The 'ACT8999 are members of the Texas Instruments SCOPETM testability integratedcircuit family. This family of components facilitates testing of complex circuit-board assemblies. The 'ACT8999 enhance the scan capability of TI's SCOPETM family by allowing augmentation of a system's primary scan path with secondary scan paths (SSPs), which can be individually selected by the 'ACT8999 for inclusion in the primary scan path. The device also provides buffering of test signals to reduce the need for external logic.