Abstract: A boundary scan cell for testing an integrated circuit comprises an output buffer for driving a pad of the integrated circuit, a capture register coupled to the pad through the output buffer, and an input buffer drives a signal present at the pad to a node coupled to core logic of the IC. A first multiplexer is included to have a first input coupled to the node, a second input coupled to data of a previous scan stage, and an output coupled to the capture register. Logic circuitry selectively enables/disables the input and output buffers responsive to first and second control signals such that the I/O buffers can drive the pad and, at the same time, drive the input buffer, the output of which is coupled to the input of the capture register.

Abstract: An integrated circuit includes: a comparator coupled in a configuration to compare two voltages. One of the two voltages includes a semiconductor junction voltage drop. The other of the two voltages includes a voltage signal, X V.sub.t, where V.sub.t is a thermal voltage and X includes a selected signal value, which modulates the thermal voltage. The configuration includes a feedback path to vary X until X V.sub.t approximately equals the voltage including the semiconductor junction voltage drop.