Abstract:
A network device may be configured to connect with an external device over a network. The network device may be provided with a light emitting element configured to indicate information concerning network communications, and a control unit. The network device may be configurable to any of a plurality of performance states including a first performance state and a second performance state. Power consumption in the second performance state may be smaller than power consumption in the first performance state. The control unit may allow emission of the light emitting element when the network device is set in the first performance state, and may control the light emitting when the network device is set in the second performance state such that power consumption of the light emitting element in the second case is smaller than power consumption of the light emitting element in the first case.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2009-073772, filed on Mar. 25, 2009, the contents of which are hereby incorporated by reference into the present application. 
     TECHNICAL FIELD 
     This specification relates to a network device to be connected with an external device in a communicable manner via a network. 
     DESCRIPTION OF RELATED ART 
     A multi-function device to be connected with a PC in a communicable manner is known. If the multi-function device is not used continuously for a predetermined time in a normal state, the multi-function device is set in a power saving state in which the power consumption is lower than the normal state. 
     SUMMARY 
     Further power saving is sought in a network device. This specification discloses technology for realizing the power saving of a network device using a method that is different from conventional methods. 
     One aspect disclosed in the present specification is a network device configured to be connected with an external device in a communicable manner via a network. The network device may comprise a first light emitting element configured to indicate a first type of information concerning a communication of data via the network, and a light emitting element control unit configured to control the first light emitting element. The network device may be configured to be set in any one of a plurality of performance states including a first performance state and a second performance state. Power consumption in the second performance state may be smaller than power consumption in the first performance state. The light emitting element control unit may be configured to allow emission of the first light emitting element in a first case where the network device is set in the first performance state, and control the first light emitting element in a second case where the network device is set in the second performance state such that power consumption of the first light emitting element in the second case is smaller than power consumption of the first light emitting element in the first case. 
     The foregoing sentence of “The network device may be configured to be set in any one of a plurality of performance states including a first performance state and a second performance state” may also be rephrased, but not limited to, as “a particular device included in the network device is set in any one of a plurality of performance states including a first performance state and a second performance state”. In addition, the foregoing expression of “first case (or second case)” may mean, but not limited to, an entire period that the network device is set in the first performance state (or the second performance state), or mean, but not limited to, a part of the entire period. For example, if the network device is set in the first performance state and a timing of switching from the first performance state to the second performance state is known in advance, a control of the first light emitting element may be started in the same manner as the second case from a predetermined period before the timing. In addition, if the network device is set in the second performance state and a timing of switching from the second performance state to the first performance state is known in advance, a control of the first light emitting element may be started in the same manner as the first case from a predetermined period before the timing. 
     Further, the light emitting element control unit will suffice so as long as it is able to control the first light emitting element as described above, and is not required to constantly control the first light emitting element as described above. For instance, the network device may be configured to be set to either mode; specifically, the first mode or the second mode. If the light emitting element control unit is set to the first mode, it may control the first light emitting element as described above. If the light emitting element control unit is set to the second mode, even if it is the second case, it may control the first light emitting element in the same manner as the first case. 
     A control method and computer program for realizing the foregoing network device are also novel and effective. A computer readable medium including the computer program is also novel and effective. The network system including the foregoing network device and external device is also novel and effective. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows an example of a configuration of a network system. 
         FIG. 2  is a diagram for explaining a situation where a state of a multi-function device is changed. 
         FIG. 3  shows a relationship between a state of the multi-function device and a state of each unit. 
         FIG. 4  shows a flowchart of processing to be executed by a main CPU. 
         FIG. 5  shows a flowchart of processing to be executed by the main CPU. 
         FIG. 6  shows a flowchart of processing to be executed by the main CPU or a sub CPU. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     (Configuration of System) 
     An embodiment is now explained with reference to the attached drawings. As shown in  FIG. 1 , a network system  2  comprises a multi-function device  10 , a network  52 , a PC  60  and so on. The multi-function device  10  and the PC  60  are mutually communicable via the network  52 . The network  52  comprises a HUB  50 . 
     (Configuration of Multi-Function Device  10 ) 
     The multi-function device  10  comprises an operation unit  12 , a storage unit  14 , a print unit  16 , an LCD (Liquid Crystal Display)  18 , a first LED  20 , a second LED  22 , an I/O port  24 , and a control unit  30 . The operation unit  12  comprises a plurality of keys  12   a ,  12   b ,  12   c . The mode change key  12   a  is a key for setting the mode to either the first mode or the second mode. The first mode is a mode for setting the first and second LEDs  20 ,  22  to an output disabled state in an L-sleep state and a D-sleep state described later. The second mode is a mode for maintaining the first and second LEDs  20 ,  22  in an output enabled state in both the L-sleep state and the D-sleep state. The specific key  12   b  is a key for temporarily setting the first and second LEDs  20 ,  22  to the output enabled in the L-sleep state or the D-sleep state state while the first mode is being set. 
     The storage unit  14  stores image data (for instance, menu image data)  14   a  to be displayed on the LCD  18 . The storage unit  14  further stores a program  14   b  to be executed by the control unit  30 . The print unit  16  prints print data sent from the PC  60 . The LCD  18  displays various types of information. The first and second LEDs  20 ,  22  are provided on the rear face of the multi-function device  10 . The I/O port  24  is also provided on the rear face of the multi-function device  10 . The first and second LEDs  20 ,  22  are provided in the vicinity of the I/O port  24 . The specific key  12   b  is disposed in the vicinity of the I/O port  24  (in other words, in the vicinity of the first and second LEDs  20 ,  22 ). One end of a LAN cable  26  is connected to the I/O port  24 . The HUB  50  is connected to the other end of the LAN cable  26 . 
     The first LED  20  is an LED of a first color (for instance, an orange color). The first LED  20  shows information concerning a line speed of the network  52 . In the ensuing explanation, this information is referred to as “Speed.” In this embodiment, the first LED  20  is controlled to continuously light in a case where the line speed is 100 Mbps, and the first LED  20  is controlled to be unlit in a case where the line speed is 10 Mbps. 
     The second LED  22  is an LED of a second color (for instance, a green color) that is different from the first color. The second LED  22  shows information indicating whether the multi-function device  10  is being connected to the network  52  in a communicable manner. In the ensuing explanation, this information is referred to as “Link.” In addition, a state where the multi-function device  10  is being connected to the network  52  in a communicable manner is referred to as the “link-up state,” and a state where the multi-function device  10  is not being connected to the network  52  in a communicable manner is referred to as the “link-down state.” As an example of the link-down state, for instance, considered may be a state where the LAN cable  26  is not being connected to the I/O port  24 , or a state where the LAN cable  26  is being connected to the I/O port  24  but the HUB  50  is inoperative. In this embodiment, the second LED  22  is controlled to continuously light in the case of the link-up state, and the second LED  22  is controlled to be unlit in the case of the link-down state. 
     The second LED  22  further shows information indicating whether data being communicated (sent and/or received) via the network  52  exists (in other words, information indicating whether the multi-function device  10  is in the midst of communicating data). In the ensuing explanation, this information is referred to as “Activity.” In this embodiment, the second LED  22  is controlled to blink in a case where the multi-function device  10  is in the midst of communicating data. As described above, the state must be a link-up state in order to communicate data. Thus, when the communication of the multi-function device  10  is ended, the blinking of the second LED  22  is also ended, and the second LED  22  is controlled to countinusouly light. 
     The control unit  30  comprises a first clock supplying unit  32 , a second clock supplying unit  34 , a main CPU  36 , a sub CPU  38 , a PHY (Physical Layer) chip  40 , and a MAC (Media Access Control) chip  42 . The first clock supplying unit  32  supplies a clock to the main CPU  36 . The second clock supplying unit  34  supplies a clock to the sub CPU  38 . The operating frequency of the main CPU  36  is greater than the operating frequency of the sub CPU  38 . 
     The main CPU  36  executes various types of processing according to the program  14   b  stored in the storage unit  14 . The types of processing to be executed by the main CPU  36  are listed below. 
     (1) The main CPU  36  executes a processing for switching a light source of the LCD  18  between a lit state and an unlit state. The main CPU  36  further executes display processing for supplying the image data  14   a  stored in the storage unit  14  to the LCD  18 , and displaying the image data  14   a  on the LCD  18 . 
     (2) The main CPU  36  executes a processing of data to be communicated with the PC  60 . For example, the main CPU  36  executes a print processing for driving the print unit  16  based on a print command packet that is sent from the PC  60 . 
     (3) The main CPU  36  executes, in the case where the first mode is being set, a processing for switching the first and second LEDs  20 ,  22  between the output disabled state and the output enabled state. Specifically, the main CPU  36  executes a processing of sending a command for setting the first and second LEDs  20 ,  22  to the output disabled state or the output enabled state to the PHY chip  40  via the MAC chip  42 . In the ensuing explanation, the command for setting the first and second LEDs  20 ,  22  to the output enabled state is referred to as an “output enable command,” and the command for setting the first and second LEDs  20 ,  22  to the output disabled state is referred to as an “output disable command.” 
     The sub CPU  38  executes various types of processing according to the program  14   b  stored in the storage unit  14 . The types of processing to be executed by the sub CPU  38  are listed below. 
     (1) The sub CPU  38  executes a processing for switching the first clock supplying unit  32  between a clock supply execution state and a clock supply suspended state. Specifically, in this embodiment, there is a state where the clock supply to the main CPU  36  is suspended (sleep state of the main CPU  36 ). In this embodiment, in a state where the power of the multi-function device  10  is ON, the clock supply to the sub CPU  38  is constantly executed. 
     (2) The sub CPU  38  executes, in a case where a particular packet is received from the PC  60  while the main CPU  36  is in the sleep state, a processing (for instance, reply processing) of the particular packet. 
     (3) The main CPU  36  executes, in the case where the first mode is being set, a processing for switching the first and second LEDs  20 ,  22  between the output disabled state and output enabled state while the main CPU  36  is in the sleep state. Specifically, the sub CPU  38  executes a processing for sending the output enable command or the output disable command to the PHY chip  40  via the MAC chip  42 . 
     The PHY chip  40  executes a processing of the physical layer of the OSI (Open Systems Interconnection) reference model. The PHY chip  40  is connected to the I/O port  24 . The PHY chip  40  is connected to the MAC chip  42 . The PHY chip  40  is also connected to the first and second LEDs  20 ,  22 . The PHY chip  40  detects Speed, Link, and Activity. In a case where the PHY chip  40  receives the output enable command from the main CPU  36  or the sub CPU  38 , the PHY chip  40  executes a processing for supplying current to the first and second LEDs  20 ,  22  according to the Speed, Link, and Activity that have been detected by itself. In a case where the PHY chip  40  receives the output disable command from the main CPU  36  or the sub CPU  38 , the PHY chip  40  executes a processing for stopping the supply of current to the first and second LEDs  20 ,  22 . 
     The MAC chip  42  executes a processing of the MAC layer which is a sub layer of the data link layer of the OSI reference model. The MAC chip  42  is connected to the PHY chip  40 . The MAC chip  42  is connected to the main CPU  36  and the sub CPU  38 . 
     (States of Multi-Function Device  10 ) 
     The states of the multi-function device  10  are now explained.  FIG. 2  shows the situation of the state of the multi-function device  10  being changed.  FIG. 3  shows the relationship between the state of the multi-function device  10  and the state of the each unit  18 ,  20 ,  22 ,  36 ,  38 . Note that  FIG. 3  shows the state of the first and second LEDs  20 ,  22  in the case of the first mode being set. As shown in  FIG. 2 , the multi-function device  10  changes among the following states; namely, processing state  70 , stand-by state  72 , L-sleep (Light sleep) state  74 , and D-sleep (Deep sleep) state 76 . The processing state  70  is a state where the main CPU  36  is executing a specific processing. Here, as examples of the specific processing, considered may be the foregoing print processing, display processing, and the like. As shown in  FIG. 3 , in the processing state  70 , the clock is supplied to the main CPU  36  and the sub CPU  38 . In the processing state  70 , the light source of the LCD  18  is in the lit state, and the image data  14   a  is supplied to the LCD  18 . In addition, in the processing state  70 , the first and second LEDs  20 ,  22  are in the output enabled state. Specifically, the first and second LEDs  20 ,  22  are allowed the emission indicating Speed, Link, and Activity. 
     As shown in  FIG. 2 , when the main CPU  36  completes the foregoing specific processing (print processing, display processing or the like), the state proceeds to the stand-by state  72 . As shown in  FIG. 3 , in the stand-by state  72 , the clock is supplied to the main CPU  36  and the sub CPU  38 . In addition, in the stand-by state  72 , the light source of the LCD  18  is in the lit state, and the first and second LEDs  20 ,  22  are in the output enabled state. 
     As shown in  FIG. 2 , if a command is input for executing the foregoing spesific processing in the stand-by state  72  (for instance, reception of the print packet or operation of the key  12   c  (refer to  FIG. 1 ) by the user), the state proceeds to the processing state  70 . Moreover, if a state where a command for executing the foregoing specific processing is not input in the stand-by state  72  continues for a predetermined time, the state proceeds to the L-sleep state  74 . As shown in  FIG. 3 , in the L-sleep state  74 , the clock is supplied to the main CPU  36  and the sub CPU  38 . In the L-sleep state  74 , the light source of the LCD  18  is in the unlit state. If the mode is being set to the first mode, the first and second LEDs  20 ,  22  are in the output disabled state in the L-sleep state  74 . As explained in detail later, even in the output disabled state, if a condition (condition of S 30  or S 32  of  FIG. 6 ) is satisfied, the first and second LEDs  20 ,  22  temporarily become the output enabled state. If the mode is being set to the second mode, the first and second LEDs  20 ,  22  are maintained in the output enabled state even in the L-sleep state  74 . 
     As shown in  FIG. 2 , if the command is input for executing the foregoing specific processing in the L-sleep state  74 , the state proceeds to the processing state  70 . If a specific condition is satisfied in the L-sleep state  74 , the state proceeds to the D-sleep state  76 . In this embodiment, the foregoing specific condition is that data is not being communicated, and there is no packet for which the main CPU  36  should execute processing. As shown in  FIG. 3 , in the D-sleep state  76 , the clock supply to the main CPU  36  is suspended. That is, the main CPU  36  is in the sleep state. In the D-sleep state  76 , the light source of the LCD  18  is in the unlit state. If the mode is being set to the first mode, the first and second LEDs  20 ,  22  are in the output disabled state in the D-sleep state  76  (however, they temporarily become the output enabled state if a condition is satisfied). If the mode is being set to the second mode, the first and second LEDs  20 ,  22  are maintained in the output enabled state even in the D-sleep state  76 . 
     As shown in  FIG. 2 , if the command in input for executing the foregoing specific processing in the D-sleep state  76 , the state proceeds the L-sleep state  74  (in other words, the clock supply to the main CPU  36  is resumed), then proceeds to the processing state  70 . 
     In this embodiment, if the state of the multi-function device  10  is in the L-sleep state  74  and the D-sleep state  76 , the light source of the LED  18  is set to the unlit state. Specifically, the L-sleep state  74  and the D-sleep state  76  are states in which the user recognizes the multi-function device  10  to be in a low power consumption state (sleep state) upon observing the multi-function device  10 . Although the main CPU  36  will not receive the supply of the clock and be set to the sleep state if the state of the multi-function device  10  is in the D-sleep state  76 , the main CPU  36  will receive the supply of the clock and be set to a non-sleep state (normal performance state) if the state of the multi-function device  10  is in the processing state  70 , the stand-by state  72 , or the L-sleep state  74 . 
     (Processing To Be Executed by Main CPU  36  and Sub CPU  38 ) 
     Contents of the processing to be executed by the main CPU  36  and the sub CPU  38  when the mode is set to the first mode are now explained in detail. In this embodiment, the main CPU  36  basically executes the processing in a state where the clock is being supplied to the main CPU  36  (in other words, in the processing state  70 , the stand-by state  72 , and the L-sleep state  74 ). 
       FIG. 4  shows the flowchart of the processing to be executed by the main CPU  36  in the stand-by state  72 . The main CPU  36  monitors whether a state where a command for executing the foregoing specific processing is not input continues for a predetermined time (S 10 ). If the determination is YES in the foregoing case, the main CPU  36  sends the output disable command to the PHY chip  40  via the MAC chip  42  (S 12 ). Consequently, the PHY chip  40  suspends the supply of current to the first and second LEDs  20 ,  22 . The first and second LEDs  20 ,  22  are thereby turned off Although not shown in the flowchart, if the determination is YES at S 10 , the main CPU  36  sets the light source of the LCD  18  to the unlit state, and suspends the supply of the image data  14   a  to the LCD  18 . The multi-function device  10  thereby shifts from the stand-by state  72  to the L-sleep state  74 . 
       FIG. 5  shows the flowchart of the processing to be executed by the main CPU  36  in the L-sleep state  74 . The main CPU  36  monitors whether a command for executing the foregoing specific processing is input (S 20 ). If the determination is YES in the foregoing case, the main CPU  36  sends the output enable command to the PHY chip  40  via the MAC chip  42  (S 22 ). Consequently, the PHY chip  40  supplies current to the first and second LEDs  20 ,  22  according to Speed, Link, and Activity that have been detected by itself For example, if the line speed of the network  52  is of a predetermined value or higher, the PHY chip  40  supplies current to the first LED  20  and turns on the first LED  20 . However, if the line speed is lower than the predetermined value, the PHY chip  40  does not supply current to the first LED  20 . In addition, for example, in the link-up state, the PHY chip  40  supplies current to the second LED  22  and turns on the second LED  22 . However, in the link-down state, the PHY chip  40  does not supply current to the second LED  22 . If data is being communicated, the PHY chip  40  supplies current so that the second LED  22  will blink. 
     Although not shown in the flowchart, the sub CPU  38  monitors whether the foregoing specific condition (data is not being communicated, and there is no packet for which the main CPU  36  should execute processing) is satisfied in the L-sleep state  74 . If the determination is YES in the foregoing case, the sub CPU  38  sends a command for suspending the clock supply to the first clock supplying unit  32 . Consequently, the first clock supplying unit  32  suspends the clock supply to the main CPU  36 . The state is thereby shifted from the L-sleep state  74  to the D-sleep state  76 . 
     The sub CPU  38  monitors whether a command for executing the foregoing specific processing is input in the D-sleep state  76 . If the determination is YES in the foregoing case, the sub CPU  38  sends a command for resuming the clock supply to the first clock supplying unit  32 . Consequently, the first clock supplying unit  32  resumes the clock supply to the main CPU  36 . The multi-function device  10  thereby shifts from the D-sleep state  76  to the L-sleep state  74 . The main CPU  36  to which the clock supply was resumed executes the foregoing specific processing according to the input command. The main CPU  36  additionally sets the light source of the LCD  18  to the lit state, and resumes supplying the image data  14   a  to the LCD  18 . The main CPU  36  further sends the output enable command to the PHY chip  40  via the MAC chip  42 . The state thereby shifts from the L-sleep state  74  to the processing state  70 . 
       FIG. 6  shows the flowchart of the processing to be executed by the main CPU  36  in the L-sleep state  74 . The sub CPU  38  executes the processing showing in  FIG. 6  in the D-sleep state  76 . The main CPU  36  or the sub CPU  38  monitors the reception of a particular packet (S 30 ). The particular packet can also be rephrased as a packet other than packets for which the main CPU  36  should execute processing. As examples of the packets for which the main CPU  36  should execute processing, for instance, considered may be a print command packet, a packet for requesting the status of the multi-function device  10 , a TCP (Transmission Control Protocol) packet and the like. As an example of the particular packet, considered may be an ICMP (Internet Control Message Protocol) packet (ping). Even if the particular packet is received, the L-sleep state  74  or the D-sleep state  76  is maintained without shifting to the processing state  70 . If the particular packet is received, the main CPU  36  or the sub CPU  38  determines this to be YES at S 30 , and proceeds to S 34 . 
     The main CPU  36  or the sub CPU  38  also monitors whether the specific key  12   b  (refer to  FIG. 1 ) is operated (S 32 ). The specific key  12   b  can be rephrased as a key for performing operations other than the operations for which the main CPU  36  should execute processing. Even if the specific key  12   b  is operated, the L-sleep state  74  or the D-sleep state  76  is maintained without shifting to the processing state  70 . If the specific key  12   b  is operated, the main CPU  36  or the sub CPU  38  determines this to be YES at S 32 , and proceeds to S 34 . If the other keys  12   a ,  12   c  shown in  FIG. 1  are operated, the main CPU  36  or the sub CPU  38  determines that a command for executing the foregoing specific processing has been input, and executes various types of processing for shifting to the processing state  70  (for example, processing for resuming the clock supply to the main CPU  36 , processing for lighting the light source of the LCD  18 , processing for sending the output enable command, and the like). 
     At S 34 , the main CPU  36  or the sub CPU  38  sends the output enable command to the PHY chip  40  via the MAC chip  42 . Consequently, the PHY chip  40  supplies current to the first and second LEDs  20 ,  22  according to Speed, Link, and Activity that have been detected by itself. The main CPU  36  or the sub CPU  38  waits for a predetermined time to elapse from the time that the first and second LEDs  20 ,  22  are set to the output enabled state at S 34  (in other words, from the time that the output enable command is sent at S 34 ) (S 36 ). When the foregoing predetermined time elapsed, the main CPU  36  or the sub CPU  38  sends the output disable command to the PHY chip  40  via the MAC chip  42  (S 38 ). Consequently, the PHY chip  40  suspends the supply of current to the first and second LEDs  20 ,  22 . 
     Contents of the processing to be executed by the main CPU  36  and the sub CPU  38  in cases where the mode is set to the first mode have been described in detail above. If the mode is set to the second mode, the first and second LEDs  20 ,  22  are maintained in the output enabled state in the L-sleep state  74  and the D-sleep state  76 . Excluding this point, the processing to be executed by the main CPU  36  and the sub CPU  38  is the same as in the case of the foregoing first mode. 
     The network system  2  of this embodiment was explained in detail above. As described above, the multi-function device  10  is able to seek power saving by causing the light source of the LCD  18  to be in the unlit state in the L-sleep state  74 . Moreover, the multi-function device  10  is able to seek further power saving by suspending the clock supply to the main CPU  36  in the D-sleep state  76 . 
     The user is able to confirm Speed, Link, and Activity by viewing the emission state of the first and second LEDs  20 ,  22  in the processing state  70  and the stand-by state  72 . Meanwhile, in the L-sleep state  74  and the D-sleep state  76 , in normal, the necessity for causing the user to understand data communication information (information concerning a communication of data via the network  52 ) is low. In addition, the first and second LEDs  20 ,  22  are both provided at the rear face of the multi-function device  10 . Thus, in the L-sleep state  74  and the D-sleep state  76 , it is considered that the frequency of the user confirming the emission state of the first and second LEDs  20 ,  22  is low. In this embodiment, if the mode is set to the foregoing first mode, it is possible to realize power saving since the first and second LEDs  20 ,  22  are in the output disabled state in the L-sleep state  74  and the D-sleep state  76 . 
     If the first and second LEDs  20 ,  22  are the an output disabled state, the user is able to temporarily set the first and second LEDs  20 ,  22  to the output enabled state by sending the particular packet from the PC  60  to the multi-function device  10  (YES at S 30  of  FIG. 6 ). Moreover, if the first and second LEDs  20 ,  22  are in the output disabled state, the user is able to temporarily set the first and second LEDs  20 ,  22  to the output enabled state by operating the specific key  12   b  (refer to  FIG. 1 ) (YES at S 32  of  FIG. 6 ). Even if the determination is YES at S 30  or S 32  of  FIG. 6 , the L-sleep state  74  or the D-sleep state  76  is maintained. According to this embodiment, even if the multi-function device  10  is shifted to the L-sleep state  74  or the D-sleep state  76  and the first and second LEDs  20 ,  22  becomes the output disabled state, the user is able to confirm Speed, Link, and Activity while maintaining the L-sleep state  74  or the D-sleep state  76 . Even if the determination is YES at S 30  or S 32  of  FIG. 6 , it is possible to inhibit the increase in the power consumption since the first and second LEDs  20 ,  22  are not continuously in the output enabled state. 
     Since the foregoing specific key  12   b  (refer to  FIG. 1 ) is disposed in the vicinity of the I/O port  24  (in other words, in the vicinity of the first and second LEDs  20 ,  22 ), the user can operate the specific key  12   b  that is disposed in the vicinity of the first and second LEDs  20 ,  22  upon confirming the emission state of the first and second LEDs  20 ,  22 . 
     As evident from the foregoing explanation, the multi-function device  10  and the PC  60  of this embodiment are respectively examples of a “network device” and an “external device.” The first LED  20  and the second LED  22  are respectively examples of a “first light emitting element” and a “second light emitting element.” The main CPU  36  is an example of a “light element control unit,” a “first processing unit,” and an “image data supplying unit.” The sub CPU  38  is an example of a “second processing unit.” The I/O port  24  and the LCD  18  respectively correspond to a “receiving unit” and a “display unit.” 
     The processing state  70  (or the stand-by state  72  or the L-sleep state  74 ) of the multi-function device  10  in which the main CPU  36  is set to the non-sleep state as a result of the clock being supplied to the main CPU  36  is an example of a “first performance state,” and the D-sleep state  76  of the multi-function device  10  in which the main CPU  36  is set to the sleep state as a result of suspending the clock supply to the main CPU  36  is an example of a “second performance state.” 
     In addition, the processing state  70  (or the stand-by state  72 ) of the multi-function device  10  in which image data is supplied to the LCD  18  is an example of a “first performance state,” and the D-sleep state  76  (or the L-sleep state  74 ) of the multi-function device  10  in which image data is not supplied to the LCD  18  is an example of a “second performance state.” 
     Modified examples of the foregoing embodiment are listed below. 
     (1) In the foregoing embodiment, although the first and second LEDs  20 ,  22  are in the output disabled state in the L-sleep state  74  in the case of the first mode, they may also be in the output enabled state. Specifically, the first and second LEDs  20 ,  22  may be set to be in the output disabled state only in the D-sleep state  76 . In this modified example, the timing of switching the main CPU  36  between the sleep state and the non-sleep state and the timing of switching the first and second LEDs  20 ,  22  between the output disabled state and the output enabled state will coincide. 
     (2) In the foregoing embodiment, the L-sleep state  74  may be omitted. Specifically, if a state where a command for executing the foregoing specific processing is not input in the stand-by state  72  continues for the predetermined time (YES at S 10  of  FIG. 4 ), the clock supply to the main CPU  36  may be suspended, the light source of the LCD  18  may become the unlit state, and, in the first mode, the first and second LEDs  20 ,  22  may be in the output disabled state. 
     (3) In the foregoing embodiment, if the mode is set to the first mode, and a state where a command for executing the foregoing specific processing is not input in the stand-by state  72  continues for the predetermined time (YES at S 10  of  FIG. 4 ), the light source of the LCD  18  becomes the unlit state, and the first and second LEDs  20 ,  22  become the output disabled state (S 12  of  FIG. 4 ). Nevertheless, it the timing that the YES will be determined at S 10  of  FIG. 4  is known in advance, the first and second LEDs  20 ,  22  may be set to the output disabled state a predetermined period before the timing. Upon subsequently reaching that timing, the light source of the LCD  18  may be set to the unlit state. 
     (4) In the foregoing embodiment, the main CPU  36  is changed to the sleep state by discontinuing the clock supply to the main CPU  36 . Nevertheless, the main CPU  36  may be changed to the sleep state by reducing the clock frequency without discontinuing the clock supply to the main CPU  36 . 
     (5) In the foregoing embodiment, in the case of the first mode, the first and second LEDs  20 ,  22  are set to the output disabled state in the L-sleep state  74  or the D-sleep state  76 . Nevertheless, power saving may be realized by setting the first and second LEDs  20 ,  22  to the output enabled state and reducing the amount of current to be supplied to the first and second LEDs  20 ,  22  in comparison to the processing state  70  or the stand-by state  72 . That is, power saving may be realized by allowing the first and second LEDs  20 ,  22  to emit light with high luminance in the processing state  70  or the stand-by state  72 , and allowing the first and second LEDs  20 ,  22  to emit light with low luminance in the L-sleep state  74  or the D-sleep state  76 . Furthermore, power saving may be realized by allowing the first and second LEDs  20 ,  22  to continuously light in the processing state  70  or the stand-by state  72 , and allowing the first and second LEDs  20 ,  22  to blink in the L-sleep state  74  or the D-sleep state  76  (in other words, to reduce the emission frequency). 
     (6) In the foregoing embodiment, the PHY chip  40  detects Speed, Link, and Activity, and controls the amount of current to be supplied to the first and second LEDs  20 ,  22  according to the detection result. Nevertheless, the main CPU  36 , the sub CPU  38 , or the MAC chip  42  may also use information from the PHY chip  40  to detect Speed, Link, and Activity, and send a command for lighting, blinking, unlighting or the like to the PHY chip  40  according to the detection result. 
     (7) In addition, the processing shown in  FIG. 4  and  FIG. 5  may be executed by the sub CPU  38 . In the case of the L-sleep state  74 , the processing shown in  FIG. 6  may be executed by the sub CPU  38 . 
     (8) In the foregoing embodiment, the multi-function device  10  is configured to be switchable between the first mode and the second mode. Nevertheless, this mode switching may be omitted, and the multi-function device  10  may be configured such that the first and second LEDs  20 ,  22  are always in the output disabled state in the L-sleep state  74  and the D-sleep state  76 . 
     (9) The technology of the foregoing embodiment can also be applied to other network devices of PC, server, printer, scanner, telephone device, facsimile device and the like. 
     (10) The foregoing term of “non-sleep state” may also be rephrased, but not limited to, as “execution state.” In addition, the foregoing term of “sleep state” may also be rephrased, but not limited to, as “state with lower power consumption than the non-sleep state.”