INPUT/OUTPUT PORT CIRCUIT

摘要

PURPOSE: An input/output port circuit is provided, which is driven by high supply voltage and low supply voltage at the same time, and reduces power consumption by selectivly driving the input/output port circuit. CONSTITUTION: A signal register(22) stores output signals, and an input/output register(23) stores an input/output control signal determining an input/output direction. A power supply switch circuit(21) supplies a high voltage or a low voltage selectively according to a control signal. A signal control circuit(24) determines a direction of a signal according to a value of the signal register and a value of the input/output register. An output control circuit(25) is driven according to a value of the control register and an output of the signal control circuit. And an output driver circuit(26) outputs the low voltage and the high voltage or a ground value according to outputs of the signal control circuit and the output control circuit. The input/output port circuit comprises a number of output control registers(27).