PATENT DOCUMENT

Abstract:
A rewriting apparatus of a vehicle program rewriting system predicts, on the basis of both a state of a battery at the time of starting rewriting the programs of ECUs and a scheduled process time period of rewiring the programs, a state of the battery after rewriting the programs, and executes rewriting the programs if the predicted state of the battery satisfies a condition on which the vehicle can be restarted.

Full Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a vehicular program rewriting system (vehicle program rewriting system), which is capable of rewriting a program for an electronic control unit. 
       BACKGROUND ART 
       [0002]    With advancements in computer technology, vehicles are becoming more and more computerized. Computerized vehicles are generally equipped with a plurality of electronic control units (ECUs). A program that is used by an ECU occasionally is rewritten to reflect a version upgrade or the like (see Japanese Laid-Open Patent Publication No. 2008-155892, hereinafter referred to as “JP2008-155892A”). 
         [0003]    According to JP2008-155892A, it is judged whether or not a program can be rewritten based on a remaining stored energy level of a battery and a predicted value of an amount of consumed electric energy required to rewrite the program (see summary). More specifically, according to JP2008-155892A, the remaining stored energy level of the battery is calculated based on the present voltage and temperature of the battery. The predicted value of the amount of consumed electric energy is calculated based on a time and a current of the battery that are required to rewrite the program. It is then judged whether or not the program can be rewritten, based on whether or not the remaining stored energy level is greater than the predicted value of the amount of consumed electric energy (see  FIGS. 5 and 6 , and paragraphs [0025] and [0026]). 
       SUMMARY OF INVENTION 
       [0004]    According to JP2008-155892A, as described above, it is judged whether or not the program can be rewritten based on whether or not the remaining stored energy level is greater than the predicted value of the amount of consumed electric energy. If the remaining stored energy level and the predicted value of the amount of consumed electric energy differ only slightly from each other, then the remaining stored energy level will be almost nil after the program is rewritten. In such a case, sufficient electric power is not available for restarting a drive source such as an engine or the like, and the possibility exists that the vehicle cannot be restarted. 
         [0005]    The present invention has been made in view of the above problems. It is an object of the present invention to provide a vehicular program rewriting system, which is capable of reliably restarting a vehicle after having rewritten a program for an ECU. 
         [0006]    According to the present invention, there is provided a vehicular program rewriting system comprising an electronic control unit including a storage unit that stores a program therein and which is capable of rewriting the program, a rewriting device for rewriting the program, and a battery for supplying electric power in order to operate a drive source of a vehicle and the electronic control unit, wherein the rewriting device predicts a state of the battery after the program is rewritten, based on a state of the battery when the program starts to be rewritten and an expected processing time for rewriting the program, and the rewriting device rewrites the program if the predicted state of the battery satisfies a condition for restarting the vehicle. 
         [0007]    According to the present invention, a state of the battery after the program is rewritten is predicted, and the program is rewritten if the predicted state of the battery satisfies the condition for restarting the vehicle. Therefore, the vehicle can reliably be restarted after the program has been rewritten. 
         [0008]    The rewriting device may change the condition for restarting the vehicle depending on at least one of an ambient temperature in the vicinity of the vehicle, an engine coolant water temperature of the vehicle, and an internal resistance of the battery. 
         [0009]    The rewriting device may predict a remaining stored energy level of the battery after the program is rewritten, based on the remaining stored energy level or charged ratio and a consumed current of the battery when the program starts to be rewritten and the expected processing time for rewriting the program, and may rewrite the program if the predicted remaining stored energy level is greater than a predetermined value. Therefore, a charged state of the battery after the program is rewritten can be predicted easily and the battery can be used. A charged ratio (SOC) may be used instead of the remaining stored energy level of the battery. The SOC (State Of Charge) is represented by the formula (remaining stored energy level [Ah]/fully charged stored energy level [Ah])×100[%]. If the SOC is 100%, the SOC indicates a fully charged state of the battery. 
         [0010]    Alternatively, the rewriting device may predict an amount of electric power discharged from the battery from a predetermined charged state thereof until after the program is rewritten, based on the amount of electric power discharged from the battery from the predetermined charged state thereof until the program starts to be rewritten, a current consumed by the battery when the program starts to be rewritten, and the expected processing time for rewriting the program, and may rewrite the program if the predicted amount of electric power discharged from the battery is smaller than a predetermined value. Therefore, a charged state of the battery after the program is rewritten can be predicted easily and the battery can be used. 
         [0011]    The rewriting device may stop rewriting the program if a current consumed by the battery or an internal resistance of the battery when the program starts to be rewritten is greater than a predetermined value, even though the predicted state of the battery satisfies the condition for restarting the vehicle. Generally, the internal resistance of the battery reflects a state of deterioration of the battery. Therefore, if the internal resistance of the battery is greater than a predetermined value, it becomes difficult to accurately predict the charged state of the battery after the program is rewritten. According to the present invention, the rewriting device stops rewriting the program if the current consumed by the battery or the internal resistance of the battery is greater than a predetermined value. Consequently, if the accuracy of the prediction is low, by stopping rewriting of the program, the possibility that the vehicle cannot be restarted is lowered. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a block diagram of a vehicular program rewriting system according to an embodiment of the present invention; 
           [0013]      FIG. 2  is a block diagram showing the manner in which electric power is supplied and signals are input and output in a vehicle; 
           [0014]      FIG. 3  is a flowchart of a general outline of a processing sequence for rewriting a program for an electronic control unit (ECU) with rewriting data (program) transmitted through a CD-ROM; 
           [0015]      FIG. 4  is a first flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a CD-ROM; 
           [0016]      FIG. 5  is a second flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a CD-ROM; 
           [0017]      FIG. 6  is a third flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a CD-ROM; 
           [0018]      FIG. 7  is a fourth flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a CD-ROM; 
           [0019]      FIG. 8  is a fifth flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a CD-ROM; 
           [0020]      FIG. 9  is a sixth flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a CD-ROM; 
           [0021]      FIG. 10  is a seventh flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a CD-ROM; 
           [0022]      FIG. 11  is an eighth flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a CD-ROM; 
           [0023]      FIG. 12  is a screen transition diagram showing an example of screen transitions on a display unit, which correspond to portions of the flowcharts shown in  FIGS. 8 and 9 ; 
           [0024]      FIG. 13  is a first flowchart of a processing sequence that is executed when an IGSW is turned off while a program is being rewritten; 
           [0025]      FIG. 14  is a second flowchart of the processing sequence that is executed when an IGSW is turned off while a program is being rewritten; 
           [0026]      FIG. 15  is a third flowchart of the processing sequence that is executed when an IGSW is turned off while a program is being rewritten; 
           [0027]      FIG. 16  is a screen transition diagram showing an example of screen transitions on the display unit, which correspond to a portion of the flowchart of  FIG. 13 ; 
           [0028]      FIG. 17  is a first flowchart of a processing sequence, which is executed when an IGSW is turned off while a program is being rewritten, and when the user (vehicle occupant) reenters the vehicle after having left the vehicle; 
           [0029]      FIG. 18  is a second flowchart of a processing sequence, which is executed when an IGSW is turned off while a program is being rewritten, and when the user (vehicle occupant) reenters the vehicle after having left the vehicle; 
           [0030]      FIG. 19  is a third flowchart of a processing sequence, which is executed when an IGSW is turned off while a program is being rewritten, and when the user (vehicle occupant) reenters the vehicle after having left the vehicle; 
           [0031]      FIG. 20  is a screen transition diagram showing an example of screen transitions on the display unit, which correspond to portions of the flowcharts shown in  FIGS. 17 through 19 ; 
           [0032]      FIG. 21  is a flowchart of a general outline of a processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a satellite broadcasting network; 
           [0033]      FIG. 22  is a first flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a satellite broadcasting network; 
           [0034]      FIG. 23  is a second flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a satellite broadcasting network; 
           [0035]      FIG. 24  is a third flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a satellite broadcasting network; 
           [0036]      FIG. 25  is a flowchart of a general outline of a processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a mobile communications network; 
           [0037]      FIG. 26  is a flowchart showing details of the processing sequence for rewriting a program for an ECU with rewriting data (program) transmitted through a mobile communications network; 
           [0038]      FIG. 27  is a diagram showing the relationship between an output signal from the IGSW and recognition of ECUs; and 
           [0039]      FIG. 28  is a flowchart of a sequence for judging whether or not a program can be rewritten using the internal resistance of a battery and a current threshold value. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     A. Present Embodiment 
     1. Overall and Local Arrangements 
     (1) Overall Arrangement: 
       [0040]      FIG. 1  is a block diagram of a vehicular program rewriting system  10  (hereinafter referred to as a “rewriting system  10 ” or a “system  10 ”) according to an embodiment of the present invention. The rewriting system  10  includes a data transmission system  12 , a management server  14  (hereinafter referred to as a “server  14 ”), and a plurality of vehicles  16 . 
         [0041]    In the system  10 , rewriting data (program), which are used to rewrite (update) programs stored in electronic control units  56   a  through  56   d  (hereinafter referred to as “ECUs  56   a  through  56   d ”) in respective vehicles  16 , are transmitted from the management server  14  through the data transmission system  12  to each of the vehicles  16 . The ECUs  56   a  through  56   d  will hereinafter be referred to collectively as ECUs  56 . 
       (2) Data Transmission System  12 : 
       [0042]    The data transmission system  12  includes a read-only compact disc  22  (hereinafter referred to as a “CD-ROM  22 ”), a satellite broadcasting network  24 , and a mobile communications network  26 . 
         [0043]    The CD-ROM  22  stores rewriting data (program) therein. The CD-ROM  22  is delivered from the manufacturer of the vehicles  16  to users by a transportation means (trucks, cargo trains, etc.) made up of transport operators (postal services, home delivery services). 
         [0044]    The satellite broadcasting network  24  can distribute rewriting data (program) via a satellite broadcast using a broadcasting satellite  28 . The satellite broadcast may be a satellite digital audio broadcast for mobile terminals (Sirius XM Radio in North America, etc.), for example. 
         [0045]    The mobile communications network  26  is a communication network capable of performing communications using a portable telephone  86 . The mobile communications network  26  can send rewriting data (program) to the vehicles  16  by way of communications with the portable telephone  86 . 
         [0046]    According to the present embodiment, rewriting data (program) can be sent to the vehicles  16  using the CD-ROM  22 , the satellite broadcasting network  24 , or the mobile communications network  26 . 
       (3) Management Server  14 : 
       [0047]    The management server  14  includes a communication device  32 , an input device  34 , a monitor  36 , a processing device  38 , a storage device  40 , and a rewriting program database  42  (hereinafter referred to as a “rewriting program DB  42 ” or a “program DB  42 ”). When the administrator or an equivalent entity (hereinafter referred to as an “administrator or the like”) of the management server  14  produces rewriting data (program), the produced rewriting data (program) is stored in the program DB  42  via the input device  34 . 
         [0048]    If rewriting data (program) are distributed using the satellite broadcasting network  24 , then the administrator or the like distributes the rewriting data (program) through the broadcasting satellite  28  or the like. 
         [0049]    If rewriting data (program) are broadcast using the mobile communications network  26 , then the administrator or the like uploads new rewriting data (program) into the server  14 . When a request for transmission of the rewriting data (program) is received from the portable telephone  86  installed in the vehicle  16 , the server  14  sends the rewriting data (program) to the portable telephone  86  through the communication device  32  and the mobile communications network  26 . 
         [0050]    If rewriting data (program) are transmitted using the CD-ROM  22 , then the administrator or the like stores the rewriting data (program) in the CD-ROM  22 , and sends the CD-ROM  22  to respective users by way of transportation operators. Strictly speaking, there may be instances in which the CD-ROM  22  is not sent from the management server  14 . However, instances in which the CD-ROM  22  is sent from the management server  14  will be described below, and the description shall be understood to include instances in which the CD-ROM  22  is not sent from the management server  14 . 
       (4) Vehicles  16 : 
     (a) Arrangement of Vehicles  16 : 
       [0051]    Each of the vehicles  16  has a receiving device  52 , a program rewriting device  54  (hereinafter referred to as a “rewriting device  54 ”), a plurality of ECUs  56 , a battery  58 , a battery sensor  60 , an alternator  62 , an ignition switch  64  (hereinafter referred to as an “IGSW  64 ”), and a door lock/vehicle occupant detecting unit  66  (hereinafter referred to as a “detecting unit  66 ”) (The term “vehicle occupant” here includes a user, a driver, and a passenger). Although the vehicles  16  are gasoline-powered vehicles in the present embodiment, the vehicles  16  may be diesel vehicles or electric vehicles (including fuel cell vehicles, hybrid vehicles, etc.). 
         [0052]    In each of the vehicles  16 , the receiving device  52  receives rewriting data (program) transmitted from the management server  14  through the data transmission system  12 . The rewriting data (program) received by the receiving device  52  are written to a target ECU  56  by the rewriting device  54 . 
         [0053]    In  FIG. 1 , the internal configuration of only the right-hand vehicle  16  is illustrated. Internal configurations of the other vehicles  16  are omitted from illustration. 
       (b) Receiving Device  52 : 
       [0054]    The receiving device  52  includes a data receiver  72 , a display unit  74 , an input unit  76 , a processor  78 , and a storage unit  80 . 
         [0055]    The data receiver  72  includes a wireless antenna  82 , a modem  84 , a portable telephone  86 , a connector  88  for the portable telephone  86 , and a CD-ROM drive  90  (hereinafter referred to as a “drive  90 ”). 
         [0056]    When rewriting data (program) are distributed through the satellite broadcasting network  24 , the receiving device  52  receives the rewriting data (program) using the wireless antenna  82  and the modem  84 . When rewriting data (program) are transmitted through the mobile communications network  26 , the receiving device  52  receives the rewriting data (program) using the portable telephone  86 . When rewriting data (program) are transmitted through the CD-ROM  22 , the receiving device  52  receives the rewriting data (program) by reading the rewriting data (program) from the CD-ROM  22 , which has been inserted into the drive  90 . The portable telephone  86 , which is carried by the user on a regular basis, is connected to the connector  88  while the vehicle  16  is traveling. Alternatively, the portable telephone  86  may be used exclusively in the vehicle  16  and connected to the connector  88  at all times. 
         [0057]    The display unit  74  displays various items of information for the user. The input unit  76  receives input signals depending on actions made by the user. According to the present embodiment, the display unit  74  and the input unit  76  may comprise a touch panel, for example. 
         [0058]    The processor  78  controls various components of the receiving device  52 . The storage unit  80 , which comprises a volatile memory and a nonvolatile memory (not shown) stores a control program for the receiving device  52 , and also stores rewriting data (program) for rewriting programs intended for the ECUs  56 . 
         [0059]    The receiving device  52  may also function as a navigation device. Stated otherwise, an existing navigation device may function as the receiving device  52  according to the present embodiment. 
       (c) Rewriting Device  54 : 
       [0060]    The rewriting device  54 , which rewrites the programs for the respective ECUs  56 , has an input/output unit  92 , a processor  94 , and a storage unit  96 . Functional and operational details of the rewriting device  54  will be described later. 
       (d) ECUs  56 : 
       [0061]    The ECUs  56  control various parts of the vehicle  16 . The ECUs  56  include, for example, an engine electronic control unit  56   a  (hereinafter referred to as an “ENG ECU  56   a ”) for controlling the output power of an engine, not shown, an antilock brake system electronic control unit  56   b  (hereinafter referred to as an “ABS ECU  56   b ”) for controlling a brake system, not shown, a supplementary restraint system electronic control unit  56   c  (hereinafter referred to as an “SRS ECU  56   c ”) for controlling air bags, not shown, an immobilizer electronic control unit  56   d  (hereinafter referred to as an “immobilizer ECU  56   d ”) for controlling an immobilizer system, not shown. As described above, the ECUs  56   a  through  56   d  will hereinafter be referred to collectively as ECUs  56 . 
         [0062]    Each of the ECUs  56  includes an input/output unit  102 , a processor  104 , and a storage unit  106 . In  FIG. 1 , only the input/output unit  102 , the processor  104 , and the storage unit  106  of the ENG ECU  56   a  are illustrated. The input/output units  102 , the processors  104 , and the storage units  106  of the other ECUs  56   b  through  56   d  are omitted from illustration. 
         [0063]    The ENG ECU  56   a  is connected to an engine rotational speed sensor  108  for detecting an engine rotational speed Ne [rpm], and to a vehicle speed sensor  110  for detecting a vehicle speed V [km/h] of the vehicle  16 . 
       (e) Battery  58 : 
       [0064]    The battery  58  supplies electric power to the receiving device  52 , the rewriting device  54 , and the ECUs  56 . The receiving device  52  is selectively supplied with electric power through the IGSW  64 , although the receiving device  52  may selectively be supplied with electric power depending on a command (startup signal Son) from the rewriting device  54 . The rewriting device  54  is connected to the battery  58  at all times. The ECUs  56  are selectively supplied with electric power through the IGSW  64 . Details will be described later with reference to  FIG. 2 . 
         [0065]    The battery  58  also supplies electric power for controlling operations of the engine, not shown (operation of a control system of the engine, etc.). 
       (f) Battery Sensor  60 : 
       [0066]    The battery sensor  60  detects a charged ratio or a state of charge (hereinafter referred to as “SOC”), an internal resistance R, a voltage (hereinafter referred to as a “battery voltage Vbat”), a consumed current (discharged current) (hereinafter referred to as a “battery current Ibat”), and a fluid temperature (hereinafter referred to as a “battery fluid temperature Tbat”) of the battery  58 . 
         [0067]    The SOC is detected from an integrated value of the battery current Ibat and an open-circuit voltage (hereinafter referred to as an “OCV”) of the battery  58 . The internal resistance R is detected based on a reduction in the battery voltage Vbat due to a large current that is discharged when the engine is started. The battery fluid temperature Tbat is estimated from the ambient temperature, which is detected by the battery sensor  60 , a charging current, and the volume of the battery  58 . The battery sensor  60  may detect a remaining stored energy level [Ah] instead of the SOC [%]. 
       (g) Alternator  62 : 
       [0068]    The alternator  62 , which is connected to a non-illustrated engine, generates electric power based on the power of the engine. Electric power generated by the alternator  62  is supplied to the battery  58  in order to charge the battery  58 , and also is supplied to other accessories, not shown. 
       (h) IGSW  64 : 
       [0069]    The IGSW  64  according to the present embodiment is a rotary type ignition switch, which is capable of selecting positions “OFF”, “ACC” (accessory), and “ON” successively from the left as viewed toward an instrument panel (not shown). When the IGSW  64  is further turned to the right (clockwise) from the “ON” position, the IGSW  64  comes to a position “ST” (engine start), thereby starting the engine. 
         [0070]    According to the present embodiment, when the IGSW  64  is in the “OFF” position, the battery  58  essentially stops supplying electric power to the receiving device  52  and the ECUs  56 . 
         [0071]    As described later, if the vehicle  16  has a so-called smart start function, then the IGSW  64  may comprise a push switch, which is used in combination with such a smart start function. 
       (i) Door Lock/Vehicle Occupant Detecting Unit  66 : 
       [0072]    The detecting unit  66  detects an unlocked/locked state of a door lock  122  as well as an operational state of a seat sensor  124 , and sends an output signal Sh ( FIG. 2 ) to the rewriting device  54 . The seat sensor  124  comprises a pressure sensor disposed in the seat, and is capable of judging whether or not the vehicle occupant is seated in the seat based on the detected value thereof. When the vehicle occupant is not seated in the seat, the detected value of the seat sensor  124  is nil. The output signal Sh represents an unlocked/locked state of the door lock  122 , and provides information concerning whether or not the vehicle occupant is seated in the seat that incorporates the seat sensor  124  therein. 
       2. Electric Power Supply Arrangement 
       [0073]      FIG. 2  is a block diagram showing the manner in which electric power is supplied and signals are input and output in the vehicle  16 . 
         [0074]    As shown in  FIG. 2 , electric power from the battery  58  (hereinafter referred to as a “battery power Pbat”) [W] is supplied directly to the receiving device  52 , the rewriting device  54 , and the detecting unit  66 . Thus, the receiving device  52 , the rewriting device  54 , and the detecting unit  66  are capable of operating regardless of the position to which the IGSW  64  is turned. 
         [0075]    According to the present embodiment, the receiving device  52  usually is turned on using the battery power Pbat when the IGSW  64  is in the “ACC” or the “ON” position, and turned off without using the battery power Pbat when the IGSW  64  is in the “OFF” position. In exceptional cases, when the receiving device  52  receives a startup signal Son from the rewriting device  54 , the receiving device  52  is turned on using the battery power Pbat until the receiving device  52  receives a canceling command from the rewriting device  54 , even if the IGSW  64  is in the “OFF” position. 
         [0076]    The battery power Pbat is supplied to the ECUs  56  through the IGSW  64 . More specifically, when the IGSW  64  is in the “ON” position, the battery power Pbat is supplied to the ECUs  56 . When the IGSW  64  is in the “OFF” or the “ACC” position, the battery power Pbat is not supplied to the ECUs  56 . 
         [0077]    The detecting unit  66  sends to the rewriting device  54  an output signal Sh (a door lock signal, a door unlock signal, a vehicle occupant detecting signal) representing an unlocked/locked state of the door lock  122  and whether the vehicle occupant is seated in a prescribed seat. The rewriting device  54  judges whether or not the user (vehicle occupant) is in the vehicle  16  based on the output signal Sh, and uses the judgment result in subsequent processing sequences (to be described later). 
       3. Program Rewriting 
       [0078]    (1) Rewriting Data (Program) Transmitted through CD-ROM  22 : 
       (a) Outline of Rewriting Process: 
       [0079]      FIG. 3  is a flowchart of a general outline of a processing sequence for rewriting a program intended for the 
         [0080]    ECU  56 , together with rewriting data (program) transmitted through the CD-ROM  22 . 
         [0081]    In step S 1 , the receiving device  52  reads rewriting data (program) from the CD-ROM  22  when the user inserts the CD-ROM  22  into the drive  90  of the receiving device  52 . 
         [0082]    In step S 2 , the vehicle  16  undertakes preparations for rewriting the program. Such preparations include confirming the state of the battery  58 , as will be described in detail later. 
         [0083]    In step S 3 , the vehicle  16  sends a notice to the user indicating completion of preparations for rewriting the program. In step S 4 , the vehicle  16  receives permission from the user to perform a process for rewriting the program. 
         [0084]    In step S 5 , the vehicle  16  requests that the user turn the IGSW  64  to the “OFF” position. At this time, a setting is made to keep the receiving device  52  on, even if the IGSW  64  is turned to the “OFF” position. In step S 6 , in response to the IGSW  64  being turned to the “OFF” position, the vehicle  16  confirms that the ECUs  56  have been turned off. The receiving device  52  remains turned on. 
         [0085]    In step S 7 , the vehicle  16  requests that the user turn the IGSW  64  to the “ON” position. In step S 8 , in response to the IGSW  64  being turned to the “ON” position, the vehicle  16  confirms that the ECUs  56  have been restarted (turned on). 
         [0086]    In step S 9 , the vehicle  16  performs a process for rewriting the program. However, as described later, in step S 9 , the vehicle  16  judges whether or not the program can be rewritten, and does not rewrite the program if it is determined that the program cannot be rewritten. 
         [0087]    During steps S 1  through S 5 , the vehicle  16  is capable of being driven. During steps S 6  through S 9 , the engine is shut off and hence the vehicle  16  is not capable of being driven. During steps S 1  through S 3 , another CD-ROM  22  (e.g., a music CD-ROM) cannot be inserted into the drive  90 . 
       (b) Details of Rewriting Process: 
       [0088]      FIGS. 4 through 11  are flowcharts showing details of a processing sequence for rewriting the program intended for the ECU  56  with rewriting data (program) that is transmitted through the CD-ROM  22 .  FIG. 12  is a screen transition diagram showing an example of screen transitions displayed on the display unit  74 , which correspond to portions of the flowcharts shown in  FIGS. 8 and 9 . 
         [0089]    Steps S 11  through S 13  correspond to step S 1  of  FIG. 3 , and steps S 14  through S 34  correspond to step S 2 . Step S 35  corresponds to step S 3 , and steps S 36  and S 37  correspond to step S 4 . Steps S 38  and S 39  correspond to step S 5 , and steps S 40  and S 41  correspond to step S 6 . Step S 42  corresponds to step S 7 , and step S 43  corresponds to step S 8 . Steps S 44  through S 67  correspond to step S 9 . 
         [0090]    In step S 11 , the CD-ROM  22  is inserted into the drive  90  of the receiving device  52 . In step S 12 , the receiving device  52  judges whether or not the inserted CD-ROM  22  contains rewriting data (program) for the ECU  56 . If the inserted CD-ROM  22  does not contain rewriting data (program) for the ECU  56  (step S 12 : NO), the present processing sequence comes to an end. If the inserted CD-ROM  22  contains rewriting data (program) for the ECU  56  (step S 12 : YES), then in step S 13 , the receiving device  52  reads the rewriting data (program) from the CD-ROM  22 . While reading the rewriting data (program), the receiving device  52  displays on the display unit  74  information indicating that reading of the rewriting data (program) is currently taking place. For example, the receiving device  52  displays a message “READING REWRITING DATA. ALTHOUGH VEHICLE CAN BE DRIVEN, YOU CANNOT USE THE CD-ROM DRIVE”, for example, on the display unit  74 . 
         [0091]    When the receiving device  52  has completed reading the rewriting data (program), the receiving device  52  notifies the rewriting device  54  in step S 14  that reading of the rewriting data (program) has been completed. 
         [0092]    In step S 15 , the rewriting device  54  judges whether or not a previous rewriting process has been completed. For example, if the rewriting device  54  stores other rewriting data (program), but has not yet performed a rewriting process using such stored rewriting data (program), then the previous rewriting process has not been completed. 
         [0093]    In step S 16 , the rewriting device  54  sends a notice to the receiving device  52  indicating the result of step S 15 . 
         [0094]    In step S 17  of  FIG. 5 , the receiving device  52  confirms whether or not a previous rewriting process has been completed based on the notice from the rewriting device  54 . If a previous rewriting process has been completed (step S 17 : YES), then control proceeds to step S 18 . If a previous rewriting process has not been completed (step S 17 : NO), then the previous rewriting process is preferentially completed. Therefore, the vehicle  16  finishes the present rewriting process. The receiving device  52  may display a message on the display unit  74  prompting the user to carry out the previous rewriting process. If the storage unit  80  of the receiving device  52  or the storage unit  96  of the rewriting device  54  has free storage space, then it is possible to store the presently received rewriting data (program) therein. 
         [0095]    In step S 18 , the receiving device  52  transfers the rewriting data (program) to the rewriting device  54 . 
         [0096]    In step S 19 , the rewriting device  54  judges whether or not the rewriting data (program) are normal based on, for example, whether the rewriting data (program) have a proper data structure and/or whether the rewriting data (program) have a proper hash value. 
         [0097]    If the rewriting data (program) are not normal (step S 19 : NO), then in step S 20 , the rewriting device  54  notifies the receiving device  52  of an error. In step S 21 , the receiving device  52  displays the error on the display unit  74 , and erases the rewriting data (program) stored in the storage unit  80 , after which the present processing sequence is brought to an end. The displayed error may be in the form of a message to the effect that, since the rewriting data (program) contains a fault therein, the dealer should be contacted. 
         [0098]    If the rewriting data (program) are normal (step S 19 : YES), then in step S 22 , the rewriting device  54  stores the rewriting data (program) in the storage unit  96 . 
         [0099]    In step S 23  of  FIG. 6 , the rewriting device  54  asks an ECU  56  into which a program is to be rewritten with rewriting data (program) stored in the storage unit  96  (hereinafter referred to as a “target ECU  56   tar ”) for program identification information (hereinafter referred to as a “program ID”) which identifies the content, such as the version, of the present program to be rewritten. 
         [0100]    In step S 24 , the target ECU  56   tar  sends the program ID of the present program to the rewriting device  54 . 
         [0101]    In step S 25 , the rewriting device  54  judges whether or not the program indicated by the program ID received from the target ECU  56   tar  is compatible with the received rewriting data (program) by comparing the respective program IDs with each other, for example. If the program is not compatible with the received rewriting data (program) (step S 26 : NO), then in step S 27 , the rewriting device  54  notifies the receiving device  52  of an error. In step S 28 , the receiving device  52  displays the error on the display unit  74 , and erases the rewriting data (program) stored in the storage unit  80 , after which the present processing sequence is brought to an end. 
         [0102]    If the program is compatible with the received rewriting data (program) (step S 26 : YES), then in step S 29 , the rewriting device  54  requests the SOC and the battery current Ibat at present from a prescribed ECU (in the present embodiment, the ENG ECU  56   a ). The rewriting device  54  may ask another component, e.g., the battery sensor  60 , for the SOC and the battery current Ibat at present, assuming that such values are available from the other component. 
         [0103]    In step S 30 , the ENG ECU  56   a  sends the SOC and the battery current Ibat at present to the rewriting device  54 . 
         [0104]    In step S 31  of  FIG. 7 , based on the SOC [%] and the battery current Ibat [A] at present, the rewriting device  54  judges whether or not the vehicle  16 , particularly the engine, can be restarted after the program is rewritten with the rewriting data (program). More specifically, the rewriting device  54  judges whether or not the following inequality (1) is satisfied: 
         [0000]      SOC−( I bat× T re× K )&gt;THsoc   (1)
 
         [0000]    where Tre represents an expected processing time [sec] required to rewrite the program, K represents a constant [%/(A·sec)] for converting electric power consumed during rewriting the program into the SOC, and THsoc [%] represents a threshold value (minimum value) for the SOC required in order to restart the vehicle  16 . 
         [0105]    The expected processing time Tre is established based on the amount Sd of the rewriting data (program), which is included in the rewriting data (program), for example. Alternatively, the processor  94  of the rewriting device  54  may calculate the expected processing time Tre based on the amount Sd of the rewriting data (program). 
         [0106]    The threshold value THsoc is a measured value or a simulated value, which is included in the rewriting data (program). Alternatively, the threshold value THsoc may be stored in advance in the storage unit  96  of the rewriting device  54 . Although the threshold value THsoc may be a single fixed value, the threshold value THsoc may also be established depending on at least one of the ambient temperature Tc [° C.] in the vicinity of the vehicle  16 , the engine coolant water temperature Tw [° C.] of the vehicle  16 , and the internal resistance R [Ω] of the battery  58 . If the ambient temperature Tc is used, then the threshold value THsoc is set to a value that becomes higher as the ambient temperature Tc is lower. If the engine coolant water temperature Tw is used, then the threshold value THsoc is set to a value that becomes higher as the engine coolant water temperature Tw is lower. If the internal resistance R is used, then the threshold value THsoc is set to a value that becomes higher as the internal resistance R is higher. 
         [0107]    In step S 32 , the rewriting device  54  sends a notice to the receiving device  52  indicating the result of step S 31 . If the result of step S 31  indicates that the vehicle  16  cannot be restarted (step S 33 : NO), then in step S 34 , the receiving device  52  displays an error message on the display unit  74  in step S 34 . For example, the receiving device  52  displays on the display unit  74  a message to the effect that, since the battery  58  does not have a sufficient energy level, the rewriting process must be carried out again after the battery  58  has been charged. If the result of step S 31  indicates that the vehicle  16  can be restarted (step S 33 : YES), then in step S 35 , the receiving device  52  displays on the display unit  74  a message to the effect that, in order to rewrite the program for the target ECU  56   tar,  the vehicle  16  should be moved to a safe location. The message is displayed together with a button, which is represented by a button image that is touched in order to approve rewriting of the program after the vehicle  16  has been moved. 
         [0108]    If the button is not touched, and hence the user does not permit rewriting of the program (step S 36 : NO), then control returns to step S 35 . If the button is touched, and hence the user approves rewriting of the program (step S 36 : YES), then in step S 37 , the receiving device  52  indicates the user&#39;s approval to the rewriting device  54 . 
         [0109]    In step S 38  of  FIG. 8 , the rewriting device  54  sends a startup signal Son to the receiving device  52  requesting that turning-off of the receiving device  52  be inhibited. Therefore, even if the IGSW  64  is in the “OFF” position, the receiving device  52  is continuously kept in an ON state. 
         [0110]    In step S 39 , the receiving device  52  displays on the display unit  74  a message requesting the user to turn the IGSW  64  to the “OFF” position. The message may be represented by the phrase “TURN OFF IGNITION SWITCH”, for example, as indicated by the screen  132  shown in  FIG. 12 . The message is displayed continuously until the receiving device  52  receives an indication from the rewriting device  54  that the ECU  56  has been turned off. 
         [0111]    In step S 40 , the rewriting device  54  reads the position to which the IGSW  64  is turned, and judges whether or not the IGSW  64  is turned off. If the user has not turned the IGSW  64  and it is not detected that the IGSW  64  is turned off (step S 40 : NO), then step S 40  is repeated. If the user has turned the IGSW  64  and the IGSW  64  is detected as being turned off (step S 40 : YES), then the rewriting device  54  indicates to the receiving device  52  that the IGSW  64  has been turned off, i.e., that the ECU  56  is turned off. The rewriting device  54  may judge whether or not the IGSW  64  is turned off by sending a response request to a certain one or more of the ECUs  56 , and judging whether or not a response is received. If a response is received from a certain one or more of the ECUs  56 , then the rewriting device  54  decides that the IGSW  64  is not turned off. If no response is received from a certain one or more of the ECUs  56 , then the rewriting device  54  determines that the IGSW  64  has been turned off. 
         [0112]    In step S 42 , the receiving device  52  displays on the display unit  74  a message requesting the user to turn on the IGSW  64  again and to inhibit starting of the engine. The message may be represented by the phrase “TURN ON IGNITION SWITCH (DO NOT START ENGINE)”, for example, as indicated by the screen  134  shown in  FIG. 12 . The message is displayed continuously until the rewriting device  54  determines that the IGSW  64  has been turned on. 
         [0113]    In step S 43 , the rewriting device  54  reads the position to which the IGSW  64  is turned, and judges whether or not the IGSW  64  is turned on. Alternatively, as in step S 40 , the rewriting device  54  may judge whether or not the IGSW  64  is turned on by sending a response request to a certain one or more of the ECUs  56  and judging whether or not a response is received. If the user has not turned the IGSW  64 , and the IGSW  64  is not detected as being turned off (step S 43 : NO), then step S 43  is repeated. If the user has turned the IGSW  64 , and the IGSW  64  is detected as being turned on (step S 43 : YES), then control proceeds to step S 44 . 
         [0114]    In step S 44  of  FIG. 9 , the rewriting device  54  requests various states of the vehicle  16  from certain ones of the ECUs  56 . The states of the vehicle  16  may include the engine rotational speed Ne, the vehicle speed V, a gearshift position, temperatures of the ECUs  56 , the operational state of the immobilizer ECU  56   d,  the operational state of the air conditioner of the vehicle  16 , the operational state of heating wires of a rear windshield of the vehicle  16 , the operational state of the headlights of the vehicle  16 , and the operational state of a seat heater of the vehicle  16 . According to the present embodiment, the aforementioned various states of the vehicle  16  are acquired from the ECUs  56 . However, such states may be acquired directly from various sensors. 
         [0115]    In step S 45 , the ECUs  56  send the states of the vehicle  16  to the rewriting device  54 . 
         [0116]    In step S 46 , the rewriting device  54  judges whether or not the vehicle  16  is in a state in which the program can be rewritten, by judging whether all of the following conditions (i) through (v), for example, are satisfied. 
         [0117]    (i) The engine rotational speed Ne is 0 [rpm]; 
         [0118]    (ii) The vehicle speed V is 0 [km/hr] 
         [0119]    (iii) The gearshift position is position P (Park); 
         [0120]    (iv) The target ECU  56   tar  is at or below a temperature (threshold value THe) at which the program can be rewritten; and 
         [0121]    (v) The immobilizer ECU  56   d  determines that a proper key has been inserted. 
         [0122]    Among the above conditions, conditions (i) through (iii) serve to confirm that the vehicle  16  is at rest, condition (iv) serves to evaluate an operation fault of the ECUs  56 , and condition (v) serves to confirm that a proper person is using the vehicle  16 . 
         [0123]    At this time, the rewriting device  54  also judges whether any one of the following conditions (vi) through (ix) is satisfied. 
         [0124]    (vi) The air conditioner is turned off; 
         [0125]    (vii) The heating wires of the rear windshield are turned off; 
         [0126]    (viii) The headlights are turned off; and 
         [0127]    (ix) The seat heater is turned off. 
         [0128]    The above conditions (vi) through (ix) are used to judge how much battery power Pbat is consumed, and to request the user to suppress consumption of electric power. Even if conditions (vi) through (ix) are not satisfied, the rewriting device  54  does not decide that the program cannot be rewritten. However, the user is warned about such conditions in step S 50 , to be described later. 
         [0129]    In step S 47 , the rewriting device  54  sends a notice to the receiving device  52  indicating the result of step S 36 . If any one of conditions (i) through (v) is not satisfied, thus indicating that the program cannot be rewritten (step S 48 : NO), then in step S 49 , the receiving device  52  displays on the display unit  74  a warning message pointing out which of the conditions (i) through (v) are not satisfied, thereby prompting the user to undertake efforts to satisfy the conditions. Thereafter, control returns to step S 44 . 
         [0130]    However, even if the program cannot be rewritten, the receiving device  52  may not send a special signal to the rewriting device  54 . Stated otherwise, if the rewriting device  54  determines that the program cannot be rewritten in step S 46 , then in step S 47 , the rewriting device  54  may send the result to the receiving device  52 , after which control returns to step S 44 . 
         [0131]    If the rewriting device  54  determines that the program can be rewritten (step S 48 : YES), then in step S 50 , the receiving device  52  displays on the display unit  74  an operation screen in order to confirm the user&#39;s approval to start the rewriting process (rewriting start approval screen). The operation screen can include the message “IS IT OK TO START REWRITING PROGRAM?”, a “YES” button for approving start of the rewriting process, and a “NO” button for not approving start of the rewriting process, as indicated by the screen  136  shown in  FIG. 12 . At this time, if any one of the conditions (vi) through (ix) is not satisfied, the display unit  74  may also display a warning message to the effect that one of the conditions (vi) through (ix) has not been satisfied. 
         [0132]    If the user does not perform any action on the operation screen, and hence does not approve start of the rewriting process (step S 51 : NO), then control returns to step S 50 . If the user performs an action on the operation screen, and hence approves start of the rewriting process (step S 51 : YES), then in step S 52 , the receiving device  52  displays on the display unit  74  a message indicating that the program is currently being rewritten. For example, the receiving device  52  displays on the display unit  74  the message “PROGRAM IS BEING REWRITTEN. DO NOT TURN OFF IGNITION SWITCH.” Although not shown, if the user touches the “NO” button for not approving start of the rewriting process, the program is not rewritten, and the processing sequence is brought to an end. In this case, if the IGSW  64  is turned at a subsequent time, the processing sequence is started from step S 29 . 
         [0133]    In step S 53 , the receiving device  52  notifies the rewriting device  54  that the user has approved start of the rewriting process. 
         [0134]    In step S 54  of  FIG. 10 , the rewriting device  54  communicates with the ECUs  56  and deactivates security features of the ECUs  56 . 
         [0135]    In step S 55 , the rewriting device  54  requests the ECUs  56  to stop a fault diagnosis process that is currently being conducted between the ECUs  56 . In step S 56 , each of the ECUs  56  stops the fault diagnosis process. 
         [0136]    In step S 57 , the rewriting device  54  requests the ECUs  56  to terminate communications between the ECUs  56 . In step S 58 , the ECUs  56  terminate communications between the ECUs  56 . 
         [0137]    In step S 59 , the rewriting device  54  rewrites the program for the target ECU  56   tar.    
         [0138]    In step S 60  of  FIG. 11 , after the rewriting device  54  has finished rewriting the program for the target ECU  56   tar,  the rewriting device  54  asks the target ECU  56   tar  for a program ID, which identifies certain content, such as the version of the present (i.e., rewritten) program. 
         [0139]    In step S 61 , the target ECU  56   tar  sends the program ID of the present program to the rewriting device  54 . 
         [0140]    In step S 62 , the rewriting device  54  ascertains whether or not the rewriting process has been successful by confirming the program ID received from the target ECU  56   tar.  If the rewriting process has been successful and has finished normally (step S 63 : YES), then in step S 64 , the rewriting device  54  sends a notice to the receiving device  52  indicating that the rewriting process has finished normally, thereby ending the rewriting process. 
         [0141]    In step S 65 , the receiving device  52  displays on the display unit  74  a message indicating that rewriting of the program has finished normally. The message may include an indication that rewriting of the program has finished, advice to turn off the IGSW  64 , a code number (a specific numerical value or the like) representative of completion of program rewriting, advice to notify the manufacturer of the code number, and contact information concerning the manufacturer. By reading the message, the user can notify the manufacturer of the code number, thereby allowing the manufacturer to confirm that program rewriting has finished. The user can also notify the manufacturer of the code number by way of a telephone call, via electronic mail, or by way of an input screen on the manufacturer&#39;s homepage. 
         [0142]    If the rewriting process has failed and did not finish normally (step S 63 : NO), then in step S 66 , the rewriting device  54  notifies the receiving device  52  of an error. In step S 67 , the receiving device  52  displays on the display unit  74  a message requesting the user to turn off the IGSW  64  and to contact the dealer. For example, the receiving device  52  displays on the display unit  74  the message “PROGRAM REWRITING FAILED. TURN OFF IGNITION SWITCH AND CONTACT DEALER”. 
         [0000]    (c) Processing Sequence Executed when IGSW  64  is Turned Off While Program is Being Rewritten: 
         [0143]      FIGS. 13 through 15  show flowcharts of a processing sequence, which is executed when the IGSW  64  is turned off and while the program is being rewritten.  FIG. 16  is a screen transition diagram showing an example of screen transitions on the display unit  74 , which correspond to a portion of the flowchart of  FIG. 13 . 
         [0144]    Although not shown in  FIGS. 13 through 15 , prior to starting to rewrite the program for the target ECU  56   tar  (step S 59  in  FIG. 10 ), the rewriting device  54  sends a startup signal Son to the receiving device  52 , in order to ask the receiving device  52  to remain turned on even if the IGSW  64  is turned to the “OFF” position (step S 38  in  FIG. 8 ). 
         [0145]    While the program is being rewritten, a message to the effect that the rewriting process is in progress and a remaining time are displayed, as indicated by the screen  142  shown in  FIG. 16 . 
         [0146]    In step S 101 , if the user erroneously turns the IGSW  64  to the “OFF” position, the rewriting device  54  detects that the IGSW  64  has been turned to the “OFF” position, and in step S 102 , the rewriting device  54  sends a notice to the receiving device  52  indicating that the IGSW  64  has been turned to the “OFF” position. Since the receiving device  52  has already received the startup signal Son in advance, the receiving device  52  remains turned on, even though the IGSW  64  has been turned to the “OFF” position. 
         [0147]    In step S 103 , after having received the notice indicating that the IGSW  64  has been turned to the “OFF” position, the receiving device  52  displays on the display unit  74  a message indicating that the rewriting process was interrupted because the IGSW  64  has been turned to the “OFF” position. The message may be represented by the phrase “REWRITING PROCESS INTERRUPTED BECAUSE IGNITION SWITCH IS TURNED OFF”, for example, as indicated by the screen  144  shown in  FIG. 16 . 
         [0148]    In step S 104 , the rewriting device  54  judges whether or not the user (vehicle occupant) is present in the vehicle  16  based on an output signal Sh from the door lock/vehicle occupant detecting unit  66 . As described above, the output signal Sh represents an unlocked/locked state of the door lock  122  together with a detected value from the seat sensor  124 , which acts as a pressure sensor. If the door lock  122  is activated and the detected value from the seat sensor  124  is nil, then the rewriting device  54  determines that the vehicle occupant is not present in the vehicle  16 . 
         [0149]    If the vehicle occupant is not present in the vehicle  16  (step S 104 : NO), then in step S 105 , the rewriting device  54  stores a subsequent startup reservation in the storage unit  96 . The startup reservation is a setting for resuming rewriting of the program when the IGSW  64  is turned to the “ON” position at a subsequent time, and is represented by a flag. In step S 106 , the rewriting device  54  stores the program ID of the program for which rewriting has failed. 
         [0150]    In step S 107 , the rewriting device  54  outputs a signal to the receiving device  52  requesting that the display on the display unit  74  be discontinued (cancellation request signal). When a vehicle occupant is not present in the vehicle  16 , the content displayed on the display unit  74  is not seen. By not displaying anything on the display unit  74 , it is possible to reduce electric power consumed by the display unit  74 . The cancellation request signal may also include a request for turning off the receiving device  52 . In step S 108 , in response to the cancellation request signal, the receiving device  52  discontinues display of content on the display unit  74 , i.e., turns off the display unit  74 . 
         [0151]    If the vehicle occupant is present in the vehicle  16  (step S 104 : YES), then in step S 109 , the rewriting device  54  reads the position to which the IGSW  64  is turned, and determines the state of the IGSW  64 . Alternatively, the rewriting device  54  may send a response request to a certain one or more of the ECUs  56  to thereby determine the state of the IGSW  64  based on whether or not a response is received. If there is a response from a certain one or more of the ECUs  56 , then the rewriting device  54  determines that the IGSW  64  is turned on. If there is no response from a certain one or more of the ECUs  56 , then the rewriting device  54  determines that the IGSW  64  is turned off. 
         [0152]    If the IGSW  64  is turned off in step S 109  (step S 109 : NO), then in step S 110 , the rewriting device  54  sends a notice to the receiving device  52  indicating that the IGSW  64  has been turned off. 
         [0153]    In step S 111 , the receiving device  52  displays on the display unit  74  a message for requesting the user to return the IGSW  64  to the “ON” position. For example, the message may be represented by the phrase “PROGRAM REWRITING IS INTERRUPTED. TURN ON IGNITION SWITCH BUT DO NOT START ENGINE (PROGRAM WILL BE REWRITTEN AGAIN)”, as indicated by the screen  146  shown in  FIG. 16 . After step S 111 , control returns to step S 104 . 
         [0154]    If the IGSW  64  is turned on in step S 109  (step S 109 : YES), then in step S 112 , the rewriting device  54  starts a timer (not shown). 
         [0155]    In step S 113  of  FIG. 14 , the rewriting device  54  requests a program ID from the ECU  56  that has interrupted rewriting of the program. If the ECU  56  to which the request has been sent is turned on, then in step S 114 , the ECU  56  sends the program ID to the rewriting device  54 . 
         [0156]    In step S 115 , the rewriting device  54  judges whether or not the program ID has been sent back and received. If the program ID has not been sent back and received (step S 115 : NO), then in step S 116 , the rewriting device  54  judges whether a given period of time (e.g., 5 seconds) has elapsed. 
         [0157]    If the given period of time has not elapsed (step S 116 : NO), then control returns to step S 113 . If the given period of time has elapsed (step S 116 : YES), then in step S 117 , in order to avoid an infinite loop, the rewriting device  54  sends a notice concerning elapse of the given time (error) to the receiving device  52 . In step S 118 , the receiving device  52  displays on the display unit  74  a message asking the user to turn off the IGSW  64  and to contact the dealer. For example, the receiving device  52  displays on the display unit  74  the message “PROGRAM REWRITING FAILED. TURN OFF IGNITION SWITCH AND CONTACT DEALER”. 
         [0158]    If the program ID has been sent back (step S 115 : YES), then steps S 119  through S 122 , which are the same as steps S 55  through S 58  of  FIG. 10 , are carried out. Then, steps S 123 , S 124  ( FIG. 15 ), which are the same as steps S 44 , S 45  of  FIG. 9 , are carried out. Thereafter, control proceeds to step S 46  of  FIG. 9 . 
         [0000]    (d) Processing Sequence Executed when IGSW  64  is Turned Off, the User (Vehicle Occupant) Leaves the Vehicle  16 , and Thereafter, the User Reenters the Vehicle  16 : 
         [0159]      FIGS. 17 through 19  are flowcharts of a processing sequence, which is executed when the IGSW  64  is turned off while the program is being rewritten, and then, after the user (vehicle occupant) has left the vehicle, the user reenters the vehicle.  FIG. 20  is a screen transition diagram showing an example of screen transitions on the display unit  74 , which correspond to portions of the flowcharts shown in  FIGS. 17 through 19 . 
         [0160]    In step S 201 , if the door lock  122  is inactivated, the door lock/vehicle occupant detecting unit  66  sends an output signal Sh indicating that the door lock  122  is inactivated to the rewriting device  54 , which detects and confirms inactivation of the door lock  122 . 
         [0161]    In step S 202 , the rewriting device  54  judges whether or not there is a next startup reservation (step S 105  of  FIG. 13 ). If there is not a next startup reservation (step S 202 : NO), the present processing sequence is brought to an end. If there is a next startup reservation (step S 202 : YES), then in step S 203 , the rewriting device  54  sends a startup signal Son to the receiving device  52 , thereby requesting the receiving device  52  to be activated (to be turned on). In step S 204 , the receiving device  52  is activated. 
         [0162]    Steps S 205  through S 211  are the same as steps S 104  through S 110  of  FIG. 13 . However, after the door lock  122  has been inactivated, a certain amount of time, which is required for the user to enter the vehicle  16 , should be taken into account. 
         [0163]    In step S 212 , the receiving device  52  displays on the display unit  74  a message indicating that the rewriting process has been interrupted because the IGSW  64  has been turned to the “OFF” position. The message may be represented by the phrase “PROGRAM REWRITING HAS BEEN INTERRUPTED BECAUSE IGNITION SWITCH IS TURNED OFF”, for example, as indicated by the screen  152  shown in  FIG. 20 . 
         [0164]    In step S 213 , the receiving device  52  outputs a warning sound. 
         [0165]    In step S 214 , the receiving device  52  displays on the display unit  74  a message prompting the user to turn the IGSW  64  to the “ON” position. The message may be represented by the phrase “PROGRAM REWRITING HAS BEEN INTERRUPTED. TURN IGNITION SWITCH ON BUT DO NOT START ENGINE (PROGRAM WILL BE REWRITTEN AGAIN)”, for example, as indicated by the screen  154  shown in  FIG. 20 . After step S 214 , control returns to step S 205 . 
         [0166]    If the IGSW  64  is turned on in step S 210  (step S 210 : YES), steps S 215  through S 229  of  FIGS. 17 through 19  are carried out. Steps S 215  through steps S 221  are the same as steps S 112  through S 118  of  FIGS. 13 and 14 . Steps S 222  through S 225  are the same as steps S 55  through S 58  of  FIG. 10 . Steps S 226 , S 227  are the same as steps S 44 , S 45  of  FIG. 9 . 
         [0167]    In step S 228 , the rewriting device  54  requests that the receiving device  52  display a message to the effect that rewriting of the program will be resumed, and that the state of the vehicle  16  will be checked for resumption of program rewriting. In step S 229 , the receiving device  52  displays such a message on the display unit  74 . The message may be represented by the phrase “PROGRAM REWRITING WILL BE RESUMED. VEHICLE STATE WILL BE CHECKED”, for example, as indicated by the screen  156  shown in  FIG. 20 . Step S 229  is followed by step S 46  of  FIG. 9 . 
       (2) Program Transmitted Through Satellite Broadcasting Network  24 : 
     (a) Outline of Rewriting Process: 
       [0168]      FIG. 21  is a flowchart of a general outline of a processing sequence for rewriting a program for an ECU  56  with rewriting data (program) transmitted through the satellite broadcasting network  24 . 
         [0169]    In step S 301 , the receiving device  52  receives rewriting data (program) transmitted through the satellite broadcasting network  24 . 
         [0170]    Steps S 302  through S 309  are the same as steps S 2  through S 9  of  FIG. 3 . 
         [0171]    During steps S 301  through S 305 , the vehicle  16  is capable of being driven. During steps S 306  through S 309 , the engine is shut off and hence the vehicle  16  cannot be driven. 
       (b) Details of Rewriting Process: 
       [0172]      FIGS. 22 through 24  are flowcharts showing details of a processing sequence for rewriting the program for the ECU  56  with rewriting data (program) transmitted through the satellite broadcasting network  24 . Processing details, which share common processing details ( FIGS. 4 through 11 ) concerning rewriting of the program with the rewriting data (program) transmitted through the CD-ROM  22 , will be described with reference to  FIGS. 4 through 11 . 
         [0173]    Steps S 311  through S 314  correspond to step S 301  of  FIG. 21 . 
         [0174]    In step S 311 , the receiving device  52  receives vehicle information through the satellite broadcasting network  24 . More specifically, upon the server  14  sending vehicle information via a non-illustrated broadcasting station, the vehicle information is relayed by the broadcasting satellite  28 , and then the vehicle information is received by the wireless antenna  82  of the receiving device  52 . The vehicle information, which is received by the wireless antenna  82 , is demodulated by the modem  84  and output to the processor  78 . 
         [0175]    In step S 312 , the receiving device  52  judges whether or not the received vehicle information agrees with the vehicle  16  (the vehicle per se) or not. If the received vehicle information agrees with the vehicle  16  (step S 312 : YES), then control proceeds to step S 313 . If the received vehicle information does not agree with the vehicle  16  (step S 312 : NO), then the present processing sequence is brought to an end. 
         [0176]    In step S 313 , the receiving device  52  receives the rewriting data (program) transmitted through the satellite broadcasting network  24 . The specific process of receiving the rewriting data (program) is the same as the process described in step S 311 . The content of the rewriting data (program) is the same as that of the CD-ROM  22  ( FIGS. 4 through 11 ). 
         [0177]    In step S 314 , the receiving device  52  judges whether or not reception of the rewriting data (program) is completed. If reception of the rewriting data (program) is not completed (step S 314 : NO), then control returns to step S 313 . If reception of the rewriting data (program) is completed (step S 314 : YES), then control proceeds to step S 315 . 
         [0178]    In step S 315 , the receiving device  52  sends a notice to the rewriting device  54  indicating reception of the rewriting data (program). 
         [0179]    Steps S 316  through S 329  of  FIGS. 22 through 24  are the same as steps S 15  through S 28  of  FIGS. 4 through 6 . If the rewriting data (program) are compatible with the target ECU  56   tar  (step S 327 : YES), then in step S 330 , the rewriting device  54  sends a notice to the receiving device  52  indicating that confirmation of compatibility is finished. Thereafter, control proceeds to step S 29  of  FIG. 9 . 
       (3) Program Transmitted Through Mobile Communications Network  26 : 
     (a) Outline of Rewriting Process: 
       [0180]      FIG. 25  is a flowchart of a general outline of a processing sequence for rewriting the program for an ECU  56  with rewriting data (program) transmitted through the mobile communications network  26 . 
         [0181]    In step S 401 , the receiving device  52  receives rewriting data (program), which is transmitted through the mobile communications network  26 . For receiving the rewriting data (program) through the mobile communications network  26 , the portable telephone  86  should be connected in advance to the connector  88 . 
         [0182]    Steps S 402  through S 409  are the same as steps S 2  through S 9  of  FIG. 3  and steps S 302  through S 309  of  FIG. 21 . 
         [0183]    During steps S 401  through S 405 , the vehicle  16  is capable of being driven. During steps S 406  through S 409 , the engine is shut off and hence the vehicle  16  cannot be driven. 
       (b) Details of Rewriting Process: 
       [0184]      FIG. 26  is a flowchart showing details of a processing sequence for rewriting the program for the ECU  56  with rewriting data (program) transmitted through the mobile communications network  26 . Processing details, which share common processing details (see  FIGS. 22 through 24 ) concerning rewriting of the program with rewriting data (program) transmitted through the satellite broadcasting network  24 , will be described with reference to  FIGS. 22 through 24 . 
         [0185]    In step S 411 , the user connects the portable telephone  86  to the connector  88 . 
         [0186]    In step S 412 , the portable telephone  86  of the receiving device  52  establishes a communication link with the server  14 . Such a communication link is established when rewriting data (program) are transferred from the server  14 . Alternatively, the receiving device  52  may send an inquiry to the server  14  via the portable telephone  86  and the mobile communications network  26 , requesting whether or not there are new rewriting data (program) at a preset time (e.g., when the portable telephone  86  and the connector  88  are connected to each other, or at a given interval from, or at a given time after connection between the portable telephone  86  and the connector  88  is established). 
         [0187]    Steps S 413  through S 417  are the same as steps S 313  through  317  of  FIG. 22 . Thereafter, control proceeds to step S 318  of  FIG. 23 . 
       4. Advantages of the Present Embodiment 
       [0188]    According to the embodiment described above, it is judged whether or not the vehicle  16  can be restarted based on a predicted state of the battery  58  after a program for the ECU  56  is rewritten, and the program is rewritten only if the vehicle  16  is capable of being restarted. Accordingly, the vehicle  16  can reliably be restarted after the program has been rewritten. 
         [0189]    According to the present embodiment, the rewriting device  54  changes the threshold value THsoc depending on the ambient temperature Tc [° C.] in the vicinity of the vehicle  16 , the engine coolant water temperature Tw [° C.] of the vehicle  16 , and the internal resistance R [Ω] of the battery  58 . Conditions for restarting the vehicle  16  can thus be established more appropriately. 
         [0190]    In the present embodiment, the rewriting device  54  predicts the SOC after the program is rewritten based on the SOC and the battery current Ibat at the time that the program starts to be rewritten, and an expected processing time Tre for rewriting the program. If the predicted SOC is greater than the threshold value THsoc, the program is rewritten. Therefore, a charged state of the battery  58  after the program has been rewritten can easily be predicted and used. 
         [0191]    According to the present embodiment, in the situation shown in  FIG. 27 , it is possible to reliably turn off the ECU  56  before the program is rewritten. 
         [0192]      FIG. 27  is a diagram showing the relationship between an output signal Sig from the IGSW  64  and recognition of the ECUs  56 . In  FIG. 27 , after the IGSW  64  has been turned from the “ON” position to the “OFF” position at time t 1 , the IGSW  64  is turned to the “ON” position at time t 5 . The period from time t 1  to time t 5  is very short, e.g., several hundred ms. 
         [0193]    As shown in  FIG. 27 , the ECUs  56  read the output signal Sig at different times. In order to eliminate adverse effects of chattering, the ECUs  56  read the output signal Sig when the signal has the same level (high or low) in two control periods. 
         [0194]    For example, a first ECU detects that the IGSW  64  is turned off at time t 2 , however, the first ECU does not immediately recognize that the IGSW  64  has been turned off, but rather, first recognizes that the IGSW  64  has been turned off only upon detecting that the IGSW  64  is turned off at time t 2  and at time t 4 . On the other hand, a second ECU detects that the IGSW  64  is turned off at time t 3 , but detects that the IGSW  64  is turned on at time t 6 . Thus, since the second ECU does not detect twice in succession that the IGSW  64  is turned off, the second ECU recognizes that the IGSW  64  remains turned on. 
         [0195]    In the above situation, according to the present embodiment, in order to rewrite the program, after the IGSW  64  is turned to the “OFF” position whereupon the ECU  56  is turned off, the IGSW  64  must be returned to the “ON” position. An instruction for prompting the user to return the IGSW  64  to the “ON” position is displayed after it is detected that the ECU  56  has been turned off in response to the IGSW  64  being turned to the “OFF” position. Consequently, the ECU  56  can be reliably turned off before the program is rewritten. 
         [0196]    Therefore, while the ECU  56  continuously performs the processing sequence, the program is prevented from being rewritten. 
         [0197]    According to the present embodiment, if the IGSW  64  is erroneously turned to the “OFF” position while the program is being rewritten, then the program cannot be rewritten. At this time, an instruction for prompting the user to return the IGSW  64  to the “ON” position is displayed on the display unit  74 . Therefore, it is possible to indicate the erroneous action to the user (vehicle occupant), and to prompt the user to return the IGSW  64  to its proper state. Therefore, at times when the user is in the vehicle  16  as well, the program can be rewritten, and the program can be rewritten more appropriately. 
         [0198]    According to the present embodiment, if the rewriting device detects that the user has left the vehicle  16  while an instruction for prompting the user to return the IGSW  64  to the “ON” position is being displayed on the display unit  74 , then a startup reservation is recorded as information concerning interruption of program rewriting, and a cancellation request signal for requesting that the receiving device  52  not be kept on is output to the receiving device  52 . 
         [0199]    Consequently, if the user mistakenly leaves the vehicle  16  with the IGSW  64  being turned to the “OFF” position while the program is being rewritten, it is possible to keep information concerning interruption of program rewriting. Therefore, the program can be rewritten again using the information that was kept. If the receiving device  52  is no longer turned on, the instruction stops being displayed on the display unit  74 . Accordingly, the display unit  74  can avoid unwanted consumption of electric power. 
         [0200]    According to the present embodiment, based on the output signal Sh from the detecting unit  66 , the rewriting device  54  detects when the user leaves the vehicle  16 . Using the output signal Sh, it is possible to determine easily if the user has left the vehicle  16 . 
         [0201]    According to the present embodiment, when the rewriting device  54  detects that the user has left the vehicle  16 , the rewriting device  54  confirms whether or not a startup reservation has been recorded. If a startup reservation has been recorded, then the rewriting device  54  displays on the display unit  74  an instruction for prompting the user to turn the IGSW  64  to the “ON” position. Thus, in the event of an interruption during rewriting of the program, appropriate information can be displayed for resuming program rewriting. 
         [0202]    According to the present embodiment, the rewriting device  54  detects when the user reenters the vehicle  16  based on the output signal Sh from the detecting unit  66 . Using the output signal Sh, it is possible to determine easily when the user enters the vehicle  16 . 
       B. Applications of the Present Invention 
       [0203]    The present invention is not limited to the above embodiment, but may adopt various alternative arrangements based on the present disclosure. For example, the present invention may adopt any of the following arrangements. 
       1. Program Rewriting System  10   
       [0204]    In the above embodiment, the system  10  is used in combination with multiple vehicles. However, the system  10  may be used in combination with other mobile objects (aircrafts, ships, helicopters, etc.), which require electric power when restarted. 
       2. Data Transmission System  12   
       [0205]    In the above embodiment, rewriting data (program) are transmitted using the CD-ROM  22 , the satellite broadcasting network  24 , and the mobile communications network  26 . However, rewriting data (program) may be transmitted using one or two of the CD-ROM  22 , the satellite broadcasting network  24 , and the mobile communications network  26 . Alternatively, rewriting data (program) may be transmitted according to other methods, for example, wireless communications that do not use broadcasting satellites or portable telephones (e.g., wireless communications by way of light beacons installed along roadsides). The CD-ROM  22  may be replaced with another storage medium (DVD-ROM, flash memory, or the like). 
       3. Vehicle  16   
       [0206]    In the above embodiment, the vehicles  16  are gasoline-powered vehicles. However, the vehicles  16  may be different types of vehicles, for example, electric vehicles (including hybrid vehicles and fuel cell vehicles) having a drive source that requires electric power when restarted. 
       4. ECUs  56   
       [0207]    In the above embodiments, the ECUs  56  include the ENG ECU  56   a,  the ABS ECU  56   b,  the SRS ECU  56   c,  and the immobilizer ECU  56   d.  However, the quantity and types of ECUs  56  are not limited to those illustrated above. 
       5. IGSW  64   
       [0208]    In the above embodiment, the IGSW  64  comprises a rotary switch. However, if the vehicle  16  includes a so-called smart start function, then the IGSW  64  may comprise a push switch, which cycles successively through the “OFF”, “ACCESSORY”, and “ON” positions when pushed. 
       6. Judgment of Restartability 
       [0209]    (1) Estimation of State of Battery  58  after Program is Rewritten: 
         [0210]    In the above embodiment, the SOC, the battery current Ibat, and the expected processing time Tre are used to estimate the state of the battery  58  after the program is rewritten (refer to the above inequality (1)). However, other data may be used insofar as such data make it possible to estimate the state of the battery  58  after the program is rewritten. For example, the state of the battery  58  after the program is rewritten may be estimated based on an amount of electric power ΔAH 1  [A·h] that has been discharged up to the present time from the battery  58  from a given charged state, and an expected amount of electric power ΔAH 2  [A·h] that will be discharged from the battery  58  from the present time until after the program is rewritten. The given charged state may be set to an appropriate value, such as a fully charged state, an SOC of 80%, an SOC of 75%, or the like. 
         [0211]    More specifically, it is judged whether or not the following inequality (2) is satisfied: 
         [0000]      Δ AH 1 +ΔAH 2&lt;TH —   ΔAH    (2)
 
         [0000]    where TH_ΔAH represents a threshold value (maximum value) for an amount of electric power that is discharged from the given charged state, and which makes it possible to start the vehicle  16 . The threshold value TH_ΔAH is a measured value or a simulated value, which is included in the rewriting data (program). The expected amount of electric power ΔAH 2  is calculated as a product of the battery current Ibat at the present time and the expected processing time Tre required for the program to be rewritten. 
         [0212]    According to the above judging process, the state of the battery  58  after the program is rewritten can simply be predicted and used. 
         [0213]    Alternatively, the state of the battery  58  after the program is rewritten can be predicted according to the method disclosed in JP2008-155892A. 
         [0000]    (2) Conditions that Make it Impossible to Rewrite the Program: 
         [0214]    According to the above embodiment, a condition that makes it impossible to rewrite the program is that the battery  58  is capable of restarting the vehicle  16  after the program is rewritten in step S 31  of  FIG. 7 . Furthermore, step S 46  of  FIG. 9  uses the condition (i) that the engine rotational speed Ne is 0 [rpm], the condition (ii) that the vehicle speed V is 0 [km/h], the condition (iii) that the gearshift position is the position P (Parking), the condition (iv) that the target ECU  56   tar  is at or below the threshold value THe, and the condition (v) that the immobilizer ECU  56   d  determines that a proper key has been inserted. 
         [0215]    However, other conditions may be used for making it impossible to rewrite the program. For example, it may be impossible to rewrite the program if the battery current Ibat at the time that rewriting of the program is started is greater than a threshold value THi [A]. The threshold value THi may be set to a current value representing a high undesirable electric load at the time that the program is rewritten. 
         [0216]    It may also be impossible to rewrite the program if the internal resistance R of the battery  58  at the time that the program is rewritten is greater than a threshold value THr [Ω]. The threshold value Thr, which serves to determine that the battery  58  has become excessively deteriorated, may be a measured value or a simulated value. 
         [0217]      FIG. 28  is a flowchart of a sequence for judging whether or not the program can be rewritten using the threshold values THi, THr in addition to the inequality (1). The flowchart of  FIG. 28  may be used in step S 31  of  FIG. 7 . 
         [0218]    In step S 501 , the rewriting device  54  acquires an SOC, a battery current Ibat, and an internal resistance R at present, which are supplied from the ENG ECU  56   a  or the battery sensor  60 . 
         [0219]    In step S 502 , the rewriting device  54  judges whether or not the internal resistance R is greater than the threshold value THr. If the internal resistance R is greater than the threshold value THr (step S 502 : YES), then in step S 503 , the rewriting device  54  decides that the program cannot be rewritten, since there is a possibility that the vehicle  16  cannot be restarted after the program has been rewritten. If the internal resistance R is equal to or smaller than the threshold value THr (step S 502 : NO), then control proceeds to step S 504 . 
         [0220]    In step S 504 , the rewriting device  54  judges whether or not the battery current Ibat is greater than the threshold value THi. If the battery current Ibat is greater than the threshold value THi (step S 504 : YES), then in step S 503 , the rewriting device  54  decides that the program cannot be rewritten as a result of a high undesirable electric load. If the battery current Ibat is equal to or smaller than the threshold value THi (step S 504 : NO), then control proceeds to step S 505 . 
         [0221]    In step S 505 , the rewriting device  54  calculates a predicted value SOCre [%] of the SOC after the program is rewritten. The predicted value SOCre is equal to SOC−(Ibat×Tre×K), which appears in the above inequality (1). 
         [0222]    In step S 506 , the rewriting device  54  judges whether or not the predicted value SOCre is greater than the threshold value THsoc. If the predicted value SOCre is equal to or smaller than the threshold value THsoc (step S 506 : NO), then in step S 503 , the rewriting device  54  decides that the program cannot be rewritten. If the predicted value SOCre is greater than the threshold value THsoc (step S 506 : YES), then in step S 507 , the rewriting device  54  determines that the program can be rewritten. 
         [0223]    Generally, the internal resistance R reflects a state of deterioration of the battery  58 . Therefore, if the internal resistance R is greater than the threshold value THr, then it is difficult to accurately predict the charged state of the battery  58  after the program is rewritten. If the battery current Ibat is large, it also is difficult to accurately predict the charged state of the battery  58  after the program is rewritten. According to the flowchart of  FIG. 28 , even though the predicted value SOCre is greater than the threshold value THsoc, the rewriting device  54  stops rewriting the program if the internal resistance R at the time that rewriting of the program is started is greater than the threshold value THr, or if the battery current Ibat is greater than the threshold value THi. Consequently, if the accuracy of the prediction is low, the rewriting device  54  stops rewriting the program, thereby lowering the possibility that the vehicle  16  cannot be restarted. 
         [0224]    The judging process, which uses the above inequality (2), may be performed instead of steps S 505  and S 506  of  FIG. 28 . 
       7. Judgment of Turning-Off of ECUs  56   
       [0225]    In the above embodiment, the rewriting device  54  reads the position to which the IGSW  64  has been turned or sends a response request to an ECU  56 , and the rewriting device  54  detects that the ECU  56  has been turned off in the absence of a response from the ECU  56 . However, other processes may be used to detect when the ECU  56  is turned off. For example, the rewriting device  54  may request a program ID, and may detect when the ECU  56  is turned off based on whether or not a response is received from the ECU  56 . Alternatively, the rewriting device  54  may read the position to which the IGSW  64  has been turned, and may regard the ECU  56  as having been turned off after a predetermined period has elapsed from when the position “OFF” of the IGSW  64  was detected, or alternatively, may regard the ECU  56  as having been turned off in the absence of a response from the ECU  56  to a response request that has been sent. 
       8. Detection of When User Leaves the Vehicle or Reenters the Vehicle 
       [0226]    In the above embodiment, the user leaving the vehicle or reentry of the user into the vehicle is detected based on the output signal from the door lock/vehicle occupant detecting unit  66 , i.e., the unlocked/locked state of the door lock  122  and the pressure on the seat. However, either one of the unlocked/locked state of the door lock  122  and the pressure on the seat may be used to detect when the user leaves the vehicle or reenters the vehicle. Moreover, another scheme (e.g., a load sensor installed in the seat or an infrared sensor for detecting infrared rays in the vicinity of the driver&#39;s seat) may be used to detect when the user leaves the vehicle or reenters the vehicle (whether the vehicle occupant is present in the vehicle  16 ).