JP4665705B2 - Acquiring credit for data communication in network printers - Google Patents

Description

  The present invention relates to obtaining data communication credits in a network printer.

  Conventionally, printer systems for printing images have been used. Some printer systems receive a print request via a network (also called a network printer). Among network printers, a printing device that executes printing (hereinafter also referred to as “printer unit”), and control data used for printing is transmitted to the printing device in response to a print request (print data) received from the network. Network devices (hereinafter also referred to as “network units”). Here, packet communication may be used for data communication between the network device and the printing device. As packet communication, for example, packet communication based on credit is known (see, for example, Patent Document 1).

JP 2000-236351 A

  By the way, the network device acquires a credit from the printing device in order to transmit control data to the printing device. Here, various schemes can be adopted as a scheme for acquiring credits. For example, it is possible to adopt a method of acquiring credits by transmitting a credit request to the printing apparatus. In addition, it is possible to adopt a method of acquiring credits voluntarily provided by the printing apparatus without transmitting a credit request. Here, in many cases, a method suitable for each printing device is employed as a method by which the printing device can operate. However, in order to use such various printing apparatuses as network printers, it is necessary to prepare a network apparatus suitable for the printing apparatus, and there is a problem that much effort is required for designing and manufacturing the network apparatus. It was.

  The present invention has been made to solve the above-described problem, and provides a technique capable of increasing the degree of freedom of the configuration of an available printing apparatus in a network printer having a network apparatus and a printing apparatus. With the goal.

  In order to solve at least a part of the above-described problem, according to a first aspect of the present invention, control data used for printing is transmitted to a printing apparatus that performs printing in response to a print request from a client on a network. A first protocol processing unit that transmits the control data according to a communication protocol using a packet, and the printing device includes a second protocol processing unit that receives the control data according to the communication protocol. The first protocol processing unit has (i) a request mode for acquiring a credit by transmitting a credit request to the second protocol processing unit as a credit acquisition mode for data transfer, and (ii) a credit Regardless of whether there is a request or not, the second protocol processing unit voluntarily causes the first protocol processing unit. A providing mode for obtaining the provided credit, wherein the first protocol processing unit inquires of the second protocol processing unit whether or not the operation can be performed in the providing mode, and is operable in the providing mode. In such a case, there is provided a network device that selects and executes credit acquisition in the provision mode, and selects and executes credit acquisition in the request mode when the operation cannot be performed in the provision mode.

  According to this network device, the first protocol processing unit inquires of the second protocol processing unit of the printing device whether or not it can operate in the provision mode. Is selected and executed, and when the operation cannot be performed in the providing mode, the credit acquisition in the request mode is selected and executed, so that the degree of freedom of the configuration of the printing apparatus that can be used in the network printer can be increased.

  In the network apparatus, the network apparatus and the printing apparatus are connected by USB, the network apparatus functions as a USB host, the printing apparatus functions as a USB device, and the communication protocol is a lower layer protocol. The USB protocol may be used.

  According to this configuration, a printer connected to a general personal computer using USB can be used as a printing apparatus.

  According to a second aspect, there is provided a network printer that executes printing in response to a print request from a client on the network, the network printer including the network device according to the first aspect and the printing device. provide.

  The present invention can be realized in various forms, for example, a network device for a network printer, a network printer having a network device and a printing device, a control method and a control device for these devices, and their The present invention can be realized in the form of a computer program for realizing the function of the method or apparatus, a recording medium recording the computer program, a data signal including the computer program and embodied in a carrier wave, and the like.

Next, embodiments of the present invention will be described in the following order based on examples.
A. Example:
B. Variations:

A. Example:
FIG. 1 is a schematic diagram showing the configuration of a network system to which an embodiment of the present invention is applied. The network system 10 has a configuration in which a personal computer 100 and a network printer 200 are connected to each other via a LAN. The LAN may be a wired network such as IEEE 802.3 or a wireless network such as IEEE 802.11b / g / a.

  The personal computer 100 uses the printer driver 100D to generate original image data that is the basis of the print image. Then, the personal computer 100 transmits a print request including the original image data to the network printer 200 via the LAN, and causes the network printer 200 to execute printing. In this embodiment, the personal computer 100 transmits a print request to the network printer 200 using LPR (Line PRinter daemon protocol). However, the format of the print request is not limited to the format using LPR, and any other format can be adopted.

  Also, any format can be adopted as the format of the original image data. For example, PDL data described in PDL (Page Description Language) may be used. Further, image data such as JPEG data or TIFF data may be employed. Moreover, you may employ | adopt the XHTML data described by XHTML (eXtensible HyperText Markup Language).

  The network printer 200 has a network unit 300 and a printer unit 400. The network unit 300 mediates data (for example, original image data) exchanged between other devices on the LAN and the printer unit 400. The printer unit 400 executes printing according to the received original image data. The network unit 300 and the printer unit 400 are connected by USB (Universal Serial Bus). However, it is also possible to connect the two with a physical interface other than USB.

  The network unit 300 includes a central control unit (CPU) 310, a RAM 320, a ROM 330, a network control unit 340, and a USB host control unit 350. In the example of FIG. 1, the network control unit 340 is connected to a wired network via a connector 342. The USB host controller 350 has a root hub 352, and the root hub 352 is provided with a USB connector 354. The USB connector 354 is connected to the USB connector 462 of the printer unit 400 via a USB cable.

  The printer unit 400 includes a central control unit (CPU) 410, a RAM 420, a ROM 430, a print engine 440, and a USB device control unit 460. The print engine 440 is a printing mechanism that performs printing in accordance with given print data. In the present embodiment, the central control unit 410 analyzes the original image data generated by the printer driver 100D, executes color conversion and halftone processing, creates print data, and supplies the print data to the print engine 440. To do. However, the print engine 440 may be configured to have color conversion and halftone processing functions instead of the central control unit 410.

  FIG. 2 is a block diagram showing a configuration of the network printer 200 centering on the ROMs 330 and 430. In FIG. 2, the components are arranged in the same order as the data communication hierarchy. The ROM 330 of the network unit 300 stores a print server module 334 that causes the printer unit 400 to execute printing in response to a print request from the LAN. The print server module 334 transfers original image data included in a print request received via the LAN to the printer unit 400.

  Below the print server module 334 are a lower layer of the network architecture and a lower layer of the USB architecture. A network module 332 is provided as a lower layer of the network architecture. A network control unit 340 is provided below the network module 332. The network module 332 performs data communication via the LAN by interpreting relatively higher-level protocols (for example, TCP (Transmission Control Protocol) and IP (Internet Protocol)). The network control unit 340 performs data communication via the LAN by interpreting a relatively low-level protocol (for example, Ethernet (registered trademark)).

  On the other hand, a D4 protocol processing module 336 is provided as a lower layer of the USB architecture of the print server module 334. A USB control module 338 is provided below the D4 protocol processing module 336. A USB host control unit 350 is provided below the USB control module 338.

  The D4 protocol processing module 336 performs data transfer according to a so-called “D4 protocol”. The D4 protocol is a communication protocol defined by IEEE P1284.4. In the D4 protocol, data is transferred through a logical channel using a packet. Hereinafter, a packet defined by IEEE P1284.4 is also referred to as a “D4 packet”.

  The USB control module 338 performs data transfer by interpreting a relatively higher-level USB protocol (for example, a communication protocol using a data transfer pipe (Bulk OUT pipe)). The USB control module 338 has functions of USB system software and USB printer class client software.

  On the other hand, the USB host control unit 350 performs data transfer by interpreting a relatively low-order USB protocol (for example, an electrical signal protocol). The USB host control unit 350 functions as a USB host controller (host-side bus interface).

  On the other hand, the ROM 430 of the printer unit 400 stores a printer function module 434 that supplies print data to the print engine 440 in response to a print request (original image data). Below the printer function module 434 is a lower layer of the USB architecture. As a lower layer of the USB architecture, a D4 protocol processing module 436 is provided. A USB control module 438 is provided below the D4 protocol processing module 436. A USB device controller 460 is provided below the USB control module 438.

  Similar to the D4 protocol processing module 336, the D4 protocol processing module 436 performs data transfer according to the D4 protocol.

  Similar to the USB control module 338, the USB control module 438 performs data transfer according to a relatively higher USB protocol. The USB control module 438 has functions of a USB logical device of the USB printer class and a USB function of the USB printer class.

  Similar to the USB host control unit 350, the USB device control unit 460 performs data transfer by interpreting a relatively low-order USB protocol. The USB device control unit 460 functions as a USB bus interface.

  When the print server module 334 transmits original image data to the printer function module 434, the D4 protocol processing module 336 and the D4 protocol processing module 436 perform data transfer according to the D4 protocol. In the lower layer, the USB control module 338 and the USB control module 438 perform data transfer according to the USB protocol. In the lower layer, the USB host control unit 350 and the USB device control unit 460 perform data transfer according to the USB protocol.

  FIG. 2 shows a logical channel dch of the D4 protocol. The transfer of the original image data is performed via this logical channel dch. Note that the logical channel is not limited to the logical channel dch for original image data, and an arbitrary plurality of logical channels can be provided. For example, a channel for transmitting and receiving status information of the print engine 440 can be provided. Such status information can be provided from the network unit 300 to another device (for example, the personal computer 100) on the network by a protocol such as SNMP.

  The logical channel identification information is registered in the header of the D4 packet (not shown). In other words, when transmitting the D4 packet, the D4 protocol processing modules 336 and 436 register the identification information of the logical channel of the D4 packet in the header. Further, when receiving the D4 packet, the D4 protocol processing modules 336 and 436 specify the logical channel of the D4 packet by referring to the header of the received D4 packet.

  FIG. 3 is a sequence diagram showing an outline of an example of a credit acquisition method in the logical channel dch. In the D4 protocol, credits are used for transfer control of D4 packets including transfer data (hereinafter also referred to as “data packets”). In data transfer using credits, a data receiver (receiver) first provides the number of receivable data packets (also referred to as “credit number”) to a data sender (sender). The transmitting side can transmit data packets to the receiving side up to the number of credits provided. The number of credits provided is consumed by packet transmission. In this sequence diagram, communication in the lower layer (USB) is not shown.

  FIG. 3 is a sequence diagram illustrating an example of data transfer according to the request method. In this sequence diagram, it is assumed that the network unit 300 transmits data (for example, original image data) to the printer unit 400. In the first step S300, the network unit 300 receives a print request from the outside. In response to this print request, the D4 protocol processing module 336 of the network unit 300 (hereinafter also referred to as “net D4 module 336”) transmits a credit request (Credit Request) to the printer unit 400 before transmitting the original image data. (Step S310). In response to this credit request, the D4 protocol processing module 436 (hereinafter also referred to as “printer D4 module 436”) of the printer unit 400 returns a credit request response (Credit Request Reply) to the network unit 300 (step S320). The printer D4 module 436 specifies the number of credits in this response. The number of credits is set according to the operation status of the printer unit 400 (for example, the free capacity of the data reception buffer memory). In the example of FIG. 3, the number of credits is set to “zero” in the response of step S320. Thereafter, the net D4 module 336 repeats the transmission of the credit request until receiving a response designating one or more credits. Then, the net D4 module 336 transmits a data packet to the printer unit 400 in response to a response designating one or more credits. The number of data packets transmitted here is limited to the specified number of credits. In the example of FIG. 3, the number of credits is set to 1 in response to the credit request in step S330 (S340). Therefore, the net D4 module 336 transmits one data packet in the next step S350. Thereafter, the net D4 module 336 repeats the credit request and the data transmission until the transfer of the original image data is completed. Note that the number of credits provided at one time may be two or more.

  In this way, a method in which the data transmitting side acquires a credit by transmitting a credit request to the data receiving side is referred to as a “request method”. In this “request method”, the data receiving side provides a credit in response to a credit request, but does not voluntarily provide a credit.

  FIG. 4 is a sequence diagram illustrating an example of data transfer according to the provision method. The difference from the sequence diagram shown in FIG. 3 is that the printer D4 module 436 voluntarily provides credit regardless of the presence or absence of a credit request.

  In the first step S400A, the network unit 300 receives a print request from the outside. However, in the providing method, the net D4 module 336 does not make a voluntary credit request and waits until credit is provided. In the example of FIG. 4, in the next step S410, the printer D4 module 436 voluntarily provides a credit. Here, the printer D4 module 436 specifies a credit number of 1 or more. In the example of FIG. 4, the number of credits is set to “1” in the credit provision in step S410. Any credit can be used as an opportunity for providing the credit. For example, it can be used when the free capacity of the data reception buffer memory of the printer unit 400 has become sufficiently large. As such a data reception buffer memory, any memory can be used. For example, a partial area of the RAM 420 (FIG. 1) can be used.

  In response to the credit provision, the net D4 module 336 returns a credit provision response indicating that the credit provision has been received (step S420). Then, the net D4 module 336 transmits a data packet to the printer unit 400 in response to the credit provision (step S430). The number of data packets transmitted here is limited to the specified number of credits. Thereafter, the net D4 module 336 repeats the standby until the credit is provided and the data transmission according to the provision of the credit until the transfer of the original image data is completed.

  In this way, a method of acquiring credits voluntarily provided by the data receiving side regardless of whether there is a credit request from the data transmitting side is referred to as a “providing method”. In this “providing method”, the data transmission side does not make a voluntary credit request.

  FIG. 5 is a sequence diagram showing another example of data transfer according to the provision method. The only difference from the example shown in FIG. 4 is that the timing at which the network unit 300 receives the print request (S400B) is after the credit provision (S410). In this case, since the network unit 300 has already received the credit when the print request is received, the network unit 300 can transmit the data packet without waiting time (S430). If the provided credit is insufficient, the network unit 300 waits for the credit to be provided again, and transmits a data packet in response to the provision of the credit (steps S440, S450, S460). Thereafter, the network unit 300 repeats the standby until the credit is provided and the data transmission according to the provision of the credit until the transfer of the original image data is completed.

  As described above, in the request method (FIG. 3), the transmission side (net D4 module 336) requests credit before transmission when attempting to transmit data. The receiving side (printer D4 module 436) provides credit in response to the credit request. As described above, in the request method, since the credit is obtained by a simple method, the configuration of the transmission side and the reception side can be simplified. However, when the transmitting side tries to transmit data in a state where the receiving side cannot provide the credit, the transmitting side repeatedly transmits the credit request until the credit is provided.

  On the other hand, in the providing method (FIGS. 4 and 5), the receiving side voluntarily provides credit regardless of the presence or absence of a credit request. On the other hand, the transmitting side does not transmit a voluntary credit request. As a result, it is possible to prevent the credit request from being repeatedly transmitted even when the transmitting side tries to transmit data in a state where the receiving side cannot provide the credit. In addition, when the receiving side can provide credit, the receiving side can provide the credit in advance before receiving the data transmission request (for example, print request). As a result, the provision of credits can be performed with a low communication load. Thus, the provision method is preferable in that the communication load can be suppressed as compared with the request method.

  Incidentally, in the example of FIG. 1, USB is used for connection between the network unit 300 and the printer unit 400. This is because a printer connected to a general personal computer using USB is used as the printer unit 400. As described above, if the same connection interface as the connection interface with the personal computer (USB in this example) is used as the connection interface, the printer for the personal computer can be easily used as the printer unit 400. At this time, the network unit 300 is configured so that the configuration of the layer higher than the USB of the personal computer printer (for example, the configuration corresponding to the printer D4 module 436 and the printer function module 434 in FIG. 2) can be used as it is. It is preferable to configure.

  In communication between a personal computer and a printer, a “request method” is often adopted. The reason is as follows. In the USB protocol, the data transfer schedule is managed by the USB host. Even when the USB device transmits data to the USB host, the USB device cannot spontaneously transmit data to the USB host. Instead, the USB device can transmit data to the USB host only after receiving a so-called “IN token” from the USB host. The issuance frequency of the “IN token” by the USB host is normally set according to a request from the USB device.

  Here, it is assumed that the providing method (FIGS. 4 and 5) is applied to communication between the personal computer and the printer. In order to realize voluntary credit provision by the USB device (printer), the USB host (personal computer) frequently transmits an “IN token” to the USB device. That is, the personal computer continues to send the “IN token” to the printer even when the printer is not used. Here, when the personal computer is executing another process (for example, execution of an application) different from the use of the printer, the other depends on the load of “IN token” transmission for the printer that is not used. The efficiency of processing may be reduced.

  On the other hand, when the network D4 module 336 on the USB host side voluntarily issues a credit request as in the request method shown in FIG. 3, the USB host sends a so-called “OUT token” to the USB device as necessary. That's fine. Here, it is assumed that the providing method is applied to the communication between the personal computer and the printer. Then, the personal computer does not need to transmit an “IN token” and an “OUT token” to the printer when the printer is not used. Therefore, it is possible to suppress a decrease in the efficiency of other processing due to a printer that is not used.

  As described above, in order to suppress an increase in the load on the personal computer when the printer is not used, the “request method” is often adopted in communication between the personal computer and the printer.

  By the way, the data amount of the USB protocol packet for “IN token” is smaller than the data amount of the USB protocol packet for upper layer data such as “credit request”. Therefore, the communication load of the “providing method” in which the “IN token” is repeatedly transmitted and received is smaller than the communication load of the “request method” in which the “credit request” is repeatedly transmitted and received. On the other hand, with respect to the network unit 300 of the network printer 200, a decrease in efficiency of other processes different from the use of the printer is rarely a problem. Therefore, it is preferable that the “providing method” is adopted in communication between the network unit 300 and the printer unit 400.

  Note that, among the printer units 400 connected to the network unit 300, those that support the “request method” instead of the “provide method”, such as printers for personal computers, and “providing method” There is a possibility that Therefore, in this embodiment, the net D4 module 336 selects either “providing method” or “request method” in accordance with the connected network unit 300.

  FIG. 6 is a flowchart illustrating a procedure of credit acquisition method selection processing. In the first step S600, the net D4 module 336 (FIG. 2) inquires of the printer D4 module 436 whether it can operate in the “providing mode”. When the operation in the “providing method” is possible, the net D4 module 336 moves to step S610 and selects and executes the credit acquisition by the “providing method”. If the operation of the “providing method” cannot be performed, the net D4 module 336 moves to step S620 and selects and executes the credit acquisition by the “request method”.

  FIG. 7 is a sequence diagram illustrating an example of data transfer when using the printer unit 400 that does not support the “providing method”. In this case, the net D4 module 336 selects and executes the credit acquisition by the “request method”. Note that the sequence diagram of FIG. 7 shows data (commands) exchanged between the network D4 module 336 and the printer D4 module 436 in more detail than the sequence diagram of FIG.

  In the D4 protocol, not only transfer data such as original image data, but also commands and responses are transmitted and received using D4 packets. However, the command packet and the response packet are transferred using a predetermined logical channel (not shown) different from the logical channel dch for data transfer.

  In the first step S200, the net D4 module 336 transmits an open channel command to the printer D4 module 436. This command is sent to open the logical channel dch (FIG. 2). Such an open channel command can be issued at an arbitrary timing. For example, it may be issued when the network printer 200 is activated. It may be issued in response to a print request. Hereinafter, description will be made on the assumption that the processing of FIG. 7 is executed in response to a print request.

The open channel command includes the following two parameters.
(1) Number of requested credits (Credit Requested. Also called “CR”)
(2) Maximum Outstanding Credit (hereinafter also referred to as “MOC”)
“CR” is set to the number of credits newly requested by the transmission side. If no credit is requested, it is set to “0x0000”. Here, the prefix “0x” means a hexadecimal number (the same applies to other parameters described later). “MOC” is set to the number of credits that the transmission side requests to hold. If no credit is requested, it is set to “0x0000”. In the command in step S200, both parameters are set to “0x0000”. Such parameter setting means that no credit is requested. When such an open channel command is issued, the data receiving side does not provide credit until a request is received from the data transmitting side. The state of the logical channel dch in which such parameter setting is accepted by the receiving side is also referred to as “No Credit Mode”.

  In the next step S210, the printer D4 module 436 returns an open channel response (Open Channel Reply) to the net D4 module 336. This response includes the result of the open channel command and the number of credits provided. In step S210 of FIG. 7, the result is success (OK), and the number of credits is “0”.

  In the next step S220, the net D4 module 336 transmits a credit request command to the printer D4 module 436. This command also includes “C.R.” and “M.O.C.”, like the open channel command. In the credit request in step S220, both parameters are set to the maximum value (0xFFFF). Such parameter setting means requesting the data receiving side to continue to provide as many credits as possible as soon as possible. In this embodiment, such parameter setting means a request for operation according to the “providing method”. Note that the state of the logical channel dch in which such parameter setting is accepted by the receiving side is also referred to as “unlimited credit mode”.

  In the next step S230, the printer D4 module 436 returns a credit request response (Credit Request Reply) to the network D4 module 336. This response includes the result of the credit request. In the example of FIG. 7, the printer D4 module 436 does not support the “providing method”, so the result is set to failure (NG). As described above, when the printer D4 module 436 does not support the “providing method”, the printer D4 module 436 returns a response indicating that the printer D4 module 436 does not support the network D4 module 336.

  When the network D4 module 336 receives a response from the printer D4 module 436 indicating that it does not support credit provision according to the “providing method”, it operates according to the “request method”.

  In the next step S240, the net D4 module 336 transmits a credit request command according to the “request method” to the printer D4 module 436. In the credit request in step S240, “C.R.” is set to a value greater than “0x0000” and less than the maximum value (0xFFFF). “M.O.C.” is set to the maximum value (0xFFFF). Such parameter setting means that the number of credits designated by “C.R.” is requested from the data receiving side. In this embodiment, such parameter setting means a credit request according to the “request method”. Note that the state of the logical channel dch in which such parameter settings are accepted by the receiving side is also referred to as “limited credit mode”.

  In the next step S250, the printer D4 module 436 returns a credit request response to the network D4 module 336. This response includes the result of the credit request and the number of credits provided. In the example of FIG. 7, the printer D4 module 436 corresponds to the “request method”, so the result is set to success (OK). However, “credit” is set to “0” at this stage.

  Thereafter, the net D4 module 336 repeatedly transmits a credit request command similar to that in step S240 until one or more credits are provided. Then, the net D4 module 336 transmits a data packet to the printer D4 module 436 in response to provision of one or more credits. In the example of FIG. 7, one credit is provided in response to the credit request in step S260 (S270). Therefore, the net D4 module 336 transmits one data packet in the next step S280. Thereafter, the net D4 module 336 repeats the credit request and the data transmission until the data transfer is completed.

  As described above, the network D4 module 336 inquires of the printer D4 module 436 whether or not the “providing method” is supported (FIG. 7: S220), and supports the credit provision according to the “providing method”. If a response indicating that there is no message is received, the operation is performed according to the “request method”.

  FIG. 8 is a sequence diagram illustrating another example of data transfer. The difference from the sequence diagram of FIG. 7 is that this sequence diagram shows a case where the printer unit 400 corresponds to the “providing method”. In this case, the net D4 module 336 selects and executes the credit acquisition by the “providing method”. Note that the sequence diagram of FIG. 8 shows data (commands) exchanged between the network D4 module 336 and the printer D4 module 436 in more detail than the sequence diagrams of FIGS. Yes.

  The first steps S100, S110, and S120 are the same as steps S200, S210, and S220 in FIG. 7, respectively.

  In the next step S130, the printer D4 module 436 returns a credit request response to the net D4 module 336. In the example of FIG. 8, since the printer D4 module 436 corresponds to the “providing method”, the result is set to success (OK). As described above, when the printer D4 module 436 supports the “providing method”, the printer D4 module 436 returns a response indicating that the printer D4 module 436 supports the network D4 module 336.

  When the network D4 module 336 receives a response from the printer D4 module 436 indicating that it supports credit provision according to the “providing method”, the net D4 module 336 operates according to the “providing method”. Specifically, the net D4 module 336 waits for spontaneous credit provision from the printer D4 module 436 without transmitting a credit request. Then, the net D4 module 336 transmits a data packet in response to the credit provision.

  In the example of FIG. 8, the printer D4 module 436 transmits a credit command in the next step S140. This command is a command for providing credit to the data transmission side. This credit command includes the number of credits provided. In the credit command in step S140, the credit is set to “1”. The network D4 module 336 that has received the credit command transmits a credit response (Credit Reply) indicating that the credit command has been accepted to the printer D4 module 436 (step S150). In the next step S160, one data packet is transmitted. Send. Thereafter, the net D4 module 336 repeats the standby until the provision of the credit and the data transmission corresponding to the provision of the credit until the data transfer is completed.

  As described above, the network D4 module 336 inquires of the printer D4 module 436 as to whether or not the “providing method” is supported (FIG. 8: S120), and supports the credit provision according to the “providing method”. If a response indicating that is received, it operates according to the “providing method”.

  As described above, in the present embodiment, the network D4 module 336 inquires of the printer D4 module 436 whether or not the operation in the “providing method” is possible, and is operable in the “providing method”. The credit acquisition by the “providing method” is selected and executed, and when the operation cannot be performed by the “providing method”, the credit acquisition by the “request method” is selected and executed. Accordingly, the network unit 300 uses an appropriate credit acquisition method for each of the printer unit corresponding to the “providing method” and the printer unit corresponding to the “request method” without corresponding to the “providing method”. Can work. As a result, it is possible to increase the degree of freedom in the configuration of available printer units.

  In this embodiment, the network unit 300 and the printer unit 400 are connected by USB. As described above, if the USB, which is often used as a connection interface between a personal computer and a printer, is adopted as the connection interface, a printer for a personal computer can be easily used as the printer unit 400. Particularly in this case, many printers support the “request method” instead of the “providing method”. However, since the network unit 300 can select one of “providing method” and “request method” according to the printer unit, such a printer can be easily used as the printer unit 400.

B. Variations:
In addition, elements other than the elements claimed in the independent claims among the constituent elements in each of the above embodiments are additional elements and can be omitted as appropriate. The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

Modification 1:
In each of the embodiments described above, a credit request command (FIG. 7: S220, FIG. 8: S120) is used as a method for inquiring whether or not the operation by the “providing method” by the printer unit 400 (printer D4 module 436) is possible. Any method can be adopted without being limited to the method using. For example, a method of inquiring using an open channel command (FIG. 7: S200, FIG. 8: S100) may be adopted. In this case, the net D4 module 336 may set both the “CR” and “MOC” parameters to the maximum value (0xFFFF) in the open channel command.

  Similarly, the response method for such an inquiry is not limited to the method using the credit request response (FIG. 7: S230, FIG. 8: S130), and any method can be adopted. For example, a method of responding to an inquiry using an open channel command as described above using an open channel response (FIG. 7: S210, FIG. 8: S110) can be employed. In this case, if the printer D4 module 436 supports the “providing method”, the printer D4 module 436 may return an open channel response indicating that the result is success (OK), and also supports the “providing method”. If not, an open channel response with a failure (NG) result may be returned.

Modification 2:
In each of the above embodiments, any timing before data transfer can be adopted as the timing of the inquiry regarding whether or not the printer unit 400 is compatible with the “providing method”. For example, the network D4 module 336 may inquire after the network printer 200 is activated regardless of whether or not there is a print request. Moreover, it is preferable that the net D4 module 336 continues to use the credit acquisition method selected according to the response to the inquiry without making an inquiry again after making an inquiry. Here, a nonvolatile memory (not shown) may be provided in the network unit 300, and the net D4 module 336 may store the selection result in the nonvolatile memory. In this way, even when the network printer 200 is restarted, the net D4 module 336 can operate with an appropriate credit acquisition method stored in the non-volatile memory without making an inquiry.

  In each of the above embodiments, a configuration in which the user of the network printer 200 can replace the printer unit 400 with another printer unit may be employed. As such a configuration, for example, a configuration in which the USB connector 462 of FIG. 1 is detachable can be adopted. Here, it is preferable that the network D4 module 336 makes an inquiry every time the printer unit 400 is connected to the network unit 300. In this way, the net D4 module 336 can operate with an appropriate credit acquisition method even when the printer unit 400 is replaced with another type of printer unit.

Modification 3:
In each of the above embodiments, the format of the print request received by the network printer 200 is not limited to a format that uses LPR, and any format can be adopted. For example, the network printer 200 can be configured as a network device compatible with UPnP (Universal Plug and Play, UPnP is a trademark of UPnP Implementers Corporation). As such a configuration, for example, the following configuration can be adopted. The network unit 300 receives a message for printing according to the UPnP protocol from another device (for example, the personal computer 100) on the LAN. Further, the network unit 300 transfers this message to the printer unit 400. The printer unit 400 executes printing according to the received message. Here, the network D4 module 336 and the printer D4 module 436 transmit and receive printing messages.

Modification 4:
In each of the above embodiments, the data transmitted / received between the network D4 module 336 and the printer D4 module 436 according to the credit is not limited to the original image data and the print message, but is used for printing control by the printer unit 400. Arbitrary control data can be adopted.

Modification 5:
In each of the above embodiments, the D4 protocol is used. However, the present invention is not limited to the D4 protocol but can be applied to any communication protocol in which data packets are transferred according to credits.

Modification 6:
In each of the above embodiments, a part of the configuration realized by hardware may be replaced with software, and conversely, a part of the configuration realized by software may be replaced by hardware. . For example, the function of the USB control module 338 in FIG. 2 may be realized by a hardware circuit having a logic circuit.

  When part or all of the functions of the present invention are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. In the present invention, the “computer-readable recording medium” is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but an internal storage device in a computer such as various RAMs and ROMs, a hard disk, and the like. An external storage device fixed to the computer is also included.

It is the schematic which shows the structure of the network system to which the Example of this invention is applied. 2 is a block diagram illustrating a configuration of a network printer 200 centered on a ROM 330430. FIG. It is a sequence diagram which shows the outline | summary of an example of the acquisition method of the credit in the logical channel dch. It is a sequence diagram which shows an example of the data transfer according to a provision system. It is a sequence diagram which shows another example of the data transfer according to a provision system. It is a flowchart which shows the procedure of the selection process of a credit acquisition system. FIG. 11 is a sequence diagram illustrating an example of data transfer when using a printer unit 400 that does not support the “providing method”. It is a sequence diagram which shows another example of data transfer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Network system 100 ... Personal computer 100D ... Printer driver 200 ... Network printer 300 ... Network unit 320 ... RAM
330 ... ROM
332 ... Network module 334 ... Print server module 336 ... D4 protocol processing module (net D4 module)
338: USB control module 340 ... Network control unit 342 ... Connector 350 ... USB host control unit 352 ... Root hub 354 ... USB connector 400 ... Printer unit 410 ... Central control unit 420 ... RAM
430 ... ROM
434 ... Printer function module 436 ... D4 protocol processing module (printer D4 module)
438 ... USB control module 440 ... Print engine 460 ... USB device control unit 462 ... USB connector

Claims (4)

A network device that transmits control data used for printing to a printing device that executes printing in response to a print request from a client on the network,
A first protocol processing unit for transmitting the control data according to a communication protocol using a packet;
The printing apparatus includes a second protocol processing unit that receives the control data according to the communication protocol,
The first protocol processing unit, as a credit transfer mode for data transfer,
(I) a request mode for acquiring credits by transmitting a credit request to the second protocol processing unit;
(Ii) a providing mode in which the credit provided to the first protocol processing unit is voluntarily acquired by the second protocol processing unit regardless of the presence or absence of a credit request;
The first protocol processing unit inquires of the second protocol processing unit whether or not it is operable in the providing mode, and
When operable in the providing mode, select and execute credit acquisition in the providing mode,
If it is not possible to operate in the provision mode, select and execute credit acquisition in the request mode,
Network device. The network device according to claim 1,
The network device and the printing device are connected by USB,
The network device functions as a USB host;
The printing device functions as a USB device;
The communication protocol uses the USB protocol as a lower layer protocol.
Network device. A network printer that performs printing in response to a print request from a client on the network,
A network printer comprising the network device according to claim 1 and the printing device. A network printer control method comprising: a printing apparatus that executes printing; and a network apparatus that transmits control data used for printing to the printing apparatus in response to a print request from a client on the network,
(A) The network device includes a step of executing a process of acquiring a data transfer credit from the printing device,
The credit acquisition process includes:
(I) a request mode in which the network device acquires a credit by transmitting a credit request to the printing device;
(Ii) the network device has a provision mode in which the printing device voluntarily acquires credit provided to the network device regardless of whether or not a credit request is made;
The step (A)
(A1) the network device inquires of the printing device whether or not it can operate in the providing mode;
(A2) If the network device is operable in the providing mode, the network device selects and executes credit acquisition in the providing mode;
If the network device is unable to operate in the provision mode, the network device selects and executes credit acquisition in the request mode.
Control method.

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