Circuitry that may be built into an integrated circuit to assist in the test, maintenance, and
support of assembled printed circuit boards is defined. The circuitry includes a standard interface
through which instructions and test data are communicated. A set of test features is defined,
including a boundary-scan register, such that the component is able to respond to a minimum set
of instructions designed to assist with testing of assembled printed circuit boards. Also, a language
is defined that allows rigorous description of the component-specific aspects of such testability
features.
