Connection circuitry couples scan test port (STP) circuitry to test access port (TAP) circuitry. The connection circuitry has inputs connected to scan circuitry control output leads from the TAP circuitry, a select input lead, and a clock input lead. The connection circuitry has outputs connected to a scan enable (SE) input lead, a capture select (CS) input lead, and the scan clock (CK) input lead of the STP circuitry. The connection circuitry includes a multiplexer having a control input connected with a clock select lead from the TAP circuitry, an input connected with a functional clock lead, an input connected with the clock input lead, an input connected with a Clock-DR lead from the TAP circuitry, an OFF lead, and an output connected with the scan clock input lead.