JP6362826B2 - Image data transfer system - Google Patents

Description

  The present invention relates to an image data transfer system.

An interface used for transferring image data is susceptible to noise including static electricity.
In high-speed serial communication performed between a print controller and an image forming apparatus, a scramble circuit and a descramble circuit are generally mounted as countermeasures against unnecessary radiation (EMI; Electro Magnetic Interference). Once an error occurs due to noise, the receiving descrambling circuit continues to output erroneous data until the transmitting scrambling circuit is reset.

  Conventionally, image data is transmitted in units of main scanning lines, and a checksum is added to the image data of each line to detect errors caused by noise or the like (see, for example, Patent Document 1). In addition, an unused bit is provided in the data of each line, and a parity bit is added to the unused bit to detect an error (see, for example, Patent Document 2).

JP 2006-191188 A JP 2010-288014 A

  As described in Patent Document 2, there is a method of correcting an error by correcting a pixel in which an error has occurred based on peripheral pixel data, but the original image data cannot always be reproduced. In order to correct the error accurately, it is necessary to retransmit the image data.

When transferring image data in units of lines, the scramble circuit can be reset for each line, so that only the line in which an error is detected can be retransmitted for error correction. However, even for an error of several pixels, the image data must be retransmitted in units of lines, and the transfer rate of the image data is reduced for error correction.
Furthermore, when noise is continuously generated, retransmission in units of one line is repeated, so that the transfer rate further decreases.

  An object of the present invention is to perform error correction while suppressing a decrease in the transfer rate of image data.

According to the invention of claim 1,
A print controller that reads out image data in packet units, adds error detection data to each packet, and transmits the data to the image forming apparatus;
Each packet received from the print controller is concatenated to acquire image data, and an error in each packet is detected using error detection data added to each packet, and error correction is performed on the packet in which the error is detected. An image forming apparatus,
When the error is detected, the image forming apparatus transmits a retransmission request signal to the print controller, performs error correction with a packet retransmitted from the print controller,
The print controller
When the retransmission request signal is received, the packet in which the error is detected is retransmitted,
After receiving the retransmission request signal, to reduce the data amount of one packet to be transmitted,
After reducing the data amount of one packet, if a packet with a certain amount of data is transmitted without receiving a new retransmission request signal, the data amount of one packet to be transmitted is restored.
An image data transfer system is provided.

According to invention of Claim 2 ,
When the print controller receives a retransmission request signal after reducing the data amount of one packet, the print controller further reduces the data amount of one packet to be transmitted.
An image data transfer system according to claim 1 is provided.

  According to the present invention, it is possible to reduce the data amount of a packet to be transmitted after an error occurs. When an error occurs a plurality of times, it is possible to correct the error while suppressing a decrease in the transfer rate of the image data by repeating retransmission of the packet.

1 is a schematic configuration diagram showing an image data transfer system according to the present embodiment. It is a block diagram of the transmission process part of FIG. (A) The example of the packet read when an error is detected once is shown. (B) shows an example of a packet that is read when an error is detected consecutively several times. (C) The example of the packet read when an error is detected odd number of times continuously is shown. An example in which the data amount of one packet is reduced is shown. An example is shown in which the data amount of one packet is restored. It is a block diagram of the reception process part of FIG. 6 is a timing chart when a packet is transferred from the print controller to the image forming apparatus. 6 is a flowchart illustrating a processing procedure when the print controller transmits one packet. 6 is a flowchart illustrating a processing procedure when the image forming apparatus receives one packet. An example in which the data amount of a packet to be retransmitted is reduced is shown.

  Hereinafter, an embodiment of an image data transfer system of the present invention will be described with reference to the drawings.

FIG. 1 shows an image data transfer system G according to the present embodiment.
As shown in FIG. 1, the image data transfer system G includes a print controller g1 and an image forming apparatus g2.
The print controller g1 and the image forming apparatus g2 are connected by a dedicated cable, and image data is transferred from the print controller g1 to the image forming apparatus g2 via the dedicated cable.

The print controller g1 receives PDL (Page Description Language) data from a computer on the network, and generates image data from the PDL data.
As illustrated in FIG. 1, the print controller g1 includes an image data generation unit 101, a transmission processing unit 102, a serial conversion unit 103, a storage unit 104, a control unit 105, and a communication unit 106.

  The image data generation unit 101 rasterizes the PDL data to generate four color image data of C (cyan), M (magenta), Y (yellow), and K (black).

The transmission processing unit 102 inputs the image data generated by the image data generation unit 101 in units of lines. The transmission processing unit 102 reads one line in units of packets smaller than one line, adds error detection data to each packet, and outputs the packet.
Further, when receiving the retransmission request signal from the image forming apparatus g2, the transmission processing unit 102 adds error detection data to the packet in which the error is detected, and re-outputs the packet.
The transmission processing unit 102 reduces the data amount of one packet to be read after receiving the retransmission request signal.

The serial conversion unit 103 includes a scramble circuit.
The serial conversion unit 103 serially converts the packet output from the transmission processing unit 102, and then scrambles and transmits the packet to the image forming apparatus g2.

  The storage unit 104 stores a program that can be read by the control unit 105. As the storage unit 104, a hard disk, a nonvolatile memory, or the like can be used.

The control unit 105 reads out a program stored in the storage unit 104 and controls each unit of the print controller g1 according to the program.
For example, the control unit 105 receives PDL data from a computer on the network via the communication unit 106 and causes the image data generation unit 101 to rasterize the PDL data.

  The communication unit 106 includes a network interface and communicates with a computer on the network and the image forming apparatus g2.

The image forming apparatus g2 forms an image on a sheet based on the image data.
As shown in FIG. 1, the image forming apparatus g2 includes a parallel conversion unit 201, a reception processing unit 202, an image memory 203, an image processing unit 204, an image forming unit 205, a communication unit 206, a control unit 207, and a storage unit 208. Configured.

The parallel conversion unit 201 includes a descrambling circuit.
The parallel conversion unit 201 receives each packet from the print controller g1, performs descrambling on each packet, performs parallel conversion, and outputs the packet.

The reception processing unit 202 concatenates each packet output from the parallel conversion unit 201 and outputs image data in units of lines.
The reception processing unit 202 detects an error in each packet using the error detection data added to each packet. When an error is detected, the reception processing unit 202 transmits a retransmission request signal to the print controller g1, and performs error correction of the packet in which the error is detected by the packet retransmitted from the print controller g1.

The image memory 203 is a memory that holds image data. As the image memory 203, a DRAM (Dynamic Random Access Memory) or the like can be used.
The image memory 203 holds the image data output from the reception processing unit 202 in units of lines. The image memory 203 holds image data that has been subjected to image processing by the image processing unit 204.

The image processing unit 204 reads image data from the image memory 203 in accordance with an instruction from the control unit 207 and performs various image processing. The image processing unit 204 outputs the processed image data to the image memory 203. For example, the image processing unit 204 can color-convert image data for color correction. The image processing unit 204 can also perform image processing such as enlargement, reduction, and rotation.
Finally, the image processing unit 204 performs halftone processing on the image data and outputs it to the image forming unit 205. Examples of halftone processing include error diffusion processing and screen processing using a dither matrix.

The image forming unit 205 forms an image on a sheet based on the image data output from the image processing unit 204.
Specifically, the image forming unit 205 includes four sets of an exposure unit, a development unit, and a photoreceptor for each of C, M, Y, and K colors. The exposure unit exposes the charged and rotating photoconductor by optical scanning based on the image data. The developing unit develops the electrostatic latent image formed on the photoreceptor by exposure with toner. In this way, the image forming unit 205 transfers the images of the respective colors formed on the four photoconductors onto the paper via an intermediate transfer belt or the like. Thereafter, the paper is fixed by a fixing device.

  The communication unit 206 includes a network interface and communicates with the print controller g1 according to instructions from the control unit 207.

The control unit 207 reads a program stored in the storage unit 208 and controls each unit of the image forming apparatus g2 according to the program.
For example, the control unit 207 causes the image processing unit 204 to perform image processing on the image data, and causes the image forming unit 205 to form an image.

  The storage unit 208 stores a program that can be read by the control unit 207. As the storage unit 208, a hard disk, a nonvolatile memory, or the like can be used.

Next, details of the transmission processing unit 102 included in the print controller g1 will be described.
FIG. 2 is a configuration diagram of the transmission processing unit 102.
As shown in FIG. 2, the transmission processing unit 102 includes a line buffer 11, a write control unit 12, a read control unit 13, and a detection data adding unit 14.

The line buffer 11 is a memory that holds one line of image data.
The line buffer 11 inputs and holds one line of image data in accordance with the enable signal and write address output from the write control unit 12.
Further, the line buffer 11 outputs the held image data in accordance with the enable signal and read address output from the read control unit 13.

The write control unit 12 outputs an enable signal and a write address to the line buffer 11 in synchronization with the synchronization signals HV (Horizontal Valid), VV (Vertical Valid) and IND input together with the image data, and outputs one line. Write the image data into the line buffer 11.
The synchronization signal HV indicates the effective area of the image in the main scanning direction, that is, the effective area of each line. The synchronization signal VV indicates the effective area of the image in the sub-scanning direction, that is, the effective area of each page. The synchronization signal IND indicates the start timing of each line.

  For example, when one line is composed of 8000 pixels, the write control unit 12 outputs a write address from 0 to 7999. Thereby, each pixel of one line is stored in the line buffer 11 in association with addresses 0 to 7999 in order from the top pixel.

The read control unit 13 outputs an enable signal and a read address to the line buffer 11, and reads one line of image data held in the line buffer 11 in units of packets.
The read control unit 13 generates and outputs a synchronization signal DE (Data Enable) and HSYNC in response to reading of the packet. The synchronization signal DE indicates each packet and an effective area of error detection data added to each packet. The synchronization signal HSYNC indicates the start timing of each line.
The synchronization signals DE and HSYNC are transmitted to the image forming apparatus g2 together with the packet.

The reading control unit 13 counts addresses 0 to 7999 for one line in units of packets while leaving an interval between packets, and outputs the counted number as a reading address.
When 128 pixels are defined as one packet, the read control unit 13 starts counting from 0, counts the address of 128 pixels, and outputs the read addresses 0 to 127 of the first packet. When the read control unit 13 outputs the read address for one packet, the read control unit 13 temporarily stops counting the address, and resumes counting the address after a predetermined interval. The read control unit 13 counts the addresses of 128 pixels and outputs read addresses 128 to 255 of the next packet.

  Note that the interval between packets may be set as appropriate according to the error detection data added to the packet and the time required for resetting the scramble process. For example, if 1 clock is required for error detection data and 2 clocks are required for resetting the scramble process, an interval of 3 clocks may be provided.

When an error is detected in the packet read immediately before, the reading control unit 13 receives a retransmission request signal from the image forming apparatus g2 during reading of the next packet.
When receiving the retransmission request signal, the read control unit 13 reads again the packet read immediately before the packet after the packet read at the time of reception.

3 (a) shows an error detected once, FIG. 3 (b) shows an even number of consecutive errors detected, and FIG. 3 (c) shows an odd number of consecutive errors detected. In each case, each packet read is represented.
In FIG. 3A to FIG. 3C, each packet is represented as packets 1 to 4 in the order in which each packet is arranged in one line. Packets 1 to 4 are packets whose addresses are 0 to 127, 128 to 255, 256 to 383, and 384 to 511, respectively. Also, the hatched packet represents a packet that has been detected again and is read again for retransmission.

As shown in FIGS. 3A to 3C, when receiving the retransmission request signal, the read control unit 13 reads a packet read immediately before the packet being read at the time of reception. As shown in the figure, the retransmission request signal is a signal that is asserted when an error is detected and negated at the end of the packet.
For example, as shown in FIG. 3A, since the retransmission request signal is received during the reading of the packet 3, the reading control unit 13 again reads the packet 2 read out immediately before the packet 3 is read out. read out.

When errors continue, the read control unit 13 receives a retransmission request signal during reading of the packet 2 as shown in FIG. The read control unit 13 reads again the packet 3 read immediately before the packet 2 being read again.
If further errors continue, the read control unit 13 receives a retransmission request signal during reading of the packet 3 as shown in FIG. The read control unit 13 reads again the packet 2 read immediately before the next three packets being read again.

If the retransmission request signal is not received after reading the packet in which the error is detected again, as shown in FIGS. 3A to 3C, the reading control unit 13 returns to the original order. Read packet 4.
When the error is detected once or is detected continuously odd number of times, as shown in FIGS. 3 (a) and 3 (c), the read control unit 13 starts the address from the continuation of the second previous packet 3. Is counted, the read address is output, and the packet 4 is read.
On the other hand, when an error is detected a number of times consecutively, as shown in FIG. 3B, the read control unit 13 counts the address from the continuation of the previous packet 3 and outputs the read address. Packet 4 is read out.

  The read control unit 13 generates the synchronization signal DE in response to reading each of the packets 1 to 4 including the packet to be retransmitted. As shown in FIGS. 3A to 3C, the synchronization signal DE is asserted while the packet and the error detection data added to the packet are valid, and negated between the packets.

After receiving the retransmission request signal, the read control unit 13 reduces the data amount of one packet to be read.
Thereby, the data amount of the packet to transmit can be reduced. It is possible to suppress a decrease in the transfer rate of image data due to the occurrence of an error a plurality of times and repeated retransmission of packets.
The amount of reduction can be determined as appropriate, but when the data amount of one original packet is used as the reference data amount, if the integer multiple of the reduced data amount becomes the reference data amount, the original reference It is preferable because it is easy to return the data amount.

Specifically, the read control unit 13 can change the data amount of one packet to be read by controlling the read address.
When the data amount of one pixel is 1 byte, the reference data amount of one packet composed of 128 pixels is 128 bytes. When the data amount of one packet is reduced from 128 bytes to, for example, 64 bytes, the read control unit 13 changes the unit for counting addresses for one packet from 128 pixels to 64 pixels. As a result, the image data held in the line buffer 11 is read out in units of 64 pixels, and the data amount of one packet becomes 64 bytes.

The read control unit 13 preferably further reduces the data amount of one packet when the retransmission request signal is newly received after reducing the data amount of one packet.
The amount of data of packets to be transmitted can be further reduced, and a reduction in the transfer rate of image data when an error occurs a plurality of times can be further suppressed.

FIG. 4 shows an example of reducing the data amount of one packet.
In FIG. 4, the packets are represented as packets 1 to 7 in the order in which the packets are arranged in one line. Also, the hatched packet represents a packet that has been detected again and is read again for retransmission.
As shown in FIG. 4, the read control unit 13 reads packets 1 and 2 with 128 pixels as one packet. Therefore, the data amount of the packets 1 and 2 is a reference data amount of 128 bytes. Since the reading control unit 13 receives the retransmission request signal during reading of the packet 2, the reading control unit 13 next reads the packet 1 again. The data amount of the packet 1 read again is 128 bytes which is the same as the previous reading. As described above, it is preferable to read out a packet to be retransmitted with the same data amount as that at the previous transmission, because address control at the time of reading by the reading control unit 13 and writing at the writing control unit 23 is facilitated.

Next, the read control unit 13 reduces the data amount of one packet to be read from 128 bytes to a half of 64 bytes, and reads packets 3 to 5 having 64 pixels.
As shown in FIG. 4, when a new retransmission request signal is received while reading packet 5, read control unit 13 reads packet 4 again. The data amount of the packet 4 that is read again is 64 bytes, which is the same as in the previous reading. Since the data amount of the packet to be retransmitted is halved and the time required for retransmission is half that of the case of retransmitting with the original reference data amount, it is possible to suppress a decrease in the transfer rate of image data due to retransmission.

Thereafter, the read control unit 13 further reduces the data amount of one packet to 32 bytes, which is half, and reads the packet 6 and subsequent data with 32 pixels as one packet.
The addresses of the packets 1 to 7 read in this way are 0 to 127, 128 to 255, 256 to 319, 320 to 383, 384 to 447, 448 to 479, and 480 to 511, respectively.

When the read control unit 13 reduces the data amount of one packet and then transmits a packet having a constant data amount without receiving a new retransmission request signal, the read control unit 13 returns the data amount of one packet to the original reference data amount. It is preferable.
When the data amount of one packet is reduced, the number of packets increases and the invalid period between each packet also increases. Since the transfer rate of image data decreases as the invalid period increases, if a new error does not occur while sending a certain amount of data, it is restored to the original reference data amount to suppress the increase in the invalid period. . Thereby, it is possible to suppress a decrease in transfer rate due to a reduction in the data amount.

The fixed data amount when returning the data amount of one packet can be set as appropriate. Considering the balance between the decrease in the transfer rate due to repeated retransmission of packets of the reference data amount and the decrease in the transfer rate due to an increase in the invalid period between each packet when the data amount is reduced from the reference data amount , You can set.
Further, the read control unit 13 may change a certain amount of data according to the frequency of occurrence of errors.

FIG. 5 shows an example in which the data amount of one packet is returned to the reference data amount.
In FIG. 5, the packets are represented as packets 1 to 11 in the arrangement order of the packets in one line. Also, the hatched packet represents a packet that has been detected again and is read again for retransmission.
As shown in FIG. 5, the read control unit 13 reads the packet 1 in which an error is detected again, then reduces the data amount from the packet 3 to 64 bytes, and reads 64 pixels as one packet. When the constant data amount is 384 bytes, when the read control unit 13 reads out six packets 3 to 8, the constant data amount is reached. After the data amount is reduced, a new retransmission request signal is not received during the period t0 until the transmitted data amount reaches 384 bytes. Therefore, the read control unit 13 returns the data amount of one packet to the reference data amount of 128 bytes, and reads 128 pixels as one packet after the packet 9.

The detection data adding unit 14 generates error detection data from the packet output from the line buffer 11.
If an error can be detected using error detection data, the method is not particularly limited, and for example, parity check, checksum, CRC (Cyclic Redundancy Check), or the like can be used. Among these, CRC is preferable because the circuit configuration is simple.

When CRC is used, the detection data adding unit 14 calculates a CRC code from the image data as error detection data. The CRC code is a remainder when a bit string of image data is divided by a predetermined generator polynomial.
The detection data adding unit 14 adds error detection data to the end of the packet and outputs the packet.

Next, details of the reception processing unit 202 included in the image forming apparatus g2 will be described.
FIG. 6 is a configuration diagram of the reception processing unit 202.
As illustrated in FIG. 6, the reception processing unit 202 includes an error detection unit 21, a line buffer 22, a write control unit 23, and a read control unit 24.

  The error detection unit 21 receives the packet and the error detection data from the parallel conversion unit 201 in synchronization with the synchronization signals DE and HSYNC transmitted from the print controller g1 together with the packet. The error detection unit 21 separates the packet and the error detection data added at the end of the packet, and outputs the separated packet to the line buffer 22.

The error detection unit 21 generates error detection data from the separated packets in the same manner as the detection data addition unit 14 of the transmission processing unit 102. The error detection unit 21 compares the generated error detection data with the error detection data separated from the packet.
The error detection unit 21 outputs a detection result indicating that no error has been detected when the two error detection data match, and outputs a detection result indicating that an error has been detected if they do not match.

The line buffer 22 is a memory that can hold one line of image data.
The line buffer 22 holds each packet output from the error detection unit 21 in accordance with the enable signal and write address output from the write control unit 23.
Further, the line buffer 22 outputs one line of held image data in accordance with the enable signal and read address output from the read control unit 24.

  The write control unit 23 outputs an enable signal and a write address to the line buffer 22 in synchronization with the synchronization signals DE and HSYNC, and writes each packet output from the error detection unit 21 to the line buffer 22.

The detection of the packet error is performed after the error detection unit 21 inputs the error detection data added to the end of the packet. Therefore, after the writing control unit 23 has already started writing the next packet, the detection result of the error of the packet written immediately before is output. When a detection result indicating that an error has been detected is output, the writing control unit 23 transmits a retransmission request signal to the print controller g1. Further, the write control unit 23 discards the packet written immediately before the packet that was being written when the detection result was output. Here, “discard” means that data can be overwritten in the line buffer 22.
In response to the retransmission request signal, the previous packet in which the error was detected is retransmitted from the print controller g1, so that the write control unit 23 next to the packet being written next to the previous packet that has been rewritten. Write the packet to the line buffer 22.

When writing a packet, the write control unit 23 counts addresses for one line from 0 to 7999 in units of packets in synchronization with the synchronization signal DE, and outputs the write address.
Specifically, when the synchronization signals DE and HSYNC are asserted, the write control unit 23 starts counting from 0, counts the address of 128 pixels, and sets the write address 0 to 127 of the first packet. Output. When the write control unit 23 outputs the write address for one packet, the write control unit 23 temporarily stops counting, restarts the count when the next synchronization signal DE is asserted, and counts the addresses 128 to 255 for one packet.

After transmitting the retransmission request signal, the writing control unit 23 controls the writing address in the same manner as the reading control unit 13 of the print controller g1 controls the reading address.
That is, the write control unit 23 reduces the data amount of one packet to be written by reducing the unit of counting addresses for one packet from 128 pixels to 64 pixels after transmitting the retransmission request signal. Further, when the write control unit 23 transmits a new retransmission request signal after reducing the data amount, the unit for counting the address for one packet is further reduced to 32 pixels to further reduce the data amount of one packet. cut back. Further, when the write control unit 23 receives a packet with a constant data amount without transmitting a new retransmission request signal after reducing the data amount, the unit for counting addresses for one packet is the original 128. Returning to the pixel, the data amount of one packet to be written is returned to the original data amount.

  Thereby, even when the packet is retransmitted and when the data amount of one packet is changed, the writing of the packet of the writing control unit 23 can be synchronized with the reading of the packet of the reading control unit 13, and the original arrangement order is maintained. Each pixel of one line can be written.

The read control unit 24 outputs an enable signal and a read address to the line buffer 22. The read control unit 24 outputs a read address for one line from 0 to 7999, and connects the packets written in the line buffer 22 to read one line of image data.
Further, the read control unit 24 generates the synchronization signals HV, VV, and IND according to the synchronization signal HSYNC. The synchronization signals HV, VV, and IND are output together with the read image data.

FIG. 7 is a timing chart when a packet is transferred from the print controller g1 to the image forming apparatus g2.
In FIG. 7, the packets represented by the assertion periods of the synchronization signal DE are represented by the order of arrangement of the packets 1 to N.

As shown in FIG. 7, the print controller g1 on the transmission side sequentially reads each of the packets 1 to N in synchronization with the synchronization signals HV and IND input together with the image data, and transmits them to the image forming apparatus g2. The print controller g1 generates the synchronization signals DE and HSYNC in response to reading of each packet.
The image forming apparatus g2 on the receiving side writes each packet received from the print controller g1 in the line buffer 22 in synchronization with the synchronization signals DE and HSYNC. The image forming apparatus g2 reads and connects the packets 1 to N after a predetermined period from the assertion of the synchronization signal HSYNC to obtain one line of image data. In response to this reading, the image forming apparatus g2 generates the synchronization signals HV and IND as shown in FIG.

When noise is applied during transmission of the packet, for example, as shown in FIG. 7 during transmission of the packet 2, the image forming apparatus g2 detects an error in the packet 2 while writing the packet 3, and retransmits the request signal. Send. The print controller g1 receives the retransmission request signal while reading the packet 3.
In response to the retransmission request signal, the print controller g1 then reads the packet 2 again and retransmits it to the image forming apparatus g2. The image forming apparatus g2 performs error correction of the packet 2 written in the line buffer 22 by the retransmitted packet 2.

  The print controller g1 can use not only the assert period t1 of the line indicated by the synchronization signal HV but also the negate period t2 up to the next line for reading one line including the packet to be retransmitted. If the reading of one line including the packet to be retransmitted can be completed by the start timing of the next line indicated by the synchronization signal HV, the original line cycle is not shifted, and the line synchronization can be maintained on the receiving side and the transmitting side. it can.

If there are many packets to be retransmitted and reading of one line including the packet to be retransmitted cannot be completed before the start timing of the next line, the print controller g1 Delay the start timing.
Since the image forming apparatus g2 on the reception side starts writing each packet in synchronization with the synchronization signal HSYNC, even if a deviation occurs in the original line period due to retransmission of the packet, the line synchronization can be maintained.

Next, a processing procedure when the image data transfer system G transfers image data will be described.
First, when the print controller g1 generates image data by the image data generation unit 101, the image data is transmitted to the image forming apparatus g2 in units of packets.

FIG. 8 shows a processing procedure when the print controller g1 transmits one packet.
At the time of transmitting the first packet, the print controller g1 has not received a retransmission request signal (step S1; N), and the data amount of one packet has not been reduced (step S4; N). Therefore, the print controller g1 reads out the first packet with the reference data amount in the packet arrangement order by the transmission processing unit 102 (step S5).

The transmission processing unit 102 adds error detection data to the read packet (step S9).
The serial conversion unit 103 serially converts the packet to which the error detection data is added, and then scrambles and transmits the packet to the image forming apparatus g2 (step S10).

If the print controller g1 receives a retransmission request signal at the time of subsequent packet transmission (step S1; Y), the print controller g1 causes the transmission processing unit 102 to immediately preceding the packet being read at the time of reception. The packet read out in (2) is read out again (step S2). Then, the transmission processing unit 102 changes the setting of the data amount of one packet to be read and reduces the data amount (step S3). Even when the amount of data has already been reduced when receiving a past retransmission request signal, the transmission processing unit 102 changes the setting and further reduces the amount of data.
Thereafter, the process proceeds to step S9 described above, and the read packet is transmitted to the image forming apparatus g2.

On the other hand, when the print controller g1 has not received the retransmission request signal (step S1; N) and the data amount of one packet has not been reduced (step S4; N), the transmission processing unit 102 uses the reference data amount as the next data amount. The packet is read (step S5).
Thereafter, the process proceeds to step S9 described above, and the read packet is transmitted to the image forming apparatus g2.

Further, when the retransmission request signal is not received (step S1; N), the data amount of one packet is reduced (step S4; Y), and after that, a packet with a fixed data amount is not transmitted (step S6). N), the transmission processing unit 102 reads the next packet by reducing the data amount of one packet to be read as set (step S7).
Thereafter, the process proceeds to step S9 described above, and the read packet is transmitted to the image forming apparatus g2.

Further, when the retransmission request signal is not received (step S1; N), the data amount of one packet is reduced (step S4; Y), and then a packet with a constant data amount is transmitted (step S6). Y), the transmission processing unit 102 returns the setting of the data amount of one packet to the original reference data amount, and reads the next packet (step S8).
Thereafter, the process proceeds to step S9 described above, and the read packet is transmitted to the image forming apparatus g2.

FIG. 9 shows a processing procedure when the image forming apparatus g2 receives one packet.
When the packet is transmitted from the print controller g1, as shown in FIG. 9, the parallel conversion unit 201 of the image forming apparatus g2 receives the packet (step S21). The parallel conversion unit 201 performs descrambling on the received packet and then converts it into parallel data (step S22).

Next, the reception processing unit 202 separates the packet and the error detection data added at the end of the packet, and writes the separated packet into the line buffer 22 (step S23).
The reception processing unit 202 detects an error in the written packet using the error detection data added at the end of the packet (step S24). When no error is detected (step S25; N), when the reception processing unit 202 reads the image data from the line buffer 22, the written packet is adopted (step S26).

On the other hand, when a packet error is detected (step S25; Y), the reception processing unit 202 discards the packet written in the line buffer 22 (step S27). In addition, the reception processing unit 202 transmits a retransmission request signal to the print controller g1 (step S28).
In response to the retransmission request signal, the image forming apparatus g2 repeats the process described above for the packet retransmitted from the print controller g1. If no error is detected in the retransmitted packet, the retransmitted packet is written in the line buffer 22 and error correction is performed.
After correcting the error in this way, the image forming apparatus g2 concatenates each packet by the reception processing unit 202 and reads it from the line buffer 22 to acquire line unit image data.

  As described above, according to the present embodiment, the image data transfer system G reads the image data in units of packets, adds the error detection data to each packet, and transmits the data to the image forming apparatus g2. The packet data received from the print controller g1 is concatenated to obtain image data, the error detection data added to each packet is used to detect an error in each packet, and the error correction of the packet in which the error is detected is performed. And an image forming apparatus g2 to be performed. When an error is detected, the image forming apparatus g2 transmits a retransmission request signal to the print controller g1, performs error correction using the packet retransmitted from the print controller g1, and the print controller g1 receives the retransmission request signal. The packet in which the error is detected is retransmitted, and after the retransmission request signal is received, the data amount of one packet to be transmitted is reduced.

  Accordingly, it is possible to perform error correction by retransmitting image data in units of packets smaller than one line, and it is possible to suppress a decrease in the transfer rate of image data due to error correction. Since the amount of data in a packet to be transmitted is reduced after an error occurs, when an error occurs a plurality of times, it is possible to correct the error by suppressing the image data transfer rate from decreasing by repeating packet retransmission.

The above embodiment is a preferred example of the present invention, and the present invention is not limited to this. Modifications can be made as appropriate without departing from the spirit of the present invention.
For example, in the above embodiment, after receiving a retransmission request signal, a packet that is read again for retransmission is not targeted for reducing the data amount, but is read with the same data amount as in the previous reading. However, a packet to be retransmitted after receiving a retransmission request signal can also be targeted for reducing the amount of data. As a result, even when errors occur continuously, the data amount of continuously retransmitted packets can be reduced, and a decrease in the transfer rate of image data can be suppressed.

FIG. 10 shows an example in which the data amount of a packet to be retransmitted is reduced.
In FIG. 10, each packet is represented as packets 1 to N in the order of packet arrangement. In addition, a hatched packet represents a packet that has been read again when an error is detected.
As shown in FIG. 10, when the retransmission request signal is received during reading of the packet 3, the reading control unit 13 reads the packet 2 by dividing it into 64 pixels. Packet 2 (1) in FIG. 10 is a packet obtained by reading the 64th pixel from the beginning of packet 2, and packet 2 (2) represents a packet obtained by reading the 65th to 128th pixels of packet 2. Yes.

G image data transfer system g1 print controller 101 image data generation unit 102 reception processing unit 11 line buffer 12 write control unit 13 read control unit 14 detection data addition unit 103 serial conversion unit g2 image forming apparatus 201 parallel conversion unit 202 reception processing Unit 21 error detection unit 22 line buffer 23 write control unit 24 read control unit 203 image memory 204 image processing unit 205 image forming unit

Claims (2)

A print controller that reads out image data in packet units, adds error detection data to each packet, and transmits the data to the image forming apparatus;
Each packet received from the print controller is concatenated to acquire image data, and an error in each packet is detected using error detection data added to each packet, and error correction is performed on the packet in which the error is detected. An image forming apparatus,
When the error is detected, the image forming apparatus transmits a retransmission request signal to the print controller, performs error correction with a packet retransmitted from the print controller,
The print controller
When the retransmission request signal is received, the packet in which the error is detected is retransmitted,
After receiving the retransmission request signal, to reduce the data amount of one packet to be transmitted,
After reducing the data amount of one packet, if a packet with a certain amount of data is transmitted without receiving a new retransmission request signal, the data amount of one packet to be transmitted is restored.
Image data transfer system. When the print controller receives a retransmission request signal after reducing the data amount of one packet, the print controller further reduces the data amount of one packet to be transmitted.
The image data transfer system according to claim 1 .

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