SN54ABT18245A

The 'ABT18245A scan test devices with 18-bit bus transceivers are members of the Texas Instruments SCOPE^TM testability 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 noninverting 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 SCOPE^TM bus transceivers.

Data flow is controlled by the direction-control (DIR) and output-enable (OE\) 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. OE\ can be used to disable the device so that the buses are effectively isolated.

In the test mode, the normal operation of the SCOPE^TM bus transceivers is inhibited and the test circuitry is enabled to observe and control the input/output (I/O) boundary of the device. When enabled, the test circuitry performs boundary-scan test operations according to the protocol described in IEEE Standard 1149.1-1990.

Four dedicated test pins observe and control the operation of the test circuitry: test-data input (TDI), test-data output (TDO), test-mode select (TMS), and test clock (TCK). Additionally, the test circuitry performs other testing functions such as parallel-signature analysis (PSA) on data inputs and pseudo-random pattern generation (PRPG) from data outputs. All testing and scan operations are synchronized to the TAP interface.

The SN54ABT18245A is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ABT18245A is characterized for operation from -40°C to 85°C.