Abstract:
A portable navigation device with a TV function includes a TV module, a navigation module, a display module, a sound module, a first processing unit, a second processing unit and a TV command storage module. The TV module generates baseband TV signals, the navigation module generates position information, the display module displays image information, the sound module plays sounds, the first processing unit performs navigation programs, the second processing unit performs TV programs, and the TV command storage module stores TV commands from the first processing unit and the second processing unit. TV command transmission between the first processing unit and the second processing unit is achieved by sending interrupt signals or reset signals.

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This patent application is based on Taiwan, R.O.C. patent application No. 97144577 filed on Nov. 28, 2008. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a portable navigation device (PND) having dual processing units, and more particularly, to a PND having dual processing units for a navigation function and a TV function. 
       BACKGROUND OF THE INVENTION 
       [0003]    A PND is a convenient tool for a driver. With preferred planned routes provided by the PND, the driver can obtain a current position and avoid getting lost or taking an undesired detour. In addition, by the PND a user can watch TV programs anywhere, in a vehicle or outdoors, no longer limited to indoors. 
         [0004]    Nowadays, a PND with a TV function can be classified into several architecture types. 
         [0005]    The first architecture is that a PND has two processing modules independent from each other. One processing module is used for processing Global Positioning System (GPS) signals from satellites; the other processing module is used for processing TV signals. Both of the processing modules, without sharing interface, have respective elements such as a display interface, a sound interface or a data bus. Therefore, the first architecture suffers from disadvantages of having high costs, large-area circuits, high degrees of design complexity, high power consumption and so on. 
         [0006]    The second architecture is that a PND only has a single processing module which needs to be powerful enough to simultaneously process GPS signals and TV signals. The second architecture has disadvantages below. First of all, a high speed processing unit having high computation capability is needed; secondly, high power consumption by the processing unit is resulted from processing images and voices; last but not least, concurrent execution of a navigation function and a TV function is unlikely to be smooth with the single processing module. 
         [0007]    Accordingly, it is preferred to provide a PND, which comprises dual processing units that share common system resources and is capable of providing a navigation function and a TV function. Such PND not only solves the foregoing problem and other problems of the prior art, but also has advantages that are not provided by the conventional technology. 
       SUMMARY OF THE INVENTION 
       [0008]    A PND having two processing units for a navigation function and a TV function is provided according to the present invention. Communication between the processing units is achieved by sending interrupt signals or reset signals. 
         [0009]    A first aspect of the present invention is to provide a PND with a TV function. A portable navigation device (PND) with a TV function, comprises a data bus; a TV module, coupled to the data bus, for receiving and processing TV signals to generate baseband TV signals; a navigation module, coupled to the data bus, for receiving and processing satellite signals to generate position data; a display module, coupled to the data bus, for displaying image related to one of the baseband TV signals and the position data; a sound module, coupled to the data bus, for playing sound related to one of the baseband TV signals and the position data; a storage module, coupled to the data bus, for storing TV programs and data, and navigation programs and data; a first processing unit, coupled to the data bus, for executing the navigation program to control the navigation module, the sound module, the display module and the storage module, and generating a first TV command according to a TV enable signal; a second processing unit, coupled to the data bus, for executing the TV program to control the TV module, the sound module, the display module and the storage module, and generating a second TV command according to a TV disable signal; a TV command storage module, coupled to the data bus, for storing the first TV command and the second TV command; a first interrupt controller, coupled to the first processing unit, for generating a first interrupt signal to the first processing unit according to the second TV command; and a second interrupt controller, coupled to the second processing unit, for generating a second interrupt signal to the second processing unit according to the first TV command. 
         [0010]    A second aspect of the present invention is to provide a processing module applied to a PND with a TV function. A processing module, applied to a PND with a TV function, the PND further comprising a navigation module, a TV module, a storage module, a sound module and a display module, the processing module comprises a data bus; a display interface, coupled to the data bus, for controlling the display module to display image data related to one of baseband TV signals and position data; a sound interface, coupled to the data bus, for controlling the sound interface to play sound related to one of the baseband TV signals and the position data; a storage interface, coupled to the data bus, for controlling the storage module to store TV programs and data and navigation programs and data; a first processing unit, coupled to the data bus, for executing navigation programs to control the navigation interface, the sound interface, the display interface and the storage interface, and generating a first command according to a TV function enable signal; a second processing unit, coupled to the data bus, for executing a TV associated program, controlling the TV module, controlling the sound module, the display module and the storage module via the sound interface, the display interface and the storage interface, and generating a second command according to a TV function disable signal; a TV command storage module, coupled to the data bus, for storing the first TV command and the second TV command; a first interrupt controller, coupled to the first processing unit, for generating a first interrupt signal to the first processing unit; and a second interrupt controller, coupled to the second processing unit, for generating a second interrupt signal to the second processing unit. 
         [0011]    A third aspect of the present invention is to provide an processing method for a TV function of a PND. A TV function processing method for a PND with a TV function, wherein the PND comprises a first processing unit, a second processing unit, a navigation module, a TV module, a storage module, a sound module and a display module, and the first processing unit is used for handing a navigation function and generating a TV command, and the second processing unit is used for handling a TV function, the TV function activating method comprises steps of generating the TV command by the first processing unit according a TV enable signal; generating a signal from the first processing unit to the second processing unit; receiving the signal by the second processing unit; retrieving the TV command by the second processing unit; and controlling the TV module, the storage module, the sound module and the display module by the second processing unit according to the TV command to perform the TV function. 
         [0012]    The advantages and spirit related to the present invention can be further understood via the following detailed description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a block diagram of a PND according to a first embodiment of the present invention. 
           [0014]      FIG. 2A  is a schematic diagram of a first communication approach between dual processing units. 
           [0015]      FIG. 2B  is a flow chart of a communication process between dual processing units shown in  FIG. 2A . 
           [0016]      FIG. 3A  is a schematic diagram of a second communication approach between dual processing units. 
           [0017]      FIG. 3B  is a flow chart of a communication process between dual processing units shown in  FIG. 3A . 
           [0018]      FIG. 4  is a boot flow chart of the first processing unit  101 . 
           [0019]      FIG. 5  is a flow chart of activating a TV function according to a first embodiment of the present invention. 
           [0020]      FIG. 6  is a flow chart of deactivating a TV function by a user according to a first embodiment of the present invention. 
           [0021]      FIG. 7  is a flow chart of deactivating a TV function resulting from power shortage according to a first embodiment of the present invention. 
           [0022]      FIG. 8  is a block diagram of a PND according to a second embodiment of the present invention. 
           [0023]      FIG. 9  is a flow chart of activating a TV function according to a second embodiment of the present invention. 
           [0024]      FIG. 10  is a flow chart of deactivating a TV function by a user according a second embodiment of the present invention. 
           [0025]      FIG. 11  is a flow chart of deactivating a TV function resulting from power shortage according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    A PND having two processing units for a navigation function and a TV function is provided according to an embodiment of the present invention. One of the processing units is used for handling navigation function and the other processing unit is used for handling TV function. When one of the processing units operates in a normal mode, the other processing unit is in a power saving mode to reduce power consumption of the PND. In addition, communication between the processing units is achieved by sending interrupt signals or reset signals. 
         [0027]      FIG. 1  is a block diagram of a PND  100  having two processing units according to a first embodiment of the present invention. In this embodiment, the power supplying to all elements in the PND  100  is provided by a single power supply and management module. 
         [0028]    Referring to  FIG. 1 , the PND  100  comprises a first processing unit  101 , a second processing unit  103 , an message exchange unit  105 , a navigation module  107 , a TV module  109 , a display interface  111 , a storage interface  113 , a storage device  114 , a memory interface  115 , a memory  116 , a sound interface  117 , a read only memory (ROM)  118 , a power supply and management module  119 , a bus  121 , a display module  123 , a sound module  125  and a video processing unit  127 . Further, the TV module  109  comprises a TV tuner  109 A, a TV modulator  109 B and a TV interface  109 C; the navigation module  107  comprises a GPS interface  107 A and a GPS receiver  107 B. 
         [0029]    The first processing unit  101  controls the message exchange unit  105 , the navigation module  107 , the display interface  111 , the storage interface  113 , the storage device  114 , the memory interface  115 , the memory  116 , the sound interface  117 , the power supply and management module  119 , the display module  123 , the sound module  125  and the video processing unit  127  to be used for processing a navigation function. 
         [0030]    The second processing unit  103  controls the message exchange unit  105 , the TV module  109 , the display interface  111 , the storage interface  113 , the storage device  114 , the memory interface  115 , the memory  116 , the sound interface  117 , the display module  123 , the sound module  125  and the video processing unit  127  to be used for processing a TV function. 
         [0031]    The message exchange unit  105  provides communication between the first processing unit  101  and the second processing unit  103 . Operations of the message exchange unit  105  and communication between the processing units are to be described below. 
         [0032]    The GPS receiver  107 B receives and processes satellite signals to generate current position information, which is transmitted to the first processing unit  101  via the GPS interface  107 A and the bus  121 . The first processing unit  101  performs a navigation function according to the received current position information, controls the display interface  111  and the display module  123  to display a current position on the display module  123 , and controls the sound interface  117  and the sound module  125  to play a navigation voice message. 
         [0033]    The TV module  109  is coupled to the bus  121 . The TV tuner  109 A inside the TV module  109  receives TV signals. The TV modulator  109 B de-modulates the received TV signals to generate baseband TV signals. The second processing unit  103  processes the baseband TV signals to displays TV video on the display module  123  via the display interface  111  and outputs TV audio from the sound module  125  via the sound interface  117 . 
         [0034]    The display interface  111  and the display module  123  are controlled by the first processing unit  101  to display a navigation image. In addition, the display interface  111  and the display module  123  are controlled by the second processing unit  103  to display a TV video. 
         [0035]    The sound interface  117  and the sound module  125  are controlled by the first processing unit  101  to play a navigation voice. Moreover, the sound interface  117  and the sound module  125  are controlled by the second processing unit  103  to play a TV audio. 
         [0036]    The first processing unit  101  and the second processing unit  103  access the storage device  114  via the storage interface  113 . The first processing unit  101  and the second processing unit  103  share the storage device  114 . Navigation programs and information needed by the first processing unit  101  are stored in the storage device  114 , and TV programs and information needed by the second processing unit  103  are also stored in the storage device  114 . The storage device  114  may be various types of memory cards, such as a secure digital (SD) card, for example. Therefore, the navigation and TV programs stored in the storage device  114  can be updated. 
         [0037]    The first processing unit  101  and the second processing unit  103  access the memory  116  and the ROM  118  via the memory interface  115 . The first processing unit  101  and the second processing unit  103  share the memory  116 . The ROM  118  is used for storing with a boot code needed by the first processing unit  101 . During a booting process, the first processing unit  101  executes the boot code accessed from the ROM  118  and stores system codes needed by the first processing unit  101  and the second processing unit  103  from the storage device  114  into the memory  116  such as a dynamic random access memory (DRAM). 
         [0038]    The power supply and management module  119  provides power to all electronic elements inside the PND  100 . The power supply and management module  119  is controlled by the first processing unit  101 . When the PND  100  performs the navigation function, the TV function is temporarily not needed by the user. Under such circumstances, the second processing unit  103  locks a clock gating and waits for an interruption to enter the power saving mode, so as to reduce power consumption of the PND. 
         [0039]    The bus  121  is coupled to the first processing unit  101 , the second processing unit  103 , the message exchange unit  105 , the navigation module  107 , the TV module  109 , the display interface  111 , the storage interface  113 , the memory interface  115 , the sound interface  117 , the video processing unit  127  and the power supply and management module  119 . The video processing unit  127  is applied for processing video data to reduce computing loading of the first processing unit  101  and the second processing unit  103 . 
         [0040]    Refer to  FIG. 2A  to  FIG. 3B  to obtain a better understanding of the communication between the first processing unit  101  and the second processing unit  103  according to the first embodiment of the present invention.  FIG. 2A  is a schematic diagram of a first communication approach between the processing units.  FIG. 2B  is a flow chart of the communication between the processing units shown in  FIG. 2A .  FIG. 3A  a schematic diagram of a second communication approach between the processing units.  FIG. 3B  is a flow chart of the communication between the processing units shown in  FIG. 3A . 
         [0041]    Referring to  FIG. 2A , the message exchange unit  105  comprises interrupt controllers  210  and  220 . Communication between the first processing unit  101 , the second processing unit  103 , the interrupt controller  210  and the interrupt controller  220  are illustrated in  FIG. 2B . 
         [0042]    Referring to  FIG. 2B , in Step S 210 , the first processing unit  101  sends a TV associated command and stores the TV associated command into the memory  116 . For example, the first processing unit  101  sends a TV enable command in response to a TV enable event triggered by the user. A format of the associated command is described below. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Digital code 
                 Command 
               
               
                   
                   
               
             
             
               
                   
                 0xFF 
                 None 
               
               
                   
                 0x00 
                 TV enable command 
               
               
                   
                 0x01 
                 TV disable command 
               
               
                   
                 0x02 
                 Video open command 
               
               
                   
                 0x03 
                 Video close command 
               
               
                   
                 0x04~0xFE 
                 Reserved 
               
               
                   
                   
               
             
          
         
       
     
         [0043]    In Step S 220 , the first processing unit  101  controls the interrupt controller  210  to transmit a trigger signal to the interrupt controller  220 . In Step S 240 , the interrupt controller  220  transmits an interrupt signal to the second processing unit  103 . In Step S 250 , the second processing unit  103  retrieves the associated command stored in the memory  116 . Thus, because of the interrupt controller  220 , the first processing unit  101  is able to indirectly send the associated command to the second processing unit  103  by sharing the memory  116 . 
         [0044]    Another communication approach between the processing units is to be described. Refer to  FIGS. 3A and 3  B. The message exchange unit  105  comprises a mailbox  310 , the interrupt controller  210  and the interrupt controller  220  as illustrated in  FIG. 3A . The operation between the first processing unit  101 , the second processing unit  103 , the mailbox  310 , the interrupt controller  210  and the interrupt controller  220  is illustrated in  FIG. 3B . 
         [0045]    The mailbox  310  is coupled to the bus  121 , the interrupt controller  210  and the interrupt controller  220 . The mailbox  310  stores message used for exchanging between the first processing unit  101  and the second processing unit  103 . 
         [0046]    In Step S 310 , the processing unit  101  stores a TV associated command into the mailbox  310  via the bus  121 . In Step S 320 , upon receiving the TV associated command from the first processing unit  101 , the mailbox  310  sends a trigger signal to the interrupt controller  220 . In Step S 330 , the interrupt controller  220  sends an interrupt signal to the second processing unit  103 . In Step S 340 , the second processing unit  103  retrieves the TV associated command stored in the mailbox  310  via the bus  121 . Thus, the communication between the first processing unit  101  and the second processing unit  103  is completed so that the first processing unit  101  is able to indirectly send the TV associated command to the second processing unit  103  via the mailbox  310  and the interrupt controllers  220 . 
         [0047]    In  FIG. 2B  and  FIG. 3B , the first processing unit  101  sends the TV associated command, which is received by the second processing unit  103 . However, a person having ordinary skill in the art should understand that the second processing unit can also send the TV associated command to the first processing unit  101 , as also being encompassed within the spirit and scope of the present invention. 
         [0048]      FIG. 4  is a flow chart of booting the first processing unit  101 . In Step S 410 , the first processing unit  101  is enabled. In Step S 420 , the first processing unit  101  is initialized. In Step S 430 , the program and the boot code needed by the first processing unit  101  are loaded into the memory  116 . In Step S 440 , the program and the boot code needed by the second processing unit  103  are loaded into the memory  116 . In Step S 450 , the first processing unit  101  operates in the normal mode. While the first processing unit  101  is in the normal mode and the user has not triggered a TV enable event, the second processing unit  103  operates in the power saving mode. 
         [0049]    Refer to  FIG. 5  to get a better understanding of a TV boot flow according to the first embodiment of the present invention.  FIG. 5  is a flow chart of booting a TV function according to the first embodiment of the present invention. 
         [0050]    In Step S 510 , the first processing unit  101  is in the normal mode. At this point, the second processing unit  103  is in the power saving mode. In Step S 520 , the first processing unit  101  receives a signal of the TV enable event, e.g., the user&#39;s pushing of a TV power on/off button of the PND  100 . 
         [0051]    In Step S 530 , the first processing unit  101  sends a TV enable command in response to the TV enable event. The TV enable command is stored in the memory  116  or the mailbox  310 . 
         [0052]    In Step S 540 , in response to the TV enable command from the first processing unit  101 , an interrupt signal is transmitted to the second processing unit  103  to activate the second processing unit  103 . Refer to  FIG. 2B  and  FIG. 3B  for illustrations on sending the interrupt signal to the second processing unit  103 —the description shall not be again given for brevity. 
         [0053]    In Step S 550 , in response to the interrupt signal, the second processing unit  103  retrieves the TV enable command from the memory  116  or the mailbox  310 . 
         [0054]    In Step S 560 , the second processing unit  103  accesses a user profile from the storage device  114 . 
         [0055]    In Step S 570 , hardware, related to the TV function, such as the TV module  109 , is enabled to perform the TV function. 
         [0056]    In Step S 580 , when the user is watching TV and the navigation function is not needed temporarily, the first processing unit  101  enters the power saving mode. Moreover, the second processing unit  103  operates in the normal mode to operate the TV function of the PND  100 . 
         [0057]    Refer to  FIG. 6  and  FIG. 7  to obtain a better understanding of a TV function deactivating method according to the first embodiment of the present invention. In this embodiment, the TV disable event begins with the processing unit  103  when the TV disable event is triggered by the user as illustrated in  FIG. 6 , or begins with the processing unit  101  when the TV disable event is triggered for the reason that the PND  100  has power shortage as illustrated in  FIG. 7 . 
         [0058]      FIG. 6  is a flow chart of deactivating the TV function by the user according to the first embodiment of the present invention. In Step S 610 , when the user watches TV via the PND  100 , the second processing unit  103  operates in the normal mode and the first processing unit  101  operates in the power saving mode as described. 
         [0059]    In Step S 620 , the user triggers a TV associated event, such as by pushing a TV power on/off button of the PND  100 . 
         [0060]    In Step S 630 , the second processing unit  103  stores a user profile. For example, the second processing unit  103  stores the user profile into the storage device  114 . 
         [0061]    In Step S 640 , the second processing unit  103  sends a TV disable command. 
         [0062]    In Step S 650 , the second processing unit  103  controls the interrupt controller  210  to send an interrupt signal to activate the first processing unit  101 . Refer to  FIGS. 2B and 3B  showing the communication between the first processing unit  101  and the second processing unit  103 —the description shall not be again given for brevity. 
         [0063]    In Step S 660 , the first processing unit  101  retrieves/receives the TV disable command from the memory  116  or the mailbox  310 . 
         [0064]    In Step S 670 , the first processing unit  101  in the normal mode controls the PND  100  to deactivate the TV function according to the TV disable command as retrieved. In addition, in Step S 670 , the second processing unit  103  enters the power saving mode for power saving purpose. 
         [0065]      FIG. 7  is a flow chart of deactivating the TV function for the reason of having power shortage according to the first embodiment of the present invention. In Step S 710 , an interruption of a power shortage event shall activate the first processing unit  101 . The power supply and management module  119  then detects the remaining power of the PND  100 . When the remaining power is insufficient, the power supply and management module  119  sends an interrupt signal to the first processing unit  101  to wake up the first processing unit  101  originally operating in the power saving mode. 
         [0066]    In Step S 715 , the first processing unit  101  sends the TV disable command indirectly transmitted to the second processing unit  103 , so as to deactivate the TV function. 
         [0067]    In Step S 720 , the first processing unit  101  controls the interrupt controller  220  to send the interrupt signal to the second processing unit  103 . 
         [0068]    In Step S 725 , the second processing unit  103  retrieves the TV disable command. 
         [0069]    In Step S 730 , the second processing unit stores a user profile. In Step S 735 , the second processing unit sends the TV disable command indirectly transmitted to the first processing unit  101 . 
         [0070]    In Step S 740 , the second processing unit  103  controls the interrupt controller  210  to send the interrupt signal to the first processing unit  101 . 
         [0071]    In Step S 745 , the first processing unit  101  determines whether the interrupt signal is received within a predetermined time. When the result of Step S 745  is no, the first processing unit  101  considers the second processing unit  103  does not receive the TV disable command, and the first processing unit  101  sends the TV disable command again. Thus, the flow returns to Step S 715 . When the result of Step S 745  is yes, the first processing unit  101  considers the second processing unit  103  has received the TV disable command so that the flow goes to Step S 750 . 
         [0072]    In Step S 750 , the first processing unit  101  retrieves the TV disable command. 
         [0073]    In Step S 755 , the first processing unit  101  enters the normal mode and controls the PND  100  to deactivate the TV function according to the retrieved TV disable command. In addition, the second processing unit  103  enters the power saving mode in Step S 755  for power saving purpose. 
         [0074]      FIG. 8  is a block diagram of a PND  800  according to a second embodiment of the present invention. Elements of the PND  800  are the same as or similar to that of the PND  100 , and details thereof shall not be described for brevity. 
         [0075]    In the second embodiment, the elements inside the PND  800  belong to two power fields. Power supply and management of a first power field is controlled by a first power supply and management module  810 , and power supply and management of a second power field is controlled by a second power supply and management module  820 . 
         [0076]    In the second embodiment, the first processing unit  101 , the message exchange unit  105 , the navigation module  107 , the display interface  111 , the storage interface  113 , the storage device  114 , the memory interface  115 , the memory  116 , the sound interface  117 , the ROM  118 , the display module  123  and the sound module  125  belong to the first power field. When the PND  800  performs the navigation function, the first power supply and management module  810  provides a power supply for the elements that belong to the first power field. 
         [0077]    In addition, the TV module  109 , the second processing unit  103  and the message exchange unit  105  belong to the second power field. When the PND  800  performs the TV function, the second power supply and management module  820  provides a power supply for the elements that belong to the second power field. 
         [0078]      FIG. 9  is a flow chart of activating the TV function according to the second embodiment of the present invention. In Step S 910 , the first processing unit  101  is in the normal mode and the second processing unit  103  is powered off to enter the power saving mode. In Step S 915 , the user triggers a TV enable event. 
         [0079]    In Step S 920 , the first processing unit  101  sends a TV enable command in response to the TV enable event triggered by the user. In 
         [0080]    Step S 925 , the power supply is provided to the second power field, so as to reset the second processing unit  103 . 
         [0081]    In Step S 940 , after the second processing unit  103  is reset, the second processing unit  103  retrieves the TV enable command from the memory  116  or the mailbox  310 . 
         [0082]    In Step S 945 , the second processing unit  103  accesses the user profile from the storage device  114 . 
         [0083]    In Step S 950 , hardware, related to the TV function, such as the TV module  109 , is enabled to perform the TV function. 
         [0084]    In Step S 955 , while the user watches TV and the navigation function is not needed temporarily, the first processing unit  101  enters the power saving mode. Furthermore, the second processing unit  103  enters the normal mode to control the TV function of the PND  800 . 
         [0085]    Refer to  FIGS. 10 and 11  to obtain a better understanding of a TV display deactivating method according to the second embodiment of the present invention. 
         [0086]      FIG. 10  is a flow chart of deactivating the TV function by the user according to the second embodiment of the present invention. In Step S 1010 , when the user watches TV via the PND  800 , the second processing unit  103  operates in the normal mode and the first processing unit  101  operates in the power saving mode. In Step S 1020 , the user triggers a TV close event. 
         [0087]    In Step S 1030 , the second processing unit  103  stores a user profile. In Step S 1040 , the second processing unit  103  sends a TV disable command. 
         [0088]    In Step S 1050 , the second processing unit  103  controls the interrupt controller  210  and sends an interrupt signal to wake up the first processing unit  101 . In Step S 1060 , the first processing unit  101  retrieves/receives the TV disable command. In Step S 1070 , the first processing unit  101  enters the normal mode and controls the PND  100  to deactivate the TV function according to the retrieved TV disable command. In Step S 1080 , under control of the first processing unit  101 , the power supply of the second power field covering the second processing unit  103  is shut down. 
         [0089]      FIG. 11  is a flow chart of deactivating the TV function resulting from having power shortage according to the second embodiment of the present invention. In Step S 1110 , an interruption from a power shortage event wakes up the first processing unit  101 . In Step S 1115 , the first processing unit  101  sends a TV disable command indirectly transmitted to the second processing unit  103  to deactivate the TV function. 
         [0090]    In Step S 1120 , the first processing unit  101  controls the interrupt controller  220  to send an interrupt signal to the second processing unit  103 . 
         [0091]    In Step S 1125 , the second processing unit  103  retrieves the TV disable command. 
         [0092]    In Step S 1130 , the second processing unit  103  stores a user profile. In Step S 1135 , the second processing unit  103  sends the TV disable command indirectly transmitted to the first processing unit  101 . 
         [0093]    In Step S 1140 , the second processing unit  103  controls the interrupt controller  210  to send the interrupt signal to the first processing unit  101 . In Step S 1145 , the first processing unit  101  determines whether the interrupt signal is received in a predetermined period. The result of no from Step S 1145  means that the second processing unit  103  does not receive the TV disable command so that the first processing unit  101  sends the TV disable command again and the flow returns to Step S 1115 . The result of yes from Step S 1145  means that the second processing unit  103  receives the TV disable command and the flow proceeds to Step S 1150 . 
         [0094]    In Step S 1150 , the first processing unit  101  retrieves the TV disable command. 
         [0095]    In Step S 1155 , the first processing unit  101  enters the normal mode and controls the PND  800  to deactivate the TV function according to the retrieved TV disable command. In Step S 1160 , under control of the first processing unit  101 , the power supply of the second power field covering the second processing unit  103  is shut down. 
         [0096]    In conclusion, according to the embodiments of the present invention, a PND having two processing units needs less elements by sharing a display interface, a sound interface, a bus and so on. Compared to the prior art, the embodiments at least achieves advantages of having low cost, small circuit area, simple design and low power consumption. In addition, according to the embodiments of the present invention, the two processing units respectively process a navigation function and a TV function so that each of the processing units need not have a high computation capability. Moreover, the navigation function and the TV function can be simultaneously performed smoothly via the two processing units according to the embodiments of the present invention. 
         [0097]    While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not to be limited to the above embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.