The 'ABT18640 scan test devices with 18-bit inverting bus transceivers are members of the Texas Instruments SCOPETMtestability integrated-circuit family. This family of devices supports IEEE Standard 1149.1-1990 boundary scan to facilitate testing of complex circuit-board assemblies. Scan access to the test circuitry is accomplished via the 4-wire test access port (TAP) interface.

In the normal mode, these devices are 18-bit inverting bus transceivers. They 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 SCOPETMbus transceivers.

Data flow is controlled by the direction-control (DIR) and output-enable () inputs. Data transmission is allowed from the A bus to the B bus or from the B bus to the A bus, depending on the logic level at DIR.can be used to disable the device so that the buses are effectively isolated.Read more