Circuitry that may be built into an integrated circuit to assist in the test, maintenance, and support of assembled printed circuit boards, assembled multi-die packages, and the test of die internal circuits is defined in this standard. The circuitry includes a high-speed TAP (HSTAP) with a packet encoder/decoder and distribution architecture through which instructions and test data are communicated. The standard leverages the languages of IEEE Std 1149.1? to describe and operate the on-chip circuits.