Abstract:
An electronic control unit includes a microcomputer that controls an operation of a control target. A transceiver circuit is placed in a bench room to rapidly communicate data with the external unit for development, the external unit checking operation of the electronic control unit. A power supply unit supplying electrical power to the microcomputer is designed to operate the microcomputer under normal operation, using a battery, is insufficient to supply power at a speed sufficient during development testing of the electronic control unit using the wire coupling the transceiver to the external unit. The microcomputer includes a debug circuit that communicates data with the transceiver circuit during testing. The transceiver circuit operates on electrical power supplied from an external power supply unit, which differs from the power supply unit included in the electronic control unit.

Description:
[0001]    This application is a Continuation application of U.S. patent application Ser. No. 13/655,312, filed on Oct. 18, 2012, now U.S. Pat. No. (tbd). 
       CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0002]    The disclosure of Japanese Patent Application No. 2011-231538 filed on Oct. 21, 2011 including the specification, drawings, and abstract is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0003]    The present invention relates to an information processing unit. The invention also relates to a technology that the information processing unit uses to establish specific communication with an external unit, for example, to a technology effective for a microcomputer having a communication function. 
         [0004]    Many hardware products having an electronic control unit (ECU) have been widely used due to advanced electronic control technologies. For example, in most of vehicles, ships, airplanes, and other moving bodies, an electronic control unit is used to control, for instance, engines and navigation equipment. An information processing unit having a microcomputer (e.g., LSI) is built in such an electronic control unit. 
         [0005]    When a hardware product having an electronic control unit (ECU) is to be designed, various tests are conducted at stages, for instance, of prototype production and outgoing inspection for the purpose of verifying the operations of a target to be controlled by the electronic control unit (ECU) and checking for faults in the electronic control unit (ECU). In currently marketed automobiles, for example, a plurality of electronic control units (ECUs) are used to provide engine control and vehicle control. For example, an electronic control unit (ECU) for engine control is equipped, for instance, with a power train control microcomputer. An electronic control unit (ECU) for vehicle control is equipped, for instance, with a chassis control microcomputer that controls an electrically-assisted power steering motor. The microcomputer in the electronic control unit (ECU) is provided with a debug circuit that outputs the results (software execution results and computed data) obtained when a control target device (e.g., engine or motor) is controlled. At stages, for instance, of prototype production and outgoing inspection, data derived from the debug circuit in the microcomputer is transferred to a development unit external to the electronic control unit (ECU) and used to check the operations of the electronic control unit (ECU). A known technology disclosed, for instance, in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372 adjusts an electronic control unit (ECU) provided for a vehicle by arbitrarily correcting data used for control operations by a microcomputer. 
         [0006]    A technology described in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372 makes it possible to check for improper communication and transfer data between the electronic control unit and a controller before a power supply system switch for the electronic control unit is turned on. A technology described in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372 makes it possible to prevent erroneous control caused by a communication error and initiate ROM emulation and RAM monitoring upon startup. Another technology described in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372 relates to a system that has an electronic control unit for providing engine control with a control CPU and a controller coupled to communicate with the control CPU. 
         [0007]    In the system disclosed in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372, the electronic control unit includes an evaluation board and an input/output board. A control CPU is mounted on the evaluation board. Input/output terminals for various signals are mounted on the input/output board. The electronic control unit turns on when an ignition switch is placed in the ON position. When a power switch for the controller is turned on, electrical power is supplied only to the evaluation board in the electronic control unit through the controller. 
         [0008]    The above technologies described in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372 prevent a control target from being erroneously controlled due to an error in the communication between the electronic control unit and the controller. The technologies described in Japanese. Unexamined Patent Publication No. Hei 9 (1997)-44372 also make it possible to initiate ROM emulation and RAM monitoring immediately after the power supply system switch for the electronic control unit is turned on. 
       SUMMARY 
       [0009]    When an automotive power train system is to be tested, control targets (engine and motor) and an electronic control unit (ECU) are placed in a space such as a bench room. A control room in which a worker performs operations and makes measurements is located at a distance from the bench room. In some cases, therefore, the electronic control unit (ECU) may be positioned at a distance of 5 m or longer from an external unit for development arranged in the control room. Further, when a running test with an actual vehicle is conducted, the electronic control unit (ECU) is placed in an engine room, whereas the external unit for development is placed in a space for occupants or in a cargo room. Therefore, the wiring coupling the electronic control unit (ECU) to the external unit for development is very long, as is the case with the aforementioned long distance between the bench room and the control room. 
         [0010]    The electronic control unit (ECU) for automobiles is designed to minimize its electrical power consumption because it operates on an in-vehicle battery (secondary battery). Therefore, it is demanded that the electrical power consumption of the microcomputer built in the electronic control unit (ECU) be also minimized. The debug circuit in the microcomputer needs to operate at a high speed. Therefore, it consumes a larger amount of electrical power when it is used than when it is not used. Further, a transceiver circuit that consumes a large amount of electrical power and requires a large circuit area is necessary when debug information is to be transferred at a high speed and over a long distance while the debug circuit operates at a high speed. 
         [0011]    It is generally known that the transceiver circuit, which provides high-speed communication over a long distance, consumes a large amount of electrical power. In recent automobiles, various in-vehicle electric devices need to operate on a limited secondary battery. It is therefore difficult to consider an additional electrical power margin for measurement and operational tests only. Further, a high-speed transceiver circuit cannot easily be miniaturized and increases the size of a chip and the amount of electrical power consumption. Moreover, the debug circuit and the high-seed transceiver circuit are not essential to mass-produced finished electronic control units (ECUs) in most cases. It is extremely difficult to use additional electrical power for functions that will be disused in the future. It is demanded that the supply of extra electrical power for functions disused in the future be suppressed while the performance of communication between the electronic control unit and the external unit for development is maintained. 
         [0012]    In order to solve the above problem, according to an aspect of the present invention, there is provided a debug system including an electronic control unit, a transceiver circuit, and an external unit for development. The electronic control unit has a microcomputer for controlling the operation of a control target. The transceiver circuit is capable of communicating data with the microcomputer. The external unit for development is capable of rapidly communicating data with the transceiver circuit. The electronic control unit includes a power supply unit for supplying electrical power to the microcomputer. The transceiver circuit operates on electrical power supplied from an external power supply unit, which differs from the power supply unit included in the electronic control unit. 
         [0013]    Electrical power required for communication between the electronic control unit and the external unit for development and electrical power required for debugging are supplied from a source other than an in-vehicle battery. Therefore, a configuration very close to that of an end product can be debugged, measured, and tested. 
         [0014]    In short, a representative aspect of the present invention disclosed in this document is advantageous in that it makes it possible to avoid a situation where a secondary battery is requested to have an extra electrical power supply capability, which is irrelevant to the functionality of the electronic control unit, when the electronic control unit operates on the secondary battery. 
         [0015]    In other words, stable communication can be established when it is demanded that the external unit for development to be directly coupled to the microcomputer or the external unit for development to be coupled to the electronic control unit having the microcomputer be remotely installable. Stable, high-speed, long-distance communication generally consumes a large amount of electrical power. In such an instance, appropriate test data can be obtained even if the amount of electrical power available for the microcomputer to establish long-distance communication is limited or if the performance or scale of a communication circuit is limited due to an employed semiconductor manufacturing technology. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Embodiments of the present invention will be described in detail based on the following figures, in which: 
           [0017]      FIG. 1  is a block diagram illustrating a configuration of a debug system  1  for developing an information processing unit provided by the present invention; 
           [0018]      FIG. 2  is a block diagram illustrating another configuration of the debug system  1 ; 
           [0019]      FIG. 3  is a block diagram illustrating a detailed configuration of the debug system  1  according to a first embodiment of the present invention; 
           [0020]      FIG. 4A  is a block diagram illustrating a configuration of a transceiver circuit  13 ; 
           [0021]      FIG. 4B  is a block diagram illustrating another configuration of the transceiver circuit  13 ; 
           [0022]      FIG. 4C  is a block diagram illustrating still another configuration of the transceiver circuit  13 ; 
           [0023]      FIG. 5  is a block diagram illustrating the configuration of the debug system  1  according to a second embodiment of the present invention; 
           [0024]      FIG. 6  is a block diagram illustrating the configuration of the debug system  1  according to a third embodiment of the present invention; 
           [0025]      FIG. 7  is a block diagram illustrating the configuration of the debug system  1  according to a fourth embodiment of the present invention; 
           [0026]      FIG. 8A  is a block diagram illustrating a configuration of a transceiver circuit  42  according to the fourth embodiment; 
           [0027]      FIG. 8B  is a block diagram illustrating another configuration of the transceiver circuit  42  according to the fourth embodiment; 
           [0028]      FIG. 8C  is a block diagram illustrating still another configuration of the transceiver circuit  42  according to the fourth embodiment; 
           [0029]      FIG. 9A  is a block diagram illustrating a configuration of a target microcomputer  41  according to the fourth embodiment; 
           [0030]      FIG. 9B  is a block diagram illustrating another configuration of the target microcomputer  41  according to the fourth embodiment; 
           [0031]      FIG. 10  is a block diagram illustrating the configuration of the debug system  1  according to a fifth embodiment of the present invention; and 
           [0032]      FIG. 11  is a block diagram illustrating the configuration of the debug system  1  according to a sixth embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    Embodiments of the present invention will now be described with reference to the accompanying drawings. In the drawings illustrating the embodiments, like elements are basically designated by the same reference numerals and will not be redundantly described. In order to facilitate the understanding of the present invention, the embodiments of the present invention will be described by illustrating a case where a plurality of in-vehicle electronic control units (ECUs) are tested. 
       First Embodiment 
       [0034]      FIG. 1  is a block diagram illustrating a configuration of a debug system  1  for developing an information processing unit provided by the present invention. The system configuration shown in  FIG. 1  is used when a test is conducted before an engine to be developed or the like is mounted in an actual vehicle (completed vehicle). Referring to  FIG. 1 , the debug system  1 , which is used for conducting a test before an engine is mounted in an actual vehicle, includes an engine test bench room  2  and a test control room  3 . The engine test bench room  2  includes an engine (control target)  4  and an ECU (electronic control unit)  5 . The test control room  3  includes an external unit for development  6  and a host computer  7 . 
         [0035]    As shown in  FIG. 1 , the engine test bench room  2  is coupled to the test control room  3  with a long-distance wire  8 . Data for debugging and measurement is exchanged through the long-distance wire  8 . In the first embodiment, the distance between the engine test bench room  2  in which the engine (control target)  4  and the ECU (electronic control unit)  5  are arranged and the test control room  3  in which a worker conducts tests and makes measurement is much longer than the distance between the engine (control target)  4  and the ECU (electronic control unit)  5  (e.g., 5 m or longer). Further, high-speed communication at a rate between several megabits per second and several hundred megabits per second is established between the ECU (electronic control nit)  5  and the external unit for development  6 . Such high-speed data communication is implemented by the long-distance wire  8 . 
         [0036]      FIG. 2  is a block diagram illustrating another configuration of the debug system  1  for developing the information processing unit provided by the present invention. The system configuration shown in  FIG. 2  is used when a test is conducted after the engine to be developed is mounted in an actual vehicle (completed vehicle). As shown in  FIG. 2 , the debug system  1 , which is used for conducting a test after the engine is mounted in an actual vehicle, is configured in a vehicle  9 . The vehicle  9  includes an in-vehicle battery  11 . The in-vehicle battery  11  supplies electrical power to the ECU (electronic control unit)  5 , which is configured in the vehicle  9 . 
         [0037]    The ECU (electronic control unit)  5  arranged in various sections of the vehicle  9  is coupled to the external unit for development  6  arranged in the vehicle  9  with the long-distance wire  8 . When the long-distance wire  8  is to be laid in the vehicle  9 , a place where the wire can be routed is limited. Therefore, as is the case with the debug system  1  illustrated in  FIG. 1 , the distance between the ECU (electronic control unit)  5  and the external unit for development  6  is much longer than the distance between the engine (control target)  4  and the ECU (electronic control unit)  5  (e.g., 1 m or longer). 
         [0038]      FIG. 3  is a block diagram illustrating a detailed configuration of the debug system  1  according to the first embodiment. In order to facilitate the understanding of the present invention,  FIG. 3  shows an arbitrary one of a plurality of ECUs (electronic control units)  5  to be developed. In the debug system  1  according to the first embodiment, the ECU  5  includes a target microcomputer  12 , a transceiver circuit  13 , and a power supply circuit  14 . The external unit for development  6  includes an external power supply  31  and various development tools. The power supply circuit  14  in the ECU  5  is coupled to the in-vehicle battery  11 . In accordance with electrical power supplied from the in-vehicle battery  11 , the power supply circuit  14  generates electrical power for driving the target microcomputer  12  and supplies the generated electrical power to the target microcomputer  12 . The present embodiment may be configured so that the ECU  5  includes a plurality of target microcomputers  12  in relation to the transceiver circuit  13 . 
         [0039]    As shown in  FIG. 3 , the target microcomputer  12  includes a CPU (central processing unit)  21 , a DMAC (Direct Memory Access Controller)  22 , a RAM (Random Access Memory)  23 , a flash memory  24 , and an ERAM (Emulation RAM)  25 . These components are coupled through a bus  26 . The CPU  21  is a functional block that performs central arithmetic processing in the target microcomputer  12 . The RAM  23  is formed by a semiconductor device and used as a storage unit that can be directly accessed by the CPU  21 . The RAM  23  functions as a main memory (main storage unit) in the target microcomputer  12 . The DMAC  22  is a functional block that functions to permit data transfer between the RAM  23  and a peripheral device without using the CPU. The flash memory  24  retains a computer program that is to be executed by the CPU  21 . The ERAM  25  is a memory that temporarily stores a correction program, a correction data value, and the like without directly rewriting the flash memory  24  when the computer program retained in the flash memory  24  is to be corrected. 
         [0040]    The target microcomputer  12  also includes a debug circuit  27 . The debug circuit includes a trace  28 , a JTAG  29 , and a RAM monitor  30 . The trace  28  is a functional block that traces instructions executed by the CPU  21  in the target microcomputer  12 . The trace  28  includes a dedicated high-speed interface, directly reads operations of the CPU  21 , and supplies large-size data for tracing the operations of the CPU  21  to the external unit for development  6 . The JTAG  29  is an interface functional block that establishes communication between the debug circuit  27 , which is built in the target microcomputer  12  to exercise a debugging function, and the external unit for development  6  in compliance with a common communication standard. The JTAG  29  provides basic data communication between the external unit for development  6  and the target microcomputer  12 , transmits a computer program to the target microcomputer  12 , and performs control register setup for the debug circuit  27 . The RAM monitor  30  is a functional block that reads a data value stored in the RAM  23  of the target microcomputer  12  when an operational test is conducted on the target microcomputer  12 . The RAM monitor  30  includes a dedicated high-speed interface, directly reads data stored in the RAM  23 , and supplies the read data to the external unit for development  6 . 
         [0041]    The transceiver circuit  13  according to the present embodiment receives a signal indicative of internal information about the target microcomputer  12  from the debug circuit  27  and transmits the received signal to the external unit for development  6 . The transceiver circuit  13  also receives a signal supplied from the external unit for development  6  and transmits the received signal to the target microcomputer  12 . The target microcomputer  12  is generally capable of directly communicating with an emulator or measuring device of the external unit for development  6  as far as such a device is at a distance of shorter than 1 m from the target microcomputer  12 . However, to achieve high-speed, long-distance communication, which cannot be implemented by the functionality incorporated in the target microcomputer  12 , it is necessary to couple the transceiver circuit  13  to the target microcomputer  12 . The transceiver circuit  13  may include, for example, a CPU, a memory, a logic circuit, and an analog circuit in order to deliver target performance. As shown in  FIG. 3 , the transceiver circuit  13  according to the present embodiment operates on electrical power supplied from the external power supply  31  in the external unit for development  6 . For example, a standard technology called “Power over Ethernet (PoE)” can be applied to simultaneously exercise the above communication and power supply functions. PoE is a technology that simultaneously provides a communication line and a power supply at low cost when, for instance, no power supply is available for an access point of Ethernet (registered trademark). 
         [0042]      FIG. 4A  is a block diagram illustrating a configuration of the transceiver circuit  13  according to the present embodiment. As shown in  FIG. 4A , the transceiver circuit  13  according to the present embodiment includes a transceiver power supply circuit  32 . The transceiver power supply circuit  32  receives electrical power supplied from the external power supply  31  in the external unit for development  6 , adjusts the voltage and current of the received electrical power as appropriate for the transceiver circuit, and generates transceiver electrical power. As the transceiver circuit  13  receives the supply of electrical power from the external unit for development  6 , the ECU  5 , which is a customer system, does not have to incorporate a function of additionally supplying electrical power to the transceiver circuit  13 . 
         [0043]    The transceiver circuit  13  illustrated in  FIG. 4A  also includes a transceiver section  33  for maintaining the performance of communication between the target microcomputer  12  and the external unit for development  6 . The transceiver section  33  is a circuit that includes a transmitter, which operates as a transmitting device, and a receiver, which operates as a receiving device. 
         [0044]    The debug system  1  according to the present embodiment selectively uses either a bidirectional communication interface or a unidirectional communication interface, which provides output only. In the transceiver circuit  13  illustrated in  FIG. 4A , a “JTAG debug control signal” and a “RAM monitor signal” are transmitted and received when bidirectional communication is established through the transceiver section  33 . A “trace signal”, which is only output from the target microcomputer  12 , is unidirectionally output through the transceiver section  33 . An arbitrary circuit design may be applied to the transceiver section  33  as far as it can deliver target performance. 
         [0045]      FIG. 4B  is a block diagram illustrating another configuration of the transceiver circuit  13  according to the present embodiment. The transceiver circuit  13  illustrated in  FIG. 4B  includes a transceiver power supply circuit  32  for receiving electrical power supplied from the external unit for development  6 , a short-distance input/output buffer (microcomputer side input/output buffer)  34  for maintaining the performance of communication between the target microcomputer  12  and the transceiver circuit  13 , and a long-distance transceiver (external unit side input/output buffer)  35  for maintaining the performance of communication between the transceiver circuit  13  and the external unit for development  6 . 
         [0046]    A FIFO buffer  36 , which includes storage devices such as a memory and an F/F, is arranged between the short-distance input/output buffer  34  and the long-distance transceiver  35 . Further, a control circuit  37  is incorporated to control the FIFO buffer  36 . The control circuit  37  may be formed by a dedicated logic circuit or by a CPU that provides software control. 
         [0047]    When the FIFO buffer  36  is used as in the transceiver circuit  13  illustrated in  FIG. 4B , changes in a data transfer rate can be absorbed even if the amount of data transferred between the target microcomputer  12  and the external unit for development  6  changes. When the FIFO buffer  36  is separately installed for each interface of the target microcomputer  12 , optimum design can be made as appropriate for the protocol of each interface. 
         [0048]    For example, a large amount of data is rapidly output from the trace  28  in the debug circuit  27 . It is therefore preferred that the employed design permit high-speed operations. Further, as the trace  28  provides data output only, the employed FIFO buffer may merely provide unidirectional data output from the target microcomputer  12  to the external unit for development  6 . As the JTAG  29  and the RAM monitor  30  provide bidirectional communication, the FIFO buffer  36  needs to be configured to provide communication from the external unit for development  6  to the target microcomputer  12  and communication from the target microcomputer  12  to the external unit for development  6 . Moreover, when the FIFO buffer  36  can be controlled by a CPU, it is possible to stop an unused portion of the transceiver circuit and instruct the transceiver power supply circuit  32  to provide power supply control. 
         [0049]      FIG. 4C  is a block diagram illustrating still another configuration of the transceiver circuit  13  according to the present embodiment. The transceiver circuit  13  illustrated in  FIG. 4C  is obtained by adding a protocol conversion control circuit  38  to the transceiver circuit  13  illustrated in  FIG. 4B . The transceiver circuit  13  shown in  FIG. 4C  permits the use of an optimum communication method for the communication between the transceiver circuit  13  and the external unit for development  6 . The transceiver circuits  13  shown in  FIGS. 4A to 4C , respectively, are each formed by a single semiconductor device (IC chip) that is separate from the target microcomputer  12 . 
         [0050]    As described earlier, the debug system  1  according to the present embodiment aims, for instance, to let the transceiver circuit  13  establish high-speed, long-distance communication. In some cases, a communication protocol owned by the target microcomputer  12  is unstable in terms of electrical characteristics and noise immunity when used as a long-distance communication protocol. The transceiver circuit  13  illustrated in  FIG. 4C  applies communication protocol data optimum for long-distance communication, which also covers an interface protocol for the microcomputer, to the communication between the target microcomputer  12  and the external unit for development  6 . 
         [0051]    When, for instance, the target microcomputer  12  is provided with an interface for the JTAG  29 , information indicating what JTAG standard sequences are used to perform what type of data transfer is handled as a chunk of data and used as input data for the long-distance communication protocol. As the long-distance communication protocol makes a data transfer while error correction information and other relevant information are added to transfer information, a JTAG transfer, which is unstable, can be properly made with a steady transfer path. Conversely, JTAG sequence operations and transferred data can be restored from data transmitted through the long-distance communication protocol. 
         [0052]    Various technologies are applicable to the long-distance communication protocol. However, when PoE is applied to the long-distance communication protocol, it is possible not only to establish communication but also to provide power supply control. As PoE is an extension of Ethernet, it delivers such communication performance that a rate of 100 Mbps can be obtained over a distance of 100 m. Although the electrical power consumption of the transceiver circuit may increase, no problem arises because PoE supplies electrical power to the transceiver circuit  13  according to the present embodiment. 
         [0053]    As described earlier, the ECU  5  includes the target microcomputer  12 , which is to be developed; the transceiver circuit  13 , which is coupled to the target microcomputer  12 ; and the power supply circuit  14 , which supplies electrical power to the target microcomputer  12 . A commonly used in-vehicle battery  11  is used as a power supply for the target microcomputer  12 . Meanwhile, the transceiver circuit  13  differs from the target microcomputer  12  in the method of power supply. The external unit for development  6  directly supplies electrical power to the transceiver circuit  13 . 
         [0054]    In the debug system  1  according to the first embodiment, the target microcomputer  12  and the ECU  5 , which incorporates the target microcomputer  12 , communicate with external units (external unit for development  6  and host computer  7 ) through the transceiver circuit  13  while exercising automobile control. A plurality of communication operations are performed, for instance, to verify program operations and reference a memory that stores control parameters. 
         [0055]    As indicated in  FIG. 3 , which was referenced earlier, when the debug system  1  according to the present embodiment is configured as described above, the target microcomputer  12  does not have to include a circuit (transceiver circuit  13 ) for establishing long-distance, high-speed communication. Further, the transceiver circuit  13  obtains the electrical power for operating itself from an external unit such as the external unit for development  6 . Therefore, the ECU  5  does not have to acquire the electrical power used only for long-distance, high-speed communication from a power supply circuit (power supply circuit  14 ) in the ECU  5 . In other words, the debug system  1  according to the present embodiment does not have to acquire the electrical power required for the transceiver circuit  13 , which is used for communication purposes, from the in-vehicle battery  11 . Consequently, debugging and measurement can be performed while the electrical power consumption is very close to that of an end product. 
         [0056]    Moreover, when the PoE technology is applied to the long-distance wire  8 , it is possible to provide a communication rate of 100 Mbps and a maximum wiring length of 100 m at low cost. Meanwhile, electrical power having a rated voltage of 48 V and a maximum current of 350 mA (approximately 15 W) can be supplied. This makes it possible to supply adequate electrical power to the transceiver circuit  13  and to a debug circuit and measurement circuit included in the target microcomputer  12 . In addition, these functions can be implemented by using a single Ethernet cable to provide increased user-friendliness. 
         [0057]    The PoE technology is applied as an exemplary technology for a case where communication is to be established in accordance with an Ethernet-compliant protocol. Other technologies are also applicable as far as they satisfy certain conditions. For example, USB is a technology that simultaneously provides communication and supplies electrical power. The Ethernet cable can also be used as a cable other than an Ethernet network cable. The Ethernet cable includes a combination of eight wires. It can be merely regarded as means of allocating power supply wires and communication wires. 
       Second Embodiment 
       [0058]    A second embodiment of the present invention will now be described.  FIG. 5  is a block diagram illustrating the configuration of the debug system  1  according to the second embodiment. As shown in  FIG. 5 , the debug system  1  according to the second embodiment is configured so that the transceiver circuit  13  is arranged external to the ECU  5 . When the ECU  5  is offered as a housing, the ECU housing houses various devices including the target microcomputer  12 . Such an ECU housing may not be able to provide an installation space for the transceiver circuit  13 , which is used for communication. 
         [0059]    The debug system  1  according to the second embodiment is configured so that the transceiver circuit  13  is arranged as an external part to solve the above problem. As the target microcomputer  12  is positioned at a distance from the transceiver circuit  13 , an increased burden may be placed on the target microcomputer  12  to maintain the performance of communication. However, when the distance between the target microcomputer  12  and the transceiver circuit  13  is not longer than several tens of centimeters, the increased burden can be compensated for by adopting a general design technique and manufacturing technique. 
         [0060]    In the debug system  1  according to the second embodiment, too, long-distance communication is to be established between the transceiver circuit  13  and the external unit for development  6 . However, the electrical power required for the transceiver circuit  13  is supplied from the external power supply  31  in the external unit for development  6 . Therefore, no load is imposed on the target microcomputer  12  or on the power supply circuit  14 . Further, in the debug system  1  according to the second embodiment, the internal configuration of the transceiver circuit  13  is not limited. Therefore, the transceiver circuit  13  may include the circuits illustrated in  FIGS. 4A to 4C , as is the case with the first embodiment. 
       Third Embodiment 
       [0061]    A third embodiment of the present invention will now be described.  FIG. 6  is a block diagram illustrating the configuration of the debug system  1  according to the third embodiment. In the debug system  1  according to the third embodiment, the target microcomputer  12  mounted in the ECU  5  is formed by a SIP (System In Package). As shown in  FIG. 6 , a microcomputer chip  15  in the target microcomputer  12  according to the third embodiment is formed by a single semiconductor device (IC chip). Similarly, a transceiver circuit chip  16  is formed by a single semiconductor device (IC chip), which is separate from the microcomputer chip  15 . 
         [0062]    In the debug system  1  according to the third embodiment, the target microcomputer  12  is offered as a SIP. Therefore, it is not necessary to perform a process of sealing the transceiver circuit chip  16  to another package. Further, the configuration employed in the third embodiment makes it possible to manufacture the microcomputer chip  15  and the transceiver circuit chip  16  as different semiconductor devices (IC chips). Consequently, an optimum design technique and manufacturing technique can be applied as appropriate for their respective functions. 
         [0063]    Even when the above-described configuration is employed, a power supply for the microcomputer chip  15  can be separated from a power supply for the transceiver circuit chip  16 . Thus, the third embodiment can provide the same advantages as the first and second embodiments. Further, the distance between the microcomputer chip  15  and the transceiver circuit chip  16  is extremely short due to the use of a SIP. This makes it possible to use a mounting method that excels in electrical characteristics. Moreover, in the debug system  1  according to the third embodiment, the internal configuration of the transceiver circuit chip  16  is not limited. Therefore, the transceiver circuit chip  16  may include the circuits illustrated in  FIGS. 4A to 4C , as is the case with the first embodiment. 
       Fourth Embodiment 
       [0064]    A fourth embodiment of the present invention will now be described.  FIG. 7  is a block diagram illustrating the configuration of the debug system  1  according to the fourth embodiment. As shown in  FIG. 7 , the ECU  5  in the debug system  1  according to the fourth embodiment includes a target microcomputer  41  and a transceiver circuit  42 . The target microcomputer  41  includes a debug circuit  43 . The transceiver circuit  42  includes a power supply circuit  44 . 
         [0065]    As the debug circuit  43  of the target microcomputer  41  operates at a high speed, the target microcomputer  41  with the debug circuit  43  consumes a larger amount of electrical power than the target microcomputer  41  without the debug circuit  43 . When the transceiver circuit  42  is applied to the ECU  5  according to the fourth embodiment, it is possible to suppress an increase in the electrical power consumption of the target microcomputer  41 . 
         [0066]    As shown in  FIG. 7 , the power supply configuration for the target microcomputer  41  is divided. More specifically, the target microcomputer  41  is designed so that a power supply for main body functions and a power supply for the debug circuit  43  are separated from each other. The electrical power required for the debug circuit  43  is supplied from the power supply circuit  44  included in the transceiver circuit  42 . The power supply circuit  44  included in the transceiver circuit  42  is capable of generating electrical power for the transceiver circuit itself and electrical power to be supplied to the debug circuit  43 . Configuring the target microcomputer  41  and the transceiver circuit  42  as described above decreases the amount of electrical power consumed when she debug circuit  43  is not used. Therefore, the power supply circuit  14  in the ECU is requested to supply only the electrical power required for the target microcomputer  41 . 
         [0067]    As the transceiver circuit  42  receives the supply of electrical power from the external unit for development  6 , the ECU  5 , which is a customer system, does not have to incorporate a function of additionally supplying electrical power to the transceiver circuit  42 . In addition, the transceiver circuit  42  is also capable of further supplying the electrical power supplied from the outside to a measurement circuit and debug circuit built in the target microcomputer  41 . Using the above-described transceiver circuit  42  makes it possible to reduce an electrical burden imposed on the target microcomputer  41  itself and on the ECU  5 . This results in a decrease in the burden imposed on an automobile&#39;s battery (in-vehicle battery  11 ). 
         [0068]      FIGS. 8A ,  8 B, and  8 C are block diagrams illustrating a configuration of the transceiver circuit  42  according to the fourth embodiment. In the transceiver circuit  42  according to the fourth embodiment, the power supply circuit  44  is capable of operating as a power supply for a plurality of circuits. The power supply circuit  44  in the transceiver circuit  42  is capable of adjusting the voltage and current of the electrical power supplied from the external power supply  31  in the external unit for development  6  as appropriate for the transceiver circuit. This type of power supply circuit is generally built in a semiconductor and may be based, for instance, on a technology for designing a built-in power supply circuit of a microcomputer. In most cases, this type of power supply circuit is not limited to a specific single power supply output and is capable of generating a plurality of power supply voltages. 
         [0069]    As shown in  FIGS. 8A ,  8 B, and  8 C, the power supply circuit  44  can supply electrical power to the target microcomputer  41 . The power supply circuit  44  is capable of receiving electrical power from the external unit for development  6  and supplying the electrical power to another unit such as the target microcomputer  41 . The electrical power supplied to the target microcomputer  41  is used to operate the debug circuit  43 . The other portion of the transceiver circuit  42  shown in  FIGS. 8A to 8C  has the same configuration as illustrated in  FIGS. 4A to 4C . 
         [0070]      FIG. 9A  is a block diagram illustrating a detailed configuration of the target microcomputer  41  according to the fourth embodiment. As shown in  FIG. 9A , the target microcomputer  41  according to the fourth embodiment includes a digital I/O area  45 , an analog I/O area  46 , a debug power supply circuit  47 , and a digital circuit section I/O power supply circuit  48 , and is formed by a single semiconductor device (IC chip). An isolator  49  is arranged between a main body functional block of the target microcomputer  41  and the debug circuit  43 . When the debug circuit  43  stops to shut off the supply of electrical power, the isolator  49  inhibits a through current flowing between the main body functional block of the target microcomputer  41  and the debug circuit  43 . 
         [0071]    The target microcomputer  41  also includes a debug power supply terminal  51 , a digital power supply terminal  52 , an analog power supply terminal  53 , a PLL power supply terminal  54 , and a debug circuit dedicated I/O terminal  55 . The digital power supply terminal  52 , the analog power supply terminal  53 , and the PLL power supply terminal  54  are coupled to the power supply circuit  14 . The debug power supply terminal  51  is coupled to the power supply circuit  44  in the transceiver circuit  42 . The power supply circuit  44  contains a debug power supply circuit  44   a  and a transceiver power supply circuit  44   b . The debug power supply circuit  44   a  supplies electrical power for the debug circuit built in the microcomputer to the debug power supply circuit  47  through the debug power supply terminal  51 . 
         [0072]    In accordance with the electrical power received through the digital power supply terminal  52 , the digital circuit section I/O power supply circuit  48  generates the electrical power to be supplied to each circuit block in the target microcomputer  41 . The digital I/O area  45  operates in accordance with the electrical power supplied from the digital circuit section I/O power supply circuit  48 . A part of the digital I/O area  45  functions as an I/O buffer for the debug circuit  43 . The debug circuit dedicated I/O terminal  55  couples the I/O buffer for the debug circuit  43  to the transceiver circuit  42 . 
         [0073]    In the target microcomputer  41  illustrated in  FIG. 9A , the common digital I/O area  45  is used to transmit and receive data without providing a dedicated I/O buffer for the debug circuit  43 . When the general-purpose digital I/O area  45  is used to multiplex a terminal for the debugging function with a main body function terminal of the target microcomputer  41 , the debug circuit  43  can be built in a mounted device. Using the above-described configuration makes it possible not only to receive electrical power for the debug circuit  43 , which consumes a large amount of electrical power, but also to implement the target microcomputer  41  having the digital I/O area  45  that operates on electrical power supplied from the digital circuit section I/O power supply circuit  48 . 
         [0074]      FIG. 9B  is a block diagram illustrating another configuration of the target microcomputer  41  according to the fourth embodiment. As shown in  FIG. 9B , the target microcomputer  41  includes a debug circuit dedicated I/O buffer  56 . The debug circuit dedicated I/O buffer  56  is an I/O buffer having special characteristics for supporting a high-speed operation of the debug circuit  43 . The debug power supply circuit  47  in the target microcomputer  41  illustrated in  FIG. 9B  not only supplies electrical power to the debug circuit  43 , but also supplies electrical power appropriate for the debug circuit dedicated I/O buffer  56 . When the debug circuit  43  stops to shut off the supply of electrical power, the isolator  49  not only inhibits a through current flowing between the main body functional block of the target microcomputer  41  and the debug circuit  43 , but also inhibits a through current between the digital I/O area  45  and the analog I/O area  46 , on one hand, and the debug circuit dedicated I/O buffer  56 , on the other. 
         [0075]    As a dedicated I/O buffer is provided for the debug circuit  43  in the target microcomputer  41  illustrated in  FIG. 9B , multiplexing of terminals is not required. Hence, the main body function terminal of the target microcomputer  41  is differentiated from another terminal. This makes it possible to provide complete electrical isolation between the functions of the debug circuit  43  and the main body functions of the target microcomputer  41 . 
       Fifth Embodiment 
       [0076]    A fifth embodiment of the present invention will now be described.  FIG. 10  is a block diagram illustrating the configuration of the debug system  1  according to the fifth embodiment. As shown in  FIG. 10 , the debug system  1  according to the fifth embodiment is configured so that the transceiver circuit  42  is arranged external to the ECU  5 . Further, the transceiver circuit  42  according to the fifth embodiment includes the power supply circuit  44 , which is capable of supplying electrical power to another, circuit, as is the case with the transceiver circuit  42  according to the fourth embodiment. 
         [0077]    When the ECU  5  is offered as a housing, the ECU housing houses various devices including the target microcomputer  41 . Such an ECU housing may not be able to provide an installation space for the transceiver circuit  42 , which is used for communication. The debug system  1  according to the fifth embodiment is configured so that the transceiver circuit is arranged as an external part to solve the above problem. As the target microcomputer  41  is positioned at a distance from the transceiver circuit  42 , an increased burden may be placed on the target microcomputer  41  to maintain the performance of communication. However, when the distance between the target microcomputer  41  and the transceiver circuit  42  is not longer than several tens of centimeters, the increased burden can be compensated for by adopting a general design technique and manufacturing technique. 
         [0078]    In the debug system  1  according to the fifth embodiment, too, long-distance communication is to be established between the transceiver circuit  42  and the external unit for development  6 . However, the electrical power required for the transceiver circuit  42  is supplied from the external power supply  31  in the external unit for development  6 . Therefore, no load is imposed on the target microcomputer  41  or on the power supply circuit  14 . 
         [0079]    The power supply circuit  44  in the transceiver circuit  42  is capable of generating electrical power for the transceiver circuit itself and electrical power to be supplied to the debug circuit  43 . Configuring the target microcomputer  41  and the transceiver circuit  42  as described above decreases the amount of electrical power consumed when the debug circuit  43  is not used. Therefore, the power supply circuit  14  in the ECU is requested to supply only the electrical power required for the target microcomputer  41 . In the debug system  1  according to the fifth embodiment, the internal configuration of the transceiver circuit  42  is not limited. Therefore, the transceiver circuit  42  may include the circuits illustrated in  FIGS. 8A to 8C , as is the case with the fourth embodiment. 
       Sixth Embodiment 
       [0080]    A sixth embodiment of the present invention will now be described.  FIG. 11  is a block diagram illustrating the configuration of the debug system  1  according to the sixth embodiment. The debug system  1  according to the sixth embodiment is configured so that the target microcomputer  41  mounted in the ECU  5  is formed by a SIP (System In Package). As shown in  FIG. 11 , a microcomputer chip  57  in the target microcomputer  41  according to the sixth embodiment is formed by a single semiconductor device (IC chip). Similarly, a transceiver circuit chip  58  is formed by a single semiconductor device (IC chip). The transceiver circuit chip  58  according to the sixth embodiment includes the power supply circuit  44 , which is capable of supplying electrical power to another circuit, as is the case with the transceiver circuit  42  according to the fourth embodiment. 
         [0081]    In the debug system  1  according to the sixth embodiment, the target microcomputer  41  is offered as a SIP. Therefore, it is not necessary to perform a process of sealing the transceiver circuit chip  58  to another package. Further, the configuration employed in the sixth embodiment makes it possible to manufacture the microcomputer chip  57  and the transceiver circuit chip  58  as different semiconductor devices (IC chips). Consequently, an optimum design technique and manufacturing-technique can be applied as appropriate for their respective functions. 
         [0082]    Even when the above-described configuration is employed, a power supply for the microcomputer chip  57  can be separated from a power supply for the transceiver circuit chip  58 . More specifically, the power supply circuit  44  of the transceiver circuit chip  58  generates electrical power for the transceiver circuit itself and electrical power to be supplied to the debug circuit  43 . Configuring the target microcomputer  41  to include the microcomputer chip  57  and the transceiver circuit chip  58  as described above decreases the amount of electrical power consumed when the debug circuit  43  is not used. Therefore, the power supply circuit  14  in the ECU is requested to supply only the electrical power required for the target microcomputer  41 . Consequently, the sixth embodiment provides the same advantages as the fourth and fifth embodiments. Further, as the target microcomputer  41  is offered as a SIP, the distance between the microcomputer chip  57  and the transceiver circuit chip  58  is extremely short. This makes it possible to decrease the amount of electrical power that is slightly consumed in a power supply path, and use a mounting method that excels in electrical characteristics. In the debug system  1  according to the sixth embodiment, the internal configuration of the transceiver circuit chip  58  is not limited. Therefore, the transceiver circuit chip  58  may include the circuits illustrated in  FIGS. 8A to 8C , as is the case with the fourth embodiment. 
         [0083]    While the embodiments of the present invention have been described in detail, the present invention is not limited to the specific embodiments described above. It is to be understood that many variations and modifications of the present invention may be made without departing from the spirit and scope of the present invention.