Abstract:
A job processing device capable of preventing a poor communication while keeping the sufficient communication speed. The job processing device is connected to a host, which has a host interface supporting a first connection mode for communicating in a first communication speed and a second connection mode for communicating in a second communication speed being slower, and processes a job transmitted from the host. A device interface has the first and second connection modes. A connection control means changes the device interface from the second connection mode to the first connection mode when the device interface is connected to the host interface in the second connection mode and when a first operation mode for processing a job is shifted to a second operation mode being lower in power consumption. A mode control means shifts to the second operation mode from the first operation mode after changing the connection mode.

Description:
This application is a U.S. National Phase Application of PCT International Application PCT/JP2011/068994 filed on Aug. 17, 2011 which is based on and claims priority from JP 2010-184169 filed on Aug. 19, 2010, the contents of which is incorporated herein in its entirety by reference. 
     TECHNICAL FIELD 
     The present invention relates to a job processing device, a control method and a control program therefor. Particularly, the present invention relates to a communication control of the job processing device that processes a job received from a host that is connected via an interface (I/F) like a Universal Serial Bus (USB). 
     BACKGROUND ART 
     Generally, the USB I/F is used to connect a USB host with a USB device and to communicate. For example, the USB I/F has spread as a general-purpose I/F that connects a personal computer (PC) as a host with a job processing device like an image forming apparatus (for example, a printer). 
     Incidentally, communication speeds supported by USB 2.0 are 1.5 Mbps in a low speed (LS) mode, 12 Mbps in a full speed (FS) mode, and 480 Mbps in a high speed (HS) mode. Then, the communication speed is determined according to types of a USB host and a USB device connected to the USB host. 
     Further, USB 3.0 supports a super speed (SS) mode of which the communication speed is accelerated to 5 Gbps. The SS mode does not only accelerate the communication speed, but also enables the USB device to control a shift to a low power consumption state in the USB I/F communication, which was conventionally possible only from the USB host. Therefore, the SS mode is more convenient for USB device that aims to save power consumption. 
     On the other hand, the higher communication speed unescapably increases probability of poor communication due to an effect of noise. This may disturb normal data transmission from the USB host normally. 
     Here, it is assumed that a USB device of the SS mode connection and a USB device of the HS mode connection are connected to a USB host supporting USB 3.0 via a USB hub supporting USB 3.0. In this case, a communication in the SS mode and a communication in the HS mode are performed concurrently between the USB host and the USB 3.0 hub. 
     Then, the concurrent communications in the SS mode and the HS mode generate crosstalk noise that becomes a new factor to disturb the communications. 
     In order to prevent the poor communication in the communication using the USB I/F, there is a known technique that detects the poor communication caused during the communications. The technique lowers communication speed to keep a stability of communication when detecting that the poor communication continues beyond a fixed time (for example, see PTL 1). 
     However, since the technique disclosed in PTL 1 changes the communication speed after detecting the poor communication, it is difficult to prevent the poor communication before changing the communication speed. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Laid-Open Patent Publication (Kokai) No. 2007-172160 (JP 2007-172160A) 
     SUMMARY OF INVENTION 
     Technical Problem 
     The present invention provides a job processing device, a control method and a control program therefor, which is capable of preventing a poor communication by changing communication speed before a data communication while keeping the sufficient communication speed for the data communication. 
     Solution to Problem 
     Accordingly, a first aspect of the present invention provides a job processing device that is connected to a host, which has a host interface supporting a first connection mode for communicating in a first communication speed and a second connection mode for communicating in a second communication speed being slower than the first communication speed, and processes a job transmitted from the host, comprising a device interface that is provided with the first and second connection modes, a connection control means that changes the device interface from the second connection mode to the first connection mode when the device interface is connected to the host interface in the second connection mode and when an operation mode is shifted from a first operation mode for processing a job to a second operation mode being lower in power consumption than the first operation mode, and a mode control means that shifts the operation mode to the second operation mode from the first operation mode after changing the connection mode. 
     Accordingly, a second aspect of the present invention provides a job processing device that is connected to a host, which has a host interface supporting a first connection mode for communicating in a first communication speed and a second connection mode for communicating in a second communication speed being slower than the first communication speed, and processes a job transmitted from the host, comprising a device interface that is provided with the first and second connection modes, and a connection control means that sets the connection mode of the job processing device itself in the first connection mode when a mode determination result showing a connection mode of another job processing device to the host shows the first connection mode, and sets the connection mode of the job processing device itself in the second connection mode when the mode determination result shows the second connection mode. 
     Accordingly, a fifth aspect of the present invention provides a control method for a job processing device that is connected to a host, which has a host interface supporting a first connection mode for communicating in a first communication speed and a second connection mode for communicating in a second communication speed being slower than the first communication speed, has a device interface that is provided with the first and second connection modes, and processes a job transmitted from the host, the control method comprising a determination step of determining whether the device interface is connected to the host interface in the second connection mode, when an operation mode is shifted from a first operation mode for processing a job to a second operation mode being lower in power consumption than the first operation mode, a connection control step of changing the connection mode of the device interface to the first connection mode from the second connection mode when it is determined that the device interface is connected to the host interface in the second connection mode in the determination step, and a mode control step of shifting the operation mode to the second operation mode from the first operation mode after changing the connection mode. 
     Accordingly, a fourth aspect of the present invention provides a control method for a job processing device that is connected to a host, which has a host interface supporting a first connection mode for communicating in a first communication speed and a second connection mode for communicating in a second communication speed being slower than the first communication speed, has a device interface that is provided with the first and second connection modes, and processes a job transmitted from the host, the control method comprising a receiving step of receiving a mode determination result showing a connection mode of another job processing device connected to the host determined by the host, and a connection control step of setting a connection mode of the job processing device itself in the first connection mode when the mode determination result shows the first connection mode, and setting the connection mode of the job processing device itself in the second connection mode when the mode determination result shows the second connection mode. 
     Accordingly, a fourth aspect of the present invention provides a control program causing a computer to function as a job processing device that is connected to a host, which has a host interface supporting a first connection mode for communicating in a first communication speed and a second connection mode for communicating in a second communication speed being slower than the first communication speed, has a device interface that is provided with the first and second connection modes, and processes a job transmitted from the host, the control program comprising a determination step of determining whether the device interface is connected to the host interface in the second connection mode, when an operation mode is shifted from a first operation mode for processing a job to a second operation mode being lower in power consumption than the first operation mode, a connection control step of changing the connection mode of the device interface to the first connection mode from the second connection mode when it is determined that the device interface is connected to the host interface in the second connection mode in the determination step, and a mode control step of shifting the operation mode to the second operation mode from the first operation mode after changing the connection mode. 
     Accordingly, a sixth aspect of the present invention provides a control program causing a computer to function as a job processing device that is connected to a host, which has a host interface supporting a first connection mode for communicating in a first communication speed and a second connection mode for communicating in a second communication speed being slower than the first communication speed, has a device interface that is provided with the first and second connection modes, and processes a job transmitted from the host, the control program comprising a receiving step of receiving a mode determination result showing a connection mode of another job processing device connected to the host determined by the host, and a connection control step of setting a connection mode of the job processing device itself in the first connection mode when the mode determination result shows the first connection mode, and setting the connection mode of the job processing device itself in the second connection mode when the mode determination result shows the second connection mode. 
     Advantageous Effects of Invention 
     According to the present invention, since the connection mode is changed to the second connection mode that has less effect of noise before the data communication, the communication can be stable with less effect of noise. Further, the present invention can save the power consumption of the system that consists of the host and the job processing devices. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view showing an example of a printing system that uses a printer as a job processing device according to a first embodiment of the present invention. 
         FIG. 2  is a block diagram schematically showing an example of the configuration of the printer shown in  FIG. 1 . 
         FIG. 3  is a view showing another example of a printing system that uses the printer shown in  FIG. 2 . 
         FIG. 4  is a view showing USB I/F connections between a host PC, a hub, a printer, and a digital camera that are shown in  FIG. 3 . 
         FIG. 5  is a view showing relations among a working state of the printer shown in  FIG. 2 , a connecting configuration of USB I/F, and power consumption. 
         FIG. 6  is a flowchart showing a procedure executed when the printer shown in  FIG. 2  is shifted from a normal state to a sleep state. 
         FIG. 7  is a flowchart showing a procedure executed when the printer shown in  FIG. 2  returns to the normal state from the sleep state. 
         FIG. 8  is a view showing USB I/F connections among a printer as an image forming apparatus according to a second embodiment of the present invention, a hub, a host PC, and a digital camera. 
         FIG. 9  is a view showing a hierarchical structure of drivers concerning printer control in the host PC shown in  FIG. 8 . 
         FIG. 10  is a sequential chart showing communications between the host PC and the printer that are shown in  FIG. 8 , and changes of a working state of the printer. 
         FIG. 11  is a flowchart showing a procedure in which the host PC detects a change of the connecting configuration of the digital camera in  FIG. 10 , and transmits an SS mode device connection flag according to the detection result concerned to the printer. 
         FIG. 12  is a flowchart showing a procedure executed when the printer changes its connecting configuration based on the SS mode device connection flag received from the host PC and the current connecting configuration in the USB I/F in  FIG. 10 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereafter, an example of a job processing device according to an embodiment of the present invention will be described with reference to the attached drawings. 
       FIG. 1  is a view showing an example of a printing system that uses a printer as a job processing device according to a first embodiment of the present invention. 
     As shown in  FIG. 1 , in the illustrated printing system, a host PC  200  as a USB host and a printer  100  as a USB device (a job processing device) are connected via a USB I/F (interface). It should be noted that the host PC  200  that supports USB 3.0 and has a USB 3.0 interface (host interface). Similarly, the printer  100  also supports USB 3.0. 
     The host PC  200  is a general PC. Various kinds of application software are executed on an OS (operating system) of the host PC  200 . 
     A printer driver for controlling the printer  100  has been installed in the host PC  200 . Then, when a user selects a printing process on application software in the host PC  200 , the printer driver generates a print job and transmits it to the printer  100  via the USB I/F. Here, the print job that the printer driver generates is a print command that defines an image outputted from the printer called a PDL (Page Description Language), for example. The print job is generated by compressing a raster image generated on the host PC  200 . Then, when receiving the print job from the host PC  200 , the printer  100  executes a printing process according to contents of the received print job. 
       FIG. 2  is a block diagram showing an example of the configuration of the printer  100  shown in  FIG. 1 . 
     As shown in  FIG. 2 , the printer  100  has a printer controller  101  that executes an image process required for the printing process and controls the entire printer. In the illustrated example, a display unit  104  and an operation unit  106  are connected to the printer controller  101 , and a printer unit  110  is also connected. The printer controller  101  is connected to the host PC  200  ( FIG. 1 ) via a USB 3.0 PHY (physical interface)  113 . 
     The printer controller  101  has a CPU  102 , a display unit interface (I/F)  103 , an operation unit I/F  105 , a ROM  107 , a RAM  108 , a printer I/F  109 , an image processing unit  111 , and a USB 3.0 device controller (it is only called a device controller)  112 . 
     The CPU  102  operates according to a control program stored in the ROM  107  to process a print job, etc. The CPU  102  is a processor that controls the entire printer, and controls various processes performed by the printer controller  101 . 
     The RAM  108  is a system work memory for the CPU  102  to operate, and is also used as an image memory for storing image data for printing temporarily. The ROM  107  is a boot ROM and is a nonvolatile memory in which a boot program is stored. 
     The display unit I/F  103  is an interface that transmits or receives a command and data to or from the display unit  104 . The display unit  104  comprises an LCD (a liquid crystal display), and displays a current status of the printer  100 , user&#39;s set information, etc., for example. The operation unit I/F  105  transmits or receives a command and data to or from the operation unit  106 . The operation unit  106  comprises a hardkey etc. and receives the input instruction from a user. 
     The CPU  102  controls an operation of the printer  100  according to an input instruction that the operation unit  106  received. The device controller  112  controls a communication of USB 3.0, and is connected to the host PC  200  via the above-mentioned USB 3.0 PHY  113 . The USB I/F (device interface) is specified by the device controller  112  and the USB 3.0 PHY  113 . Then, a print job, various status information, and a control signal are exchanged between the host PC  200  and the printer  100  via the USB I/F. 
     The image processing unit  111  performs an image processing for a print output to the image data for a print, and transmits printing data to the printer unit  110  connected via the printer I/F  109 . The printer unit  110  prints an image on a sheet based on the received printing data. 
     The printer unit  110  employs an electrophotography process that fixes toner onto a sheet to form an image using a photoconductive drum or a photo conductor belt, for example. 
     The illustrated printer  100  has a normal working state (a normal state, a normal mode), and a sleep working state (a sleep state, a sleep mode) in which power consumption is lower than that in the normal working state. For example, the CPU  102 , the display unit I/F  103 , the display unit  104 , the printer I/F  109 , the printer unit  110 , the image processing unit  111 , and the device controller  112 , which are shown in  FIG. 2 , are not energized in the sleep state. This shifts the printer to a low power consumption state as a whole. 
     Thus, the power supplied to the power-off section of the printer  100  is stopped in the sleep state. In the sleep state, the supply of clock used to operate a digital circuit is stopped. This reduces the power consumption in the printer  100 . 
     In addition, the illustrated printer  100  shifts the USB connection in the SS mode with the host PC  200  to a power down state, and shifts to the lower power consumption state while keeping the USB connections to the host PC  200 . Since the SS mode supported by USB 3.0 achieves the high transfer speed as mentioned above and does not require the host side to check until the device side transmits an Endpoint Ready Packet, it can reduce the power consumption of the system. 
     The printer  100  shifts to the sleep state from the normal state when a fixed time elapses without any actions of the printer  100 , or when a user&#39;s instruction is received via the operation unit  106 , for example. Then, the printer  100  returns to the normal state from the sleep state when the print job is received in the sleep state and will start printing, or when a user&#39;s instruction is received via the operation unit  106 . 
     Specifically, the operation unit I/F  105  interrupts the CPU  102  according to an input instruction received via the operation unit  106 . As mentioned above, when the CPU  102  that is working in the low power consumption mode receives the interruption, the CPU  102  returns to a normal operation mode. 
     Next, the CPU  102  that returned to the normal operation mode performs the process that returns each section of the printer  100  from the sleep state to the normal state. When the host PC  200  executes a print job while the printer  100  is in the sleep state, the USB connection with the printer  100  in the SS mode is exited from the power down state. At this time, the device controller  112  detects the exit from the power down state in the printer  100 , and the CPU  102  is interrupted to return from the sleep state in the same manner as mentioned above. 
     Thus, the printer  100  saves the power consumption by selecting a suitable mode from the modes that are different in the power consumption according to the operation situation thereof. 
     It should be noted that this embodiment shall supply the electric power to all the hardware modules shown in  FIG. 2  in the normal state, but shall supply to a part of the hardware modules in the sleep state. However, the power supplying control is not limited to the embodiment. For example, the supply of electric power to apart of the hardware modules shown in  FIG. 2  may be stopped even in the normal state. Supply of electric power to a part other than the above-mentioned power-off section may be stopped, or the electric power may be supplied to a part of the power-off section. Namely, the normal state is in the condition where the power consumption of the entire printer is higher than the sleep state, and the sleep state is in the condition where the power consumption of the entire printer is lower than the normal state. 
       FIG. 3  is a view showing another example of printing system that uses the printer  100  shown in  FIG. 2 . 
     In the example shown in  FIG. 3 , a USB 3.0 hub (it is only called a hub hereafter)  400  is included in addition to the host PC  200  and the printer  100 . The host PC  200  and the printer  100  are connected via the hub  400  concerned. The digital camera  300 , which is a USB 2.0 device, is connected with the host PC  200  via the hub  400 . It should be noted that the hub  400  relays a USB host and a USB device. 
     As shown in  FIG. 3 , the hub  400  and the digital camera  300  are connected by a USB 2.0 cable  500 , and the hub  400  and the host PC  200  are connected by a USB 3.0 cable  501 . The hub  400  and the printer  100  are connected by a USB 3.0 cable  502 . 
     The USB 2.0 cable  500  comprises four signal lines of VBUS, GND, D + , and D − , and is used for connections in an HS (High Speed) mode, an FS (Full Speed) mode, and a LS (Low Speed) mode. On the other hand, each of the USB 3.0 cables  501  and  502  comprises ten signal lines that include four signal lines, which are common to the USB 2.0 cable  500  used for the connections in the HS (high speed: a second communication speed) mode, the FS and LS modes (second connection modes), and six signal lines of SSTX+, SSTX−, SSRX+, SSRX−, and two GNDs, which are used for a connection in the SS (super speed: a first communication speed) mode (a first connection mode). Therefore, the connecting configurations between the host PC  200 , the hub  400 , the printer  100 , and the digital camera  300  in the printing system shown in  FIG. 3  are as shown in  FIG. 4 . 
       FIG. 4  is a view showing the USB I/F connections between the host PC  200 , the hub  400 , the printer  100 , and the digital camera  300  that are shown in  FIG. 3 . 
     In  FIG. 4 , the host PC  200  has a USB 3.0 host controller  201  and a USB 3.0 PHY (physical interface)  202 . The USB 3.0 host controller  201  controls a communication in USB 3.0. The USB 3.0 host controller  201  communicates with a USB device in the SS, HS, FS, or LS mode via the USB 3.0 PHY  202  to which the USB 3.0 cable  501  is connected. 
     The host PC  200  communicates with a USB device to which the USB 3.0 host controller  201  is connected by outputting and inputting data via the host PC internal bus (not shown). 
     The digital camera  300  has a USB 2.0 device controller  301  and a USB 2.0 PHY  302 . The USB 2.0 device controller  301  controls a communication in USB 2.0. The USB 2.0 device controller  301  communicates with a USB host in the HS, FS, or LS mode via the USB 2.0 PHY  302  to which the USB 2.0 cable  500  is connected. 
     The digital camera  300  communicates with a USB host to which the USB 2.0 device controller  301  is connected by outputting and inputting data between the USB host and an internal bus (not shown) of the digital camera. 
     Although the digital camera  300  is illustrated as the USB 2.0 device as an example, the USB 2.0 device is not limited to the digital camera. 
     As shown in  FIG. 4 , each of the USB 3.0 PHY  202  of the host PC  200  and the USB 3.0 PHY  113  of the printer  100  that support USB 3.0 have an SS mode supporting unit, and HS, FS, and LS mode supporting units in parallel so as to correspond to each of the USB 3.0 cables  501  and  502 . 
     On the other hand, the USB 2.0 PHY  302  of the digital camera  300  that supports up to USB 2.0 has the HS, FS, and LS mode supporting units only. A connection between a USB host and a USB device is detected by termination of a receiving unit in the SS mode, and is detected by pull-up of D+ or D− in the HS, FS, or LS mode. 
     The USB 3.0 device is connectable by either of the USB 2.0 cable  500  and the USB 3.0 cable  502 . The detected result mentioned above determines whether the connecting configuration is in the SS mode, or the HS, FS or LS mode. 
     As mentioned above, the hub  400  is connected with the digital camera  300  using the USB 2.0 cable  500 , and the connecting configuration between the hub  400  and the digital camera  300  is in the HS mode. The hub  400  is connected with the printer  100  using the USB 3.0 cable  502 , and the connecting configuration between the hub  400  and the printer  100  is in the SS mode. Then, the host PC  200  and the hub  400  are connected by the USB 3.0 cable  501 , and the hub  400  relays the SS mode connection between the printer  100  and the host PC  200 . The hub  400  also relays the HS mode connection between the digital camera  300  and the host PC  200 . 
     Thus, when the job processing devices are connected to the hub  400  in the SS mode and the HS, FS, or LS mode, the communication in the HS, FS, or LS mode and the communication in the high-speed SS mode are performed in concurrency between the host PC  200  and the hub  400 . Therefore, the crosstalk noise produced in the concurrency communications becomes a factor that deteriorates the communication quality. 
     Particularly, the influence of the crosstalk noise on the communication quality becomes larger in the connection in the SS mode that allows higher speed communication. In the SS mode, when the USB device sends a power-down request to the USB host, the connecting condition under which the power consumption is lower than that in the HS, FS, or LS mode is achieved. 
       FIG. 5  is a view showing relations among a working state of the printer  100  shown in  FIG. 2 , a connecting configuration of USB I/F, and power consumption. 
     In the illustrated example, when the printer  100  is in the normal state  900 , the CPU  102  controls the device controller  112  so that the printer  100  is connected to the host PC  200  in the HS mode and communicates in order to stabilize the communication. On the other hand, when the printer  100  is in the sleep state  901 , the CPU  102  controls the device controller  112  so that the printer  100  is connected to the host PC  200  in the SS mode in order to reduce the power consumption. 
     Here, the communication speed in the HS mode is sufficient to perform the printing process by the printer  100 . The larger the ratio of the sleep state occupied in the working time of the printer is, the lower the power consumption is. 
       FIG. 6  is a flowchart showing a procedure executed when the printer  100  shown in  FIG. 2  is shifted from the normal state to the sleep state. 
     In the following description, the USB I/F of the printer  100  shall be connected to the host PC  200  in the HS mode, and the printer  100  shall be working in the normal state  900 . 
     In the above-mentioned condition, the CPU  102  determines whether the printer  100  shifts to the sleep state  901  from the normal state  900  (step S 1001 ). For example, when standby time in which the printer  100  does not execute a printing process etc. becomes larger than a predetermined time that has been set by a user beforehand, the CPU  102  determines to shift to the sleep state  901  from the normal state  900 . When a user instructs to shift to the sleep state  901  from the normal state  900  through the operation unit  106 , the CPU  102  determines to shift to the sleep state  901  from the normal state  900 . 
     When determining that the printer does not shift to the sleep state  901  (NO in the step S 1001 ), the CPU  201  enters in the standby condition. On the other hand, when determining that the printer shifts to the sleep state  901  (YES in the step S 1001 ), the CPU  102  controls the device controller  112  so as to disconnect the HS mode connection established by the USB I/F (step S 1002 ). When the connection is disconnected, the pull-up of D+ detected by the host PC  200  is changed by a switch, for example. 
     Next, the CPU  102  controls the device controller  112  so as to connect the USB I/F to the host PC  200  in the SS mode (step S 1003 ). When the mode is changed to the SS mode, the termination is changed by the switch so that the host PC  200  enables to detect the termination, for example. 
     This makes the printer  100  be connectable to the USB I/F in the SS mode, and the printer  100  is connected to the host PC  200  in the SS mode (step S 1004 ). 
     Next, the CPU  102  notifies the host PC  200  of the power-down request in the SS mode (step S 1005 ). Then, the CPU  102  makes the printer  100  shift to the sleep state in the SS mode connection (step S 1006 ), and finishes a process. 
       FIG. 7  is a flowchart showing a procedure executed when the printer  100  shown in  FIG. 2  returns to the normal state from the sleep state. 
     Here, the USB I/F of the printer  100  shall be connected to the host PC  200  in the SS mode, and the printer  100  shall be in the sleep state  901 . 
     In the above-mentioned condition, the CPU  102  determines whether the printer  100  returns to the normal state  900  from the sleep state  901  (step S 2001 ). For example, when detecting a change of the connecting condition in the SS mode, the CPU  102  determines to return to the normal state  900  from the sleep state  901 . When a user instructs to return to the normal state  900  from the sleep state  901  through the operation unit  106 , the CPU  102  determines to return to the normal state  900  from the sleep state  901 . 
     The change of the connecting condition in the SS mode means that the host PC  200  shifts to the normal state from the sleep state in the SS mode in order to transmit a print job to the printer  100 . 
     When determining that the printer does not return to the normal state  900  (NO in the step S 2001 ), the CPU  201  enters in the standby condition. On the other hand, when determining that the printer returns to the normal state  900  (YES in the step S 2001 ), the CPU  102  controls the device controller  112  so as to disconnect the SS mode connection established by the USB I/F (step S 2002 ). When the connection is disconnected, the termination detected by the host PC  200  is changed by a switch, for example. 
     Next, the CPU  102  controls the device controller  112  so as to connect the USB I/F to the host PC  200  in the HS mode (step S 2003 ). When the mode is changed to the HS mode, the HS mode connection starts when the host PC  200  does not detect the termination while keeping the termination in the changed state by the switch, for example. 
     This makes the USB I/F of the printer  100  establish the connection with the host PC  200  in the HS mode (step S 2004 ). And the CPU  102  finishes the process. 
     As mentioned above, when a print job is executed in the first embodiment, since the connection is changed from the SS mode (super speed mode) to the HS mode (high speed mode) with less influence in a noise before the printer  100  receives the print job, the influence of a noise decreases, and a print job can be received with stability. 
     When a print job is not executed, the connection mode between the host PC  200  and the printer  100  is shifted to the SS mode and the printer  100  is in the sleep state that is low in the power consumption. This achieves the power-saving of the printing system itself. 
       FIG. 8  is a view showing USB I/F connections among the printer  100  as an image forming apparatus according to a second embodiment of the present invention, the hub  400 , the host PC  200 , and a digital camera  600 . 
     It should be noted that the digital camera  600  (another job processing device) that is a device supporting USB 3.0 is connected to the hub  400  via a USB 3.0 cable  503  instead of the digital camera  300 . The configurations of the printer  100 , the hub  400 , and the host PC  200  are identical to those in the first embodiment. 
     In  FIG. 8 , the digital camera  600  has a USB 3.0 device controller  601  and a USB 3.0 PHY (physical interface)  602 . The USB 3.0 device controller  601  controls a communication of USB 3.0, and communicates with the host PC  200  as the USB host via the USB 3.0 PHY  602 . 
     Therefore, the connecting configuration by the USB I/F between the hub  400  and the digital camera  600  is the SS, HS, FS, or LS mode. In this case, unlike the first embodiment, there are three types of the connecting configurations between the host PC  200  and the hub  400  according to the connecting configurations of the printer  100  and the digital camera  600 . The first type is the SS mode only, the second type is mixture of the SS mode and the HS mode, and the third type is the HS mode only. 
     Accordingly, the printing system shown in  FIG. 8  controls to change the connecting configuration of the printer  100  according to the connecting configuration of the digital camera  600  connected to the host PC  200  so that the printer  100  communicates with stability. 
     Specifically, when the connecting configuration of the digital camera  600  connected to the host PC  200  is the SS mode, the connection mode of the printer  100  is also changed to the SS mode. This reduces the influence of the crosstalk noise. When the connecting configuration of the digital camera  600  connected to the host PC  200  is the HS mode, the connection mode of the printer  100  is also changed to the HS mode in order to reduce the influence of the crosstalk noise. 
       FIG. 9  is a view showing a hierarchical structure of drivers concerning a control of the printer  100  in the host PC  200  shown in  FIG. 8 . 
     As shown in  FIG. 9 , a host driver/bus driver  700  is installed in the host PC  200 . The host driver/bus driver  700  is a device driver in a low order hierarchy that controls the USB 3.0 host controller  201 . 
     The printer driver  701  is a device driver that controls the printer  100 , and communicates with the printer  100  via the host driver/bus driver  700 . Similarly, a digital camera driver  703  is a device driver that controls the digital camera  600 . 
     However, as mentioned above, the combination of the digital camera  600  and the digital camera driver  703  is an example, and a USB device is not limited to a digital camera. In this case, the host PC  200  has a device driver according to a USB device instead of the digital camera driver  703 . 
     A USB device monitoring application  702  operates as a background service of an OS, and monitors the management information about USB devices, for example. Then, the USB device monitoring application  702  monitors a change of the configuration (for example, connection or disconnection) of a USB device connected to the host PC  200 . 
     When detecting a change of the configuration of the USB device connected to the host PC  200 , the USB device monitoring application  702  determines whether the connecting configuration is the SS mode connection, or the HS, FS, or LS mode connection. Further, the USB device monitoring application  702  has the information about SS mode device connection flag corresponding to the determination result concerned, and is provided with a function to notify the printer  100  of the information about the flag via the printer driver  701 . 
       FIG. 10  is a sequential chart showing communications between the host PC  200  and the printer  100  that are shown in  FIG. 8 , and changes of a working state of the printer  100 . It should be noted that details of operations of the host PC  200  and the printer  100  will be described later. 
       FIG. 10  shows the operations at the time when another USB device, which is the digital camera  600  in this example, is connected to the host PC  200  to which the printer  100  that is working in the normal state  900  has been connected. The USB device monitoring application  702  of the host PC  200  is monitoring the connecting configuration of a USB device, and detects a change (connection or disconnection) (S 3001 ). Connection of the digital camera  600  is detected in this example. 
     Next, when the host PC  200  detects the connection of another USB device, the USB device monitoring application  702  determines whether the connecting configuration of the connected USB device (the digital camera  600 ) is the SS mode connection, or the HS, FS, or LS mode connection (S 3002 ). Then, the USB device monitoring application  702  sets ON/OFF of an SS mode device connection flag based on the determination result concerned, and transmits the flag information concerned to the printer  100  via USB I/F. 
     When receiving the SS mode device connection flag from the host PC  200 , the printer  100  changes the connecting configuration based on the SS mode device connection flag and the current connection mode of the USB I/F of the printer  100  (S 3003 ). Then, as described in the first embodiment, when the condition shifting to the sleep state  901  is satisfied, the printer  100  is shifted to the sleep state  901  from the normal state  900  (S 3004 ). 
     In this case, the printer  100  is shifted from the normal state  900  to the sleep state  901  in the low power consumption state in the SS mode connection irrespective of the current connecting configuration of the USB I/F. 
     The USB device monitoring application  702  of the host PC  200  is monitoring the connecting configuration of the USB device (the digital camera  600 ) like the step S 3001  and detects a change (connection or disconnection) (S 3005 ). Then, the USB device monitoring application  702  of the host PC  200  determines whether the connecting configuration of the connected USB device (the digital camera  600 ) is the SS mode, or the HS, FS, or LS mode connection like the step S 3002 . Then, according to the determination result concerned, the USB device monitoring application  702  sets ON/OFF of the SS mode device connection flag (S 3006 ). 
     In this case, since the printer  100  is in the sleep state  901 , the host PC  200  does not transmit the flag information to the printer  100 , but waits until the printer  100  returns from the sleep state  901 . 
     When receiving a user&#39;s instruction to return from the sleep state through the operation unit  106 , the CPU  102  of the printer  100  starts a return process from the sleep state  901  (S 3007 ). Then, when returning from the sleep state  901 , the printer  100  notifies the host PC  200  of the request to cancel the sleep state in the SS mode connection. Accordingly, in the host PC  200 , the printer driver  701  determines that the printer  100  has returned from the sleep state  901 , and transmits the SS mode device connection flag to the printer  100 . 
     When receiving the SS mode device connection flag from the host PC  200 , the printer  100  changes the connecting configuration based on the SS mode device connection flag and the current connection mode of the USB I/F of the printer  100  (S 3008 ). 
       FIG. 11  is a flowchart showing a procedure in which the host PC  200  detects a change of the connecting configuration of the digital camera  600  in  FIG. 10 , and transmits the SS mode device connection flag according to the detection result concerned to the printer  100 . 
     The USB device monitoring application  702  of the host PC  200  is monitoring the connecting configuration of the USB device (the digital camera  600 ), and detects whether the connecting configuration is changed (connection or disconnection) (step S 4001 ). When a connecting configuration is not changed (NO in the step S 4001 ), the USB device monitoring application  702  continues to monitor. 
     When a change of the connecting configuration is detected (YES in the step S 4001 ), the USB device monitoring application  702  determines whether the USB device (the digital camera  600 ) connected to the host PC  200  in addition to the printer  100  has connected in the SS mode, or the HS, FS, or the LS mode (step S 4002 ). 
     When the connection mode of the USB device (the digital camera  600 ) is the SS mode (SS mode in the step S 4002 ), the USB device monitoring application  702  sets the SS mode device connection flag to ON (step S 4003 ). 
     On the other hand, when the connection mode of the USB device (the digital camera  600 ) is the HS, FS, or LS mode (HS, FS, or LS in the step S 4002 ), the USB device monitoring application  702  sets the SS mode device connection flag to OFF (step S 4004 ). 
     Next, the USB device monitoring application  702  determines whether communication with the printer  100  is possible according to the connecting condition of the USB I/F between the host PC  200  and the printer  100  (step S 4005 ). 
     When the communication with the printer  100  is impossible (NO in the step S 4005 ), the USB device monitoring application  702  waits until the communication becomes possible. On the other hand, when the communication with the printer  100  is possible (YES in the step S 4005 ), the USB device monitoring application  702  transmits the SS mode device connection flag (a mode determination result) to the printer  100  (step S 4006 ), and finishes the process. 
     When the USB I/F is in the low power consumption state in the SS mode connection, the printer  100  is in the sleep state  901  that disables the communication. On the other hand, when the USB I/F is in the normal state in the SS mode connection or the HS mode connection, the printer  100  is possible to communicate. 
       FIG. 12  is a flowchart showing a procedure executed when the printer  100  changes its connecting configuration based on the SS mode device connection flag received from the host PC  200  and the current connecting configuration in the USB I/F in  FIG. 10 . 
     The CPU  102  of the printer  100  determines whether the SS mode device connection flag (the mode determination result) has been received from the host PC  200 , when the communication with the host PC  200  is possible (step S 5001 ). When the SS mode device connection flag is not received (NO in the step S 5001 ), the printer  100  waits until receiving the SS mode device connection flag. 
     When the SS mode device connection flag is received (YES in the step S 5001 ), the CPU  102  of the printer  100  determines whether the SS mode device connection flag is ON or OFF (step S 5002 ). 
     When the SS mode device connection flag is OFF (NO in the step S 5002 ), the CPU  102  of the printer  100  determines whether the USB I/F connection is in the SS mode or the HS mode (step S 5003 ). In the case of the SS mode (SS mode in the step S 5003 ), the CPU  102  controls the device controller  112  to disconnect the SS mode connection (step S 5004 ). 
     Then, the CPU  102  controls the device controller  112  so as to change the USB I/F to the HS mode (step S 5003 ). Then, the USB I/F in the printer  100  establishes the HS mode connection with the host PC  200  (step S 5006 ), and the CPU  102  finishes the process. 
     In the case of the HS mode (HS mode in the step S 5003 ), the CPU  102  finishes the process. It should be noted that the method for re-connecting in the HS mode is identical to that in the first embodiment. 
     Thus, when the host PC  200  and the printer  100  are connected in the SS mode and when the digital camera  600  is connected to the host PC  200  in the HS, FS, or LS mode, the printer  100  changes the USB I/F connection to the host PC  200  to the HS mode connection. When the host PC  200  and the printer  100  are connected in the HS mode and when the digital camera  600  is connected to the host PC  200  in the HS mode, the printer  100  keeps the HS mode connection with the host PC  200 . 
     When the SS mode device connection flag is ON (YES in the step S 5002 ), the CPU  102  of the printer  100  determines whether the USB I/F connection is in the SS mode or the HS mode (step S 5007 ). In the case of the SS mode (SS mode in the step S 5007 ), the CPU  102  finishes the process. 
     In the case of the HS mode (HS mode in the step S 5007 ), the CPU  102  controls the device controller  112  to disconnect the HS mode connection (step S 5008 ). Then, the CPU  102  controls the device controller  112  so as to change the USB I/F to the SS mode (step S 5009 ). Then, the USB I/F in the printer  100  establishes the SS mode connection with the host PC  200  (step S 5010 ), and the CPU  102  finishes the process. 
     It should be noted that the method for changing from the HS mode to the SS mode and for re-connecting is identical to that in the first embodiment. 
     Thus, when the host PC  200  and the printer  100  are connected in the HS mode and when the digital camera  600  is connected to the host PC  200  in the SS mode, the printer  100  changes the USB I/F connection to the host PC  200  to the SS mode connection. 
     On the other hand, when the host PC  200  and the printer  100  are connected in the SS mode and when the digital camera  600  is connected to the host PC  200  in the SS mode, the printer  100  keeps the SS mode connection with the host PC  200 . 
     Thus, in the second embodiment, since the connection mode between the host PC  200  and the printer  100  is changed according to the connection mode between the digital camera  600  and the host PC  200 , the crosstalk noise due to the communication speed gap can be reduced. 
     As is evident from the above-mentioned description, the USB 3.0 controller  112  and the USB 3.0 PHY  113  function as the device interface (USB 3.0 interface) in  FIG. 2 . The CPU  102  functions as a connect control means and a mode control means. The CPU  102  and the USB 3.0 device controller  112  function as a connection control means. 
     Although the embodiments of the invention have been described, the present invention is not limited to the above-mentioned embodiments, the present invention includes various modifications as long as the concept of the invention is not deviated. 
     For example, a computer with which the printer  100  is provided may execute the control method that is defined by the functions of the above-mentioned embodiments. Further, the computer with which the printer  100  is provided may execute a control program that has the functions of the above-mentioned embodiments. 
     In this case, each of the control method and the control program has a determination step, a connection control step, and a mode control step at least. Each of the control method and the control program may have a receiving step and a connection control step. It should be noted that the control program is recorded into a computer-readable storage medium, for example. 
     The embodiments are described using the USB 3.0 interface as an example of an interface. However, the interface is not limited to the USB 3.0 interface, and the present invention can be applied to another interface. 
     Aspects of the present invention can also be realized by a computer of a system or apparatus (or devices such as a CPU or MPU) that reads out and executes a program recorded on a memory device to perform the functions of the above-described embodiment(s), and by a method, the steps of which are performed by a computer of a system or apparatus by, for example, reading out and executing a program recorded on a memory device to perform the functions of the above-described embodiment(s). For this purpose, the program is provided to the computer for example via a network or from a recording medium of various types serving as the memory device (e.g., computer-readable medium). 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     REFERENCE SIGNS LIST 
     
         
           100  Printer 
           102  CPU 
           112  USB 3.0 Device Controller 
           113  USB 3.0 PHY 
           200  Host PC 
           300 ,  600  Digital cameras 
           400  USB 3.0 Hub 
           500  USB 2.0 Cable 
           501 ,  502 ,  503  USB 3.0 cables