| 摘要 |
PURPOSE: To easily discriminate a defective element inside a circuit board by making a diagnostic circuit generate a diagnostic output signal only in the case that a normal voltage is supplied through an operating voltage supply structure, connecting the diagnostic output signal to the diagnostic output pin of a chip and connecting it to a diagnostic interface. CONSTITUTION: The circuit board 17 is provided with the diagnostic circuit 35 and it is connected to operating signal supply structures 30-33 and also connected to a diagnostic terminal pin 22. The diagnostic circuit 35 generates the individual diagnostic output signals only when the operating signal supply structures connected to it supply a normal operating voltage. That is, the diagnostic circuit of the chip 18 generates the diagnostic output signals different from the ones of the chip 17, the cyclic signals of a different frequency for instance. Then, a computer 13 detects and analyzes the diagnostic output signals sent through the diagnostic interface and displays the result at a display 16. Thus, the defective element present inside the circuit board is easily discriminated. |
