This scan test device with a 18-bit bus transceiver and register is a member of the Texas Instruments SCOPE™ testability IC family. This device supports IEEE Std 1149.1-1990 boundary scan to facilitate testing of complex circuit board assemblies. Scan access to the test circuitry is accomplished via the four-wire test access port (TAP) interface.

In the normal mode, this device is an 18-bit bus transceiver and register that allows for multiplexed transmission of data directly from the input bus or from the internal registers. It can be used either as two 9-bit transceivers or one 18-bit transceiver. The test circuitry can be activated by the TAP to take snapshot samples of the data appearing at the device pins or to perform a self-test on the boundary test cells. Activating the TAP in the normal mode does not affect the functional operation of the SCOPE bus transceivers and registers.

Transceiver function is controlled by output-enable (OE)\ and direction (DIR) inputs. When (OE)\ is low, the transceiver is active and operates in the A-to-B direction when DIR is high or in the B-to-A direction when DIR is low. When (OE)\ is high, both the A and B outputs are in the high-impedance state, effectively isolating both buses.Read more