The 'ACT8990 test-bus controllers (TBC) are members of the Texas Instruments SCOPETM testability integrated-circuit family. This family of components supports IEEE Standard 1149.1-1990 (JTAG) boundary scan to facilitate testing of complex circuit-board assemblies. The 'ACT8990 differ from other SCOPETM integrated circuits. Their function is to control the JTAG serial-test bus rather than being target boundary -scannable devices.