Patent Abstract:
There is provided a cellular phone taking into consideration enhancement in processing speed and reduction in current consumption, and the cellular phone comprises a processing unit capable of executing plural kinds of processing, an oscillator for generating a clock signal to be fed to the processing unit, and a clock controller for converting the frequency of the clock signal received from the oscillator, wherein the clock controller changes the frequency of the clock signal for each of the plural kinds of the processing in response to the control by the central processing unit.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a continuation application of U.S. application Ser. No. 10/405,368 filed Apr. 3, 2003, now abandoned, the subject matter of which is incorporated herein by reference. This application claims the benefit of Japanese Patent Application 2002-100735 filed on Apr. 3, 2002, the disclosure of which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a cellular phone comprising a central processing unit (CPU). 
   A hand-held terminal or mobile terminal, for switching the frequency of a clock signal delivered from the side of an application program, is disclosed in JP-A NO. 73237/1999 (Heisei 11). 
   Further, in JP-A No. 148475/2000, there is disclosed a computer for a mobile unit, capable of switching a clock frequency to a high-speed mode frequency higher than a normal frequency when conditions, such as power source voltage, ambient temperature, and so forth, are satisfied. 
   In the case of the conventional technology described above, speed control of a clock signal has been implemented by an application program or has been dependent on the conditions such as power source voltage, ambient temperature, and so forth, so that there is no room for interposition of the will of a user in switching the speed of the clock signal. Further, if the CPU is driven at a high frequency, there has been a tendency toward an increase in current consumption although a processing speed is enhanced. With a cellular phone, in particular, since its battery capacity is small, there has been a risk of premature depletion of the battery capacity occurring when the clock signal has been automatically switched over to the high-speed side without knowledge of the user. 
   SUMMARY OF THE INVENTION 
   To attain both enhancement in processing speed and reduction in current consumption, it is an object of the invention to provide a mobile terminal comprising clock control means capable of changing the frequency of a clock signal received from an oscillator under control by a central processing unit, and converting an operation frequency of the central processing unit to a different frequency, wherein a clock signal at the different frequency as converted by the clock control means becomes a clock signal of the central processing unit. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing the configuration of a first embodiment of a cellular phone according to the invention; 
       FIG. 2  is a block diagram showing the configuration of a second embodiment of a cellular phone according to the invention; 
       FIG. 3  is a block diagram showing the configuration of a third embodiment of a cellular phone according to the invention; 
       FIG. 4  is a block diagram showing the configuration of a fourth embodiment of a cellular phone according to the invention; and 
       FIG. 5  is a graph showing the relationship between an operation frequency of a central processing unit of the cellular phone according to the first to fourth embodiments, respectively, and current consumption. 
   

   Other and further objects, features and advantages of the invention will appear more fully from the following description. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A first embodiment of a cellular phone according to the invention is described hereinafter with reference to  FIGS. 1 and 5 .  FIG. 1  is a block diagram showing the internal configuration of the cellular phone according to the first embodiment. 
   A central processing unit (CPU)  100  controls the operation of the cellular phone in accordance with a control program stored in a memory  110 . The CPU  100  performs operation in accordance with an input pushbutton as pressed via an operation panel (input pushbutton group)  120 , executing processing in response to the input pushbutton as pressed. 
   Upon dialing, a telephone number as inputted from the operation panel  120  is shown on a display unit  130 , a speech signal delivered from a speech input unit (microphone)  140  is sent out in the form of radio waves from an antenna  160  to the outside via a transmit/receive unit  150  in accordance with a transmission directive delivered from the operation panel  120 . 
   At the time of signal reception, radio waves from the outside are received by the antenna  160 , and upon recognition by the transmit/receive unit  150  that the radio waves received are radio waves corresponding to a telephone number dedicated to the present cellular phone, speech is delivered from a speech output unit (speaker)  170 . 
   The CPU  100  receives a clock signal from an oscillator  180  through the intermediary of a clock controller  200 . Because an operation frequency of the CPU  100  is dependent on the frequency of the clock signal as received, a processing speed of the CPU  100  is regulated by the frequency of the clock signal. The clock controller  200  converts the frequency of the clock signal into any suitable frequency by use of a PLL (Phase Locked Loop) circuit under control by the CPU  100 , and the clock signal is delivered to the CPU  100  as a clock signal of the CPU  100 . The frequency of the clock signal delivered to the CPU  100  becomes the operation frequency of the CPU  100 . 
     FIG. 5  is a graph showing the relationship between the operation frequency and current consumption. In proportion as the frequency of the clock signal is changed to a higher frequency, the operation frequency of the CPU  100  becomes higher, thereby enhancing the processing speed of the CPU  100  although current consumption increases. 
   With the present embodiment, when executing a specific processing, the frequency of the clock signal of the CPU  100  is caused to change to a higher frequency, thereby enhancing the processing speed. Upon completion of the execution of the specific processing, the frequency of the clock signal of the CPU  100  is caused to change to a lower frequency, thereby reducing current consumption. In the initial condition at the time when power is turned on, the frequency of the clock signal of the CPU  100  is set to a low frequency in order to reduce current consumption. 
   Herein, the specific processing refers to, for example, processing for image decoding, address retrieval processing, and application processing such as kana-kanji conversion processing used in entering characters. These processing often have effects on the response of the user. 
   With the present embodiment, the user can change the operation frequency of the CPU  100  by changing the output frequency of the clock controller  200  at will with the use of a clock manipulation unit  300  connected with the CPU  100 . 
   If the user enters a request for change via the clock manipulation unit  300 , the CPU  100  receives an input from the clock manipulation unit  300 , and controls the clock controller  200 , thereby controlling a clock frequency to be fed to the CPU  100 . That is, in response to the input from the clock manipulation unit  300 , the frequency of the clock signal to be fed to the CPU  100  is set. 
   Further, with the present embodiment, depending on an application to be used, and use environments, the user can change the frequency of the clock signal in every processing. For example, if the user wants to increase the processing speed of the CPU  100 , the frequency of the clock signal can be raised, and if the user wants to reduce current consumption, the frequency of the clock signal can be changed to a lower frequency. By virtue of such a function as described, the user can set the frequency of the clock signal as appropriate at will depending on the user&#39;s use environments, such as the user&#39; desire to execute high speed processing, or to use the cellular phone for many hours, the amount of the actual battery capacity that remains in a battery being small, and so forth, so that operability can be enhanced. 
   In  FIG. 1 , the clock manipulation unit  300  is shown as a single pushbutton (clock manipulation pushbutton), but may be made up of a plurality of keys instead. In order to implement the clock manipulation unit  300  with the single pushbutton, for example, the lowest frequency is set as the initial condition of the frequency of the clock signal, thereby carrying out control such that every time when the single pushbutton is once operated, the frequency of the clock signal of the CPU  100  is changed to sequentially higher frequencies by stages. The frequency is changed cyclically, and if the frequency of the clock signal of the CPU  100  is changed to the highest frequency, upon operation of the single pushbutton the next time, the frequency of the clock signal of the CPU  100  reverts to the lowest frequency. Thus, every time when the single pushbutton is operated, the output frequency of the clock controller  200  can be changed, thereby enabling the operation frequency of the CPU  100  to be changed. 
   The CPU  100  causes the display unit  130  to display a numerical value of the frequency after changed in such a way as to explicitly advise the user of the frequency of the clock signal after changed. Since it is sufficient for such display to indicate simply which stage the processing speed of the CPU  100  is in, indication of a specific numerical value of the frequency is not necessarily required. Numbers to indicate respective stages, such as 1, 2 , 3 . . . , or characters such as high, middle, low, etc. may be displayed. Alternatively, the respective stages of the processing speed may be displayed in number of stars, exhibiting one star on the display unit  130  for the lowest speed, increasing the number of stars exhibited on the display unit  130  in ascending order of the stage. Otherwise, the status of the processing speed may be displayed with the use of a bar graph, icons, and so forth. 
   Further, for changing the output frequency of the clock controller  200  at the user&#39;s will, there may be adopted a method whereby an operation menu directing change of the frequency of the clock signal is caused to be displayed on the display unit  130  without the use of the clock manipulation pushbutton, and the user selects or directs at will the output frequency of the clock controller  200  by use of the operation panel  120 , thereby changing the operation frequency of the CPU  100 . In such a case, the operation panel  120  functions as the clock manipulation unit  300 , so that the clock manipulation unit  300  can be omitted. 
   Now, a second embodiment of a cellular phone according to the invention is described hereinafter with reference to  FIG. 2 .  FIG. 2  is a block diagram showing the internal configuration of the cellular phone according to the second embodiment. 
   With the present embodiment, a central processing unit (CPU) is made up so as to be divided into a first central processing unit  400  concerned with transmit/receive of signals, and a second central processing unit  410  handling processing that has effects on the response of a user. In  FIG. 2 , blocks denoted by the same reference numerals as those in  FIG. 1  correspond to those blocks of the first embodiment, having the same functions. 
   The first central processing unit  400  controls operation concerned with transmit/receive by the cellular phone in accordance with a control program stored in a first memory  420 , and the second central processing unit  410  controls operation concerned with processing that has effects on the response of a user in accordance with a control program stored in a second memory  430 . More specifically, the second central processing unit  410  controls operation concerned with processing of an application program. 
   A clock signal from an oscillator  180  is directly delivered to the first central processing unit  400  as a clock signal. Meanwhile, a clock signal at any suitable frequency converted by control of the second central processing unit  410  is delivered to the second central processing unit  410  through the intermediary of a clock controller  200 . 
   With such a configuration as described, when executing a specific processing, the frequency of the clock signal delivered to the second central processing unit  410  can be changed to a high frequency, thereby enhancing a processing speed, and upon completion of execution of the processing that has effects on the response of the user, the frequency of the clock signal delivered to the second central processing unit  410  can be changed to a low frequency, thereby reducing current consumption. 
   For example, during a standby (waiting) period for communications by the cellular phone, the first central processing unit  400  is in intermittent operation to receive radio waves from the outside via an antenna  160 , executing processing for recognition by the transmit/receive unit  150  that the radio waves received are radio waves corresponding to a telephone number dedicated to the present cellular phone. In this case, the frequency of the clock signal delivered to the second central processing unit  410  is changed to a low frequency to thereby reduce current consumption. As shown  FIG. 5 , the relationship between an operation frequency and current consumption is such that in proportion as the operation frequency becomes higher, the current consumption increases while in proportion as the operation frequency becomes lower, the current consumption decreases. 
   The cellular phone shown in  FIG. 2  further comprises a power supply controller  500 . The power supply controller  500  controls power to be supplied from a battery  510  to the second central processing unit  410  in response to control by the first central processing unit  400 . For example, during a standby (waiting) period for communications by the cellular phone or upon completion of the processing by the second central processing unit  410 , the power supply controller  500  can turn off power to be supplied to the second central processing unit  410  in response to control by the first central processing unit  400 . Since the second central processing unit  410  handles application, its power consumption at the time of processing is large, and consequently, effective saving in power can be attained by controlling the power supplied. 
   Next, a third embodiment of a cellular phone according to the invention is described hereinafter with reference to  FIG. 3 . 
   The cellular phone shown in  FIG. 3  comprises a battery voltage detector  600  in place of the power supply controller  500  incorporated in the cellular phone shown in  FIG. 2 . In  FIG. 3 , blocks denoted by the same reference numerals as those in  FIG. 2  have the same functions as those of the blocks of the second embodiment, omitting therefore description thereof. 
   The battery voltage detector  600  detects a voltage of a battery  510 . A first central processing unit  400  determines whether or not the voltage detected is lower than a predetermined value. In the case where it is determined that the amount of the actual battery capacity that remains in the battery  510  is less than a predetermined amount, the frequency of a clock signal delivered to a second central processing unit  410  is changed to a lower frequency even when executing a specific processing, thereby reduging current consumption. Hence, it is possible to effect control so as to reduce current consumption in case that the amount of the actual battery capacity that remains in the battery becomes small, thereby prolonging operable time of the cellular phone. 
   Further, a fourth embodiment of a cellular phone according to the invention is described hereinafter with reference to  FIG. 4 .  FIG. 4  is a block diagram showing the internal configuration of the cellular phone of a folded structure, according to the fourth embodiment. In  FIG. 4 , blocks denoted by the same reference numerals as those in  FIGS. 2 and 3 , respectively, have the same functions as those of the blocks of the second and third embodiments, respectively, omitting therefore description thereof. 
   The cellular phone shown in  FIG. 4  comprises a folding condition detector  700  for detecting whether the cellular phone is in a folded (closed) condition or in an unfolded (open) condition. 
   With the cellular phone according to the present embodiment, a first display unit  710  and a second display unit  720  are added to a first central processing unit  400  and a second central processing unit  410 , respectively. The first display unit  710  is disposed at a position as can be seen by a user even in the folded condition. The second display unit  720  is disposed at the folded-down side of the cellular phone. 
   Since the operation of the cellular phone in the open condition is the same as that of the cellular phone according to the second and third embodiments, respectively, the operation of the cellular phone in the closed condition is described hereinafter. 
   Normally, in the closed condition, the cellular phone is often on standby (waiting) for cellular phone communications, and the first central processing unit  400  is in intermittent operation to receive radio waves from the outside via an antenna  160 , executing processing for recognition through the intermediary of a transmit/receive unit  150  that the radio waves received are radio waves corresponding to a telephone number dedicated to the present cellular phone. Meanwhile, since a load on the second central processing unit  410  is light at this point in time, the frequency of a clock signal delivered to the second central processing unit  410  can be changed to a low frequency, thereby reducing power consumption. When executing a specific processing even in the closed condition, the frequency of the clock signal delivered to the second central processing unit  410  is caused to change to a higher frequency, thereby enhancing a processing speed, and upon completion of execution of the specific processing, the frequency of the clock signal is caused to change to a low frequency, thereby reducing current consumption. 
   Further, in the closed condition, the user is unable to see the second display unit  720 . Accordingly, as for processing concerning the second display unit  720 , upon detection of the closed condition, the frequency of the clock signal delivered to the second central processing unit  410  is caused to change to a low frequency, thereby enabling current consumption to be reduced. 
   Furthermore, even when executing the specific processing, the frequency of the clock signal delivered to the second central processing unit  410  may be changed to a low frequency in the case of the closed condition. In the case of the cellular phone being in the closed condition, the user does not look at a display screen of the cellular phone, and is often in no hurry to do processing. Accordingly, in the case of the closed condition, processing can be executed while reducing power consumption by changing the frequency of the clock signal to a lower frequency. When the cellular phone is shifted to the open condition, the processing speed is enhanced by changing the frequency of the clock signal delivered to the second central processing unit  410  to a higher frequency. 
   The cellular phone shown in  FIG. 4  further comprises a lighting controller  800  for controlling backlight of the second display unit  720 . Since the user is unable to see the second display unit  720  in the folded condition, further reduction in power consumption can be attained by turning off the backlight of the second display unit  720 . 
   In addition, the power supply controller  500  shown in  FIG. 2  or the battery voltage detector  600  shown in  FIG. 3  may be added to the cellular phone according to the present embodiment. In such a case, when the amount of the actual battery capacity that remains in the battery  510  is less than a predetermined amount, power consumption can be reduced and waiting time can be extended by implementing control such that the backlight of the second display  720  is turned off even in the open condition. 
   Still further, the operability of the cellular phone can be improved by providing the cellular phone shown in  FIGS. 2 through 4 , respectively, with the clock manipulation unit  300  shown  FIG. 1 , thereby enabling the user to change the frequency of the clock signal as with the case of the first embodiment. Also, the operation panel  120  may have the function of the clock manipulation unit  300 . 
   The respective embodiments described hereinbefore may be carried out singly or in combination as appropriate. 
   With the embodiments described hereinbefore, the clock controller, the memories, and so forth are disposed outside of the central processing unit, however, these components together with the central processing unit may be integrated so as to be incorporated in one chip. 
   As described in the foregoing, with the embodiments of the invention, it is possible to attain both enhancement in the processing speed and reduction in the power consumption. 
   The foregoing invention has been described in terms of preferred embodiments. However, those skilled, in the art will recognize that many variations of such embodiments exist. Such variations are intended to be within the scope of the present invention and the appended claims.

Technology Classification (CPC): 8