| 摘要 |
PURPOSE:To enable a test mode control simply without setting a testing terminal, by detecting a specified voltage fed to a terminal for oscillator to output a test mode signal from a voltage detection circuit. CONSTITUTION:An oscillation element 13 is connected to the oscillator input and output terminals Xin and Xout of a chip 11 of a single chip computer to generate a clock from an oscillator 12 while the normal power source voltage is detected with a voltage detection circuit 14, from which an L signal is outputted to be a normal mode specifying signal. On the other hand, when a specified voltage such as high voltage is applied to the terminal Xin from a high voltage generation circuit 15 or the like, it is detected with the circuit 14, the output of which is inverted to H to be a test mode specifying signal. Here, the clock from a clock signal source 16 in which the output impedance connected to the terminal Xout is lower than the oscillator 12 is fed to the computer. Thus, a single chip microcomputer can be tested simply without providing a testing terminal or the like. |
