The 'ABT18640 scan test devices with 18-bit inverting 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)
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 SCOPETM 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. 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 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 SN74ABT18640 is available in TI's shrink small-outline (DL)
and thin shrink small-outline (DGG) packages, which provide twice the
I/O pin count and functionality of standard small-outline packages in
the same printed-circuit-board area.
The SN54ABT18640 is characterized for operation over the full
military temperature range of -55°C to 125°C. The
SN74ABT18640 is characterized for operation from -40°C to
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