| 摘要 |
PURPOSE:To use a control terminal as an input line and to utilize terminals effectively by turning on and off a transistor (TR) switch according to control information written in a latch circuit, and permitting and inhibiting the input of a signal from an input terminal. CONSTITUTION:On the same semiconductor chip, a latch circuit 21 and an open drain transistor (TR) 22 which is connected at one terminal to an input buffer 23 and driven by the circuit 21 are formed. According to the control information inputted to the latch circuit 21, the TR22 is turned on and off. When the TR22 is turned off, the output of a buffer 24 for an external signal is inputted as it is to the buffer 23, but when the TR22 turned on, the input to the buffer 23 is nearly clamped at the source potential VSS of the TR22, so that none of the output of the buffer 24 reaches the buffer 23. Therefore, an external connection is made through only one terminal. |
