Patent Publication Number: US-2009228734-A1

Title: Electronic device and system start method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefits of priority from the prior Japanese Patent Application No. 2008-056948, filed on Mar. 6, 2008, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     This invention relates to an electronic device and a system start method, and more particularly, to an electronic device in which a system start is controlled and a system start method for controlling a system start. 
     (2) Description of the Related Art 
     Usually the portable device which is a kind of electronic device is powered by a battery for the purpose of miniaturization and lightening. In addition, electric power obtained by a small battery used in a portable device is low. Accordingly, in order to lengthen time for which a portable device operates, it is necessary to efficiently use electric power stored in a battery. 
     With a portable device having a telephone function or a radio communication function in particular, electric power consumption is high at telephone conversation time or radio communication time. If the electric power the portable device cannot be maintained because of a drop in voltage caused by the internal resistance of a battery. If high electric power is supplied with a lack of electric power at the time of a drop in voltage taken into consideration, then the duration of the battery becomes short. That is to say, in order to maintain the operating state of the portable device for a long period of time, it is necessary to suppress maximum electric power consumption. 
     A method for suppressing the maximum electric power consumption of a portable device having a radio communication function by inhibiting sending operation corresponding to the receiving of radio communication during a period of time for which the other system is consuming high electric power by performing a process is known as a method for solving these problems (see, for example, Japanese Patent Laid-Open Publication No. 2001-111655). Furthermore, a method for reducing the maximum electric power consumption of a portable device which can be used for imaging and carrying out a radiotelephone conversation by stopping or restricting, at the time of receiving a radiotelephone call during imaging, an imaging function and having a radiotelephone conversation is known (see, for example, Japanese Patent Laid-Open Publication No. 2004-166005 or No. 2005-156741). 
     Usually a central processing unit (CPU) which is a processing circuit included in an electronic device realizes the saving of electric power under conditions of a light load by lowering an operation clock frequency. Under conditions of a heavy load, the CPU demonstrates maximum performance. That is to say, the CPU operates at a maximum clock frequency. At this time the CPU consumes electric power the most. The electronic device includes a plurality of electronic circuits. When the plurality of electronic circuits operate at the same time, the load on the CPU increases. Accordingly, the CPU consumes comparatively high electric power to perform each process. 
     With the method disclosed in the above Japanese Patent Laid-Open Publication No. 2001-111655, radio communication is limited and another process is preferentially performed. By doing so, the processing load on an electronic device decreases and the electric power consumption of the electronic device is reduced. However, the usability of both functions is reduced. This is inconvenient. 
     SUMMARY OF THE INVENTION 
     The present invention was made under the background circumstances described above. An object of the present invention is to provide a very convenient device and system start method which can reduce electric power consumption. 
     In order to achieve the above object, an electronic device powered by a battery is provided. This electronic device comprises a first information processing section, a second information processing section operable in parallel with the first information processing section for realizing a portable telephone function, a state check section for outputting instructions to lower a frequency of an operation clock of a processing circuit included in the first information processing section at the time of detecting that the first information processing section is being booted and that a telephone conversation is being carried out by the use of the second information processing section, and a clock control section for lowering the frequency of the operation clock of the processing circuit at the time of accepting the instructions outputted from the state check section to lower the frequency of the operation clock of the processing circuit. 
     The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view showing an electronic device according to the present invention. 
         FIG. 2  is a view showing the hardware configuration of a portable device according to the embodiment of the present invention. 
         FIG. 3  is a block diagram showing the functions of the portable device. 
         FIG. 4  is a view showing an example of the data structure of a system state table. 
         FIG. 5  is a flow chart showing a clock control process. 
         FIG. 6  is a flow chart showing a clock control process performed in the case where a telephone conversation by the use of a portable telephone section is begun. 
         FIG. 7  is a sequence diagram showing a first concrete example of the flow of a clock control process. 
         FIG. 8  is a sequence diagram showing a second concrete example of the flow of a clock control process. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention will now be described in detail with reference to the drawings. An overview of an embodiment of the present invention will be given first. Then the concrete contents of the embodiment of the present invention will be described. 
       FIG. 1  is a schematic view showing an electronic device according to the present invention. An electronic device  1  shown in  FIG. 1  can realize the function of an information processing section  1   c  and the function of an information processing section  1   d  having a portable telephone function in parallel. The electronic device  1  includes a set of hardware resources required to realize the function of the information processing section  1   c  and a set of hardware resources required to realize the function of the information processing section  1   d  having a portable telephone function. These sets of hardware resources can operate as independent information processing sections. In this case, a set of hardware resources means a group of hardware, such as a CPU or a random access memory (RAM), required to form a single system. The information processing sections  1   c  and  1   d  execute individual operating systems (OSes). The function of the information processing section  1   c  and the function of the information processing section  1   d  having a portable telephone function are realized by the electronic device  1 . Each CPU is an example of a processing circuit. 
     The electronic device  1  includes a state check section  1   a  and a clock control section  1   b.    
     When the state check section  1   a  detects that the information processing section  1   c  is being booted and that a telephone conversation is being carried out by the use of the information processing section  1   d , the state check section  1   a  outputs instructions to lower the frequency of an operation clock of the CPU included in the information processing section  1   c.    
     By, for example, accepting notice of a boot start from the information processing section  1   c , the state check section  1   a  can check whether the information processing section  1   c  is being booted. 
     In addition, by, for example, accepting notice of a telephone conversation start from the information processing section  1   d , the state check section  1   a  can check whether a telephone conversation is being carried out by the use of the information processing section  1   d . Furthermore, the following method may be used. The state check section  1   a  sends the information processing section  1   d  a confirmation request in order to check the state of the information processing section  1   d . On the basis of a response to the confirmation request, the state check section  1   a  checks whether a telephone conversation is being carried out by the use of the information processing section  1   d.    
     When the clock control section  1   b  accepts the instructions outputted from the state check section  1   a  to lower the frequency of the operation clock of the CPU included in the information processing section  1   c , the clock control section  1   b  lowers the frequency of the operation clock of the CPU included in the information processing section  1   c . The extent to which the clock control section  1   b  lowers the frequency of the operation clock is set in advance in a storage area of the clock control section  1   b.    
     The following effect can be obtained by the electronic device  1  having the above structure. For example, even if the information processing section  1   c  is being booted at the time of a telephone conversation being begun by the use of the information processing section  1   d , the electric power consumption of the information processing section  1   c  can be reduced by lowering the frequency of the operation clock of the CPU which performs a boot process in the information processing section  1   c . Accordingly, the electric power consumption of the entire electronic device  1  can be reduced. This avoids the discontinuance of a telephone conversation caused by the inability to maintain the operation of the information processing sections  1   c  and  1   d . For example, when there is a sharp drop in the voltage of a power source of the electronic device  1 , the operation of the information processing sections  1   c  and  1   d  cannot be maintained. Furthermore, there is no need to inhibit a telephone conversation realized by the use of the information processing section  1   d  having a portable telephone function while the information processing section  1   c  is being booted. This is convenient. In addition, an electric power load on the power source can be reduced. Accordingly, if a battery, for example, is used as the power source, its duration can be lengthened. 
     If the frequency of the operation clock of the CPU included in the information processing section  1   c  remains low, then the information processing section  1   c  cannot demonstrate its performance fully. Therefore, when the process of booting the information processing section  1   c  is completed or when a telephone conversation by the use of the information processing section  1   d  is completed, the frequency of the operation clock of the CPU included in the information processing section  1   c  may automatically be returned to the original frequency. 
     The above electronic device will now be described more concretely with reference to the drawings. 
       FIG. 2  is a view showing the hardware configuration of a portable device according to the embodiment of the present invention. A portable device  100  includes a computer section  130  and a portable telephone section  150  and can make these two information processing sections operate in parallel. Sections of the portable device  100  are connected to one another via a bus  107 . 
     A display section  101  is a monitor on which an image is displayed in accordance with an instruction issued by a CPU of each section. A liquid crystal monitor, for example, is used as the display section  101 . 
     An input section  102  provides input to the computer section  130  or the portable telephone section  150 . A keyboard, a pointing device, or the like is used as the input section  102 . 
     A microphone  103  provides audio input to the computer section  130  or provides audio input at telephone conversation time to the portable telephone section  150 . 
     Audio output from the computer section  130  or audio output from the portable telephone section  150  at telephone conversation time is provided to a speaker  104 . 
     An input-output switching section  105  switches the object of operation between the computer section  130  and the portable telephone section  150 . A source from which output is provided to the display section  101  or the speaker  104  can be switched by the input-output switching section  105 . Similarly, a destination to which input is provided from the input section  102  or the microphone  103  can be switched. A user operates, for example, a changeover switch (not shown) on the portable device  100 . By doing so, the user can give the input-output switching section  105  instructions to perform switching operation. 
     A power source section  106  is connected to a battery (not shown) and supplies electric power to each section of the portable device  100 . 
     A start control section  110  monitors the operating state of the computer section  130  and the portable telephone section  150 . In addition, the start control section  110  controls the frequency of a clock of the CPU when the computer section  130  is being booted. The start control section  110  includes a RAM  111 . The RAM  111  stores data required for a process performed by the start control section  110 . 
     The hardware configuration of the computer section  130  will now be described. 
     The whole of the computer section  130  is controlled by a CPU  131 . A RAM  132 , a flash memory  133 , and a communication module  134  are connected to the CPU  131  via a bus  135 . 
     The RAM  132  temporarily stores at least part of an OS or an application program (hereafter application) executed by the CPU  131 . The RAM  132  also stores various pieces of data required for a process performed by the CPU  131 . 
     The flash memory  133  stores the OS or the application program on the computer section  130 . The flash memory  133  also stores the various pieces of data required for a process performed by the CPU  131 . 
     The communication module  134  sends data to or receives data from another computer via a network  10 . 
     The hardware configuration of the portable telephone section  150  will now be described. 
     The whole of the portable telephone section  150  is controlled by a CPU  151 . A RAM  152 , a flash memory  153 , and a radio communication module  154  are connected to the CPU  151  via a bus  156 . In addition, an antenna  155  is connected to the radio communication module  154 . 
     The RAM  152  temporarily stores at least part of an OS or an application program executed by the CPU  151 . The RAM  152  also stores various pieces of data required for a process performed by the CPU  151 . 
     The flash memory  153  stores the OS or the application program on the portable telephone section  150 . The flash memory  153  also stores the various pieces of data required for a process performed by the CPU  151 . 
     The radio communication module  154  includes a radio frequency (RF) circuit for radio communication, a circuit for modulating and demodulating signals sent and received, and the like. The portable telephone section  150  performs radio communication with a base station via the radio communication module  154  and the antenna  155 . By doing so, the portable telephone section  150  can send data to or receive data from another information processing device and hold a telephone conversation with another information processing device. In this case, an information processing device is, for example, a portable telephone. 
     By adopting the above hardware configuration, the functions of the portable device according to the embodiment of the present invention can be realized. 
     The functions of the portable device  100  will now be described. 
       FIG. 3  is a block diagram showing the functions of the portable device. The portable device  100  includes the start control section  110 , the computer section  130 , and the portable telephone section  150 . 
     The start control section  110  includes a state storage  121 , a state checker  122 , and a clock controller  123 . 
     The state storage  121  stores a system state table in which information indicative of whether the computer section  130  is being booted and whether a telephone conversation is being carried out by the use of the portable telephone section  150  is included. 
     The state checker  122  accepts notice of a boot start and notice of a boot end sent from a start state notice sender  141  of the computer section  130 . In addition, the state checker  122  accepts notice of a telephone conversation start and notice of a telephone conversation end sent from a telephone conversation state notice sender  161  of the portable telephone section  150 . When the state checker  122  accepts the above notice, the state checker  122  updates the system state table stored in the state storage  121  on the basis of information the state checker  122  accepts. Then the state checker  122  refers to the above system state table. If the state checker  122  detects that the computer section  130  is being booted and that a telephone conversation is being carried out by the use of the portable telephone section  150 , then the state checker  122  outputs instructions to lower the frequency of an operation clock of the CPU  131  of the computer section  130 . The system state table will be described in detail in  FIG. 4 . 
     Furthermore, when the state checker  122  detects at the least one of the end of booting the computer section  130  and the end of the telephone conversation by the use of the portable telephone section  150  after detecting that the computer section  130  is being booted and that the telephone conversation is being carried out by the use of the portable telephone section  150 , the state checker  122  outputs instructions to return the frequency of the operation clock of the CPU  131  of the computer section  130 . 
     When the clock controller  123  accepts the instructions outputted from the state checker  122  to lower the frequency of the operation clock of the CPU  131  of the computer section  130 , the clock controller  123  controls a clock supplier  142  of the computer section  130  to lower the frequency of the operation clock of the CPU  131 . In addition, when the clock controller  123  accepts the instructions outputted from the state checker  122  to return the frequency of the operation clock of the CPU  131 , the clock controller  123  controls the clock supplier  142  of the computer section  130  to return the frequency of the operation clock of the CPU  131  to the original frequency. 
     The computer section  130  includes the start state notice sender  141  and the clock supplier  142 . 
     When the computer section  130  shifts from a power off state to a state in which the computer section  130  is being booted, the start state notice sender  141  outputs notice of a boot start to the state checker  122 . When the booting of the computer section  130  ends, the start state notice sender  141  outputs notice of a boot end to the state checker  122 . 
     The clock supplier  142  supplies a clock necessary for the operation of the CPU  131 . The clock supplier  142  is controlled by the clock controller  123  to increase or decrease the frequency of the clock supplied. The clock supplier  142  is included in, for example, the CPU  131  and converts the frequency of a clock supplied from a phase locked loop (PLL), which is not shown in  FIG. 2 , included in the computer section  130  into a frequency suitable for the operation of the CPU  131 . 
     The portable telephone section  150  includes the telephone conversation state notice sender  161 . When a state in which a telephone conversation is not being carried out by the use of the portable telephone section  150  shifts to a state in which a telephone conversation is being carried out by the use of the portable telephone section  150 , the telephone conversation state notice sender  161  outputs notice of a telephone conversation start to the state checker  122 . When the telephone conversation by the use of the portable telephone section  150  ends, the telephone conversation state notice sender  161  outputs notice of a telephone conversation end to the state checker  122 . 
     The system state table stored in the state storage  121  will now be described. 
       FIG. 4  is a view showing an example of the data structure of a system state table. A system state table  121   a  includes items indicative of a computer section start flag and a portable telephone section telephone conversation flag. 
     A flag indicative of whether the computer section  130  is being booted is set under the Computer Section Start Flag item. For example, if the computer section  130  is being booted, then “1” is set under the Computer Section Start Flag item. If the computer section  130  is not being booted, then “0” is set under the Computer Section Start Flag item. A flag indicative of whether a telephone conversation is being carried out by the use of the portable telephone section  150  is set under the Portable Telephone Section Telephone Conversation Flag item. For example, if a telephone conversation is being carried out by the use of the portable telephone section  150 , then “1” is set under the Portable Telephone Section Telephone Conversation Flag item. If a telephone conversation is not being carried out by the use of the portable telephone section  150 , then “0” is set under the Portable Telephone Section Telephone Conversation Flag item. 
     In the system state table  121   a , for example, “1” is set under the Computer Section Start Flag item and “1” is set under the Portable Telephone Section Telephone Conversation Flag item. This indicates that the computer section  130  is being booted and that a telephone conversation is being carried out by the use of the portable telephone section  150 . When the state checker  122  detects this state of the system state table  121   a , the state checker  122  outputs instructions to the clock controller  123  to lower a clock frequency. 
     In addition, it is assumed that after “1” is set under the Computer Section Start Flag item and the Portable Telephone Section Telephone Conversation Flag item included in the system state table  121   a , the telephone conversation by the use of the portable telephone section  150  ends. At this time the state checker  122  changes “1” set under the Portable Telephone Section Telephone Conversation Flag item included in the system state table  121   a  to “0”. Then the state checker  122  detects that the state in which both of the above flags (that is to say, the computer section start flag and the portable telephone section telephone conversation flag) are “1” (“1, 1”) has shifted to a state in which at the least one of these flags is “0” (“1, 0”). After the state in which the computer section  130  is being booted and in which a telephone conversation is being carried out by the use of the portable telephone section  150  has arisen, the booting of the computer section  130  ends or the telephone conversation by the use of the portable telephone section  150  ends. By using the above system state table, the state checker  122  can output instructions to return the frequency of the operation clock of the CPU  131  included in the computer section  130 , when the state checker  122  detects at the least one of the end of the booting of the computer section  130  and the end of the telephone conversation by the use of the portable telephone section  150 . 
     A process performed by adopting the above structure and data structure will now be described in detail. 
       FIG. 5  is a flow chart showing a clock control process. A process shown in  FIG. 5  will now be described in order of step number. 
     [Step S 11 ] The state checker  122  refers to the system state table  121   a . When the state checker  122  detects that the computer section  130  is being booted and that a telephone conversation is being carried out by the use of the portable telephone section  150 , the state checker  122  outputs instructions to the clock controller  123  to lower the frequency of the operation clock of the CPU  131 . 
     [Step S 12 ] When the clock controller  123  accepts the instructions outputted from the state checker  122  to lower the frequency of the operation clock of the CPU  131 , the clock controller  123  controls the clock supplier  142  of the computer section  130  to lower the frequency of the operation clock of the CPU  131 . 
     [Step S 13 ] The state checker  122  refers to the system state table  121   a . When the state checker  122  detects at the least one of the end of the booting of the computer section  130  and the end of the telephone conversation by the use of the portable telephone section  150 , the state checker  122  outputs instructions to the clock controller  123  to return the frequency of the operation clock of the CPU  131 . 
     [Step S 14 ] When the clock controller  123  accepts the instructions outputted from the state checker  122  to return the frequency of the operation clock of the CPU  131 , the clock controller  123  controls the clock supplier  142  of the computer section  130  to return the frequency of the operation clock of the CPU  131  to the original frequency. 
     A significant increase in the electric power consumption of the portable device  100  which is caused while the computer section  130  is being booted and while a telephone conversation is being carried out by the use of the portable telephone section  150  can be avoided in this way. 
     The flow of a process performed in the case where a telephone conversation by the use of the portable telephone section  150  is begun will now be described in detail as an example of the process of controlling the operation clock of the CPU  131  included in the computer section  130 . 
       FIG. 6  is a flow chart showing a clock control process performed in the case where a telephone conversation by the use of a portable telephone section is begun. A process shown in  FIG. 6  will now be described in order of step number. 
     [Step S 21 ] Telephone conversation by the use of the portable telephone section  150  is begun. For example, a telephone conversation by the use of the portable telephone section  150  is begun according to input operation performed by a user to make a call. In addition, there are cases where a telephone conversation by the use of the portable telephone section  150  is begun with a caller according to input operation performed by a user in response to a telephone call received. The state checker  122  detects that a telephone conversation is being carried out by the use of the portable telephone section  150 . 
     [Step S 22 ] The state checker  122  detects whether the computer section  130  is being booted. If the computer section  130  is being booted (that is to say, a boot is begun just before a telephone conversation is begun), then step S 23  is performed. If the computer section  130  is not being booted (in this example, the computer section  130  is in a normal operating state after a boot), then step S 24  is performed. Basically the computer section  130  is booted according to input operation performed by the user. However, the boot of the computer section  130  may automatically be begun, for example, at a specific time. 
     [Step S 23 ] The state checker  122  outputs instructions to the clock controller  123  to lower the frequency of the operation clock of the CPU  131 . When the clock controller  123  accepts the instructions outputted from the state checker  122  to lower the frequency of the operation clock of the CPU  131 , the clock controller  123  controls the clock supplier  142  of the computer section  130  to lower the frequency of the operation clock of the CPU  131 . If the frequency of the operation clock of the CPU  131  has already been lowered, then this state is maintained. 
     [Step S 24 ] The state checker  122  outputs instructions to the clock controller  123  to return the frequency of the operation clock of the CPU  131 . When the clock controller  123  accepts the instructions outputted from the state checker  122  to return the frequency of the operation clock of the CPU  131 , the clock controller  123  controls the clock supplier  142  of the computer section  130  to return the frequency of the operation clock of the CPU  131  to the original frequency. If the frequency of the operation clock of the CPU  131  has already been returned to the original frequency, then this state is maintained. 
     [Step S 25 ] The state checker  122  detects whether the telephone conversation by the use of the portable telephone section  150  has ended. If the telephone conversation by the use of the portable telephone section  150  has ended, then step S 26  is performed. If the telephone conversation by the use of the portable telephone section  150  has not ended, then step S 22  is performed. 
     [Step S 26 ] The state checker  122  outputs instructions to the clock controller  123  to return the frequency of the operation clock of the CPU  131 . When the clock controller  123  accepts the instructions outputted from the state checker  122  to return the frequency of the operation clock of the CPU  131 , the clock controller  123  controls the clock supplier  142  of the computer section  130  to return the frequency of the operation clock of the CPU  131  to the original frequency. If the frequency of the operation clock of the CPU  131  has already been returned to the original frequency, then this state is maintained. 
     The state checker  122  may check the state of the computer section  130  and the portable telephone section  150  at timing at which the state checker  122  accepts notice from each section or at regular time intervals. 
     The case where a telephone conversation by the use of the portable telephone section  150  is begun while the computer section  130  is being booted or the case where the booting of the computer section  130  is begun while a telephone conversation by the use of the portable telephone section  150  is being carried out can be cited as an example of the case where the frequency of the operation clock of the CPU  131  included in the computer section  130  is controlled. The concrete flow of communication performed in these cases between the start control section  110 , the computer section  130 , and the portable telephone section  150  will now be described. 
     The case where a telephone conversation by the use of the portable telephone section  150  is begun while the computer section  130  is being booted will be described first. 
       FIG. 7  is a sequence diagram showing a first concrete example of the flow of a clock control process. A process shown in  FIG. 7  will now be described in order of step number. 
     [Step S 31 ] When the booting of the computer section  130  is begun, the computer section  130  outputs notice of a boot start to the start control section  110 . 
     [Step S 32 ] When a telephone conversation by the use of the portable telephone section  150  is begun, the portable telephone section  150  outputs notice of a telephone conversation start to the start control section  110 . 
     [Step S 33 ] The start control section  110  gives the computer section  130  instructions to lower the frequency of the operation clock of the CPU  131 . 
     [Step S 34 ] The computer section  130  answers the start control section  110  that the frequency of the operation clock of the CPU  131  is lowered. 
     [Step S 35 ] When the telephone conversation by the use of the portable telephone section  150  ends, the portable telephone section  150  outputs notice of a telephone conversation end to the start control section  110 . 
     [Step S 36 ] The start control section  110  gives the computer section  130  instructions to return the frequency of the operation clock of the CPU  131  to the original frequency. 
     [Step S 37 ] The computer section  130  answers the start control section  110  that the frequency of the operation clock of the CPU  131  is returned to the original frequency. 
     [Step S 38 ] When the booting of the computer section  130  ends, the computer section  130  outputs notice of a boot end to the start control section  110 . 
     The order of the above steps S 35  and S 38  may reverse. That is to say, when at the least one of the booting of the computer section  130  and the telephone conversation by the use of the portable telephone section  150  ends, the frequency of the operation clock of the CPU  131  included in the computer section  130  is returned to the original frequency. 
     The case where the booting of the computer section  130  is begun while a telephone conversation by the use of the portable telephone section  150  is being carried out will be described next. 
       FIG. 8  is a sequence diagram showing a second concrete example of the flow of a clock control process. A process shown in  FIG. 8  will now be described in order of step number. 
     [Step S 41 ] When a telephone conversation by the use of the portable telephone section  150  is begun, the portable telephone section  150  outputs notice of a telephone conversation start to the start control section  110 . 
     [Step S 42 ] When the booting of the computer section  130  is begun, the computer section  130  outputs notice of a boot start to the start control section  110 . 
     [Step S 43 ] The start control section  110  gives the computer section  130  instructions to lower the frequency of the operation clock of the CPU  131 . 
     [Step S 44 ] The computer section  130  answers the start control section  110  that the frequency of the operation clock of the CPU  131  is lowered. 
     [Step S 45 ] When the booting of the computer section  130  ends, the computer section  130  outputs notice of a boot end to the start control section  110 . 
     [Step S 46 ] The start control section  110  gives the computer section  130  instructions to return the frequency of the operation clock of the CPU  131  to the original frequency. 
     [Step S 47 ] The computer section  130  answers the start control section  110  that the frequency of the operation clock of the CPU  131  is returned to the original frequency. 
     [Step S 48 ] When the telephone conversation by the use of the portable telephone section  150  ends, the portable telephone section  150  outputs notice of a telephone conversation end to the start control section  110 . 
     The order of the above steps S 45  and S 48  may reverse. That is to say, when at the least one of the booting of the computer section  130  and the telephone conversation by the use of the portable telephone section  150  ends, the frequency of the operation clock of the CPU  131  included in the computer section  130  is returned to the original frequency. 
     A significant increase in the electric power consumption of the portable device  100  which is caused while the computer section  130  is being booted and while a telephone conversation is being carried out by the use of the portable telephone section  150  can be avoided in this way. In addition, a telephone conversation by the use of the portable telephone section  150  can be carried out preferentially. 
     This avoids interruption of work or a telephone conversation caused by the inability to maintain the operation of the computer section  130  and the portable telephone section  150 . For example, when there is a sharp drop in the voltage of the battery of the portable device  100 , the operation of the computer section  130  and the portable telephone section  150  cannot be maintained. Furthermore, there is no need to inhibit a telephone conversation realized by the use of the portable telephone section  150  while the computer section  130  is being booted. As a result, convenience improves. In addition, an electric power load on the battery can be reduced, so its duration can be lengthened. 
     If the computer section  130  is being booted and a telephone conversation is being carried out by the use of the portable telephone section  150 , the method of stopping image output by the display section  101  may be adopted in order to reduce the electric power consumption of the portable device  100  further. If a liquid crystal monitor, for example, is used as the display section  101 , then the electric power consumption of the display section  101  can be reduced by dimming (backlight) illumination of the monitor in the case of operation not being performed on the display section  101  for a predetermined period of time. In addition, if operation is not performed on the display section  101  for a predetermined period of time after dimming the illumination, then the display section  101  should stop image output to the monitor. This reduces electric power consumption further and is effective. 
     The electronic device and the system start method have been described on the basis of the embodiments shown. However, the present invention is not limited to these embodiments. The structure of each section can be replaced by an arbitrary structure having the same function. Furthermore, other arbitrary components or steps may be added to these embodiments. In addition, the structure (characteristics) of any two or more of the above-mentioned embodiments may be combined. 
     In the above-mentioned embodiments a CPU is shown as an example of a processing circuit. However, a processor of another type, a controller, or hardware which is equal in function to them may be used as a processing circuit. 
     By using the above-mentioned electronic device and system start method, electric power consumption can be reduced and convenience improves. 
     The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents.