I/O CELL OF VERY LARGE SCALE INTEGRATED CIRCUIT

摘要

PURPOSE: To improve the testability of a very large scale integrated circuit by providing an output and input buffer means which respectively supplies an input from an on-chip circuit to a chip pin, and an input from the chip pin to the on-chip circuit. CONSTITUTION: A unit I/O cell introduces an input through a core logic input CLI outputted from a circuit 10 to the core logic of a chip, and receives an output from the core logic at the input point of a core logic output CLO. Functions F16 and F16B, signals F22 and F23B, and output enable line OEN are all cooperatively energized for enabling the CLO, and a signal F18 is energized for enabling an input from a pin P for allowing it to reach the CLI. A circuit 20 can be considered as the bits of an input register which stores information.