JP2023142015A - Communication device and method for controlling the same, program, and printing system - Google Patents

Abstract

To provide a communication device that can reduce processing load on apparatuses on a transmission side and a reception side when an error occurs during data transmission and reception.SOLUTION: A print control unit 102 as an example of a communication device generates a packet that has a header, image data, and a footer, wherein the header is provided with an incremented ID, transmits the generated packet to an image forming apparatus 103, receives a notification transmitted from the image forming apparatus 103, and when the notification is to require re-transmission of a packet with a predetermined ID transmitted from the print control unit 102 to the image forming apparatus 103, goes back to the requested predetermined ID, and transmits again the packet with the predetermined ID and the packets with the subsequent IDs sequentially to the image forming apparatus 103.SELECTED DRAWING: Figure 8

Description

The present invention relates to a communication device, its control method, program, and printing system.

2. Description of the Related Art In the field of production printing, a printing system is used in which a print control device controls printing of a document created on a personal computer (PC) or the like to an image forming device such as a printer or a multifunction device. In order to achieve higher image quality and higher productivity in such printing systems, there is a need for technology that enables high-speed transmission and reception of image data, etc. between the printing control device and the image forming device. .

An example of a high-speed data communication method is a method of serializing data using parallel-to-serial conversion (P/S conversion) and transmitting the data at high speed. When this data communication method is adopted in a printing system, image data is divided into multiple paths, the divided image data is P/S-converted in parallel, and transmitted as serial data through each path. It is thought that it will be possible to transmit large amounts of image data at high speed.

However, when a large amount of image data is transmitted all at once (all at once) from the print control device to the image forming device, there is a risk that the receiving image forming device will run out of space in its buffer memory. Furthermore, there is a possibility that image data is lost due to the influence of signal noise during data transmission, and in this case, it becomes necessary to retransmit a large amount of image data.

One method for solving such problems is to divide image data into predetermined sizes called packets, add a header containing the packet type and number to the divided data, and then transmit the data. In this method, the receiving side distinguishes between packet types and numbers to check whether the correct data is being received, and if it is determined that the data could not be received correctly (an error occurred), Requests the sending side to retransmit the data of the corresponding packet number.

For example, in the transmitting/receiving system described in Patent Document 1, a transmitting device divides video data into a plurality of pieces of data, assigns a sequence number to the divided data to generate packets, and then sends the packets in order of increasing sequence number. Send to receiving device. When the transmitting device receives a data retransmission request from the receiving device, the transmitting device specifies the packet that is the subject of the retransmission request, and retransmits only the specified packet to the receiving side.

JP2014-39136A

In the technology described in Patent Document 1, when transmitting and receiving data in response to a retransmission request, each device on the transmitting side and the receiving side specifies a packet to be retransmitted, reads it from memory, or writes it to memory. There is a need to do. When such processing is controlled by a software sequence, there is a risk that desired performance may not be achieved due to software overhead, and the load on the CPU may increase.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a communication device that makes it possible to reduce the processing load on each device on the sending and receiving sides when an error occurs during data transmission/reception. With the goal.

A communication device according to the present invention includes a generating means for generating a packet having a header, data, and a footer and having an ID assigned to the header according to a predetermined rule; a transmitting means for transmitting a notification to the external device; a receiving means for receiving a notification transmitted from the external device; and a request for retransmission from the external device regarding a packet with a predetermined ID for which the notification was transmitted from the transmitting means to the external device. In this case, the apparatus is characterized by comprising a control means that goes back to the predetermined ID and controls the packets with subsequent IDs to be transmitted to the external device sequentially from the packet with the predetermined ID.

According to the present invention, it is possible to reduce the processing load on each device on the sending and receiving sides when an error occurs during data transmission and reception.

FIG. 1 is a block diagram showing a schematic configuration of a printing system according to an embodiment. FIG. 2 is a block diagram showing the hardware configuration of a print control device. FIG. 2 is a block diagram showing the hardware configuration of an image forming apparatus. FIG. 2 is a block diagram showing the configuration of an image communication I/F of each of the print control device and the image forming device. FIG. 2 is a block diagram showing the configuration of a print control device and a data processing section of an image forming device. FIG. 3 is a diagram illustrating a packet configuration of image data. FIG. 2 is a block diagram showing the configuration of a packet transmitter included in the print control device. FIG. 2 is a schematic diagram showing how the print control device stores packet data. FIG. 2 is a block diagram showing the configuration of a packet decoding section included in the print control device. 3 is a flowchart of transmission control of an image busy retransmission request in the image forming apparatus and processing executed by the print control device in response to reception of the image busy retransmission request.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Here, we will discuss a printing system in which a print control device (first communication device) and an image forming device (second communication device) are communicably connected as an example of a communication device according to the present invention. However, the communication device according to the present invention is not limited to such embodiments.

<Schematic configuration of printing system>
FIG. 1 is a block diagram showing a schematic configuration of a printing system 100 according to an embodiment. The printing system 100 includes a client PC 101, a print control device 102, and an image forming device 103. The client PC 101 is communicably connected to a print control device 102 and an image forming device 103 via a network 104 . Further, the print control device 102 and the image forming device 103 are communicably connected via a network 105 and an image data communication path 106. Note that the image forming apparatus 103 is one of the external devices when the print control apparatus 102 is the reference, and vice versa, the print control apparatus 102 is one of the external devices when the image forming apparatus 103 is the reference. It is one.

Client PC 101 is specifically a personal computer. The client PC generates print data such as raster image data that has been subjected to RIP (Raster Image Processor) processing in response to a predetermined operation by the user, and transmits the print data to the print control device 102 . The client PC 101 also transmits setting information (hereinafter referred to as "print information") for printing (image formation) on the image forming apparatus 103 to the print control apparatus 102 together with print data.

The print control device 102 receives print data from the client PC 101, performs color conversion, density adjustment, format conversion, etc. in accordance with the characteristics of the image forming device 103, and generates image data that can be read by the image forming device 103. Note that the process of generating image data from print data is performed by an image processing unit (not included) included in a data processing unit 401 (see FIGS. 4 and 5(a)) included in an image communication I/F 208 (see FIG. 2), which will be described later. (as shown).

The print control apparatus 102 transmits image data to the image forming apparatus 103 via the image data communication path 106, and also transmits print information received from the client PC 101 to the image forming apparatus 103 via the network 105. The image forming apparatus 103 performs printing (forming an image on a paper medium (paper), etc.) based on the image data and print information received from the print control apparatus 102.

FIG. 2 is a block diagram showing the hardware configuration of the print control device 102. The print control device 102 includes a CPU 201, a RAM 202, a ROM 203, a storage unit 204, a first communication I/F 206, a second communication I/F 207, an image communication I/F 208, an image signal control unit 209, an operation unit 210, and a display unit. 211. These units making up the print control device 102 are communicably connected via a system bus 205.

The CPU 201 controls the operation of each unit connected to the system bus 205 by loading a control program stored in the ROM 203 into the RAM 202. The RAM 202 has a storage area for temporarily storing data processed by the CPU 201, and a storage area for executing a control program. ROM 203 stores a control program. Note that the control program may be stored in the storage unit 204. The storage unit 204 is, for example, an HDD (hard disk drive), and stores application programs, print data and print information received from the client PC 101, and image data generated from the print data. Note that the storage unit 204 is not limited to the HDD, and may be other storage means (for example, SSD, flash memory, etc.).

The first communication I/F 206 is an interface for the CPU 201 to communicate with the client PC 101 via the network 104, and receives print data and print information from the client PC 101 via the network 104. Further, the CPU 201 notifies (sends) various information regarding the image forming apparatus 103 to the client PC 101 via the first communication I/F 206 and the network 104.

The second communication I/F 207 is an interface through which the CPU 201 communicates with the image forming apparatus 103 via the network 105. The CPU 201 performs printing control on the image forming apparatus 103 by transmitting print information to the image forming apparatus 103 via the second communication I/F 207 and the network 105.

The image communication I/F 208 is an interface for transmitting image data to the image forming apparatus 103 via the image data communication path 106. The image signal control unit 209 controls the process of transmitting image data to the image forming apparatus 103 via the image communication I/F 208 and the image data communication path 106 under the control of the CPU 201 .

The operation unit 210 is configured with a touch panel, buttons, etc., and receives a user operation and notifies the CPU 201 of executing a process corresponding to the received operation. A user can set conditions for generating image data from print data via the operation unit 210. The display unit 211 displays various settings on the print control device 102 according to operations on the operation unit 210, and also displays the printing status of the image forming apparatus 103 (the status of control for the image forming apparatus 103), etc. do.

FIG. 3 is a block diagram showing the hardware configuration of the image forming apparatus 103. The image forming apparatus 103 includes a CPU 301 , a RAM 302 , a ROM 303 , a storage section 304 , a communication I/F 306 , an image communication I/F 307 , a print signal control section 308 , a print control section 309 , an operation section 310 , and a display section 311 . These units making up the image forming apparatus 103 are communicably connected via a system bus 305.

The CPU 301 controls the operation of each unit connected to the system bus 305 by loading a control program stored in the ROM 303 into the RAM 302. The RAM 302 has a storage area for temporarily storing processing data, etc., and a storage area for executing a control program. ROM 303 stores a control program. Note that the control program may be stored in the storage unit 304. The storage unit 304 is, for example, an HDD, and stores application programs as well as image data and print information received from the print control device 102. Note that the storage unit 304 is not limited to the HDD, and may be other storage means (for example, SSD, flash memory, etc.).

The communication I/F 306 is an interface for communicating with the print control device 102 via the network 105. The CPU 301 receives print information from the print control device 102 via the network 105 and communication I/F 306.

The image communication I/F 307 is an interface for acquiring image data from the print control device 102 via the image data communication path 106. The CPU 301 receives image data from the print control device 102 via the image data communication path 106 and the image communication I/F 307. The print signal control unit 308 controls the process of receiving image data from the print control device 102. The print control unit 309 performs printing based on the image data and print information received from the print control device 102.

The operation unit 310 is configured with a touch panel, buttons, etc., and receives a user operation and notifies the CPU 301 of executing a process corresponding to the received operation. The display unit 311 displays various settings on the image forming apparatus 103 according to operations on the operation unit 310, and also displays printing status and the like.

<Configuration of image communication I/F>
FIG. 4 is a block diagram showing the configurations of the image communication I/F 208 of the print control apparatus 102 and the image communication I/F 307 of the image forming apparatus 103. As described above, the image communication I/F 208 and the image communication I/F 307 are connected via the image data communication path 106.

The image communication I/F 208 is a hardware component and includes an image communication control unit 400 that controls communication of image data. The image communication control unit 400 includes a data processing unit 401 , a P/S (parallel/serial) conversion unit 402 , a transmission driver TX 403 , a reception driver RX 404 , and an S/P (serial/parallel) conversion unit 405 . Similarly, the image communication I/F 307 is a hardware component and includes an image communication control unit 410 that controls communication of image data. The image communication control section 410 includes a reception driver RX411, an S/P conversion section 412, a data processing section 413, a P/S conversion section 414, and a transmission driver TX415.

P/S conversion units 402 and 414 convert parallel data (parallel format data) output from data processing units 401 and 413, respectively, into serial data (serial format data). The converted serial data is supplied by the transmission drivers TX403, 415 to the receiving drivers RX411, 404 on the other side via the image data communication path 106.

Note that although a plurality of transmission drivers TX403 and one transmission driver TX415 are shown in FIG. 4, their hardware configurations are the same. However, since the image communication control units 400 and 410 are separate hardware, the clock frequencies supplied to the transmission drivers TX 403 and 415 may not be the same. Furthermore, the transmission drivers TX403 and 415 each operate independently, and even if the clock frequencies supplied to the transmission drivers TX403 and 415 are the same, their phase relationships are not the same. Therefore, the operations of the transmission drivers TX403 and 415 are not in a synchronous relationship.

In this embodiment, the image communication I/F 208 is configured to transmit 8 lanes of serial data and receive 1 lane of serial data. However, the number of lanes of the image communication I/F 208 is not limited to eight lanes, and can be changed according to the required band for transmitting image data.

Since the P/S conversion units 402 and 414 operate asynchronously with respect to the processing paths of the data processing units 401 and 413, respectively, skew may occur in the data to be processed depending on the timing of receiving and receiving timing signals. This skew changes with each horizontal synchronization period, and the amount is not constant. In addition, skew occurs due to differences in reset release timing of the P/S converters 402 and 414 and differences in propagation delay time due to differences in wiring lengths of transmission paths from the transmission drivers TX 403 and 415 to the reception drivers RX 404 and 411. . In this case, the amount of skew does not change and is constant because the factors that cause it do not change dynamically.

The S/P conversion units 405 and 412 respectively acquire serial data from the reception drivers RX 404 and 411 and store them in internal shift registers. Further, the S/P converters 405 and 412 each detect specific data from data having a predetermined symbol length of the stored serial data. Then, the S/P converters 405 and 412 respectively output parallel data to the data processors 401 and 413 for each predetermined symbol length according to the detection timing of specific data. Furthermore, the S/P converters 405 and 412 each restore a clock for receiving data from the serial data. Then, the S/P conversion units 405 and 412 divide the frequency of the restored clock according to the symbol length of the parallel data, and output the divided clock to the data processing units 401 and 413.

<Configuration of data processing section>
FIG. 5A is a block diagram showing the configuration of the data processing unit 401 in the image communication control unit 400 included in the image communication I/F 208 of the print control apparatus 102. The data processing section 401 includes a packet transmitting section 501, a packet decoding section 502, a received packet skew adjustment section 503, and an asynchronous clock switching section 504.

FIG. 5B is a block diagram showing the configuration of the data processing unit 413 in the image communication control unit 410 included in the image communication I/F 307 of the image forming apparatus 103. The data processing section 413 includes an asynchronous clock switching section 511, a received packet skew adjustment section 512, a packet decoding section 513, and a packet transmitting section 514.

Each of the asynchronous clock switching units 504 and 511 is configured with, for example, a FIFO into which a write clock and a read clock are input separately. As write clocks, clocks output from S/P converters 405 and 412 are used. Further, as the read clock, for example, a system clock that controls the operation of the image communication control units 400 and 410 can be selected and used.

Parallel data is output from the S/P converters 405 and 412 to the reception packet skew adjustment units 503 and 512 at the subsequent stage at a timing synchronized with the system clock that controls the operation of the image communication control units 400 and 410. In this embodiment, the asynchronous clock switching sections 504 and 511 are provided as independent modules, but the reception packet skew adjustment sections 503 and 512 may have this function.

The packet decoding unit 502 decodes the packet whose skew has been adjusted by the received packet skew adjustment unit 503, and outputs the decoded data to a subsequent image processing unit (not shown) in the data processing unit 401. Furthermore, the packet decoding section 502 outputs a transmission command packet request to the packet transmitting section 501 together with packet information.

The packet decoding unit 513 decodes the packet whose skew has been adjusted by the reception packet skew adjustment unit 512, and outputs the decoded data to a subsequent image processing unit (not shown) in the data processing unit 413. Furthermore, the packet decoding unit 513 outputs a transmission command packet request to the packet transmitting unit 514 together with packet information.

Note that examples of the transmission commands sent from the image forming apparatus 103 to the print control apparatus 102 include the following first to third transmission commands. The first transmission command is a command to notify that reception of divided image data has been successfully completed. Note that the divided image data is image data that is divided by the print control device 102 into a predetermined size according to a packet for transmitting image data to the image forming device 103. The second transmission command is a command to notify that various commands, status, etc. other than the divided image data have been successfully received. The third transmission command is a command for notifying a request to retransmit the divided image data when a loss is detected in the received divided image data. Details of the configuration of packet decoding units 502 and 513 will be described later with reference to FIG. 9.

The packet transmission unit 501 arbitrates whether to transmit the transmission command received from the packet decoding unit 502 or the image data received from the previous stage image processing unit (not shown), and sends it to the P/S conversion unit 402. Output. Similarly, the packet transmitting unit 514 arbitrates whether to transmit the transmission command received from the packet decoding unit 513 or the image data received from the previous stage image processing unit (not shown), and performs P/S conversion. 414.

<Configuration of image data packet>
FIG. 6 is a diagram illustrating the packet structure of image data. FIG. 6A shows an example of a packet configuration when image data is transmitted from the print control device 102 to the image forming device 103 using a total of eight lanes, Lanes 0 to 7, in parallel.

In FIG. 6A, the header is a control code indicating the start position and data type of the main body of the subsequent divided image data, and the data is the main body of the divided image data. The same applies to FIG. 6(b). 'N' is a natural number, and when N [cycles] of data are transmitted on each lane, the total data for the 8 lanes is 8×N. For example, if the data width is 32 [bit] and N=32 [cycle], 8×32×32=8192 [bit]=8K [Byte] of data will be transmitted.

FIG. 6B shows an example of a packet configuration when image data is transmitted from the print control device 102 to the image forming device 103 using a total of six lanes, Lanes 0 to 5, in parallel. 'M' is a natural number, and in order to transmit 8K [Byte] = 8192 [bit] data with the packet configuration of Fig. 6(b) as in the previous example, 8192 ÷ 32 ÷ 6 = 42. 6666...[cycle] is required. In this way, if the quotient is not an integer (not divisible), data transmission will actually be performed in 43 [cycles]. In that case, the data size to be transmitted is 6×32×43=8256 [bits], and 8256-8192=64 [bits] will be extra transmitted. This extra data transmission is called padding.

The packet transmission unit 501 of the print control device 102 divides the image data into equal parts according to the number of lanes to generate divided image data, distributes the generated divided image data to each lane, and divides the generated divided image data into each lane as necessary. It has a circuit that adds margins to the divided image data. On the other hand, the reception packet skew adjustment unit 512 of the image forming apparatus 103 includes a circuit that adjusts the skew and combines the divided image data received on each lane to generate data used for printing, and It has a circuit that removes blank spaces added to image data.

FIG. 6(c) is a diagram illustrating the structure of the header. Packet types include image type, command data, status data, and the like.

The image type indicates that it is divided image data. The command data includes a command indicating the size of the divided image data in the main scanning direction and the sub-scanning direction, a command notifying the start of transmission of the divided image data, etc., and a code indicating these is added to the command (COMMAND) part. . Further, the contents of the command, such as the size in the main scanning direction and the sub-scanning direction, are added to the command data section.

The status data includes an error status that notifies that an abnormal state has occurred, an ACK status that provides a response (ACK) to command data from the other party, and a code is added to the status section. Contents corresponding to the status are added to the status data section. Note that the size of the generated packet differs depending on the type of data it contains, so the side receiving the packet can determine the type of data it contains and perform appropriate processing according to the type of data. A header is added to the data body.

<Configuration and operation of packet transmitter>
FIG. 7 is a block diagram showing the configuration of the packet transmitter 501 included in the print control apparatus 102. The packet transmission section 501 includes a packet generation section 701, a buffer control section 702, a data buffer 703, a packet read section 704, and a retransmission timer 705.

The packet generation unit 701 receives image data from a preceding image processing unit (not shown) in the data processing unit 401, and divides the received image data to generate divided image data for output to each lane. However, the configuration is not limited to this, and a configuration in which divided image data is generated by the image processing unit and input to the packet generation unit 701 may be used.

The packet generation unit 701 generates the header described with reference to FIG. When transmitting divided image data, an image type is assigned to the packet type, and a predetermined value is assigned to the packet ID according to a predetermined rule. Here, the predetermined rule for assigning a value to the packet ID is to increment the value (add 1 by 1) in the order in which the divided image data is transmitted. For example, a code indicating color, monochrome, gray scale, etc. is assigned to the image type, and in the case of color, a code that can identify color information (Y, M, C, K), attribute information, etc. is assigned. . Further, as a footer, the result of calculating CRC data (Cyclic Redundancy Check data) of the header and divided image data using a 32-bit constant (hereinafter referred to as "CRC32") is added to the end of the packet.

The packet generation unit 701 generates write data (write data) to the data buffer 703 and a write operation (write operation) control signal for each lane, and outputs them to the buffer control unit 702. The write data and control signals input to the buffer control unit 702 are sequentially stored in the data buffer 703 according to the control signals.

FIG. 8 is a schematic diagram showing how write data is sequentially stored in the data buffer 703 in eight lanes. Hereinafter, in order to simplify the explanation, it is assumed that the data size transmitted for each lane is 8192 bits including the header and footer (CRC32). In this case, as shown in FIG. 8A, the memory address per lane is 0x400, and the address increases by 0x200 when one transmission data for 8 lanes is stored. Here, the packet IDs for eight lanes are the same, but different packet IDs may be assigned to each lane. Further, color information (Y, M, C, K) is given to the image type for each lane, as shown in FIG. 8(b). However, the present invention is not limited to this, and in consideration of matching with the receiving side (image forming apparatus 103), divided image data of the same color may be transmitted in all eight lanes.

The image forming apparatus 103 may request the print control apparatus 102 to resend a predetermined divided image data packet (hereinafter referred to as an "image data packet"). FIG. 8(d) is a diagram showing the structure of a status packet for a CRC error (details will be described later). Data buffer 703 has sufficient storage capacity to store image data packets so that it can process requests for retransmission of image data packets. It is assumed that the data buffer 703 has a ring buffer configuration in which when data is stored in the last address, the data returns to the first address and is overwritten from the first address.

The packet generation unit 701 generates a command packet or a status packet when receiving a request to issue a predetermined command or status from the CPU 201, the packet decoding unit 502, the received packet skew adjustment unit 503, or the like. These packet data may be stored in a separate area from the image data packets in the data buffer 703, and here, as shown in FIG. There is.

When receiving a command packet or status packet retransmission request from the image forming apparatus 103 , the packet generation unit 701 retransmits the command packet or status packet indicated by the retransmission request to the image forming apparatus 103 . When the packet generation unit 701 receives an image error retransmission request or an image busy retransmission request from the image forming apparatus 103, it retransmits the image data packet to the image forming apparatus 103, the details of which will be described later.

The packet generation unit 701 writes data for a predetermined number of cycles into the data buffer 703 via the buffer control unit 702. When the write operation is completed, the packet generation unit 701 transmits a write operation completion notification (hereinafter referred to as a “transfer request”) to the packet read unit 704. This transfer request includes the packet type and the address of the data buffer 703, and is made individually for each lane.

The packet read unit 704 transmits a read operation start notification from the data buffer 703 to the buffer control unit 702 at the timing when transfer requests corresponding to all lanes are received from the packet generation unit 701. The read operation start notification includes the address in the data buffer 703 where the data to be read is stored. The buffer control unit 702 controls access for the read operation (read access) to the designated address of the data buffer 703 based on the received read operation start notification. Note that the function of the retransmission timer 705 will be described later.

The packet transmitter 514 included in the image forming apparatus 103 has the same configuration and functions as the packet transmitter 501, so a description of the configuration will be omitted. Note that the image forming apparatus 103 does not return the divided image data received from the print control apparatus 102 to the print control apparatus 102. However, image data for testing each part of the image forming apparatus 103 (for example, a test pattern for test debugging of the S/P conversion unit 412) may be transmitted to the print control apparatus 102. Therefore, the packet transmitter 514 has the same configuration as the packet transmitter 501.

<Operation explanation of receive packet skew adjustment unit>
The reception packet skew adjustment units 503 and 512 do not read data from the data buffer 703 if they cannot recognize the control code (header) indicating the start position of the main body of data in any one or more lanes. Do it like this. At this time, the packet transmitting units 501 and 514 transmit a command requesting retransmission of data whose control code could not be recognized.

<Configuration and operation of packet decoding section>
FIG. 9 is a block diagram showing a schematic configuration of the packet decoding unit 513 included in the image forming apparatus 103. The packet decoding section 513 includes a decoding section 901, a buffer 902, a data transmitting section 905, a packet requesting section 906, and a busy timer 907. The buffer 902 includes a buffer control section 903 and a data buffer 904.

The decoding unit 901 receives a packet from the reception packet skew adjustment unit 512, decodes the received packet, and performs the following processing.

One of the processes that the decoding unit 901 performs after decoding is a process of interpreting the command and outputting a control signal when the packet is determined to be a command packet. For example, if the command indicates the image size, the main scanning size and sub-scanning size of the divided image data to be processed are extracted and notified to the data processing unit 413 as an image processing setting signal.

Another process performed by the decoding unit 901 after decoding is a process of instructing the packet requesting unit 906 to request a packet according to the data of the status packet when the packet is determined to be a status packet. For example, if the status packet data contains various statuses, CRC errors, header errors, etc., the packet transmission unit 501 issues a packet reissue request, and if it is an error in the divided image data itself, it issues an image error retransmission request. Notify. Note that the functions of the packet request unit 906 and the busy timer 907 will be described later.

Another process that the decoding unit 901 performs after decoding is a process of writing data to the buffer 902 when the packet is determined to be an image data packet. The data processing method in the buffer control unit 903, data buffer 904, and data transmission unit 905 is performed in the same manner as in the buffer control unit 702, data buffer 703, and packet read unit 704 in the packet transmission unit 514 (501), so the explanation will be omitted. Omitted.

Note that since the packet decoding unit 502 included in the print control apparatus 102 has the same configuration and function as the packet decoding unit 513 included in the image forming apparatus 103, a description of the configuration will be omitted.

<Image data packet resending process>
When the image communication control unit 400 of the print control apparatus 102 receives a request for retransmission of a predetermined image data packet from the image communication control unit 410 of the image forming apparatus 103, it first stops the operation of the packet transmission unit 501. Then, the image communication control unit 400 performs retransmission processing by sequentially retransmitting the image data packets starting from the image data packet for which the retransmission request has been received.

There are three cases in which the image communication control unit 410 requests retransmission of a predetermined image data packet (in other words, the image communication control unit 400 is required to retransmit the image data packet). One is when a header error occurs in the received packet. Another case is when a received packet has a CRC mismatch, and this CRC error is detected by inspecting the received packet. Yet another case is when the data buffer 904 of the packet decoding unit 513 does not have the capacity to store the received packet data. These will be explained below.

[In case of header error in received packet]
If the reception packet skew adjustment unit 512 cannot recognize the control code (header), it cannot start read access to the data buffer 904. Therefore, if a control code cannot be recognized in a certain lane, it becomes impossible to properly combine the divided image data after reading the divided image data from the data buffer 904. In addition, the fact that the control code cannot be recognized means that the code value at the position of the control code changes from the specified value due to the influence of noise, etc. that occurs in the transmission path, so that it cannot be recognized as a code value. It means being unable to do something.

In this case, the data in the lane in which the control code can be recognized in the data buffer 904 is not read out, but is overwritten with the next data, thereby being discarded. Then, the reception packet skew adjustment unit 512 notifies the packet transmission unit 514 of the packet ID of the header of the packet in which the header error has occurred, along with an image error retransmission request. The packet transmitting unit 514 transmits a status packet to the print control device 102 that prompts retransmission of the image data packet of the notified packet ID.

Note that if the header is damaged, there is a possibility that the packet ID cannot be read, so the reception packet skew adjustment unit 512 sends a status in which the packet ID is incremented from the last successfully received packet ID. shall be attached to the packet. The packet transmitter 514 sets the status data of the status packet to a value indicating a header error. Thereafter, the received packet skew adjustment unit 512 discards the received image packet data until the image data packet of the packet ID for which the retransmission request was made is input.

[If the CRC of the received packet does not match]
The reception packet skew adjustment unit 512 performs a CRC calculation similar to the CRC calculation performed by the packet generation unit 701 on the header and divided image data (data body), and compares the calculation result with the CRC32 added at the end of the packet. do. The reception packet skew adjustment unit 512 performs this comparison for each lane, and determines that the divided image data is damaged if the calculation results do not match.

In this case, as in the case where the header cannot be recognized, the received packet skew adjustment unit 512 notifies the packet transmitting unit 514 of the packet ID of the header of the packet whose CRC calculation result does not match, along with an image error retransmission request. As a result, the packet transmitting unit 514 transmits a status packet to the print control device 102 that urges retransmission of the image data packet with the notified packet ID. Note that at this time, the packet transmitter 514 sets the status data of the status packet to a value indicating a CRC error. Thereafter, the received packet skew adjustment unit 512 discards the received image data packets until the packet with the packet ID that requested retransmission of the divided image data is input.

[When the storage capacity of the data buffer 904 is insufficient]
When the data transmitting unit 905 receives busy information indicating that data processing in the data processing unit 413 is temporarily delayed, the packet data input to the packet decoding unit 513 is stored in the data buffer 904. Ru. If the data buffer 904 does not have enough capacity to store packet data (in other words, there is little free space), even if the packet decoder 513 can correctly receive the packet data, it cannot pass it to the subsequent stage. It disappears.

Therefore, the decoding section 901 of the packet decoding section 513 receives a buffer full signal when the used capacity of the data buffer 904 becomes full or reaches a predetermined used capacity α (hereinafter referred to as "buffer full"). It is output to the packet skew adjustment section 512. Note that when the data transmission unit 905 reads data from the data buffer 904 and the used capacity of the data buffer 904 becomes less than the predetermined used capacity β (α≧β), the output of the buffer full signal is stopped. be done.

Upon receiving the buffer full signal, the reception packet skew adjustment unit 512 stops outputting the packet data to the packet decoding unit 513. The decoding unit 901 outputs a reception start signal for the divided image data to the busy timer 907 and discards it without writing it to the data buffer 904. Furthermore, after receiving the buffer full signal, the reception packet skew adjustment unit 512 discards the input image packet data until the image data packet having the packet ID for which the retransmission request has been made is input. The packet requesting unit 906 notifies the packet transmitting unit 514 of the packet ID along with an image busy retransmission request. The packet transmitter 514 transmits to the print control device 102 a status packet that prompts retransmission of the image data packet with the packet ID notified by the packet requester 906.

<Image data packet retransmission control>
The image forming apparatus 103 periodically sends the image busy retransmission request until the image packet data can be written to the data buffer 904 again after the image busy retransmission request is sent to the print control apparatus 102 as described above. Send to. When the image communication control unit 400 of the print control device 102 receives the image busy retransmission request, it starts retransmitting the packet after a predetermined time (hereinafter referred to as "holding time") has elapsed.

The control for periodically sending the image busy retransmission request from the image forming apparatus 103 to the print control apparatus 102 in this manner will be described with reference to the flowchart of FIG. 10(a). FIG. 10A is a flowchart illustrating transmission control of an image busy retransmission request. Each process (step) indicated by an S number in FIG. 10A is executed by the busy timer 907 of the image forming apparatus 103. Note that the busy timer 907 has a configuration as a microcomputer that can execute various processes.

When the busy timer 907 receives a notification to start receiving image data from the decoding unit 901 while the data buffer 904 is in a buffer full state (receiving a buffer full signal from the buffer control unit 903), the busy timer 907 starts processing in S1001. do.

In S1001, the busy timer 907 outputs an image busy retransmission request to the packet requesting unit 906. In S1002, the busy timer 907 clears the internal time count. In step S1003, the busy timer 907 determines whether the buffer full state continues based on the buffer full signal after a certain period of time has elapsed. Note that if the buffer full signal continues to be input, it is determined that the buffer full state continues. If the busy timer 907 determines that the buffer full state continues (YES in S1003), it executes the process in S1004, and if it determines that the buffer full state has been resolved (NO in S1003), it executes this process. terminate.

In S1004, the busy timer 907 starts counting time. In S1005, the busy timer 907 determines whether the time count value exceeds a predetermined value. If the busy timer 907 determines that the time count value exceeds the predetermined value (YES in S1005), it executes the process in S1001 again in order to reissue the image busy retransmission request. On the other hand, if the busy timer 907 determines that the time count value does not exceed the predetermined value (NO in S1005), it executes the process in S1003 to determine whether the buffer full state has been resolved.

Next, a description will be given of the processing that the print control apparatus 102 executes when it receives an image busy retransmission request. When receiving the image busy retransmission request, the print control device 102 performs a process of retransmitting the image data packet having the packet ID indicated by the image busy retransmission request after the hold time has elapsed. This means that if the instructed image data packet is retransmitted immediately after receiving the image busy retransmission request, the image forming apparatus 103 will not be able to receive the image data packet, and the image busy retransmission request will be issued again. This is because unnecessary communication may occur.

FIG. 10(b) is a flowchart of processing executed by the print control apparatus 102 in response to receiving the image busy retransmission request. Each process (step) indicated by an S number in FIG. 10B is executed by a retransmission timer 705 included in the packet transmission unit 501 of the print control apparatus 102. Note that the retransmission timer 705 has a configuration as a microcomputer that can execute each process.

In S1011, the retransmission timer 705 determines whether an image busy retransmission request has been received. If the retransmission timer 705 determines that an image busy retransmission request has been received (YES in S1011), it executes the process in S1012, and if it determines that it has not received an image busy retransmission request (NO in S1011), it executes the process in S1013. Execute. In S1012, the retransmission timer 705 clears the time count, and then executes the process in S1013. That is, if an image busy retransmission request is received within a certain period of time, the time count in the retransmission timer 705 is cleared, and the transmission of the image data packet requested for retransmission to the image forming apparatus 103 is postponed.

In S1013, the retransmission timer 705 performs a time count. Note that the case where the process proceeds from S1011 to S1013 is the case where an image busy retransmission request for which the determination in S1011 is YES has been previously received. In S1014, the retransmission timer 705 determines whether the time count value exceeds a predetermined value (=holding time). If the retransmission timer 705 determines that the timer count value is less than or equal to the predetermined value (NO in S1014), it executes the process in S1011, and if it determines that the timer count value exceeds the predetermined value (YES in S1014), it executes the process in S1015. Execute the process. In S1015, the retransmission timer 705 outputs an image packet retransmission request to the packet generation unit 701, and then ends this process.

The packet generation unit 701 of the print control device 102 that has received the image packet retransmission request traces back to the packet ID indicated by the image packet retransmission request (image busy retransmission request) and sequentially increments the packet ID from there to generate the image data packet. Works to resend. Therefore, the packet generation unit 701 of the print control device 102 temporarily stops the transfer request to the packet read unit 704. Then, the packet generation unit 701 of the print control apparatus 102 completes the transmission of the image data packet from the packet read unit 704 to the image forming apparatus 103 of the image data packet corresponding to the transfer request that has already been sent to the packet read unit 704. Wait until. In the meantime, the packet generation unit 701 prepares a transfer request to respond to the image packet retransmission request.

Specifically, when sending a normal transfer request, an incremented address is passed, but this is changed to an address where the divided image data of the packet ID to be retransmitted is stored. Then, a numerical value is obtained by subtracting the packet ID to be retransmitted from the currently processed packet ID, and the address per packet ID is calculated from the current address by the calculated numerical value. At this time, if the address is a negative value, it becomes the address obtained by adding and subtracting the last address. The packet generation unit 701 notifies the packet read unit 704 of the transfer request together with the calculated address. The packet read unit 704 outputs the divided image data of the notified address to the P/S conversion unit 402. Thereafter, unless a retransmission request for an image data packet is received, the packet generation unit 701 sequentially transmits the packet ID for which the retransmission request was made and the subsequent image data packets while incrementing the address as usual.

By controlling the retransmission of image data packets as described above, the image forming apparatus 103 can perform decoding processing of the received image data packets in accordance with the order of the packet IDs. In the image forming apparatus 103, there is no need to rearrange the image data packets, thereby reducing the computational load. Furthermore, since the data buffer 904 in the image forming apparatus 103 is not at or close to full, there is no need to retransmit the retransmitted image data packet.

Note that when the print control device 102 receives the image error retransmission request, there is no situation in which the image forming device 103 is unable to receive the image data packet. Therefore, when the print control device 102 receives an image error retransmission request from the image forming device 103, it sequentially retransmits the image data packets with the packet ID indicated by the received image error retransmission request while immediately incrementing the packet ID. Perform processing.

By the way, when the image forming apparatus 103 requests the print control apparatus 102 to resend a predetermined image data packet, there is a possibility that one of the following two malfunctions will occur in the print control apparatus 102. One of the malfunctions is a malfunction in which the image data packet continues to be transmitted without retransmitting the image data packet having the packet ID for which retransmission has been requested. Another type of malfunction is a malfunction in which the packet transmitter 501 continues to stop operating and does not retransmit the image data packet of the packet ID for which retransmission has been requested. A possible cause of these malfunctions is that the print control device 102 was unable to properly receive an image error retransmission request or an image busy retransmission request. If such a malfunction is left unaddressed, the image forming apparatus 103 will not be able to supplement the missing image data packet.

In order to deal with this problem, the image communication control unit 410 of the image forming apparatus 103 controls the case where a packet scheduled to be retransmitted on at least one lane cannot be received even after a predetermined timeout determination period has elapsed. , the transmitted retransmission request is determined to be invalid. Then, the image communication control unit 410 requests the print control apparatus 102 to retransmit the image data packet of the packet ID related to the retransmission request for which the timeout has been detected (hereinafter referred to as "timeout retransmission request"). Send prompting data. Note that the timeout determination time set in the image forming apparatus 103 is set to a longer time than the hold time set in the print control apparatus 102.

When the image communication control unit 400 successfully receives a timeout retransmission request, it can sequentially retransmit the image data packets related to the timeout retransmission request. This allows the image communication control unit 410 to complement the missing image data packet and perform print processing.

As described above, according to the present invention, it is possible to efficiently transmit image data without requiring complicated control, and it is also possible to avoid data loss on the receiving side. This makes it possible to avoid an increase in the scale of the hardware (circuit) for the above-mentioned communication (data transmission and reception) between the print control device and the image forming device, and also to save power by reducing the processing load. can be realized.

Although the present invention has been described above in detail based on its preferred embodiments, the present invention is not limited to these specific embodiments, and the present invention may take various forms without departing from the gist of the present invention. included. Further, each of the embodiments described above is merely one embodiment of the present invention, and each embodiment can be combined as appropriate.

For example, in the embodiment described above, the configuration is such that the client PC transmits print data such as raster image data that has been subjected to RIP processing to the print control device 102 . The configuration is not limited to this, and the client PC may have a configuration in which the client PC transmits data such as a document to be printed to the print control device, and the print control device executes RIP processing to generate print data such as raster image data. do not have. In this case, the client PC can be configured to send the print information to the print control device separately from the data such as the document to be printed or in combination with the data such as the document to be printed.

Furthermore, in the above embodiment, the image forming apparatus 103 requests the print control apparatus 102 to resend an image data packet, and the print control apparatus 102 requests the image forming apparatus 103 to resend a predetermined packet such as a status packet. There wasn't. However, the present invention is not limited to such a configuration, and the communication device according to the present invention can perform a retransmission process in response to a packet retransmission request from an external device, and also request the external device to retransmit a packet received from the external device. It is possible to have a configuration in which this is possible. In other words, the communication device according to the present invention performs processing similar to packet transmission and retransmission by the print control device 102, and also performs processing similar to the processing performed by the image forming device 103 regarding packet data received from an external device and its retransmission request. Perform processing.

The present invention provides a system or device with a program that implements one or more functions of the embodiments described above via a network or a storage medium, and one or more processors in a computer of the system or device reads and executes the program. This can also be achieved by processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

100 Printing System 102 Printing Control Device 103 Image Forming Device 106 Image Data Communication Path 201,301 CPU
208,307 Image communication I/F
304 Storage unit 400, 410 Image communication control unit 501, 514 Packet transmission unit 502 Packet decoding unit 701 Packet generation unit 702, 903 Buffer control unit 703, 904 Data buffer 705 Retransmission timer 907 Busy timer

Claims (17)

generating means for generating a packet having a header, data, and a footer and having an ID assigned to the header according to a predetermined rule;
a transmitting means for transmitting the packet generated by the generating means to an external device;
Receiving means for receiving a notification transmitted from the external device;
If the notification is a request for retransmission from the external device of a packet with a predetermined ID transmitted from the transmitting means to the external device, the notification may be sent sequentially from the packet with the predetermined ID, going back to the predetermined ID. A communication device comprising: control means for controlling transmission of subsequent ID packets to the external device. If the notification is a retransmission request due to a header error that prevents the external device from recognizing the packet with the predetermined ID, the control means, after receiving the notification, immediately sends the packet with the predetermined ID. 2. The communication device according to claim 1, wherein the communication device controls to sequentially transmit packets with subsequent IDs to the external device. the footer includes CRC data generated from the header and the data;
If the notification is a retransmission request due to a CRC error in which CRC data generated from the header of the packet and the data in the external device does not match the CRC data included in the footer of the packet, the control means transmits the notification. 2. The communication device according to claim 1, wherein, after receiving the packet, the communication device immediately controls the transmission of packets with subsequent IDs starting from the packet with the predetermined ID to the external device. If the notification is a retransmission request due to a lack of free space in the storage means for storing the data of the packet with the predetermined ID in the external device, the control means, after receiving the notification, 2. The communication device according to claim 1, wherein after a hold time has elapsed, control is performed to sequentially transmit packets with IDs after the predetermined ID to the external device. receiving means for receiving from an external device a packet having a header, data, and a footer and having an ID assigned to the header according to a predetermined rule;
storage means for storing packets received by the receiving means;
detection means for detecting whether an error has occurred in the packet received by the receiving means;
When it is detected that an error has occurred in a packet received by the receiving means, a request is made to trace back to the ID of the packet in which the error was detected and retransmit packets with subsequent IDs sequentially from the packet with the ID. notification means for transmitting a notification to the external device;
The apparatus further comprises a discarding means for discarding the packet with the ID in which the error has been detected and the packet received between the time the packet with the ID is received and the packet with the ID is retransmitted from the external device. Characteristic communication device. 6. The communication device according to claim 5, wherein the error is a header error in which the ID of the packet cannot be recognized. the footer includes CRC data generated from the header and the data;
6. The error is caused by a mismatch between CRC data included in the footer of the packet and CRC data generated by the detection means from the header of the packet and the data. Communication device. receiving means for receiving from an external device a packet having a header, data, and a footer and having an ID assigned to the header according to a predetermined rule;
storage means for storing packets received by the receiving means;
detection means for detecting whether or not the storage means has a capacity capable of storing the packets received by the reception means;
When the detection means detects that the storage means does not have the capacity to store the packets received by the reception means, the storage means sequentially traces back to the ID of the packet that cannot be stored in the storage means and sequentially starts from the packet with that ID. notification means for transmitting a notification requesting retransmission of packets with subsequent IDs to the external device;
a discarding means for discarding packets with an ID that cannot be stored in the storage means, and packets received between the time the packet with the ID is received and the packet with the ID is retransmitted from the external device; A communication device comprising: The notification means transmits the notification to the external device if a packet with the ID that requested retransmission is not received from the external device even after a predetermined timeout determination period has elapsed after transmitting the notification to the external device. The communication device according to any one of claims 5 to 8, wherein the communication device retransmits the information to an external device. A method for controlling a communication device, the method comprising:
generating a packet having a header, data, and a footer and having an ID assigned to the header according to a predetermined rule;
transmitting the packet to an external device;
receiving a notification sent from the external device;
If the notification is a request from the external device to retransmit a packet with a predetermined ID that was sent to the external device, the packets with the predetermined ID and subsequent IDs are sequentially sent back to the predetermined ID. A method for controlling a communication device, comprising the step of transmitting a packet to the external device. A method for controlling a communication device, the method comprising:
receiving from an external device a packet having a header, data, and a footer and having an ID assigned to the header according to a predetermined rule;
storing the received packet in a storage means;
detecting whether an error has occurred in the received packet;
When it is detected that an error has occurred in the received packet, the external device is instructed to go back to the ID of the packet in which the error was detected and retransmit packets with subsequent IDs sequentially from the packet with the ID. a step of notifying;
The present invention is characterized by comprising the step of discarding the packet with the ID in which the error has been detected, and the packets received from the reception of the packet with the ID until the packet with the ID is retransmitted from the external device. A method of controlling communication equipment. A method for controlling a communication device, the method comprising:
receiving from an external device a packet having a header, data, and a footer and having an ID assigned to the header according to a predetermined rule;
storing the received packet in a storage means;
detecting whether or not the storage means has a capacity to store the received packet;
When it is detected that the storage means does not have the capacity to store the received packets, the storage means traces back to the ID of the packet that cannot be stored in the storage means and sequentially stores packets with subsequent IDs from the packet with that ID. Notifying the external device to retransmit;
The method further comprises the steps of discarding packets with IDs that cannot be stored in the storage means, and packets received between the time the packets with the IDs are received and the packets with the IDs are retransmitted from the external device. A method for controlling a communication device, characterized in that: A printing system including a print control device and an image forming device that are communicably connected,
The image forming apparatus includes:
receiving means for receiving from the print control device a packet having a header, image data, and a footer and having an ID assigned to the header according to a predetermined rule;
storage means for storing packets received by the receiving means;
detection means for detecting whether an error has occurred in the packet received by the receiving means;
When it is detected that an error has occurred in a packet received by the receiving means, a request is made to trace back to the ID of the packet in which the error was detected and retransmit packets with subsequent IDs sequentially from the packet with the ID. notification means for transmitting a notification to the print control device;
comprising: a packet with the ID in which the error has been detected; and a discard unit that discards the packet received between the time the packet with the ID is received and the packet with the ID is retransmitted from the printing control device;
The print control device includes:
generating means for generating the packet;
transmitting means for transmitting the packet generated by the generating means to the image forming apparatus;
receiving means for receiving the notification transmitted from the image forming apparatus;
a control means for controlling, when the receiving means receives the notification, to trace back to the ID of the packet in which the error was detected and sequentially transmit packets with subsequent IDs from the packet with the ID to the image forming apparatus; A printing system comprising: The footer includes CRC data generated from the header and the image data,
The image forming apparatus includes a calculation means for calculating CRC data from the header of the packet and the data,
The control means may cause the notification to indicate that the detection means of the image forming apparatus has detected a header error in which the ID of the packet in which the error has been detected cannot be recognized, or If the CRC data calculated by the calculation means of the forming device and the CRC data included in the footer of the packet do not match, immediately after receiving the notification, the ID where the error was detected. 14. The printing system according to claim 13, wherein the printing system performs control to sequentially transmit packets with subsequent IDs to the image forming apparatus. A printing system including a print control device and an image forming device that are communicably connected,
The image forming apparatus includes:
receiving means for receiving from the print control device a packet having a header, image data, and a footer and having an ID assigned to the header according to a predetermined rule;
storage means for storing packets received by the receiving means;
detection means for detecting whether or not the storage means has a capacity capable of storing the packets received by the reception means;
When the detection means detects that the storage means does not have the capacity to store the packets received by the reception means, the storage means sequentially traces back to the ID of the packet that cannot be stored in the storage means and sequentially starts from the packet with that ID. notification means for transmitting a notification to the print control device to resend packets with subsequent IDs;
a discard unit for discarding packets with the ID that cannot be stored in the storage unit, and packets received from the time the packet with the ID is received until the packet with the ID is retransmitted from the print control device; Prepare,
The print control device includes:
generating means for generating the packet;
transmitting means for transmitting the packet generated by the generating means to the image forming apparatus;
receiving means for receiving the notification transmitted from the image forming apparatus;
When the notification is received from the image forming apparatus, after a predetermined hold time has elapsed since the notification was received, the ID of the packet that cannot be stored in the storage means is traced back to the packet with the ID. 1. A printing system comprising: control means for controlling packets with subsequent IDs to be sequentially transmitted to the image forming apparatus. When the notification means does not receive a packet of the ID for which retransmission is requested by the notification from the print control device even after a predetermined timeout determination period has elapsed after transmitting the notification to the print control device, resending the notification to the print control device;
16. The printing system according to claim 15, wherein the timeout determination time is longer than the hold time. A program that causes a computer to function as each means of the communication device according to any one of claims 1 to 9.

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