Mixed signal integrated circuit architecture and test methodology

Abstract

An integrated circuit architecture and test methods for use in designing, fabricating and testing mixed-signal application specific integrated circuits. The architecture comprises a plurality of mixed-signal integrated circuits, bidirectional buffers coupled to the integrated circuits that provide for circuit reconfigurability, a bidirectional digital/analog test bus, and a serial test controller coupled to the buffers that controls normal operation and testing of the integrated circuits. The controller and plurality of buffers cooperate to couple signals from signal pads to the integrated circuits to provide for 'normal' operation thereof, and to re-route external test signals applied to selected signal pads to the integrated circuits to permit testing. Logic in the buffers provides for functional configurability, enabling them to be logically altered under control of the controller, and allowing the test bus to be connected directly to signal pads. All of the signal pads are available for use in testing, and provide a means of directly accessing key test points within the circuit without resorting test vectors. Test methods are disclosed and comprise: selecting an integrated circuit for testing; selecting signal pads that are to be used to test the selected integrated circuit, which selected signal pads are different from those used during normal operation of the integrated circuit; applying external test signals to the selected signal pads; routing the external test signals by way of the plurality of configurable buffers and the bidirectional bus from the selected signal pads to the integrated circuit; and monitoring input signals and output signals applied to and derived from the selected signal pads to test the selected integrated circuit.