| 摘要 |
PURPOSE:To prevent information of an IC from flowing out, by starting a test mode by applying voltages at plural levels to a specified terminal of the IC by a specified sequence, and also setting a mask to the sequence for applying the voltage. CONSTITUTION:An input level selecting part 12 is provided with an inverter 20 which is operated by a voltage level at the time of a usual operation, and a high voltage detecting circuit 21 for detecting a voltage level whose voltage is higher than said voltage, identifies plural input voltages, and also plural F/Fs 1-4 are provided on a test mode starting part 13. Outputs 1-3 of the selecting part 12 and inputs 4-8 of the starting part 13 can be connected by a mask option in accordance with a request of a user. Accordingly, a test mode can be started by applying plural level voltage to a specified terminal in accordance with a sequence which has been set by the mask option. A condition (a sequence for applying a voltage) for starting the test mode can be set separately at every user by a small quantity of wiring, therefore, flowing out of internal information of an IC can be prevented. |
