Patent Publication Number: US-8543853-B2

Title: Information processing apparatus with power saving mode and method for controlling information processing apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 12/434,497, filed on May 1, 2009, entitled “INFORMATION PROCESSING APPARATUS WITH POWER SAVING MODE AND METHOD FOR CONTROLLING INFORMATION PROCESSING APPARATUS”, which claims priority to Japanese Patent Application No. 2009-082082 filed Mar. 30, 2009, and Japanese Patent Application No. 2008-120406 filed May 2, 2008, each of which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an information processing apparatus and a method for controlling an information processing apparatus. 
     2. Description of the Related Art 
     For the purpose of environmental protection, the consumption of large amounts of electric power in electronic devices is restricted. To this end, an information processing apparatus can be configured to operate in a power saving mode, according to which electric power supply to each module (such as a storage unit) of the apparatus can be selectively stopped if necessary. 
     For example, in order to reduce the consumption amount of electric power, it maybe relatively simple to restrictively supply electric power to each module only when the electric power supply is necessary. However, the storage unit may tend to become damaged if the number of ON/OFF times increases. Therefore, if users frequently repeat the ON/OFF operation, a storage unit may be damaged at an earlier time compared to an expected product lifetime of an information processing apparatus that incorporates the storage unit. As a result, the information processing apparatus may fail to operate normally before the product lifetime expires. The number of ON/OFF times of a storage unit is a number of times assured for the storage unit, until which the electric power supply to the storage unit can be safely increased or decreased without causing any failure in the storage unit. The product lifetime of an information processing apparatus is an operation time assured for the information processing apparatus, during which the information processing apparatus can operate without failure. 
     An information processing apparatus can also set a standby time beforehand and, if the processing of a job that involves activation of a storage unit is completed, it may be useful to wait for a while (i.e., the standby time) before stopping electric power supplied to the storage unit. 
     In general, the standby time of a storage unit can be calculated based on a product lifetime of an information processing apparatus and the number of ON/OFF times assured for the storage unit. As discussed in Japanese Patent Application Laid-Open No. 2005-186426, the standby time may be obtained by dividing the product lifetime of the apparatus by the number of ON/OFF times assured for the storage unit. In this case, the apparatus is controlled to continuously supply electric power to the storage unit until the standby time has elapsed. 
     However, the system discussed in the Japanese Patent Application Laid-Open No. 2005-186426 may not be able to easily stop electric power supplied to the storage unit, even though the system may be able to prevent the number of ON/OFF times of the storage unit from exceeding a predetermined value before the product lifetime of the apparatus expires. The number of ON/OFF times of a storage unit is a number of times assured for the storage unit, until which the electric power supply to the storage unit can be safely increased or decreased without causing any failure in the storage unit. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, an information processing apparatus is provided that includes a storage unit configured to store data, a supply unit configured to supply electric power to the storage unit, a determination unit configured to determine whether to cause the information processing apparatus to operate in a power saving mode, a measuring unit configured to measure an elapsed time after a power source of the information processing apparatus is turned on and until the determination unit determines to cause the information processing apparatus to operate in a power saving mode, and a control unit configured to control the supply unit to decrease electric power supplied from the supply unit to the storage unit at a timing determined based on the elapsed time and a predetermined reference time, in case that the determination unit determines to cause the information processing apparatus to operate in a power saving mode. 
     Further features and aspects of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments and features of the invention and, together with the description, serve to explain at least some of the principles of the invention. 
         FIG. 1  illustrates a configuration of a system according to a first exemplary embodiment. 
         FIG. 2  is a block diagram illustrating a configuration of a printer according to the first exemplary embodiment. 
         FIG. 3  is a block diagram illustrating a configuration of a control unit according to the first exemplary embodiment. 
         FIG. 4  is a circuit diagram illustrating a state of electric power supplied to constituent components of a power source unit and a configuration of power supply control for constituent components of a CPU and a power supply control unit according to the first exemplary embodiment. 
         FIG. 5  is a flowchart illustrating example control that can be performed by the printer according to the first exemplary embodiment. 
         FIG. 6  illustrates an example of a relationship between an elapsed time measured by a timer and an operation time of the printer, the count-up of which starts upon turning on the power source, according to the first exemplary embodiment. 
         FIG. 7  illustrates an example of transitional states of a CPU and an HDD in their ON/OFF operations in comparison with a transitional state of a power supply operation according to the first exemplary embodiment. 
         FIG. 8  is a circuit diagram illustrating a state of electric power supplied to constituent components of a power source unit and a configuration of power supply control for constituent components of a CPU and a power supply control unit according to a second exemplary embodiment. 
         FIG. 9  illustrates an example of transitional states of a CPU and an HDD in their ON/OFF operations in comparison with a transitional state of a power supply operation according to the second exemplary embodiment. 
         FIG. 10  is a circuit diagram illustrating a state of electric power supplied to constituent components of a power source unit and a configuration of power supply control for constituent components of a CPU and a power supply control unit according to a third exemplary embodiment. 
         FIG. 11  illustrates an example of transitional states of a CPU and an HDD in their ON/OFF operations in comparison with a transitional state of a power supply operation according to the third exemplary embodiment. 
         FIG. 12  is a flowchart illustrating example control that can be performed by the printer according to a fourth exemplary embodiment. 
         FIG. 13  is a flowchart illustrating example control that can be performed by the printer according to a fifth exemplary embodiment. 
         FIG. 14  illustrates an example of transitional states of a CPU and an HDD in their ON/OFF operations in comparison with a transitional state of a power supply operation according to a conventional exemplary embodiment. 
         FIG. 15  is a circuit diagram illustrating a state of electric power supplied to constituent components of a power source unit and a configuration of power supply control for constituent components of a CPU and a power supply control unit according to a sixth exemplary embodiment. 
         FIG. 16  is a flowchart illustrating example control that can be performed by the printer according to the sixth exemplary embodiment. 
         FIG. 17  illustrates a transitional state of power supply to a CPU and an HDD according to a conventional technique. 
         FIG. 18  illustrates a transitional state of power supply to a CPU and an HDD according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Various exemplary embodiments, features, and aspects of the invention will be described in detail below with reference to the drawings. In the drawings, elements and parts which are identical throughout the views are designated by identical reference numerals, and duplicate description thereof is omitted. 
       FIG. 1  illustrates a configuration of a system according to a first exemplary embodiment. The system illustrated in  FIG. 1  includes a personal computer (i.e., PC)  101 , a printer  102 , and a network  103 . The PC  101  and the printer  102 , which are connected via the network  103 , can perform processing for transmitting and receiving data (e.g., image data) via the network  103 . The connection between the PC  101  and the printer  102  may be realized by a local connection. 
       FIG. 2  is a block diagram illustrating a configuration of the printer  102  according to the first exemplary embodiment. The printer  102  is an example of an information processing apparatus according to the present exemplary embodiment. However, the information processing apparatus according to another exemplary embodiment may also be an apparatus other than the printer  102 . 
     The printer  102  includes a control unit  201  that can control an operation unit  202 , a reading unit  203 , a printing unit  204 , and a power supply unit  205 . Namely, the control unit  201  can control the constituent components  202  to  205  of the printer  102 . The control unit  201  is described below in more detail with reference to  FIG. 3 . The operation unit  202  may include a display unit and an input unit. In one version, the display unit may provide an operation screen that enables users to operate the printer  102 . The input unit may accept various operations entered by users to operate the printer  102 . The reading unit  203  can read image data from an original (e.g., a paper document) and can input the read image data to the control unit  201 . When the printing unit  204  receives image data processed by the control unit  201 , the printing unit  204  can execute processing for forming an image on an output sheet based on the received image data. The power supply unit  205  can supply electric power to the constituent components  201  to  204  of the printer  102 . 
       FIG. 3  is a block diagram illustrating a configuration of the control unit  201  according to the first exemplary embodiment. The control unit  201  includes a central processing unit (i.e., CPU)  301 , a read only memory (i.e., ROM)  302 , a random access memory (i.e., RAM)  303 , a hard disk drive (i.e., HDD)  304 , an image processor  305 , an image memory  306 , a network interface (i.e., IF)  307 , and a power supply control unit  308 . 
     The CPU  301  can control the constituent components  202  to  205  of the printer  102  and the constituent components  302  to  308  of the printer control unit  201  based on programs rasterized into the RAM  303 . The ROM  302 , which may be constituted by a nonvolatile storage medium, may store a boot program that can be executed by the CPU  301 . The RAM  303 , which may be constituted by a volatile storage medium, is a storage medium into which the OS or application programs executed by the CPU  301  can be rasterized from the HDD  304 . The HDD  304 , which may be constituted by a nonvolatile storage medium, may store the OS and the application programs that the CPU  301  can execute. The image processor  305  can execute various processing on image data stored in the image memory  306 . 
     The image memory  306 , which may be constituted by a volatile storage medium, can temporarily store image data received from the reading unit  203  or the network IF  307 . The network IF  307  can input and output image data from and to an external apparatus (e.g., the PC  101 ). The power supply control unit  308  can switch the state of electric power supplied from the power source unit  205  to the constituent components  201  to  204  of the printer  102  and to the constituent components  301  to  307  of the control unit  201 . 
       FIG. 4  is a circuit diagram illustrating a state of electric power supplied to constituent components of the power source unit  205  and a configuration of power supply control for constituent components of the CPU  301  and the power supply control unit  308  according to the first exemplary embodiment. In  FIG. 4 , an arrow of a solid line indicates a power supply route and an arrow of a dotted line indicates a power supply control route. 
     An alternating-current (AC) power source  401  can supply electric power to a sub power source  402  and a main power source  403 . The sub power source  402  can supply electric power to constituent components of the power supply control unit  308 . The main power source  403  can supply electric power to the CPU  301  and the HDD  304  via an ON/OFF switching unit  601 . The main power source  403  may be configured to supply electric power, via an ON/OFF switching unit, to the constituent components  201  to  205  of the printer  102  and the constituent components  301  to  307  of the control unit  201 . 
     A trigger detection unit  501  can detect an input data received from the operation unit  202 , the reading unit  203 , or the network IF  307 . The trigger detection unit  501  can turn the ON/OFF switching unit  601  on in response to the input data. A timer  502  can measure a power ON time of the printer  102 . The timer  502  may also be able to measure a power OFF time of the printer  102 , for example, using a battery. 
     The ON/OFF switching unit  601  performs ON/OFF switching operations under the control of the CPU  301  and the trigger detection unit  501 , to supply electric power from the main power source  403  to the CPU  301  and the HDD  304 . In the first exemplary embodiment, the trigger detection unit  501  performs ON control for the ON/OFF switching unit  601  while the CPU  301  performs OFF control for the ON/OFF switching unit  601 . As a result, the CPU  301  and the HDD  304  can be turned on and off in response to the ON/OFF switching of the ON/OFF switching unit  601 . 
       FIG. 5  is a flowchart illustrating example control that can be performed by the printer  102  according to the first exemplary embodiment. In one version, to execute the control processing of the flowchart illustrated in  FIG. 5 , the CPU  301  reads and executes a program loaded into the RAM  303  from the HDD  304 . 
     In the exemplary embodiment, the job includes a reading job performed by the reading unit  203 , a print job performed by the printing unit  204 , an operation response job performed by the operation unit  202 , and a network response job performed by the network IF  307 . The above-described jobs are roughly classified into a job group that involves, and may even require activation of the HDD  304 , and another job group that does not involve (i.e., may not require) activation of the HDD  304 . In general, the reading job and the print job belong to the job group that involved and may even require activation of the HDD  304 . The operation response job and the network response job belong to the job group that does not involve activation of the HDD  304 . 
     In step S 101 , the CPU  301  determines whether the power source of the printer  102  is turned on. If in step S 101  the CPU  301  determines that the power source of the printer  102  is in an ON state (YES in step S 101 ), the processing proceeds to step S 102 . If it is determined that the power source of the printer  102  is in an OFF state (NO in step S 101 ), then step S 101  is repeated. When the processing proceeds to step S 102 , the CPU  301  causes the timer  502  to start measuring the elapsed time “t.” 
     In step S 102 , the CPU  301  determines whether there is any input job. The trigger detection unit  501  detects a trigger of the input job. If in step S 102  the CPU  301  determines that an input job is present (YES in step S 102 ), then processing proceeds to step S 103 , where the trigger detection unit  501  performs the ON control for the ON/OFF switching unit  601  to start supplying electric power to the HDD  304 . If it is determined that there is no input job present (NO in step S 102 ), then step S 102  is repeated. In step S 104 , the CPU  301  executes job processing. More specifically, to perform the job processing, the CPU  301  controls a constituent component of the printer  102 , which may be used to process a job (i.e., a processing object), according to a job type. If the processing of step S 104  is completed and there is not any subsequent job to be processed next, the CPU  301  determines that the present state satisfies a condition for stopping electric power supplied from the power source unit  205  to the HDD  304  via the ON/OFF switching unit  601 . The processing proceeds to step S 105 . 
     In step S 105 , the CPU  301  determines whether the elapsed time “t” is equal to or greater than a reference time “S.” In other words, the CPU  301  determines whether to stop the electric power supplied to the HDD  304  based on a comparison result. The elapsed time “t” is a time that can be measured by the timer  502  until the processing proceeds to step S 105 . The reference time “S” represents a standby time for the HDD  304 , which is generally a fixed value. The reference time “S” is time information that can be referred to by the CPU  301  to determine whether to stop the electric power supplied to the HDD  304 . When “P” represents the product lifetime of the printer  102  and “H” represents the number of ON/OFF times that is assured for the HDD  304 , a formula S=P/H may define the reference time “S.” 
     The reference time “S” can be stored in the HDD  304  and can optionally be loaded into the RAM  303 . The printer  102  may calculate the reference time “S.” The HDD  304  may store the reference time “S” beforehand. If in step S 105  the CPU  301  determines that the elapsed time “t” is equal to or greater than the reference time “S” (YES in step S 105 ), the processing proceeds to step S 106 . If in step S 105  the CPU  301  determines that the elapsed time “t” is less than the reference time “S” (NO in step S 105 ), the processing proceeds to step S 109 . 
     In step S 106 , i.e., when the elapsed time “t” is equal to or greater than the reference time “S” in step S 105 , the CPU  301  executes the OFF control for the ON/OFF switching unit  601  to stop the electric power supplied to the HDD  304  at this timing (i.e., a first timing). In step  106 , the CPU  301  may also wait for a predetermined time before stopping the electric power supplied to the HDD  304 . 
     In step S 107 , the CPU  301  subtracts the reference time “S” from the elapsed time “t.” In step S 108 , the CPU  301  determines whether the power source of the printer  102  is turned off. If in step S 108  the CPU  301  determines that the power source of the printer  102  is in an OFF state, the CPU  301  terminates the processing of the routine illustrated in  FIG. 5 . When the power source of the printer  102  is turned off, the timer  502  terminates the measurement of the elapsed time “t.” When the power source of the printer  102  is turned off (YES in step S 108 ), the CPU  301  stores the value of the elapsed time “t” in the HDD  304 . The CPU  301  reads the stored value of the elapsed time “t” from the HDD  304  when the power source of the printer  102  is turned on in the next processing of step S 101 . If in step S 108  the CPU  301  determines that the power source of the printer  102  is in an ON state (NO in step S 108 ), the processing returns to step S 102 . 
     If in step S 105  the CPU  301  determines that the elapsed time “t” is less than the reference time “S” (NO in step S 105 ), then processing proceeds to step S 109 , where the CPU  301  calculates a value of a predetermined standby time “w.” The standby time “w” is a time set as a temporal duration from a termination of the job processing in step S 104  to an initiation of HDD power supply stop processing in step S 112 , in a state where no job is input in the printer  102 . The standby time “w” can be calculated by subtracting the elapsed time “t” from the reference time “S”. Then, in step S 110 , the CPU  301  waits for a predetermined time that is equivalent to the standby time “w” calculated in step S 109 , while continuously supplying electric power to the HDD  304 . 
     In step S 111 , the CPU  301  determines whether any job is input in the standby state of step S 110 . If in step S 111  the CPU  301  determines that an input job is present (YES in step S 111 ), the processing returns to step S 104 . If in step S 111  the CPU  301  determines that there is not any input job (NO in step S 111 ), the processing proceeds to step S 112 . In step S 112 , the CPU  301  executes the OFF control for the ON/OFF switching unit  601  to stop the electric power supplied to the HDD  304  at this timing (i.e., second timing). In step S 113 , the CPU  301  resets the elapsed time “t” to 0. After completing the processing of step S 113 , the processing proceeds to step S 108 . 
     In the above-described example, the timer  502  measures the elapsed time only when the power source of the printer  102  is in a turned-on state. However, the timer  502  can continuously measure the elapsed time even after the power source of the printer  102  is turned off. In this case, only when the processing initially proceeds to step S 102  after starting the operation of the printer  102 , the timer  502  starts measuring the elapsed time “t.” When the CPU  301  terminates the processing, the timer  502  does not stop measuring the elapsed time “t” and continuously measures the elapsed time “t” even after the processing is terminated. 
     In the above-described processing in step S 106  or step S 112 , the CPU  301  stops supplying electric power to the HDD  304 . Alternatively, the CPU  301  can reduce the amount of electric power supplied to the HDD  304 . For example, as a method for reducing the electric power supplied to the HDD  304 , it is possible to stop the electric power supplied to a motor that is configured to rotate a disk of the HDD  304 . In this state, the CPU  301  cannot read and write data from and to the HDD  304 . 
       FIG. 6  illustrates an example of a relationship between the elapsed time “t” measured by the timer  502  and an operation time “p” of the printer  102 , the count-up of which starts upon turning on the power source, in the first exemplary embodiment.  FIG. 6  illustrates, in its lower part, a transition of the elapsed time “t” when the reference time “S” is one hour and illustrates, in its upper part, a corresponding transition of the ON/OFF state of the power source of the HDD  304 . In  FIG. 6 , the scale of the abscissa is sufficiently large compared to a processing time of each job, which is finished immediately upon entering in  FIG. 6 . 
     At the moment when the processing of a job  1  or a job  2  is completed, the elapsed time “t” is less than the reference time (=one hour). Therefore, the CPU  301  waits for a while until the elapsed time “t” reaches one hour and then the CPU  301  stops the electric power supplied to the HDD  304 . This procedure corresponds to a case where the processing proceeds from step S 105  to step S 109 . On the other hand, at the moment when the processing of a job  4  or a job  5  is completed, the elapsed time “t” is longer than the reference time (=one hour). Therefore, the CPU  301  immediately stops the electric power supplied to the HDD  304 . This procedure corresponds to a case where the processing proceeds from step S 105  to step S 106 . 
     If a long time has elapsed in a state where no electric power is supplied to the HDD  304 , for example, when the time “p” is in the duration from 10 to 18 hours, the elapsed time “t” increases correspondingly. As a result, the CPU  301  can continuously execute the processing for stopping electric power supplied to the HDD  304 , after the job processing is completed, until the accumulated elapsed time “t” decreases to a value less than the reference time (=one hour). 
       FIG. 7  illustrates an example of transitional states of the CPU  301  and the HDD  304  in their ON/OFF operations in comparison with a transitional state of a power supply operation according to the first exemplary embodiment. In  FIG. 7 , a hatched region indicates the amount of electric power that can be reduced compared to that in a conventional case (see, e.g.,  FIG. 14 ). A job “A” is a job that may involve, and may even require, activation of the HDD  304 . A job “B” is a job that does not involve (i.e., does not require) activation of the HDD  304 . 
     As described above, an information processing apparatus according to the first exemplary embodiment can appropriately control the electric power supplied to a storage unit based on a reference time and an elapsed time. Accordingly, aspects of the present invention may provide an information processing apparatus and a method for controlling the information processing apparatus, which can appropriately control power supply to a storage unit based on a reference time and an elapsed time. The first exemplary embodiment takes a power ON time of an HDD into consideration to determine whether to execute the processing for stopping electric power supplied to the HDD. Therefore, the first exemplary embodiment may be capable of easily stopping the electric power supplied to the HDD. 
     A block diagram illustrating a configuration of a system according to a second exemplary embodiment is similar to that of the above-described first exemplary embodiment illustrated in  FIG. 1 , therefore its description is not repeated. A block diagram illustrating a configuration of the printer  102  according to the second exemplary embodiment is similar to that of the first exemplary embodiment illustrated in  FIG. 2 , therefore its description is not repeated. 
     A block diagram illustrating a configuration of the control unit  201  according to the second exemplary embodiment is similar to that of the first exemplary embodiment illustrated in  FIG. 3 , therefore its description is not repeated.  FIG. 8  is a circuit diagram illustrating a state of electric power supplied to constituent components of the power source unit  205  and a configuration of power supply control for constituent components of the CPU  301  and the power supply control unit  308  according to the second exemplary embodiment. 
     The circuit diagram illustrated in  FIG. 8  is different from that of the first exemplary embodiment (illustrated in FIG.  4 ) in that an additional ON/OFF switching unit  602  is provided. Under the control of the CPU  301 , the ON/OFF switching unit  602  can perform ON/OFF control of electric power supplied to the HDD  304 . 
     A flowchart illustrating overall control of the printer  102  according to the second exemplary embodiment is fundamentally similar to that of the first exemplary embodiment illustrated in  FIG. 5  and includes the following control contents. 
     Example control processing according to the second exemplary embodiment is described below with reference to  FIG. 5 . In step S 102  and step S 111 , the CPU  301  determines whether there is any input job that involves activation of the HDD  304 . 
     In step S 103 , the CPU  301  executes the ON control for the ON/OFF switching unit  602  to start supplying electric power to the HDD  304 . In step S 106 , the CPU  301  executes the OFF control for the ON/OFF switching unit  602  to stop the electric power supplied to the HDD  304 .  FIG. 9  illustrates an example of transitional states of the CPU  301  and the HDD  304  in their ON/OFF operations in comparison with a transitional state of a power supply operation according to the second exemplary embodiment. 
     In  FIG. 9 , a hatched region indicates the amount of electric power that can be reduced compared to that in a conventional case (see, e.g.,  FIG. 14 ). The job “A” is a job that may involve, and even require, activation of the HDD  304 . The job “B” is a job that does not involve (i.e., does not require) activation of the HDD  304 . 
     As described above, an information processing apparatus according to the second exemplary embodiment can appropriately control the electric power supplied to a storage unit based on a reference time and an elapsed time. The second exemplary embodiment takes a power ON time of an HDD into consideration to determine whether to execute the processing for stopping electric power supplied to the HDD. Therefore, the second exemplary embodiment may be capable of easily stopping the electric power supplied to the HDD. 
     If a job entered in a state where no electric power is supplied to the HDD  304  does not involve activation of the HDD, the second exemplary embodiment can execute job processing without activating the HDD  304 . Therefore, the second exemplary embodiment may be able to reduce a great amount of electric power consumption. 
     A block diagram illustrating a configuration of a system according to a third exemplary embodiment is similar to that of the above-described first exemplary embodiment illustrated in  FIG. 1 , therefore its description is not repeated. A block diagram illustrating a configuration of the printer  102  according to the third exemplary embodiment is similar to that of the first exemplary embodiment illustrated in  FIG. 2 , therefore its description is not repeated. 
     A block diagram illustrating a configuration of the control unit  201  according to the third exemplary embodiment is similar to the configuration of the first exemplary embodiment illustrated in  FIG. 3  and its description is not provided below.  FIG. 10  is a circuit diagram illustrating a state of electric power supplied to constituent components of the power source unit  205  and a configuration of power supply control for constituent components of the CPU  301  and the power supply control unit  308  according to the third exemplary embodiment. 
     The circuit diagram illustrated in  FIG. 10  is different from that of the first exemplary embodiment (illustrated in  FIG. 4 ) in that an HDD power control unit  503  and the ON/OFF switching unit  602  are additionally provided. Under the control of the HDD power control unit  503 , the ON/OFF switching unit  602  can perform ON/OFF control of electric power supplied to the HDD  304 . A flowchart illustrating overall control of the printer  102  according to the third exemplary embodiment is fundamentally similar to that of the first exemplary embodiment illustrated in  FIG. 5 , however, includes the following control contents. 
     Example control processing according to the third exemplary embodiment is described below with reference to  FIG. 5 . In step S 103 , the trigger detection unit  501  executes the ON control for the ON/OFF switching unit  601  immediately before executing the job processing. The CPU  301  executes the OFF control for the ON/OFF switching unit  601  immediately after completing the job processing. 
     The HDD power control unit  503  can execute the processing of steps S 102  to S 103  and steps S 105  to S 112 . Namely, in the present exemplary embodiment, the CPU  301  may not execute the processing of steps S 102  to S 103  and steps S 105  to S 112 .  FIG. 11  illustrates examples of transitional states of the CPU  301  and the HDD  304  in their ON/OFF operations in comparison with a transitional state of a power supply operation according to the third exemplary embodiment. In  FIG. 11 , a hatched region indicates the amount of electric power that can be reduced compared to that in a conventional case (see, e.g.,  FIG. 14 ). The job “A” is a job that may involve, and even require activation of the HDD  304 . The job “B” is a job that does not involve (i.e., does not require) activation of the HDD  304 . 
     As described above, an information processing apparatus according to the third exemplary embodiment can appropriately control the electric power supplied to a storage unit based on a reference time and an elapsed time. The third exemplary embodiment takes a power ON time of an HDD into consideration to determine whether to execute the processing to stop the electric power supplied to the HDD. Therefore, the third exemplary embodiment may be able to easily stop the electric power supplied to the HDD. 
     The third exemplary embodiment can stop the electric power supplied to the CPU  301  if job processing is not performed. Therefore, the third exemplary embodiment may be capable of further reducing electric power consumption. 
     A block diagram illustrating a configuration of a system according to a fourth exemplary embodiment is similar to the configuration of the first exemplary embodiment illustrated in  FIG. 1 , and thus its description is not repeated. A block diagram illustrating a configuration of the printer  102  according to the fourth exemplary embodiment is similar to the configuration of the first exemplary embodiment illustrated in  FIG. 2 , and thus its description is not repeated. A block diagram illustrating a configuration of the control unit  201  according to the fourth exemplary embodiment is similar to the configuration of the first exemplary embodiment illustrated in  FIG. 3 , and thus its description is not repeated. 
     A circuit diagram illustrating a state of electric power supplied to constituent components of the power source unit  205  and a configuration of power supply control for constituent components of the CPU  301  and the power supply control unit  308  according to the fourth exemplary embodiment may be similar to the circuit diagram of the first exemplary embodiment illustrated in  FIG. 4 , and therefore its description is not repeated.  FIG. 12  is a flowchart illustrating example control that can be performed by the printer  102  according to the fourth exemplary embodiment. In one version, to execute the control processing of the flowchart illustrated in  FIG. 12 , the CPU  301  reads and executes a program loaded into the RAM  303  from the HDD  304 . 
     In step S 201 , the CPU  301  determines whether the power source of the printer  102  is turned on. If in step S 201  the CPU  301  determines that the power source of the printer  102  is in an ON state (YES in step S 201 ), the processing proceeds to step S 202 . If it is determined that the power source of the printer  102  is in an OFF state (NO in step S 201 ), then step S 201  is repeated. When the processing proceeds to step S 202 , the timer  502  starts measuring the elapsed time “t.” 
     In step S 202 , the CPU  301  determines whether there is any input job. The trigger detection unit  501  detects a trigger of the input job. If in step S 202  the CPU  301  determines that an input job is present (YES in step S 202 ), then processing proceeds to step S 203 , where the trigger detection unit  501  performs the ON control for the ON/OFF switching unit  601  to start supplying electric power to the HDD  304 . If the CPU determines that there is no input job present (NO in step S 202 ), then step S 202  is repeated. In step S 204 , the CPU  301  executes job processing. More specifically, to perform the job processing, the CPU  301  controls a constituent component of the printer  102 , which may be used to process a job (i.e., a processing object), according to a job type. If the processing of step S 204  is completed and there is not any job to be next processed, the CPU  301  determines that the present state satisfies a condition for stopping electric power supplied from the power source unit  205  to the HDD  304  via the ON/OFF switching unit  601 . The processing proceeds to step S 205 . 
     In step S 205 , the CPU  301  determines whether a sum of the elapsed time “t” and a storage time “r” is equal to or greater than a reference time “S.” In other words, the CPU  301  determines whether to stop the electric power supplied to the HDD  304  based on a comparison result. The elapsed time “t” is a time that can be measured by the timer  502  until the processing proceeds to step S 205 . The storage time “r” is a value that can be calculated in the previous step S 207  of the loop processing including steps S 202  to S 208 . 
     The reference time “S” represents a standby time for the HDD  304 , which is generally a fixed value. The reference time “S” is a time that can be referred to by the CPU  301  to determine whether to stop the electric power supplied to the HDD  304 . When “P” represents the product lifetime of the printer  102  and “H” represents the number of ON/OFF times that can be assured for the HDD  304 , a formula S=P/H may define the reference time “S.” The reference time “S” can be stored in the HDD  304  and can optionally be loaded into the RAM  303 . The printer  102  may calculate the reference time “S.” The HDD  304  may store the reference time “S” beforehand. If in step S 205  the CPU  301  determines that the sum of the elapsed time “t” and the storage time “r” is equal to or greater than the reference time “S” (YES in step S 205 ), the processing proceeds to step S 206 . If in step S 205  the CPU  301  determines that the sum of the elapsed time “t” and the storage time “r” is less than the reference time “S” (NO in step S 205 ), the processing proceeds to step S 209 . 
     In step S 206 , i.e., when the sum of the elapsed time “t” and the storage time “r” is equal to or greater than the reference time “S” in step S 205 , the CPU  301  executes the OFF control for the ON/OFF switching unit  601  to stop the electric power supplied to the HDD  304  at this timing (i.e., first timing). In step S 206 , the CPU  301  may wait for a predetermined time before stopping the electric power supplied to the HDD  304 . 
     In step S 207 , the CPU  301  subtracts the reference time “S” from the sum of the elapsed time “t” and the storage time “r” and sets an obtained value as a new storage time “r.” After completing the processing of step S 207 , the timer  502  resets the elapsed time “t” to 0. 
     In step S 208 , the CPU  301  determines whether the power source of the printer  102  is turned off. If in step S 208  the CPU  301  determines that the power source of the printer  102  is in an OFF state, the CPU  301  terminates the processing of the routine illustrated in  FIG. 12 . When the power source of the printer  102  is turned off, the timer  502  terminates the measurement of the elapsed time “t.” When the power source of the printer  102  is turned off (YES in step S 208 ), the CPU  301  stores the value of the storage time “r” in the HDD  304 . The CPU  301  reads the stored value of the storage time “r” from the HDD  304  when the power source of the printer  102  is turned on in the next processing of step S 201 . If in step S 208  the CPU  301  determines that the power source of the printer  102  is in an ON state (NO in step S 208 ), the processing returns to step S 202 . 
     In step S 209 , i.e., when the sum of the elapsed time “t” and the storage time “r” is less than the reference time “S” in step S 205 , the CPU  301  calculates a value of a predetermined standby time “w.” The standby time “w” is a time set as a temporal duration from a termination of the job processing in step S 204  to an initiation of HDD power supply stop processing in step S 212 , in a state where no job is input in the printer  102 . The standby time “w” can be calculated by subtracting the sum of the elapsed time “t” and the storage time “r” from the reference time “S”. Then, in step S 210 , the CPU  301  waits for a predetermined time that is equivalent to the standby time “w” calculated in step S 209 , while continuously supplying electric power to the HDD  304 . 
     In step S 211 , the CPU  301  determines whether any job is input in the standby state of step S 210 . If in step S 211  the CPU  301  determines that an input job is present (YES in step S 211 ), the processing returns to step S 204 . If in step S 211  the CPU  301  determines that there is not any input job (NO in step S 211 ), the processing proceeds to step S 212 . In step S 212 , the CPU  301  executes the OFF control for the ON/OFF switching unit  601  to stop the electric power supplied to the HDD  304  at this timing (i.e., second timing). In step S 213 , the CPU  301  resets the storage time “r” to 0. After completing the processing of step S 213 , the timer  502  resets the elapsed time “t” to 0. Then, the processing proceeds to step S 208 . 
     In the above-described processing, when the sum of the elapsed time “t” and the storage time “r” is equal to or greater than the reference time “S”, the CPU  301  executes processing for stopping electric power supplied to the HDD  304 . Alternatively, the CPU  301  can execute any other equivalent determination. For example, if the elapsed time “t” is equal to or greater than a value that can be obtained by subtracting the storage time “r” from the reference time “S”, the CPU  301  may determine to stop the electric power supplied to the HDD  304 . For example, if the storage time “r” is equal to or greater than a value that can be obtained by subtracting the elapsed time “t” from the reference time “S”, the CPU  301  may determine to stop the electric power supplied to the HDD  304 . 
     In the above-described processing in step S 206  or step S 212 , the CPU  301  stops supplying electric power to the HDD  304 . Alternatively, the CPU  301  can reduce the amount of electric power supplied to the HDD  304 . For example, as a method for reducing the electric power supplied to the HDD  304 , it is possible to stop the electric power supplied to a motor that is configured to rotate a disk of the HDD  304 . In this state, the CPU  301  cannot read and write data from and to the HDD  304 . 
     As described above, an information processing apparatus according to the fourth exemplary embodiment can appropriately control the electric power supplied to a storage unit based on a reference time and an elapsed time. The fourth exemplary embodiment takes a power ON time of an HDD into consideration to determine whether to execute the processing for stopping electric power supplied to the HDD. Therefore, the fourth exemplary embodiment may be capable of easily stopping the electric power supplied to the HDD. 
     A block diagram illustrating a configuration of a system according to a fifth exemplary embodiment is similar to the configuration of the first exemplary embodiment illustrated in  FIG. 1 , and thus its description is not repeated. A block diagram illustrating a configuration of the printer  102  according to the fifth exemplary embodiment is similar to the configuration of the first exemplary embodiment illustrated in  FIG. 2 , and thus its description is not repeated. A block diagram illustrating a configuration of the control unit  201  according to the fifth exemplary embodiment is similar to the configuration of the first exemplary embodiment illustrated in  FIG. 3 , and thus its description is not repeated. 
     A circuit diagram illustrating a state of electric power supplied to constituent components of the power source unit  205  and a configuration of power supply control for constituent components of the CPU  301  and the power supply control unit  308  according to the fifth exemplary embodiment is similar to the circuit diagram of the first exemplary embodiment illustrated in  FIG. 4 , and thus its description is not repeated.  FIG. 13  is a flowchart illustrating example control that can be performed by the printer  102  according to the fifth exemplary embodiment. In one version, to execute the control processing of the flowchart illustrated in  FIG. 13 , the CPU  301  reads and executes a program loaded into the RAM  303  from the HDD  304 . 
     In step S 301 , the CPU  301  determines whether the power source of the printer  102  is turned on. If in step S 301  the CPU  301  determines that the power source of the printer  102  is in an ON state (YES in step S 301 ), the processing proceeds to step S 302 . If it is determined that the power source of the printer  102  is in an OFF state (NO in step S 301 ), then step S 301  is repeated. When the processing proceeds to step S 302 , the timer  502  starts measuring the elapsed time “t.” 
     In step S 302 , the CPU  301  determines whether there is any input job. The trigger detection unit  501  detects a trigger of the input job. If in step S 302  the CPU  301  determines that an input job is present (YES in step S 302 ), then processing proceeds to step S 303 , where the CPU  301  performs the ON control for the ON/OFF switching unit  601  to start supplying electric power to the HDD  304 . If it is determined that no input job is present (NO in step S 302 ), then step S 302  is repeated. In step S 304 , the CPU  301  increments a number “n” of times of the start operation, which indicates the number of times of the operation for starting supplying electric power to the HDD in step S 303 . The number “n” of times of the start operation may be recorded in the HDD  304  and can optionally be loaded into the RAM  303 . In step S 305 , the CPU  301  executes job processing. 
     More specifically, to perform the job processing, the CPU  301  controls a constituent component of the printer  102 , which may be used to process a job (i.e., a processing object), according to a job type. If the processing of step S 305  is completed and there is not any job to be next processed, the CPU  301  determines that the present state satisfies a condition for stopping electric power supplied from the power source unit  205  to the HDD  304  via the ON/OFF switching unit  601 . The processing proceeds to step S 306 . 
     In step S 306 , the CPU  301  determines whether the elapsed time “t” is equal to or greater than a value obtained by multiplying the reference time “S” by the number “n” of times of the start operation. In other words, the CPU  301  determines whether to stop the electric power supplied to the HDD  304  based on a comparison result. The elapsed time “t” is a time that can be measured by the timer  502  until the processing proceeds to step S 305 . 
     The reference time “S” represents a standby time for the HDD  304 , which is generally a fixed value. The reference time “S” is a time that can be referred to by the CPU  301  to determine whether to stop the electric power supplied to the HDD  304 . When “P” represents the product lifetime of the printer  102  and “H” represents the number of ON/OFF times that can be assured for the HDD  304 , a formula S=P/H may define the reference time “S.” The reference time “S” can be stored in the HDD  304  and can optionally be loaded into the RAM  303 . The printer  102  may calculate the reference time “S.” The HDD  304  may store the reference time “S” beforehand. 
     If in step S 306  the CPU  301  determines that the elapsed time “t” is equal to or greater than the value obtained by multiplying the reference time “S” by the number “n” of times of the start operation (YES in step S 306 ), the processing proceeds to step S 307 . If in step S 306  the CPU  301  determines that the elapsed time “t” is less than the value obtained by multiplying the reference time “S” by the number “n” of times of the start operation (NO in step S 306 ), the processing proceeds to step S 309 . 
     In step S 307 , i.e., if in step S 306  it is determined the elapsed time “t” is equal to or greater than the value obtained by multiplying the reference time “S” by the number “n” of times of the start operation, the CPU  301  promptly executes the OFF control for the ON/OFF switching unit  601  to stop the electric power supplied to the HDD  304  at this timing. In step S 307 , the CPU  301  may also wait for a predetermined time before stopping the electric power supplied to the HDD  304 . 
     In step S 308 , the CPU  301  determines whether the power source of the printer  102  is turned off. If in step S 308  the CPU  301  determines that the power source of the printer  102  is in an OFF state, the CPU  301  terminates the processing of the routine illustrated in  FIG. 13 . When the power source of the printer  102  is turned off, the timer  502  terminates the measurement of the elapsed time “t.” When the power source of the printer  102  is turned off (YES in step S 308 ), the CPU  301  stores the value of the elapsed time “t” in the HDD  304 . The CPU  301  reads the stored value of the elapsed time “t” from the HDD  304  when the power source of the printer  102  is turned on in the next processing of step S 301 . If in step S 308  the CPU  301  determines that the power source of the printer  102  is in an ON state (NO in step S 308 ), the processing returns to step S 302 . 
     In step S 309 , i.e., if in step S 306  it is determined that the elapsed time “t” is less than the value obtained by multiplying the reference time “S” by the number “n” of times of the start operation, the CPU  301  calculates a value of the predetermined standby time “w.” The standby time “w” is a time set as a temporal duration from a termination of the job processing in step S 305  to an initiation of HDD power supply stop processing in step S 307 , in a state where no job is input in the printer  102 . 
     The standby time “w” can be calculated by subtracting the elapsed time “t” from the value obtained by multiplying the reference time “S” by the number “n” of times of the start operation. Then, in step S 310 , the CPU  301  waits for a predetermined time that is equivalent to the standby time “w” calculated in step S 309 , while continuously supplying electric power to the HDD  304 . In step S 311 , the CPU  301  determines whether any job is input in the standby state of step S 310 . If in step S 311  the CPU  301  determines that an input job is present (YES in step S 311 ), the processing returns to step S 305 . If in step S 311  the CPU  301  determines that there is not any input job (NO in step S 311 ), the processing proceeds to step S 307 . 
     In the above-described processing, when the elapsed time “t” is equal to or greater than the value obtained by multiplying the reference time “S” by the number “n” of times of the start operation, the CPU  301  executes processing for stopping electric power supplied to the HDD  304 . 
     Alternatively, the CPU  301  may execute other determinations, which may be equivalent determinations. For example, if the reference time “S” is less than a value obtained by dividing the elapsed time “t” by the number “n” of times of the start operation, the CPU  301  may determine to stop the electric power supplied to the HDD  304 . For example, if the number “n” of times of the start operation is less than a value obtained by dividing the elapsed time “t” by the reference time “S”, the CPU  301  may determine to stop the electric power supplied to the HDD  304 . 
     In the above-described processing in step S 307 , the CPU  301  stops supplying electric power to the HDD  304 . Alternatively, the CPU  301  can reduce the amount of electric power supplied to the HDD  304 . For example, as a method for reducing the electric power supplied to the HDD  304 , it is possible to stop the electric power supplied to a motor that is configured to rotate a disk of the HDD  304 . In this state, the CPU  301  cannot read and write data from and to the HDD  304 . 
     The above-described exemplary embodiment executes the control for turning off the power source of the HDD  304  based on the number of times of the starting (or increasing) operation for starting (or increasing) the electric power supply to the HDD  304 . However, the control for turning off the power source of the HDD  304  can be performed based on the number of times of the stopping (or decreasing) operation for stopping (or decreasing) the electric power supply to the HDD  304 . 
     In this case, the CPU  301  increments the number “n” of times of the stop operation when the CPU  301  stops the electric power supply to the HDD  304  in step S 307 . In this case, the control for turning off the power source of the HDD  304  may be performed by determining whether to stop supplying electric power to the HDD  304  based on a determination result of step S 306 , in which it is determined whether the elapsed time “t” is equal to or greater than a value obtained by adding one to the number “n” of times of the stop operation and then multiplying an obtained sum by the reference time “S.” 
     As described above, an information processing apparatus according to the fifth exemplary embodiment may be able to appropriately control the electric power supplied to a storage unit based on a reference time and an elapsed time. The fifth exemplary embodiment takes a power ON time of an HDD into consideration to determine whether to execute the processing for stopping electric power supplied to the HDD. Therefore, the fifth exemplary embodiment may be capable of easily stopping the electric power supplied to the HDD. 
     A block diagram illustrating a configuration of a system according to a sixth exemplary embodiment is similar to the configuration of the first exemplary embodiment illustrated in  FIG. 1 , and thus its description is not repeated. A block diagram illustrating a configuration of the printer  102  according to the sixth exemplary embodiment is similar to the configuration of the first exemplary embodiment illustrated in  FIG. 2 , and thus its description is not repeated. A block diagram illustrating a configuration of the control unit  201  according to the sixth exemplary embodiment is similar to the configuration of the first exemplary embodiment illustrated in  FIG. 3 , and thus its description is not repeated. 
     A circuit diagram illustrating a state of electric power supplied to constituent components of the power source unit  205  and a configuration of power supply control for constituent components of the CPU  301  and the power supply control unit  308  according to the sixth exemplary embodiment is similar to the circuit diagram of the first exemplary embodiment illustrated in  FIG. 4 . 
       FIG. 15  is a circuit diagram illustrating a state of electric power supplied to constituent components of the power source unit  205  and a configuration of power supply control for constituent components of the CPU  301  and the power supply control unit  308  according to the sixth exemplary embodiment. The circuit diagram illustrated in  FIG. 15  is different from that of the first exemplary embodiment (illustrated in  FIG. 4 ) in that the HDD power control unit  503  and the ON/OFF switching unit  602  are additionally provided. Under the control of the CPU  301  and the ON/OFF switching unit  602 , the ON/OFF switching unit  602  can execute ON/OFF control of electric power supplied to the HDD  304 . 
     The circuit diagram illustrated in  FIG. 15  is further different from that of the first exemplary embodiment (illustrated in  FIG. 4 ) in that the timer  502  is replaced with a combination of an adder timer  504  and a subtractor timer  505 . Operations of the adder timer  504  and the subtractor timer  505  are described below with reference to a flowchart of  FIG. 16 . The adder timer  504  and the subtractor timer  505  can be, for example, constituted by a real-time clock (e.g., a calendar IC) or a system timer of the OS. 
     The trigger detection unit  501  can detect a state of the ON/OFF switching unit  602  via the HDD power control unit  503  and can determine whether the electric power supply to the HDD  304  is stopped based on a detected state.  FIG. 16  is a flowchart illustrating example control that can be performed by the printer  102  according to the sixth exemplary embodiment. In one version, to execute the control processing of the flowchart illustrated in  FIG. 16 , the CPU  301  reads and executes a program loaded into the RAM  303  from the HDD  304 . 
     In the present exemplary embodiment, the job includes a reading job performed by the reading unit  203 , a print job performed by the printing unit  204 , an operation response job performed by the operation unit  202 , and a network response job performed by the network IF  307 . 
     In the present exemplary embodiment, the operation modes of the printer  102  include a normal mode and a power saving mode. In the normal mode, the power source of the CPU  301  and the HDD  304  is turned on (i.e., electric power is supplied to the CPU  301  and the HDD  304 ). In the power saving mode (i.e., in a power saving state), the power source of one or more of the CPU  301  or the HDD  304  is turned off (i.e., electric power is not supplied to both of the CPU  301  or the HDD  304 ). The power saving mode (i.e., the power saving state) includes a first power saving mode (i.e., a first power saving state) in which only the power source of the CPU  301  is turned off and a second power saving mode (i.e., a second power saving state) in which the electric power supply to both the CPU  301  and the HDD  304  is stopped. 
     In step S 401 , the CPU  301  determines whether the power source of the printer  102  is turned on. If in step S 401  it is determined that the power source of the printer  102  is in an ON state (YES in step S 401 ), the processing proceeds to step S 402 . If it is determined that the power source of the printer is in an OFF state (NO in step S 401 ), the step S 401  is repeated. In step S 402 , the CPU  301  determines whether there is any input job. The trigger detection unit  501  detects a trigger of the input job. If in step S 402  it is determined that an input job is present (YES in step S 402 ), the processing proceeds to step S 403 . If it is determined that there is no input job present (NO in step S 402 ), then step S 402  is repeated. 
     In step S 403 , the CPU  301  starts supplying electric power to the CPU  301  and the HDD  304 . Before the CPU  301  executes the processing of step S 403 , the trigger detection unit  501  detects whether the electric power supply to the HDD  304  is stopped. The trigger detection unit  501  stores the information in its built-in memory. When the processing returns from step S 417  to step S 403 , the electric power supply to the HDD  304  is already started and therefore the CPU  301  starts supplying electric power to the CPU  301  in step S 403 . 
     In step S 404 , the CPU  301  causes the adder timer  504  to increment the time “t” that indicates the power ON time of the CPU  301 . In the processing of step S 404 , the adder timer  504  resets the time “t” to 0 every time before starting incrementing the time “t.” 
     In step S 405 , the CPU  301  determines whether the electric power supply to the HDD  304  has been stopped at the time when the processing proceeds to step S 403 . The determination of step S 405  is performed based on the information stored in the built-in memory of the trigger detection unit  501 . The information indicates whether the electric power supply to the HDD  304  has been stopped before the CPU  301  performs the processing of step S 403 . At the time when the processing proceeds to step S 403  from step S 402  or step S 412 , the electric power supply to the HDD  304  is in a stopped state. On the other hand, at the time when the processing proceeds to step S 403  from step S 417 , the electric power supply to the HDD  304  is not stopped. 
     If in step S 405  it is determined that the electric power supply to the HDD  304  has been stopped at the time when the processing proceeds to step S 403  (YES in step S 405 ), the processing proceeds to step S 406 . If in step S 405  it is determined that the electric power supply to the HDD  304  has not been stopped at the time when the processing proceeds to step S 403  (NO in step S 405 ), the processing proceeds to step S 407 . 
     In step S 406 , i.e., if in step S 405  it is determined that the electric power supply to the HDD  304  has been stopped at the time when the processing proceeds to step S 403 , the CPU  301  sets the reference time “S” as a value C (i.e., a comparison object in the determination of step S 409 ). Processing then proceeds to step S 408 . 
     In step S 407 , i.e., if in step S 405  it is determined that the electric power supply to the HDD  304  has not been stopped at the time when the processing proceeds to step S 403 , the CPU  301  sets a standby time “w” as the value C (i.e., the comparison object in the determination of step S 409 ). The standby time “w” is a value that can be calculated in step S 414  and decremented in step S 415 . Processing then proceeds to step S 408 . 
     In step S 408 , the CPU  301  executes job processing. If in step S 408  there is any other job that may remain after completing the processing of one job, the CPU  301  processes the remaining job. A predetermined waiting time can be set before the processing proceeds to step S 409  from step S 408 . 
     In step S 409 , the CPU  301  determines whether the time “t” (i.e., the value that is incremented in step S 404 ) is greater than the value C (i.e., the value having been set in step S 406  or step S 407 ). If in step S 409  it is determined that the time “t” is greater than the value C (YES in step S 409 ), the processing proceeds to step S 410 . If in step S 409  it is determined that the time “t” is not greater than the value C (NO in step S 409 ), the processing proceeds to step S 414 . 
     In step S 410 , i.e., if in step S 409  it is determined that the time “t” is greater than the value C, the CPU  301  controls the ON/OFF switching unit  602  to stop the electric power supplied to the HDD  304  at this timing (i.e., first timing). In step S 411 , the CPU  301  controls the ON/OFF switching unit  601  to stop the electric power supplied to the CPU  301 . 
     In step S 412 , the CPU  301  causes the trigger detection unit  501  to determine whether any job is input. If in step S 412  the trigger detection unit  501  detects an input job (YES in step S 412 ), the processing returns to step S 403 . If in step S 412  the trigger detection unit  501  does not detect any input job (NO in step S 412 ), the processing proceeds to step S 413 . 
     In step S 413 , i.e., if in step S 412  it is determined that there is not any input job, the CPU  301  determines whether the power source of the printer  102  is turned off. If in step S 413  it is determined that the power source of the printer  102  is in an OFF state (YES in step S 413 ), the CPU  301  terminates the processing of the routine illustrated in  FIG. 16 . If in step S 413  it is determined that the power source of the printer  102  is in an ON state (NO in step S 413 ), the processing returns to step S 412 . 
     In step S 414 , i.e., if in step S 409  it is determined that the time “t” is not greater than the value C, the CPU  301  sets the standby time “w” during which the control for stopping the electric power supply to the HDD  304  is postponed. The standby time “w” is a value that can be obtained by subtracting the time “t” from the value C. 
     In step S 415 , the CPU  301  causes the subtractor timer  505  to decrement the standby time “w” obtained in step S 414 . In step S 416 , the CPU  301  controls the ON/OFF switching unit  601  to stop the electric power supplied to the CPU  301 . 
     In step S 417 , the CPU  301  causes the trigger detection unit  501  to determine whether any job is input. If in step S 417  the trigger detection unit  501  detects an input job (YES in step S 417 ), the processing returns to step S 403 . If in step S 412  the trigger detection unit  501  does not detect any input job (NO in step S 417 ), the processing proceeds to step S 418 . 
     In step S 418 , i.e., if in step S 417  it is determined that there is not any input job, the CPU  301  determines whether the standby time “w” decremented in step S 415  is equal to 0. If in step S 418  it is determined that the standby time “w” decremented in step S 415  is equal to 0 (YES in step S 418 ), the processing proceeds to step S 419 . If in step S 418  it is determined that the standby time “w” decremented in step S 415  is not equal to 0 (NO in step S 418 ), the processing returns to step S 417 . 
     In step S 419 , i.e., if in step S 418  it is determined that the standby time “w” decremented in step S 415  is equal to 0, the HDD power control unit  503  controls the ON/OFF switching unit  602  to stop the electric power supplied to the HDD  304  at this timing (second timing). 
     A similar result may also be obtained even if the flowchart illustrated in  FIG. 16  is partly changed. For example, the flowchart may include a modified step S 404  in which the value of “t” is not reset if the processing proceeds to step S 404  via step S 417 . The flowchart may further include a modified step S 405  in which the processing proceeds to step S 406  irrespective of a determination result in step S 405 . 
     The processing illustrated in  FIG. 16  may be advantageous in that the effects of the present exemplary embodiment can be obtained even when the value of “t” is deleted in response to the stop of the electric power supply to the CPU, compared to the above-described modified processing resulting from the processing illustrated in  FIG. 16 . The above-described modified processing resulting from the processing illustrated in  FIG. 16  may also be advantageous in that it is possible that the processing can be simplified compared to the processing illustrated in  FIG. 16 . 
     In the above-described processing in step S 410  or step S 419 , the CPU  301  stops supplying electric power to the HDD  304 . Alternatively, the CPU  301  can reduce the amount of electric power supplied to the HDD  304 . For example, as a method for reducing the electric power supplied to the HDD  304 , it is possible to stop the electric power supplied to a motor that is configured to rotate a disk of the HDD  304 . In this state, the CPU  301  cannot read and write data from and to the HDD  304 . 
       FIG. 17  illustrates a transitional state of power supply to a CPU and a HDD according to a conventional technique. In  FIG. 17 , the abscissa axis represents an elapsed time and the ordinate axis represents an amount of electric power consumption. The conventional technique calculates a standby time set after completing the job processing and before stopping electric power supply to the HDD by subtracting, from the reference time, an elapsed time in a state where electric power is supplied to the CPU. For example, the conventional technique may obtain a standby time “w 2 ” at time T 4  by subtracting a CPU power ON time t 2  from the reference time “S.” 
     Therefore, if a job is newly input after the electric power supply to the CPU is stopped and before the electric power supply to the HUD is stopped, it was impossible to appropriately stop the electric power supplied to the HUD  304 . For example, when the standby time “w 2 ” is set at time T 4 , the electric power supply to the HUD cannot be stopped at time T 5 . 
       FIG. 18  illustrates an example of a transitional state of power supply to the CPU and the HUD according to the present exemplary embodiment. In  FIG. 18 , the abscissa axis represents an elapsed time and the ordinate axis represents an amount of electric power consumption. 
     The present exemplary embodiment calculates a standby time set after completing the job processing and before stopping electric power supply to the HUD by subtracting, from the reference time, an elapsed time in a state where electric power is supplied to the HUD. For example, the present exemplary embodiment can obtain a standby time “w 3 ” at time T 4  by subtracting an HUD power ON time t 3  from the reference time “S.” 
     Therefore, even if a job is newly input after the electric power supply to the CPU is stopped and before the electric power supply to the HUD is stopped, the present exemplary embodiment can appropriately stop the electric power supplied to the HUD  304 . For example, when the standby time “w 3 ” is set at time T 4 , the electric power supply to the HDD  304  can be stopped at time T 5 . 
     As apparent from the comparison between  FIG. 17  and  FIG. 18 , the present exemplary embodiment may be capable of reducing the amount of electric power consumption as indicated by a hatched portion illustrated in  FIG. 18 . 
     To realize aspects of the present invention, the above-described system or the apparatus can read software programs and/or computer-executable instructions from a storage medium and execute the program and/or computer-executable instructions to realize functions according to aspects of the above-described exemplary embodiments. 
     The storage medium having the program and/or computer-readable instructions read out therefrom can realize aspects according to the present invention. Accordingly, the storage medium storing the program and/or computer-executable instructions may constitute an aspect according to the present invention. 
     A storage medium supplying the program code and/or computer-executable instructions can be selected from any one or more of a floppy disk, a hard disk, a ROM, an optical disk, a magneto-optical (MO) disk, a compact disc-ROM (CD-ROM), a digital versatile disc (DVD (e.g., DVD-ROM, DVD-RAM)), a magnetic tape, and a memory card. Moreover, an operating system (OS) or other application software running on a computer can execute part or all of actual processing based on instructions of the programs to realize the functions according to the above-described exemplary embodiments. 
     Additionally, the program and/or computer-executable instructions can be written into a memory of a function expansion unit connected to a computer. In this case, based on instructions of the program and/or computer-executable instructions, a CPU provided on the function expansion unit can execute part or all of the processing to realize functions according to aspects of the above-described exemplary embodiments. 
     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 modifications, equivalent structures, and functions. 
     This application claims priority from Japanese Patent Application Nos. 2008-120406 filed May 2, 2008, and 2009-082082 filed Mar. 30, 2009, which are hereby incorporated by reference herein in their entirety.