In a first embodiment a Test Access Port (TAP) of IEEE standard 1149.1 is allowed to commandeer control from a Wrapper Serial Port (WSP) of IEEE standard P1500 such that the P1500 architecture, normally controlled by the WSP, is rendered controllable by the TAP. In a second embodiment (1) the TAP and WSP based architectures are merged together such that the sharing of the previously described architectural elements are possible, and (2) the TAP and WSP test interfaces are merged into a single optimized test interface that is operable to perform all operations of each separate test interface. One approach provides for the TAP to maintain access and control of the TAP instruction register, but provides for a selected data register to be accessed and controlled by either the TAP+ATC (Auxiliary Test Control bus) or by the discrete CaptureDR, UpdateDR, TransferDR, ShiftDR, and ClockDR WSP data register control signals.