Abstract:
A power-supply connection portion connects a power supply and a main body device. Operation information for operating the apparatus main body is stored in a volatile memory. A power feeder feeds power fed from the power supply, to the volatile memory. A non-operation state request receiver receives a non-operation state request for moving the apparatus main body from an operation state to a non-operation state. When the non-operation state request is received by the non-operation state request receiver, a power-feeding controller performs control such that the power feeder feeds the power to the volatile memory for a predetermined period. A mode determiner determines a mode of the non-operation state request. A changer is provided with a setter which sets the predetermined period depending on the mode determined by the mode determiner.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an electronic apparatus, and more particularly, relates to an electronic apparatus which controls power feeding to a device other than a main device of the apparatus main body when the power feeding to the main device of the apparatus main body is stopped. 
       BACKGROUND ART 
       [0002]    Conventionally, for example, in an electronic apparatus such as a digital camera, a process is executed in which when a power-supply button is off-manipulated by a user, a current state is changed from a power-on state in which power is fed to the entire apparatus to a power-off state in which power is not fed to a main device of the apparatus except for some devices (for example, a sub microcomputer which detects depressing of a manipulation button including the power-supply button). 
         [0003]    However, in the electronic apparatus such as a digital camera, it is necessary to execute a process of loading (developing), to a volatile memory such as an SDRAM, information (including setting information necessary for a photographing process) required for an activation and an operation of the apparatus main body that is stored in the nonvolatile memory, after moved from the above-described power-off state to the power-on state. 
         [0004]    When a user uses such an electronic apparatus, the shorter a time period from the movement from the power-off state of the apparatus main body to the power-on state thereof to the actual activation of the apparatus main body, the more convenient usability becomes. Thus, it is demanded to shorten a time period from the movement from the power-off state to the power-on state until the activation. 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    In the apparatus described above, if a battery charge amount at the time of receiving a stop command is lower than a threshold value, the current state is moved to a shutdown state in which power is not fed to a circuit system unnecessary to operate during the stop, and if the battery charge amount is higher than the threshold value, the current state is moved to a standby state in which a process necessary during the activation is performed in advance in the middle of the stop in order to shorten an activation processing time at the time of a reactivation, and the state that is established at this time is maintained, thereby shortening a system activation time and normally starting-up the system. 
         [0006]    However, the above-described apparatus inevitably becomes under a standby state if the battery charge amount at the time of receiving the stop command is higher than the threshold value, and therefore, power is fed to the volatile memory even when a user does not plan to perform an operation for the reactivation next time. As a result, unnecessary power is fed to the volatile memory. In consideration of such a case, it is possible to conceive a technique of shortening a time period for feeding power to the volatile memory at the time of receiving the stop command so that the unnecessary power is prevented from being fed to the volatile memory. However, it is necessary for a user to issue a user&#39;s reactivation command in the said time period, and if it is not possible to issue the command within the time period, then the result is that the loading process and the like are performed as described above, and thus, it takes time until the reactivation. 
         [0007]    The present invention solves the above-described problems and provides an electronic apparatus by which it is possible to stop, when an instruction to stop a function of one portion (main device) of an apparatus main body is issued, feeding power to a device relating to the function, and to feed the power to a volatile memory for an optimal period. 
       Solution to Problem 
       [0008]    An electronic apparatus according to the invention of the subject application includes: a volatile memory which stores operation information for operating an apparatus main body; a power feeder which feeds first power for retaining the operation information stored in the volatile memory and second power for maintaining an operation state to the apparatus main body; a request receiver which receives a non-operation state request for moving the apparatus main body from the operation state to a non-operation state in which one portion of the apparatus main body is not operated; a power-feeding controller which controls the power feeder such that the first power only is fed for a predetermined period when the non-operation state request is received by the request receiver; a mode determiner which determines a mode of the non-operation state request; and a setter which sets the predetermined period depending on the mode determined by the mode determiner. 
         [0009]    Based on the electronic apparatus according to the present invention, when an instruction to stop a function of one portion (main device) of an apparatus main body is issued, it is possible to stop feeding the power to a device relating to the function and to feed the power to a volatile memory for an optimal period 
         [0010]    The above described object, other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the embodiment when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a block diagram showing a digital camera according to this embodiment 
           [0012]      FIG. 2  is a flowchart showing one portion of operations in a sub CPU applied to this embodiment. 
           [0013]      FIG. 3  is a flowchart showing one portion of operations in a main CPU applied to this embodiment. 
           [0014]      FIG. 4  is a flowchart showing another portion of operations in the main CPU applied to this embodiment. 
           [0015]      FIG. 5  is a flowchart showing one portion of operations in a power-supply control portion applied to this embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0016]    Hereinafter, as one embodiment of an electronic apparatus of the present invention, an embodiment carried out for a digital camera  10  will be described along with the drawings.  FIG. 1  shows a block diagram of the digital camera  10 . The digital camera  10  includes an optical lens  16  and an aperture (not shown). An optical image of a subject is captured to a CMOS imager unit  18  through the optical lens  16  and the aperture controlled by a motor drive portion (not shown) in response to an instruction from a main CPU  22 . Then, by a capturing pulse applied by a timing generator (not shown) connected to the main CPU  22 , one frame of a digital imaging signal is outputted from the CMOS imager unit  18 . Herein, the CMOS imager unit  18  amplifies electric charges accumulated in each pixel, reads them out as a signal from each pixel through a wiring line, and subjects the signal to a gain adjustment, a clamp process, and an A/D conversion process. The digital imaging signal that has undergone the processes has any one of colors signals, i.e., R, G, and B, for each pixel, and is temporarily stored in an SDRAM  32  via a bus  40  by control of the main CPU  22 . 
         [0017]    The digital imaging signal temporarily stored in the SDRAM  32  is inputted to a signal processing circuit  20  by control of the main CPU  22 . In the signal processing circuit  20 , a color separation process is performed on the inputted digital imaging signal, and furthermore, by a YUV conversion, the resultant signal is converted into Y, U, and V signals. Then, the digital image signal converted in the signal processing circuit  20  is stored in the SDRAM  32  again via the bus  40 . In this embodiment, a process performed from the digital imaging signal outputted from the above-described CMOS imager unit  18  is subjected to a converting process into the digital image signal by the signal processing circuit  20  until the resultant signal is stored in the SDRAM  32  is defined as a photographing process. 
         [0018]    Moreover, the digital image signal stored in the SDRAM  32  is outputted to an LCD  38  by control of the main CPU  22 . The LCD  38  includes an LCD driver not shown, and the LCD driver converts Y, U, and V signals into an RGB signal, and causes the LCD  38  to display an image signal that is based on the digital image signal. 
         [0019]    Furthermore, in a case where a still image is recorded, the digital image signal stored in the SDRAM  32  is subjected to a compression process in a compression/decompression processing portion (not shown) and stored in an internal memory (not shown) as a still image file of a JPEG format. It is noted that in a case where a moving image is recorded, the digital image signal is subjected to a compression process in a compression/decompression processing portion (not shown) and stored in an internal memory (not shown) as a moving image file of an MPEG format. 
         [0020]    Also, a manipulation portion  36  is provided with a main switch which switches on/off states (moves a current state from an on state to an off state or from the off state to the on state) of a power feeding from a power supply to a main body of the digital camera  10 . It is noted that in this embodiment, a source of the power fed to one or entire portion of the digital camera  10  is a battery  30  or an external power supply  42 . The external power supply  42  is, for example, an AC device such as an AC adaptor, and when the external power-supply  42  is connected, a power-supply control portion  28  controls such that power from the external power-supply  42 , rather than power from the battery  30 , is fed to the digital camera  10 . 
         [0021]    The manipulation portion  36  is connected to a sub CPU  34 , and each manipulation signal including a signal corresponding to the on/off manipulation of the power supply of the main switch is inputted to the sub CPU  34  as a result of the manipulation portion  36  being manipulated. The sub CPU  34  is connected to the main CPU  22  and the power-supply control portion  28 , and when the manipulation signal is inputted, the sub CPU  34  transmits each manipulation command to the main CPU  22  and the power-supply control portion  28  with reference to the manipulation signal. 
         [0022]    Meanwhile, an operation of the main CPU  22  is executed based on a firmware stored in the volatile memory  24 . The firmware is a software, i.e., a program, necessary for activating the main body of the digital camera  20  (a system activation process), which includes the above-described photographing process. Moreover, the firmware is stored in a nonvolatile memory  26 , and when the current state is moved from a power-supply sleeping state to a main-power-supply supplying state in response to the power-on manipulation of the main switch, the main CPU  22  develops the firmware in the volatile memory  24 . 
         [0023]    Herein, in this embodiment, a state in which the power is fed from the power supply only to the sub CPU  34  and the power-supply control portion  28  and the power supply is not provided to devices other than the sub CPU  34  and the power-supply control portion  28  is defined as a power-supply sleeping state, a state in which the power is fed from the power supply only to the power-supply control portion  28 , the sub CPU  34 , and the volatile memory  24  is defined as a memory-power-supply supplying state, and a state in which the power is fed from the power supply to the entire digital camera  10  is defined as a main-power-supply supplying state. 
         [0024]    As a result of user&#39;s intentional power-off manipulation of the main switch, the main CPU  22  transitions the current state from the main-power-supply supplying state through the memory-power-supply supplying state to the power-supply sleeping state. In addition, when it is determined by a management of a timer  22   a  in the main CPU  22  that a manipulation from a user is not performed on the manipulation portion  36  for a predetermined time period, the current state is transitioned from the main-power-supply supplying state through the memory-power-supply supplying state to the power-supply sleeping state (hereinafter, referred to as a “sleep operation”). The power-off manipulation and the sleep operation are a manipulation and an operation for a purpose of turning off the power supply. 
         [0025]    Now, the digital camera  10  according to this embodiment calculates a state retaining time T 1  of the memory-power-supply supplying state according to Equation 1, for example, based on coefficients α, β, and γ corresponding to the power-off manipulation or the sleep operation by which the transition is triggered and other elements described below. 
         [0000]        T 1=α*β*γ  (Equation 1)
 
         [0026]    In addition, the state retaining time T 1  is measured by a timer  28   a  in the power-supply control portion  28 , and a time-up is reached when the state retaining time T 1  elapses. When the time-up is reached, the power-supply control portion  28  controls the power supply such that the current state is transitioned from the memory-power-supply supplying state to the power-supply sleeping state. 
         [0027]    Hereinafter the coefficients α, β, and γ are described. 
         [0028]    The coefficient α is a numerical value corresponding to the trigger for the transition, as described above. The coefficient α is stored in a manipulation lookup table (not shown) in the nonvolatile memory  26 , and when the main CPU  22  determines that the current manipulation is the power-off manipulation that serves as the trigger for transition, the coefficient corresponding to the power-off manipulation is stored in a register  22   e  with reference to the manipulation lookup table. It is noted that in the manipulation lookup table, values corresponding to the power-off manipulation and the sleep operation are arranged. Meanwhile, if the main CPU  22  determines that the current operation is the sleep operation that serves as the trigger for transition, the coefficient corresponding to the sleep operation is stored in the register  22   e  with reference to the manipulation lookup table. 
         [0029]    Specifically, if it is determined that the current manipulation is the power-off manipulation, the main CPU  22  raises an off-manipulation flag F 3  that has been stored in a register  22   h  (F 3 =1), and if it is determined that the current operation is the sleep operation, the CPU  22  resets the off-manipulation flag F 3  (F 3 =0). 
         [0030]    In this case, the coefficient cc corresponding to the power-off manipulation is smaller in value than the coefficient cc corresponding to the sleep operation. This is because when the user turns off the power, which arises from the power-off manipulation, the user intentionally turns off the power, and therefore, there is a low possibility that the user performs the power-on manipulation immediately after turning off the power and uses the digital camera  10 . On the other hand, when the user turns off the power, which arises from the sleep operation, the user unintentionally turns off the power, and therefore, there is a high possibility that the user performs the power-on manipulation by manipulating the main switch immediately after turning off the power and uses the digital camera  10 . 
         [0031]    Therefore, when the power-off manipulation is performed, if the state retaining time T 1  is shortened, then unnecessary power is not fed. This serves to achieve power-saving. On the other hand, when the sleep operation is executed, if the state retaining time T 1  is extended, then it is possible to shorten the activation time of the digital camera  10 , and when the power-on manipulation of the main switch is performed within the state retaining time T 1 , it is possible to promptly execute the firmware stored in the volatile memory  24 , and therefore, it is possible to shorten the activation time of the digital camera  10 . 
         [0032]    The coefficient β is a numerical value corresponding to a voltage level of a battery  30  if the battery  30  is used as the power supply. The coefficient β is stored in a voltage lookup table (not shown) in the nonvolatile memory  26 . It is noted that a value corresponding to the voltage level is arranged in the voltage lookup table. When the voltage level of the battery  30  is detected, the main CPU  22  refers to the voltage lookup table so that the coefficient corresponding to the voltage level is stored in a register  22   f.    
         [0033]    Furthermore, the coefficient β when the voltage level is high is larger in numerical value as compared to when the voltage level is low. The reason for this is as follows: unlike when the voltage level is low, i.e., when the remaining amount of the battery  30  is small, when the voltage level is high, i.e., when the remaining amount of the battery  30  is large, there is a sufficient remaining amount of the battery  30 , and thus, the state retaining time T 1  may be extended. In this case, when the power-on manipulation on the main switch is performed within the state retaining time T 1 , if the firmware stored in the volatile memory  24  is promptly executed, then it is possible to shorten the activation time of the digital camera  10 . Moreover, when the voltage level is low, it is possible to extend the lifetime of the battery  30  by shortening the state retaining time T 1  to achieve power-saving. 
         [0034]    Furthermore, when the external power-supply  42  is used as the power supply, the power is fed to the main CPU  22  without interruption. Therefore, the state retaining time T 1  is set to infinity without detecting the coefficients α and β. 
         [0035]    The coefficient γ is a numerical value corresponding to a current time set to the digital camera  10 . The coefficient γ is stored in a time lookup table (not shown) in the nonvolatile memory  26 . It is noted that a value corresponding to a time is arranged in the time lookup table. When the current time is detected from a clock  22   d , the main CPU  22  refers to the time lookup table and stores the coefficient corresponding to the detected time in a register  22   g.    
         [0036]    Moreover, the coefficient γ for a midnight time is smaller in numerical value as compared to the coefficient γ that is not for a midnight time but for a time at which user&#39;s activity is relatively vigorous. This is because as compared to the midnight at which the time is detected, the user may use the digital camera  10  more frequently during a time during which the user&#39;s activity is relatively vigorous, rather than at midnight. Thus, if the state retaining time T 1  is extended, then when the power-on manipulation of the main switch is performed within the state retaining time T 1 , it is possible to shorten the activation time of the digital camera  10  by promptly executing the firmware stored in the volatile memory  24 . In addition, when the time is detected at midnight, if the state retaining time T 1  is shortened to achieve the power-saving, then it is possible to extend the lifetime of the battery  30 . 
         [0037]    The control such that the current state is transitioned from the main-power-supply supplying state through the memory-power-supply supplying state to the power-supply sleeping state as a result of the above-described power-off manipulation or the sleep operation being performed is realized by respectively executing a program developed from the nonvolatile memory  26  to the volatile memory  24  by using microcomputers (not shown) of the main CPU  22 , the sub CPU  34 , and the power-supply control portion  28 . In addition, a multitasking environment is constructed in the digital camera  10 , and thus, the main CPU  22  is capable of performing a plurality of tasks at the same time. Hereinafter, a power-supply managing task, a sleep transition task, a power-feeding-time calculating task, and a power-supply control task respectively executed by microcomputers (not shown) of the sub CPU  34 , the main CPU  22 , and the power-supply control portion  28  are described with reference to  FIGS. 2 to 5 . 
         [0038]      FIG. 2  shows a flowchart of the power-supply managing task executed by the sub CPU  34 . In a step S 1 , the sub CPU  24  determines whether or not the power is fed from the external power-supply  42  by monitoring the power-supply control portion  28 . If YES is determined in the step S 1 , the process advances to a step S 3  so as to transmit a request command for raising an external power feeding flag F 2  (F 2 =1) stored in a register  22   c  to the main CPU  22 , and then, the process advances to a step S 7 . If NO is determined in the step S 1 , the process advances to a step S 5  so as to transmit a request command for resetting the external power feeding flag F 2  (F 2 =0) stored in the register  22   c  to the main CPU  22 , and then, the process advances to the step S 7 . 
         [0039]    In the step S 7 , it is determined whether or not the power-off manipulation has been performed as a result of the main switch being manipulated by the user. If YES is determined in the step S 7 , the process advances to a step S 9  so as to transmit a request command for raising the off-manipulation flag F 3  (F 3 =1) stored in a register  22   h  to the main CPU  22 , and then, the process advances to a step S 13 . If NO is determined in the step S 7 , the process advances to a step S 11  so as to determine whether or not the power-off request command has been transmitted from the main CPU  22 . The power-off request from the main CPU  22  is performed based on the sleep operation. If NO is determined in the step S 11 , the process returns to step S 1 , and if YES is determined, the process advances to a step S 13 . 
         [0040]    In the step S 13 , a power-off request flag F 1  stored in a register  34   a  is raised (F 1 =1). Then, the process advances to a step S 15  so as to transmit a command corresponding to the power-off instruction to the main device, to the power-supply control portion  28 , and then, the process advances to a step S 17 . In the step S 17 , it is determined whether or not the power-on manipulation has been performed as a result of the main switch being manipulated by the user, and the determination is repeated until YES is determined. If YES is determined in the step S 17 , the process advances to a step S 19  so as to transmit a command corresponding to the power-on instruction to the main device, to the power-supply control portion  28 , and then, the process returns to the step S 1 . 
         [0041]    Subsequently, with reference to the flowchart, shown in  FIG. 3 , of the sleep transition task executed by the main CPU  22 , the operation of the digital camera  10  is described. 
         [0042]    First, in a step S 31 , the timer  22   a  is reset and started. Then, the process advances to a step S 33  so as to determine whether or not any manipulation has been performed by the user on the manipulation portion  36 , based on the command transmitted from the sub CPU  34 . If NO is determined in the step S 33 , the process advances to a step S 31 , and YES is determined in the step S 33 , the process advances to a step S 35  in which the timer  22   a  measures the time for a predetermined time period so as to determine whether or not the time is up. If NO is determined in the step S 35 , the process advances to a step S 33 , and if YES is determined in the step S 35 , the process advances to a step S 37 . In the step S 37 , the power-off request command is transmitted to the sub CPU  34 , and the process advances to a step S 39 . In the step S 39 , the off-manipulation flag F 3  stored in the register  22   h  is reset (F 3 =0), and this task is ended. 
         [0043]    Subsequently, with reference to the flowchart of the power-feeding-time calculating task executed by the main CPU  22  shown in  FIG. 4 , the operation of the digital camera  10  is described. 
         [0044]    In a step S 51 , the sub CPU  34  is inquired of whether or not the power-off request flag F 1  is raised (F 1 =1 or 0), and the result of a response from the sub CPU  34  is determined. Until it is determined in the step S 1  that the power-off request flag F 1  is 1, the determination in the step S 1  is repeated, and if it is determined that F 1  is 1, the process advances to a step S 53 . In the step S 53 , it is determined whether or not the external power feeding flag F 2  stored in the register  22   c  is raised (F 2 =1 or 0). If NO is determined in the step S 53 , the process advances to a step S 55  so as to detect the state of the off-manipulation flag F 3 , and with reference to the manipulation lookup table, store the coefficient α in the register  22   e.    
         [0045]    Then, the process advances to a step S 57  so as to detect the voltage level of the battery  30 , and with reference to the voltage lookup table, store the coefficient β corresponding to the voltage level into the register  22   f . Next, the process advances to a step S 59  so as to detect the current time from the clock  22   d , and with reference to the time lookup table, store the coefficient γ corresponding to the detected time into the register  22   g . Then, the process advances to a step S 61  so as to calculate the state retaining time T 1 , and then, the process advances to a step  63 . In the step S 63 , the request command is transmitted in order to set the state retaining time T 1  calculated in the step S 61  to a register  28   b  of the power-supply control portion  28 , and then, the process advances to a step S 67 . 
         [0046]    If YES is determined in the step S 53 , the process advances to a step S 65  so as to transmit the request command to the power-supply control portion  28  in order that the state retaining time T 1  is set to the register  28   b  to the infinity, and then, the process advances to a step S 67 . 
         [0047]    In the step S 67 , a request command for resetting the power-off request flag F 1  stored in the register  34   a  (F 1 =0) is transmitted to the sub CPU  22 . Then, this task is ended. 
         [0048]    Next, with reference to the flowchart of the power-supply control task executed by a microcomputer in the power-supply control portion  28  shown in  FIG. 5 , the operation of the digital camera  10  is described. 
         [0049]    In a step S 71 , it is determined whether or not a command corresponding to the power-off instruction to the main device is issued from the sub CPU  34 . The determination is repeated until YES is determined in the step S 71 , and if YES is determined in the step S 71 , the process advances to a step S 73  so as to control the power of the battery  30  or the external power-supply  42  such that the main-power-supply supplying state is transitioned to the memory-power-supply supplying state. 
         [0050]    Then, the process advances to a step S 75  so as to set the state retaining time T 1  stored in the register  28   b  to the timer  28   a , and start the measurement. Then, the process advances to a step S 77  so as to determine whether or not a power-on request has been issued to the main device from the sub CPU  34 . If YES is determined in the step S 77 , the process advances to a step S 79  so as to control the power of the battery  30  or the external power-supply  42  such that the current mode, which is the power-supply sleeping state, is transitioned to the main-power-supply supplying state. Then, the process returns to the step S 71 . 
         [0051]    If NO is determined in the step S 77 , the process advances to a step S 81  so as to determine whether or not the timer  28   a  has reached time-up, and if NO is determined, the process returns to the step S 77 . If YES is determined in the step S 81 , the process advances to a step S 83  so as to control the power of the battery  30  or the external power-supply  42  such that the memory-power-supply supplying state is transitioned to the power-supply sleeping state. Then, the process advances to a step S 85  so as to determine whether or not a power-on request has been issued to the main device from the sub CPU  28 . The determination is repeated until YES is determined, and if YES is determined, the process advances to a step S 79 . 
         [0052]    As described above, according to this embodiment, in a case where any trigger that may result in the power-off occurs to the operating digital camera  10 , a period during which the firmware is preventing from becoming volatile, which would occur if the firmware executed by the main CPU  22  at the time that the digital camera  10  is activated next time is developed from the non-volatile memory  26  so that the power supply is provided to the stored volatile memory  24 , is differed depending on the mode of the trigger. Therefore, it is possible to optimize a balance between shortening the activation time of the digital camera  10  and inhibiting an unnecessary power supply depending on a user&#39;s usage and the like. 
         [0053]    It is noted that in this embodiment, the control such that the current state is transitioned from the main-power-supply supplying state through the memory-power-supply supplying state to the power-supply sleeping state as a result of the power-off manipulation or the sleep operation being performed is realized by respectively executing a program developed from the nonvolatile memory  26  to the volatile memory  24  by using microcomputers (not shown) of the main CPU  22 , the sub CPU  34 , and the power-supply control portion  28 . However, this control may be processed by a single CPU, and may also be processed in a distributed manner by further providing other CPUs or microcomputers. 
         [0054]    Although the present invention has been described in terms of the digital camera  10  in this embodiment, the invention is not limited to the digital camera  10 , but may be applied to an IC recorder, a digital photo frame, a music reproduction music player, a television, and the like. In this case, for example, the lens  16 , the CMOS imager unit  18 , the signal processing circuit  20 , and the LCD  38  of this embodiment are substituted with functions of each device. 
         [0055]    Although the description has been provided by using the CMOS imager unit  18  as the image-pickup element in this embodiment, a CCD imager may be employed instead of the CMOS imager. 
         [0056]    Although an internal memory (not shown) in the digital camera  10  is employed as a device for recording a still image file and a moving image file according to this embodiment, devices such as a detachable external memory card, an HHD, and an optical disc may be applied. 
         [0057]    Moreover, in this embodiment, although the power-supply managing task, the sleep transition task, the power-feeding-time calculating task, and the power-supply control task are executed using the sub CPU  34 , the main CPU  22 , and the power-supply control portion  28  by applying soft-processing, one or all of these may be executed through hard-processing. 
         [0058]    Furthermore, in this embodiment, although the image signal based on the digital image signal is displayed on the LCD  38 , an organic EL may be applied to display the image signal. 
         [0059]    Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10  . . . digital camera 
           22  . . . main CPU 
           24  . . . volatile memory 
           26  . . . nonvolatile memory 
           28  . . . power-supply control portion 
           30  . . . battery 
           32  . . . SDRAM 
           36  . . . manipulation portion 
           42  . . . external power supply