Abstract:
An electronic control device having an input processing circuit capable of arbitrarily connecting one or both of a pull-up resistor and a pull-down resistor to an input signal from outside and capable of arbitrarily setting a resistance value of the pull-up resistor and/or the pull-down resistor connected, to diagnose whether the resistance value of the pull-up/pull-down resistor is a designed value. The input processing circuit has a unit that diagnoses whether the resistance value of the pull-up resistor and/or the pull-down resistor is within an expected range. The pull-down resistor is connected to the pull-up resistor when the resistance value of the pull-up resistor is to be diagnosed, the pull-up resistor is connected to the pull-down resistor when the resistance value of the pull-down resistor is to be diagnosed, and the resistance value is diagnosed based on the voltage divided by both the pull-up resistor and the pull-down resistor.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an electronic control device which carries out control of an engine, etc. of an automobile and relates to a unit that carries out processing so that signals input from various sensors or switches (hereinafter, described as sensors or the like), which are attached to control targets, to the electronic control device are suitable for computing in the electronic control device. 
       BACKGROUND ART 
       [0002]    Conventionally, as a unit that highly controls an engine, etc. of an automobile, there has been used an electronic control device which inputs the state of control targets from sensors or the like connected to the control targets such as the engine, etc. and drives actuators such as a fuel injector by computing results according to a computing unit such as a microcontroller. This electronic control device uses an input processing circuit which carries out processing so that various input signals from the sensors or the like are suitable to be processed in the electronic control device. Specifically, for example, when outputs of the sensors or the like or outputs of switches expressed as opening/closing of contact points, which have variable resistance values like thermistors or potentiometers, are converted to voltage signals by pull-up/pull-down resistors, A/D conversion enables the signals to be directly handled by a computing unit in the electronic control device such as a microcomputer. 
         [0003]    The input processing circuit like this may have various forms. For example, a sensor abnormality diagnosis device according to PTL 1 discloses an example in which inputs from sensors are converted to voltage signals by pull-up/pull-down resistors, furthermore, the resistance values of the pull-up/pull-down resistors are changed, and malfunctioning of the sensors can be diagnosed by evaluating responses in this process. 
       CITATION LIST 
     Patent Literature 
       [0004]    PTL 1: Japanese Patent Application Laid-Open No. H3-210047 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    Generally, high reliability and safety are required for control systems of automobiles including electronic control devices, particularly, for the control systems related to important functions such as engines. In order to realize safety from a viewpoint of function safety for which importance has been particularly increased recently, a function of diagnosing malfunctioning of the elements which constitute the control system is required. PTL 1 shows an example which enables detection of malfunctioning of the sensors, which constitute the control system, by varying the pull-up/pull-down resistance values. 
         [0006]    On the other hand, in order to ensure reliability and safety of the control system, diagnosis of the pull-up/pull-down resistors per se is also required. This is for a reason that, if the pull-up/pull-down resistors cause malfunctioning such as disconnection, short-circuiting, and drift of the resistance values, the input signals from the sensors or the like cannot be correctly processed, and there is a risk of carrying out erroneous control. 
         [0007]    Particularly when the pull-up/pull-down resistance values are variable, the mechanism therefor becomes complex, and a malfunctioning rate is generally increased compared with the case in which the pull-up/pull-down resistance values are not variable. Therefore, there is a problem that the necessity of diagnosis is high. 
         [0008]    The present invention has been accomplished in view of the above described points, and it is an object to provide an electronic control device, wherein, in an input processing circuit of the electronic control device capable of varying resistance values of pull-up/pull-down resistors, whether the resistance values of the pull-up/pull-down resistors are designed values can be diagnosed. 
       Solution to Problem 
       [0009]    An example of an electronic control device accomplished in order to achieve the object is an electronic control device having an input processing circuit capable of arbitrarily connecting a pull-up resistor or a pull-down resistor or both of the pull-up resistor and the pull-down resistor to an input signal from outside and capable of arbitrarily setting resistance value(s) of the pull-up resistor and/or the pull-down resistor connected, and the electronic control device includes the input processing circuit having a unit that diagnoses whether the resistance value of the pull-up resistor and/or the pull-down resistor is within an expected range. 
       Advantageous Effects of Invention 
       [0010]    According to the present invention, the resistance value of the set pull-up resistor and/or pull-down resistor can be diagnosed, and malfunctioning such as disconnection, short-circuiting, and drift of the resistance value can be diagnosed by comparing that with an expected value. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a functional block diagram showing a configuration of an electronic control device  1  of a first embodiment of the present invention. 
           [0012]      FIG. 2  is a circuit diagram showing a configuration example of a comparator unit  5  of the first embodiment of the present invention. 
           [0013]      FIG. 3  is a correspondence table of a voltage V 44  and comparator output logics of the first embodiment of the present invention. 
           [0014]      FIG. 4  is a functional block diagram showing a configuration of an electronic control device  1  of a second embodiment of the present invention. 
           [0015]      FIG. 5  is a correspondence table of a voltage V 44  and abnormality presence/absence judgement of the second embodiment of the present invention. 
           [0016]      FIG. 6  is a flow chart of the abnormality presence/absence judgement of the second embodiment of the present invention. 
           [0017]      FIG. 7  is a functional block diagram showing a configuration of an electronic control device  1  of a third embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       [0018]    Hereinafter, an electronic control device according to a first embodiment of the present invention will be described by using drawings. 
         [0019]      FIG. 1  is a block diagram showing a configuration of an electronic control device  1  of the present embodiment. 
         [0020]    The electronic control device  1  is composed of an input processing circuit  2 , a microcomputer  6 , and an unshown output unit, and a plurality of sensors or the like  31  and  32  are connected to input terminals  3  thereof. The sensors or the like  31  and  32  are mounted on unshown control targets and have characteristics that the resistance values thereof are changed depending on the state of the control targets. 
         [0021]    Meanwhile, one end thereof is connected to power-source wiring  41  or GND wiring  47 , and the other end thereof is connected to the input processing circuit  2  via the input terminals  3 . 
         [0022]    Hereinafter, first, operations of the input processing circuit  2  in a case of normal operations will be described. A control circuit  21  is a circuit which carries out control of circuits in the input processing circuit  2  and is controlled by a computing unit  62  in the microcomputer  6 . In detail, selection operations of a multiplexer  22  and setting of a pull-up/pull-down setting register  23  and the pull-up/pull-down diagnosis register  24  are carried out, and output from a window comparator  51  is transmitted to the computing unit  62 . 
         [0023]    One signal is selected by the multiplexer  22  from among the signals input to the input terminals  3 , is connected to an intermediate point  44  of a pull-up/pull-down resistor group  4 , and, at the same time, is input to an AD converter  61  in the microcomputer  6 . Since the sensors or the like  31  and  32  are connected by time-division by using the multiplexer  22  in this manner, the circuits in the subsequent stage of the multiplexer can be shared, and the circuit size thereof can be reduced. 
         [0024]    The AD converter  61  converts the voltage of the input signal to a digital signal and transmits that to the computing unit  62 . The computing unit  62  determines the state of the control target based on the input signal, carries out control computing, gives instructions to the unshown output unit, and realizes intended control. 
         [0025]    The pull-up/pull-down resistor group  4  is composed of common power-source wiring  41 , a plurality of pull-up resistors  421  and  422 , a plurality of pull-up selecting switches  431  and  432 , the intermediate point  44 , a plurality of pull-down selecting switches  451  and  452 , a plurality of pull-down resistors  461  and  462 , and common GND wiring  47 . The pull-up resistors  421  and  422  have mutually different resistance values and are selectively connected to the intermediate point  44  by the pull-up selecting switches  431  and  432 , thereby realizing pull-up processing with an arbitrary resistance value. Similarly, the pull-down resistors  461  and  462  have mutually different resistance values and are selectively connected to the intermediate point  44  by the pull-down selecting switches  451  and  452 , thereby realizing pull-down processing with an arbitrary resistance value. 
         [0026]    Note that the pull-up resistors  421  and  422  and the pull-down resistors  461  and  462  are configured to have approximately equal resistance values of the respective combinations thereof. For example, if the pull-up resistors  421  and  422  are composed of resistors of 1 kΩ and 10 kΩ, the pull-down resistors  461  and  462  are similarly composed of resistors of 1 kΩ and 10 kΩ. This is a configuration which is required in a later-described operation of malfunction diagnosis. 
         [0027]    The pull-up selecting switches  431  and  432  and the pull-down selecting switches  451  and  452  are composed of analog switches, and ON/OFF thereof is controlled to be ON when one of or both of corresponding bits of the pull-up/pull-down setting register  23  and the pull-up/pull-down diagnosis register  24  is true. However, in a normal operation, the pull-up/pull-down diagnosis register  24  is not used, and only the pull-up/pull-down setting register  23  is used. The selected (turned ON) pull-up selecting switch may be only single, or a configuration which realizes more various resistance values by synthesizing resistance values by turning ON two or more switches at the same time may be employed. Meanwhile, a configuration in which an arbitrary bias voltage is applied to the sensor or the like by connecting the pull-up resistor and the pull-down resistor at the same time may be employed. 
         [0028]    This is the operation of the input processing circuit  2  in the case of a normal operation. By switching the signals (sensors or the like), which are serving as targets, by the multiplexer  22  in accordance with needs and carrying out similar operations, input processing of carrying out pull-up processing or pull-down processing with an arbitrary resistance value with respect to the plurality of connected sensors or the like can be realized. 
         [0029]    Next, operations of the input processing circuit  2  in a case of malfunction diagnosis will be described. Herein, the operations of a case in which the resistance value of the pull-up resistor  421  is diagnosed will be described. 
         [0030]    First, the multiplexer  22  temporarily stops the connections to the sensors or the like  31  and  32  and connects to a diagnosis-dedicated no-connection input  25 . This is for avoiding the influence of the input from the sensors or the like  31  and  32  and obtaining a stable diagnosis result. Note that the no-connection input  25  of the present embodiment may truly have no connection or may be connected to the power-source wiring  41  or the GND wiring  47  with impedance which is sufficiently higher than the resistance values of the resistors in the pull-up/pull-down resistor group  4 . 
         [0031]    Then, the pull-up/pull-down setting register  23  is set so that only the pull-up resistor  421  is connected to the intermediate point  44 . Then, the pull-up/pull-down diagnosis register  24  is set so that the pull-down resistor  461 , which has the same resistance value as that of the pull-up resistor  421 , is connected to the intermediate point  44 . Herein, the resistance value of the pull-up resistor  421  is assumed to be R 421 , and the resistance value of the pull-down resistor  461  is assumed to be R 461 ; in this case, the voltage (V 44 ) of the intermediate point  44  is subjected to voltage dividing by the voltage (V 41 ) of the power-source wiring  41  and the voltage (0) of the GND wiring  47  and becomes the voltage represented by below Formula 1. 
         [0000]        V 44= V 41× R 461/( R 421+ R 461)  Formula 1
 
         [0032]    Herein, if both of the pull-up resistor  421  and the pull-down resistor  461  are normal (R 421 =R 461 ), it becomes a voltage Vh which is exactly the middle as shown in below Formula 2. 
         [0000]        V 44= V 41/2= Vh   Formula 2
 
         [0033]    On the other hand, if the resistance value of either one of the pull-up resistor  421  or the pull-down resistor  461  is abnormal, the voltage-dividing result is deviated from this voltage. For example, if the pull-up resistor  421  is disconnected (R 421 =infinite), the voltage (0) of the GND wiring appears at the intermediate point  44 . Meanwhile, if the pull-up resistor  421  is short-circuited, the voltage V 41  of the power-source wiring appears at the intermediate point  44 . 
         [0034]    By utilizing this characteristic and judging whether the voltage of the intermediate point  44  is deviating from Vh, malfunctioning of the pull-up resistor  421  and the pull-down resistor  461  can be judged. This judgement is carried out by the comparator unit  5 . 
         [0035]    The comparator unit  5  is composed of the window comparator  51 , an upper-limit threshold voltage source  52 , and a lower-limit threshold voltage source  53 . The internal configuration of the comparator unit is shown in  FIG. 2 . 
         [0036]    The upper-limit threshold voltage source  52  and the lower-limit threshold voltage source  53  are composed of fixed voltage-dividing circuits and generate unique voltages (V 52  and V 53 , respectively) between the voltage V 41  of the power-source wiring  41  and the voltage (0) of the GND wiring  47 . V 52  and V 53  are set so as to satisfy a below inequality of Formula 3. 
         [0000]        V 53&lt; Vh&lt;V 52  Formula 3
 
         [0037]    The window comparator  51  is composed of analog comparators  511  and  512  and an AND circuit  513  and outputs digital values as shown in a correspondence table shown in  FIG. 3  depending on the voltage V 44  of the input point. By employing this configuration, if V 44  is in the vicinity of Vh, in other words, there is no abnormality in the resistance value of the pull-up resistor or the pull-down resistor, true output can be obtained; and, if V 44  is deviated from the vicinity of the intermediate point, in other words, there is abnormality in the pull-up resistor or the pull-down resistor, false output can be obtained. 
         [0038]    Note that the difference between V 53  and Vh and the difference between Vh and V 52  are margins for reducing erroneous reports caused by the errors which are within a normal range, and the differences are set based on the errors which are allowable with respect to the pull-up resistors and the pull-down resistors. Note that, by employing a configuration in which the margins to reduce the erroneous reports are set depending on the types, etc. of the connected sensors or the like, a configuration can be also implemented in which an effect of reducing the erroneous reports in a necessary and sufficient manner can be obtained. 
         [0039]    The control circuit  21  transmits the output value of the comparator unit  5 , which has been obtained in this manner, to the computing unit  62 . 
         [0040]    The computing unit  62  can easily carry out diagnosis of malfunctioning based on this value. 
         [0041]    These are the operations of the input processing circuit  2  in the case of malfunctioning diagnosis in the present embodiment. According to the present embodiment, abnormality in the resistance values of the pull-up resistors and the pull-down resistors can be diagnosed. In the present embodiment, a point that diagnosis of the resistance value of the pull-up/pull-down resistor can be carried out without carrying out significant addition of circuits by utilizing, also for diagnosis, the configuration used in a resistance-value variable function of the pull-up/pull-down resistor serving as an original function is a major characteristic. 
         [0042]    Note that, in the present embodiment, the connection of the pull-down resistor  461  uses the pull-up/pull-down diagnosis register  24  instead of the pull-up/pull-down setting register  23 , and, by virtue of this configuration, malfunctioning of the pull-up/pull-down setting register  23  per se can be also diagnosed. More specifically, in a case of a state that all bits of the pull-up/pull-down setting register  23  are fixed to the values representing switch OFF and are malfunctioning and that the resistors cannot be connected to the intermediate point  44  even when the register is set, if the (malfunctioning) pull-up/pull-down setting register  23  is used also in the connection of the pull-down resistor  461 , both of the pull-up resistor  421  and the pull-down resistor  461  are not connected to the intermediate point  44 , and the voltage V 44  of the intermediate point  44  becomes indefinite. In this case, if V 44  is accidentally in the vicinity of Vh, it is diagnosed to be normal regardless of the presence/absence of abnormality in the resistance value. 
         [0043]    On the other hand, if the diagnosis-dedicated pull-up/pull-down diagnosis register  24  is used in the connection of the pull-down resistor  461  like the present embodiment, the pull-down resistor  461  is connected regardless of malfunctioning of the pull-up/pull-down setting register  23 , and, therefore, the voltage of the intermediate point  44  becomes the vicinity of 0, which is an abnormal region, and can be diagnosed as malfunctioning. 
         [0044]    By employing this configuration, malfunctioning of the pull-up/pull-down setting register  23  per se can be also diagnosed. 
         [0045]    The above description is an example of diagnosing the pull-up resistor  421  and the pull-down resistor  461 . However, by switching the pull-up resistor and pull-down resistor connected to the intermediate point  44  in accordance with needs and carrying out similar operations, diagnosis of malfunctioning can be carried out with respect to the plurality of pull-up resistors and pull-down resistors. Herein, the control circuit  21  may transmit the diagnosis result of each resistor of the diagnosis target to the computing unit  62  or, after diagnosis of all the resistors of the diagnosis targets is completed, may collectively transmit the diagnosis results thereof to the computing unit  62 . Particularly in the latter case, there is an advantage that computing load in the computing unit  62  can be reduced. 
         [0046]    Note that, as described above, since the above described diagnosis is carried out by connecting the input of the multiplexer  22  to the no-connection input  25  for diagnosis, this cannot be carried out at the same time as a normal input processing operation, but has to be exclusively carried out. In order to realize this, this can be realized by employing a method of carrying out in a time period such as that immediately after key-ON, after key-OFF, or idling-stopped period of an automobile when stopping a normal operation and dedicating to diagnosis is allowed or a method of alternately carrying out the input processing of a normal operation and the input processing of the malfunctioning diagnosis by time division. 
         [0047]    Moreover, the electronic control device  1  of the present embodiment has a characteristic that a unique through-current flows from the power-source wiring  41  toward the GND wiring  47  since the pull-up resistor and the pull-down resistor of the diagnosis target are temporarily connected at the same time for diagnosis. More specifically, when the pull-up resistor  421  and the pull-down resistor  461  are connected to the intermediate point  44  for diagnosis, a through-current Ip expressed by below Formula 4 flows from the power-source wiring  41  toward the GND wiring  47 . 
         [0000]        Ip=V 41/( R 421+ R 461)  Formula 4
 
         [0048]    Moreover, in the present embodiment, the resistance values of the pull-up resistor and the pull-down resistor connected in the malfunctioning diagnosis are approximately equal; however, the configuration of the present invention is not limited by this. More specifically, even when the resistance values of the pull-up resistor and the pull-down resistor connected in malfunctioning diagnosis are different from each other, similar diagnosis can be carried out by setting the upper-limit threshold voltage and the lower-limit threshold voltage used in the malfunctioning determination to the values obtained by adding/subtracting margins to/from the value of V 44  calculated by Formula 1. However, as shown in the present embodiment, the case in which the resistance values of the pull-up resistor and the pull-down resistor are approximately equal is preferred since the resistance values can be diagnosed under the condition that the sensitivity to V 44  from the errors of the resistors is the highest. 
       Second Embodiment 
       [0049]    Next, as an electronic control device according to a second embodiment, an example which realizes similar effects by a method different from the first embodiment will be described by using drawings.  FIG. 4  is a block diagram showing the configuration of an electronic control device  1  of the present embodiment. A difference in a hardware configuration between the present embodiment and the above described first embodiment is a point that the comparator unit  5 , which is provided in the first embodiment, is not provided. Moreover, a difference in operation between the present embodiment and the above described first embodiment is a point that the comparison between the intermediate voltage  44  and the voltage Vh, which is carried out in the comparator unit  5  in the first embodiment, is carried out in the microcomputer  6 . 
         [0050]    Hereinafter, operations of the input processing circuit  2  and the microcomputer  6  in the present embodiment will be described. First, the operations of the input processing circuit  2  and the microcomputer  6  in normal operations are the same as those of the first embodiment. 
         [0051]    Next, the operations of the input processing circuit  2  and the microcomputer  6  in a case in which the resistance value of the pull-up resistor  421  is diagnosed in malfunctioning diagnosis will be described. Also in the malfunctioning diagnosis, the no-connection input  25  is connected to the intermediate point  44  by the multiplexer  22 , then the pull-up resistor  421  and the pull-down resistor  461  having the approximately equal resistance value as the resistor is connected, and V 44  becomes the voltage expressed by Formula 1; and, until this point, the operations are the same as the operations of the first embodiment. However, the operations after this are different. 
         [0052]    In the present embodiment, the voltage of V 44  is converted to digital values by the AD converter  61  as well as a normal operation and is input to the computing unit  62 . Then, in the computing unit  62 , in accordance with a correspondence table shown in  FIG. 5 , whether the voltage of V 44  shows abnormality of the pull-up resistor  421  or the pull-down resistor  461  is judged. 
         [0053]    More specifically, as well as the first embodiment, the upper-limit threshold voltage V 52  and the lower-limit threshold voltage V 53  are selected so as to satisfy the inequality of Formula 3 and are stored in a memory area (not shown), which is present in the computing unit  62 . Then, in the computing unit  62 , in accordance with a flow chart shown in  FIG. 6 , malfunctioning judgement is carried out according to measurement of V 44  and the magnitude relations of V 44 , V 53 , and V 52 . The operations herein are implementation of the function, which has been carried out by the window comparator  51  in the first embodiment, by a program in the computing unit  62 . 
         [0054]    These are the operations of the input processing circuit  2  in the malfunctioning diagnosis of the present embodiment. According to the present embodiment, as well as the first embodiment, abnormality in the resistance values of the pull-up resistor and the pull-down resistor can be diagnosed. Moreover, compared with the first embodiment, hardware required for diagnosis can be further reduced. However, on the other hand, there is a tradeoff that the processing load in the computing unit  62  is increased. 
         [0055]    Note that the above description is an example of diagnosing the pull-up resistor  421  and the pull-down resistor  461 . However, by switching the pull-up resistor and the pull-down resistor connected to the intermediate point  44  in accordance with needs and carrying out similar operations, diagnosis of malfunctioning can be carried out with respect to the plurality of pull-up resistors and pull-down resistors. 
         [0056]    Moreover, in the present embodiment, the resistance values of the pull-up resistor and the pull-down resistor connected in the malfunctioning diagnosis are approximately equal; however, the configuration of the present invention is not limited by this. More specifically, even when the resistance values of the pull-up resistor and the pull-down resistor connected in malfunctioning diagnosis are different from each other, similar diagnosis can be carried out by setting the upper-limit threshold voltage V 52  and the lower-limit threshold voltage V 53  used in the malfunctioning determination to the values obtained by adding/subtracting margins to/from the value of V 44 , which is calculated by Formula 1 when the resistance values are normal. However, the case in which the resistance values of the pull-up resistor and the pull-down resistor are approximately equal is preferred since the resistance values can be diagnosed under the condition that the sensitivity to V 44  from the errors of the resistors is the highest. 
       Third Embodiment 
       [0057]    Next, as an electronic control device according to a third embodiment of the present invention, an example in which similar effects are realized by a further different method will be described by using drawings.  FIG. 7  is a block diagram showing the configuration of an electronic control device  1  of the present embodiment. Differences in a hardware configuration between the present embodiment and the above described second embodiment is a point that the options of the multiplexer  22  in malfunctioning diagnosis is an external reference resistor group  26 , which is composed of external resistors  27  and  28 , and a point that the pull-up/pull-down diagnosis register  24  is removed. 
         [0058]    Moreover, as a difference in operations between the present embodiment and the above described second embodiment, while both of the pull-up resistor  421  and the pull-down resistor  461  are connected to the intermediate point  44  in the malfunctioning diagnosis in the second embodiment, the present embodiment is different in a point that only one resistor (pull-up resistor or pull-down resistor) of a diagnosis target is connected. 
         [0059]    Hereinafter, operations of the input processing circuit  2  and the microcomputer  6  in the present embodiment will be described. First, the operations of the input processing circuit  2  and the microcomputer  6  in normal operations are the same as those of the first and second embodiments. 
         [0060]    Next, operations of the input processing circuit  2  and the microcomputer  6  in a case in which the resistance value of the pull-up resistor  421  is diagnosed in malfunctioning diagnosis will be described. 
         [0061]    First, the multiplexer  22  temporarily stops connection to the sensors or the like  31  and  32  and, instead, connects to the reference resistor group  26 . The reference resistor group  26  is composed of the reference resistors  27  and  28 , which are connected in series and have known resistance values, the reference resistors  27  and  28  are connected in series, a connection point thereof is connected to the input terminal  3 , the other end of the reference resistor  27  is connected to the power-source wiring  41 , and the other end of the reference resistor  28  is connected to the GND wiring  47 . 
         [0062]    Then, the pull-up/pull-down setting register  23  is set so that only the pull-up resistor  421 , which is a diagnosis target, is connected to the intermediate point  44 . Herein, the resistance value of the pull-up resistor  421  of the diagnosis target is assumed to be R 421 , the resistance value of the reference resistor  27  is assumed to be R 27 , and the resistance value of the reference resistor  28  is assumed to be R 28 ; in this case, the voltage (V 44 ) of the intermediate point  44  is subjected to voltage-dividing by the voltage (V 41 ) of the power-source wiring  41  and the voltage (0) of the GND wiring  47  and becomes the voltage expressed by below Formula 6. 
         [0000]        V 44= V 41× R 28×( R 27+ R 421)/( R 27× R 28+ R 27× R 421+ R 28× R 421)  Formula 6
 
         [0063]    The voltage of V 44  obtained in this manner is converted to digital values by the AD converter  61  as well as normal operations and is input to the computing unit  62 . Then, in the computing unit  62 , in accordance with the correspondence table shown in  FIG. 5 , whether the voltage of V 44  is showing abnormality of the pull-up resistor  421  or the pull-down resistor  461  is judged. 
         [0064]    More specifically, a voltage Vn 44  of V 44  of a normal case is calculated by using Formula 6 from the resistance value of the pull-up resistor  421  of a normal case, and the upper-limit threshold voltage V 52  and the lower-limit threshold voltage V 53  are selected so as to satisfy the inequality of Formula 6 and are stored in the memory area (not shown), which is present in the computing unit  62 . Then, the computing unit  62  carries out malfunctioning judgement according to measurement of V 44  and the magnitude relations of V 44 , V 53 , and V 52  in accordance with the flow chart shown in  FIG. 6 . Herein, in the present embodiment, different from the second embodiment, the voltage Vn 44  of V 44  of a normal case is different every time depending on the resistance value of the resistor of the diagnosis target, and, therefore, attention is required for the point that the calculations have to be carried out every time. 
         [0065]    These are the operations of the input processing circuit  2  in the malfunctioning diagnosis of the present embodiment. According to the present embodiment, as well as the first and second embodiments, abnormality in the resistance values of the pull-up resistors and the pull-down resistors can be diagnosed. 
         [0066]    The above description is about the case in which the resistance value of the pull-up resistor  421  is diagnosed. However, if the pull-down resistor  461  is a diagnosis target, similar diagnosis operations can be carried out by setting the pull-up/pull-down setting register  23  so that only the pull-up resistor  461  is connected to the intermediate point  44 . However, there is a different point that the voltage (V 44 ) of the intermediate point  44  of this case becomes the voltage expressed by below Formula 7, wherein the resistance value of the pull-down resistor  461  is R 461 . 
         [0000]        V 44= V 41× R 28× R 461/( R 27× R 28+ R 27× R 461+ R 28× R 461)   Formula 7
 
         [0067]    Note that, regarding the counterpart of voltage-dividing in diagnosis of the resistance value, compared with the first and second embodiments in which the resistor in the pull-up/pull-down resistor group  4  is used as the resistor, the reference resistors  27  and  28 , which are externally connected, are commonly used in the present embodiment, and there is an advantage that it is easy to ensure absolute precision. More specifically, in the first and second embodiments, the diagnosis precision of the resistance value depends on the resistance precision of the resistors in the pull-up/pull-down resistor group  4 , and all of the resistors in the pull-up/pull-down resistor group  4  have to have high precision to carry out high-precision diagnosis. 
         [0068]    On the other hand, in the present embodiment, the diagnosis precision of the resistance value depends only on the precision of the reference resistors  27  and  28 , and high-precision diagnosis can be realized when these two resistors have high precision. This advantage becomes notable particularly when the input processing circuit  2  including the pull-up/pull-down resistor group  4  is formed into an integrated circuit (IC). This is for a reason that, generally in an integrated circuit, it is comparatively easy to relatively equalize the resistance values among resistors, but it is difficult to carry out manufacturing with highly-precise absolute resistance values. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1 : electronic control device,  2 : input processing circuit,  21 : control circuit,  22 : multiplexer,  23 : pull-up/pull-down setting register,  24 : pull-up/pull-down diagnosis register,  26 : reference resistor group,  3 : input terminal,  31 ,  32 : sensors or the like,  4 : pull-up/pull-down resistor group,  41 : power-source wiring,  421 ,  422 : pull-up resistors,  431 ,  432 : pull-up selecting switches,  451 ,  452 : pull-down selecting switches,  461 ,  462 : pull-down resistors,  47 : GND wiring,  5 : comparator unit,  51 : window comparator,  6 : microcomputer,  61 : AD converter,  62 : computing unit