SELF-TESTING INPUT/OUTPUT PAD

The present invention teaches an apparatus for testing the circuitry in an input/output (I/O) pad without probing the contact site on the I/O pad. A dominant driving circuit has an output coupled to a first contact site on a semiconductor chip. A subordinate driving circuit also has an output coupled to the first contact site on the semiconductor chip. A test control circuit sets a drive fight up between the dominant and subordinate driving circuits, the test control circuit selecting a stronger drive strength for the dominant driving circuit than for the subordinate driving circuit. The drive fight produces a test value at the first contact site. The test value from the first contact site is transferred to a second contact site on the semiconductor chip to be probed by an external prober.