| 摘要 |
<p>PURPOSE:To use power source pads for a microcomputer also as input/output pads by providing at least one circuit of input/output circuits connected to pads connected with power source lines, and selectively connecting the circuit between the pads or the pad to the lines. CONSTITUTION:If pads for a microcomputer are used as power source pads, a power source selection signal (1) is input to a gate of an Nch FET of a transmission gate 1, and the gate is turned ON. An output control signal (3) of an H level is input to a gate of a Pch FET of a series circuit 3 of an FET, an output control signal (3) of an L level is input to the gate of the Nch FET, and the circuit 3 is turned OFF. On the other hand, when the pads for the microcomputer are used as input/output pads, the signal (1 is set to an L level, the gate 1 is turned OFF, the signal (1) is input to an input terminal 21 through an inverter 4, an output of a NAND circuit 2 is set to a signal corresponding to a signal to be input to the other input terminal 22, and the pad is used as a function of the input pad.</p> |
