Integrated circuit system

PURPOSE: To make it possible to select a special test mode without adding test pins on a chip, by connecting an integrated circuit having an operating voltage in a specified voltage range to pins and pads on a semiconductor substrate or the chip. CONSTITUTION: When a specified voltage is applied to each voltage supplying source terminal VDD and pins or pads AX in a test mode, a control voltage and the node NA of a authorized circuit 10 are set to a voltage of about 1.5V or more in a very short time, turning on the diode N6 of a latch condition setting circuit 12, and the voltage of each terminal VDD increases turning a latch 14 on. As the result, its output voltage is increased, or it becomes a latch to flip to a logic 1V. Accordingly, the output of a buffer circuit 16 i.e., the voltage of the node NE becomes high, is used as an authorized voltage and activates a test circuit formed on a chip. Incidentally, the voltage of the terminals VDD is removed to recover from the test mode. Consequently, it becomes possible to obtain a test selection system for integrated circuits without increasing the size of a semiconductor circuit package. COPYRIGHT: (C)1991,JPO