Signal transfer system in microcomputer having circuits operating with different source voltage

摘要

First signal from control circuit is applied to first level shifter that shifts signal voltage depending upon voltage difference with second voltage, and outputs it to input- output unit. Second signal from input-output unit is fed to second level shifter that shifts signal level depending upon its difference with first voltage. Output of second level shifter is fed back to control circuit. Input-output unit operates with first source voltage whereas control circuit and internal circuit operate with second source voltage. Control circuit is connected with input-output unit and internal circuit.