In one embodiment, a test system comprises: a test partition configured to perform test operations; a centralized test controller for controlling testing by the test partition; and a test link interface controller configured to communicate between the centralized test controller and the test partition, wherein the test link interface controller controls dynamic changes to external pads associated with the test operations. The test link interface controller dynamically selects between an input direction and output direction for the external pads. The test link interface includes a pin direction controller that generates direction control signals based on the state of local test controller and communicates the desired direction to a boundary scan cell associated with the pin. The boundary scan cell programs the pad to either input or output direction depending on direction control signals. The input direction corresponds to driving test data and the output direction corresponds to observing test data.