This standard defines a mixed-signal test bus architecture that provides the means of control and access to both analog and digital test signals such that the testability structure for digital circuits described in IEEE Std 1149.1-2001 has been extended effectively to provide similar facilities for mixed-signal circuits. In addition to testing of interconnections in the conventional sense of IEEE 1149.1-2001, the mixed-signal test bus defined by this standard also provides the means for parametric testing and, optionally, the means to access internal test structures.