The 'ABT8245 scan test devices with octal bus transceivers are
members of the Texas Instruments SCOPETM 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 functionally equivalent to
the 'F245 and 'ABT245 octal bus transceivers. 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 normal mode does not
affect the functional operation of the SCOPETM octal bus
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. The output-enable
() input can be
used to disable the device so that the buses are effectively
isolated.
In the test mode, the normal operation of the SCOPETM
bus transceivers is inhibited and the test circuitry is enabled to
observe and control the I/O boundary of the device. When enabled, the
test circuitry can perform boundary-scan test operations as described
in IEEE Standard 1149.1-1990.
Four dedicated test pins 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 SN54ABT8245 is characterized for operation over the full
military temperature range of -55°C to 125°C. The
SN74ABT8245 is characterized for operation from -40°C to
85°C.
