image information is incorrect. Writing to the image memory. This reduces the possibility that the received image information of each frame is stored in the wrong area of the image memory.

According to the second invention, the frame number to be received at each time is identified by the reception time per data frame, so that the image information of each received frame is stored in the wrong area of the image memory. It will not be stored.

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

FIG. 1 is a block diagram showing a vehicle-mounted facsimile system according to a first embodiment of the present invention. In the figure, a facsimile apparatus 1 is connected to a car telephone apparatus 3 via an interface circuit 2, and a handset 4 for a telephone call and a predetermined operation of the car telephone is connected to the interface circuit 2.

In the facsimile machine 1, a scanner 11 reads a document image and extracts image information of a predetermined resolution, and a plotter 12 records the image information on a recording sheet. The encoding / decoding section 13 encodes image information to be transmitted and decodes received image information. The image memory 14 temporarily stores image information of one block to be transmitted and received.

The modem 16 modulates and demodulates image information and transmits the same, and also transmits various procedure signals in a transmission control procedure. The communication control unit 17 executes transmission control by the ECM to execute predetermined facsimile communication.

The operation display unit 18 displays the operation state of the apparatus and the like, and allows the operator to perform various operations.
The system control unit 19 is configured by a microcomputer system, and controls the above-described units to execute a predetermined operation of the facsimile apparatus.

Next, an image receiving operation of the facsimile apparatus 1 having the above configuration will be described. In this case, the operator discusses that facsimile communication is to be performed by a telephone call with the transmitting side on the handset 4 and presses the receive button of the operation display unit 18.

As a result, a predetermined transmission control procedure by the ECM is executed, and a data signal of one block in which image information is set is transmitted from the other party.

As shown in FIG. 2, the data signal of one block includes a synchronization signal section in which a large number of flag sequences F are arranged, an encoding information section in which image information is set, and transmission control in which image information ends. And a return information section indicating return to the procedure. The encoded information section is composed of up to 256 frames FCDF0 to FCDFn, and the return information section is composed of three frames RCP1 to RCP3.

Each of the frames FCDFi and RCPi is formed in the data format of the HDLC frame. The frame FCDFi includes a flag sequence F, an address field A, a control field C, a facsimile control field FCF, a facsimile information field FIF, a frame check sequence FCS, and a flag sequence F.

In each of the above fields, each of the fields other than the facsimile information field FIF and the facsimile control field FCF is 1-byte data. The flag sequence F is for identifying the start and end of a frame, and is data of “0111 1110”. In facsimile communication, since address designation is not required, in a facsimile apparatus using a normal telephone line network, the address field A is set to all "1" data.

The control field C indicates the last frame in the coded information section and the return information section, and is set to "1100 1000" in the last frame and "1100 0000" in other frames.

The facsimile control field FCF indicates the type of the frame. In the encoding information section, information "FCD" indicating an image information frame is set, and in the return information section, information "RCP" indicating the end of the image information is set. "Is set.

The facsimile information field FIF
The frame information No. exists only in the frame of the encoded information section, and a frame number No. of 0 to 255 and an encoded image information CD having a fixed number of bits of 256 bits or 64 bits are set. In the case of the last frame FCDFn, after the image information CD, R
All "0" dummy data for setting the TC code and the data to be set to the above-mentioned constant bit is set.

In the frame check sequence FCS, a CRC code for detecting a transmission error of each data of the frame is set.

FIGS. 3 (a) and 3 (b) show the reception processing of the data signal transmitted in this way, and the facsimile machine 1
Receives the data signal transmitted from the other party (step 101), and sequentially stores the data signal in a data buffer (not shown). Then, synchronization is established by detecting the preamble flag sequence F (process 102), and an HDLC frame following the preamble is determined (process 103).

Then, first, each frame FC of the frames FCDF0 to FCDFn
For each DFi, the detection of the address field A, the detection of the control field C, and the detection of the information "FCD" in the facsimile information field FIF are sequentially executed (processing 104 to 106).
Processing 105 from Y of 104, Processing 106 from Y of Processing 105, Processing 10
6, Y), the frame number is read (process 107).

If it is not the first data reception, that is, the reception of retransmitted data (N of processing 108), it is determined whether or not writing inhibition to the image memory 14 is designated for the received frame number No (processing 108). 109). As will be described later, this write-protection is specified every time image information of one frame is correctly received, for a frame whose frame number is equal to or less than the received frame number.

By the way, in the image memory 14, each frame FCDF0 to 255
A storage area is formed corresponding to. If the write-protection is not specified (N in process 109), the currently received image information CD of one frame is stored in the storage area of the image memory 14 corresponding to the frame number No. (process 11).
0).

By the way, when receiving data as described above, the reception result of the image information of each frame in one block is stored as a 256-bit PPR flag corresponding to the number of frames. This PPR flag is set in the PPR signal at the time of a retransmission request and transmitted to the transmitting side.
All the 256 bits are set to the "error present" state.

Therefore, the transmission error of the received frame is checked by the CRC code of the frame check sequence FCS (process 111), and if there is no error, the corresponding bit of the PPR flag is reset (process 112).

Next, in the currently executed one-block reception process, the storage of the image information having the frame number equal to or smaller than the frame number of the received frame in the image memory 14 is prohibited (process 11).
3). Thereafter, the same operation is repeated for the next frame (to processing 101).

If a transmission error is detected by the above check (N in process 110), the process for the next frame is immediately executed similarly (to process 101). In this way, the image information of each frame of the encoded information section is sequentially received.

Then, when the reception of the encoded information section ends, the frame RCPFi of the return information section is received. In this case, the information “FCD” is not detected in the facsimile information field FIF, and the information “RCP” is detected.
When this "RCP" is detected (N in processing 106, processing 114 and processing 114 Y), the data of each of the frames RCP1 to RCP3 is checked using a CRC code (processing 115).

If there is no error in the data (Y in step 115), the presence / absence of an error frame in the received data signal is determined based on the PPR flag (step 116). here,
If there is no error frame (N in process 116), the image information stored in the image memory 14 is sequentially read out and the received image is recorded (process 117), and the above-described receiving process is terminated.

Now, for example, as shown in FIG.
When the image information of No. 1 to No. 5 is received, data errors occur in frames No. 2 and No. 4, and as shown in FIG.
It is assumed that the R flag is set to that effect. And
As shown in FIG. 9C, the next transmitted frame No. 6
However, it is assumed that the frame number changes to No. 4 as shown in FIG. In this case, frame N
When o.5 is received, writing of image information of frame No. 5 or lower to the image memory 14 is prohibited (processing
113). Therefore, when frame No. 6 is received as No. 4, it is determined that frame No. 4 is designated as write-protected (Y in process 109), and the detection state of that frame is cleared (process 109). 118). Then, the processing shifts to processing of the next frame (to processing 101). As a result, the frame No.
The image information of No. 6 is prevented from being erroneously stored in the area of frame No. 4 of the image memory 14.

Also, as described above, when there is an error frame in the data signal of one block (Y in step 116), it is determined whether a retransmission request is possible (step 119). The retransmission request becomes unexecutable if the retransmission limit is repeated a preset number of times.

Here, if a retransmission request is possible (Y in step 119), the information of the PPR flag is set in the PPR signal and transmitted to the transmitting side, and an error frame retransmission request is made (step 120). Then, the next data signal to be retransmitted is similarly received (processing
101).

On the other hand, when the above-described frames are received, the address field A or the control field C is not detected (N of the processing 104, N of the processing 105), and the information "RCP" is not detected (N of the processing 114). Then, the detection state is cleared in the same manner as described above (process 118), and the process returns to data signal reception (to process 101). When an error is detected in frames RCP1 to RCP3 (N in process 115), the process returns to data signal reception similarly (to process 101). Note that due to such various detection errors, the last frame of one block may not be correctly identified, and the reception state may be held in the process 101. In this case, a timer routine (not shown) is provided, and when a data signal is not received for a certain period of time, the processing is performed from step 116.

As a result, when the address field A and the control field C are not detected, the corresponding bits of the PPR flag remain set in the “error present” state. Even if the information "RCP" is not detected, or even if an error is detected in frames RCP1 to RCP3, if the image information of one block up to that point has been normally received without error, the image information Is valid.

On the other hand, the data signal retransmitted from the transmitting side in response to the retransmission request is also received in the same manner as described above, and the frame number of one frame is determined (process 107). Then, in this case (Y in processing 108), it is checked whether the frame number is the frame number for which retransmission has been requested (processing 121). Here, if the frame is a retransmission-requested frame (Y in processing 121), the processing 1
Enter 09. If the frame is not a retransmission-requested frame (N in process 121), the process of that frame is skipped and the process proceeds to the process of the next frame (to process 118).

Here, for example, as shown in FIG. 5 (a), image information of frames No. 1 to No. 8 is received, and as shown in FIG. 5 (b), frames No. 2, No. 4, It is assumed that data errors occur in No. 6 and that the three frames are retransmitted from the transmitting side as shown in FIG. At this time, it is assumed that a data error occurs again in the retransmitted frames No. 2 and No. 6 and the frame No. 6 changes to No. 4 as shown in FIG.

In this case as well, as in the case of FIG. 4, when frame No. 6 is received, writing of image information of frame No. 5 and below is prohibited to the image memory 14, and the frames received correctly
The image of No.4 will be protected.

As described above, in this embodiment, when one frame is received without error, even if the frame number of the subsequent frame indicates an already received frame number due to an error, the image information is incorrectly stored in the image memory. Will not be written to. This reduces the possibility that the received image information of each frame is stored in the wrong area of the image memory.

 Next, a second embodiment of the present invention will be described.

In this embodiment, when the first data signal is not received, that is, when the retransmission data is not received, the reception processing is performed in the same manner as in the above-described embodiment.

On the other hand, in the case of receiving the retransmission data, the reception frame determination processing is executed in parallel with the start of the reception of the encoded information part of the data signal shown in FIG.

FIG. 6 shows this received frame determination processing, in which the data amount of one frame is first determined (processing 20).
1). When the data amount of one frame is 256 bytes (processing 20
1, "256"), the data transmission speed d of the image information at that time
(Bps) is determined, and the reception time t is calculated as t = 2112 / d (process 202).

Here, “2112” is the number of bits per frame. That is, the flag sequence F, the address field A, the control field C, and the facsimile control field FCF are each 1 byte. The frame check sequence FCS is 2 bytes. Also, facsimile information field
The FIF includes a 1-byte frame number and 256-byte image information. These are summed up to 2112 bits.

When the data amount of one frame is 64 bytes (processing
201 “64”), the data transmission speed d of the image information at that time
(Bps) is determined, and the transmission time t is calculated as t = 576 / d (process 203).

Here, “576” is the total number of bits per frame when the image information of one frame is 64 bytes.

Next, the first frame number of the retransmission-requested frame is instructed to the reception processing side operating at the same time. This instruction is executed, for example, by storing the frame number in a fixed area of the RAM of the system control unit 19 (processing
204).

Next, a timer is started (Step 205), and the elapsed time is monitored (N loop of Step 206). When the transmission time t has elapsed (Y in step 206), it is determined whether there is a next frame for which retransmission has been requested (step 207). Here, if there is a next frame (Y in step 207),
The next frame number for which retransmission has been requested is instructed to the reception processing side (processing 208), the timer is restarted (processing 205), and the same operation is repeated (to processing 206).

Here, for example, as shown in FIG. 7A, assuming that data signals of three frames No. 2, No. 4, and No. 6 have been retransmitted, As shown in (1), a frame number is sequentially designated for each transmission time t of each frame.

In this way, each frame number is designated, and when the designation of the last frame is completed (N in process 207), the timer is stopped (process 209), and the above process is completed.

FIG. 8 shows a part of the receiving process according to the present embodiment which is different from FIGS. 3 (a) and 3 (b). In this embodiment, after receiving one frame of the encoded information part of the data signal and reading the frame number (Y in process 108),
If the frame number is a retransmission request frame (Y in process 301), the frame number designated by the received frame determination process is read (process 302).

Then, the frame number and the frame number read from the received frame are collated (step 303), and if they match (Y in step 303), the received image information of the frame is stored in the image memory 14. Thereafter, the same processing as in the above-described embodiment is performed (to processing 110).

Here, for example, as shown in FIG. 9 (a), image information of frames No. 1 to No. 8 is received, and as shown in FIG. 9 (b), frames No. 2, No. 4, It is assumed that data errors occur in No. 6 and that these three frames are retransmitted from the transmitting side as shown in FIG. At this time, as shown in FIG.
Suppose that No. 6 changes to No. 4 respectively.

In this case, the frame number to be received is specified in the reception period of each frame by the reception frame determination process as shown in FIG. As a result, the frame numbers of the frames No. 6 and No. 4 where the above error has occurred do not match, and the image information is not stored in the image memory 14 but the image information is stored in the wrong area of the image memory. Will not be done.

In the above-described embodiment, only when retransmission data is received,
Although the frame number to be received is indicated by the reception frame determination processing, even at the time of the first data reception, if the frame number is sequentially specified from No. 1 for each transmission time t and the same processing is performed, the image information is obtained. Is stored in the wrong area of the image memory.

Further, in each of the embodiments described above, the case where the image information is transmitted by the G3 standard ECM has been described, but not limited to the ECM,
The present invention can be similarly applied to a case where image information is sequentially transmitted together with a frame number. Further, it goes without saying that the present invention is not limited to a facsimile apparatus connected to a car telephone, but can be similarly applied to a case where the apparatus is connected to a normal subscriber telephone line, a wireless device, or the like.

[Effects of the Invention] As described above, in the first invention, after the image information of each data frame is stored in the storage area of the image memory corresponding to the frame number, if there is no transmission error of the data frame, Then, even if image information is received at a frame number or less, the image information is not written to the image memory, so that the received image information of each frame is stored in the wrong area of the image memory. Less.

Further, in the second invention, the reception time per one data frame is calculated based on the number of bits of the data frame and the data transmission rate, and the reception time is calculated for each reception time from the data frame reception start time. The frame number of the received data frame is identified by identifying the frame number to be used.
Since the image information is stored in the image memory when it matches the identified frame number, the received image information of each frame is not stored in the wrong area of the image memory.

[Brief description of the drawings]

FIG. 1 is a block diagram of an in-vehicle facsimile system according to a first embodiment of the present invention, FIG. 2 is a frame diagram of a data signal transmitting image information, and FIGS. 3 (a) and 3 (b) are images. 4 and 5 are explanatory diagrams showing the processing of received image information, FIG. 6 is an operation flowchart showing the received frame identification processing in the second embodiment, and FIG. FIG. 8 is an explanatory diagram showing the function of the received frame identification process, FIG. 8 is an operation flowchart showing a portion different from FIGS. 3 (a) and 3 (b) in the reception process of the embodiment, and FIG. FIGS. 10 and 11 are explanatory diagrams showing processing of received image information, and FIGS. 10 and 11 are explanatory diagrams showing processing of conventional received image information. 1 ... facsimile machine, 2 ... interface circuit,
3 ... car phone device, 4 ... handset, 11 ... scanner, 12 ... plotter, 13 ... encoding / decoding unit, 14 ...
... Image memory, 16 ... Modem, 17 ... Communication control unit, 18 ...
... Operation display unit, 19 ... System control unit.

Claims (2)

(57) [Claims] 1. A data communication apparatus for receiving a plurality of data frames, each of which has a frame number and image information set therein and transmitted in the order of frame number, as a data signal of one block, stores image information corresponding to each frame number. An image memory in which an area is formed; image information storage means for storing image information of each received data frame in a storage area of the image memory corresponding to a frame number indicated by the data frame; Error determining means for determining the presence or absence of a transmission error of the image memory; and determining whether there is no transmission error by determining one data frame. A data communication device comprising: a write-protection unit that does not write image information to the data communication device. 2. A data communication apparatus for receiving a plurality of data frames, each of which is set in a frame number and image information and transmitted in the order of the frame number, as a data signal of one block, stores image information corresponding to each frame number. An image memory in which an area is formed; a receiving time calculating means for calculating a receiving time per one data frame based on the number of bits of the data frame and a data transmission speed; and a receiving time calculated from the first data frame receiving start time. Received frame identification means for identifying a frame number to be received next for each time, and each time a data frame is received, the frame number indicated by the data frame and the frame number identified by the received frame identification means are identified. Frame number collating means to be collated, received when the two frame numbers match Data communication apparatus characterized by and an image information storage means for storing image information of the data frame to the storage area of the image memory corresponding to the frame number was.