SN74LVTH182512 - 3.3-V ABT Scan Test Devices With 18-Bit Universal Bus Transceivers

The 'LVTH18512 and 'LVTH182512 scan test devices with 18-bit universal bus transceivers are members of the Texas Instruments SCOPE^TM testability integrated-circuit family. This family of devices 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 4-wire test access port (TAP) interface.

Additionally, these devices are designed specifically for low-voltage (3.3-V) V_CC operation, but with the capability to provide a TTL interface to a 5-V system environment.

In the normal mode, these devices are 18-bit universal bus transceivers that combine D-type latches and D-type flip-flops to allow data flow in transparent, latched, or clocked modes. 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 universal bus transceivers.

Data flow in each direction is controlled by output-enable (OEAB\ and OEBA\), latch-enable (LEAB and LEBA), and clock (CLKAB and CLKBA) inputs. For A-to-B data flow, the devices operate in the transparent mode when LEAB is high. When LEAB is low, the A data is latched while CLKAB is held at a static low or high logic level. Otherwise, if LEAB is low, A data is stored on a low-to-high transition of CLKAB. When OEAB\ is low, the B outputs are active. When OEAB\ is high, the B outputs are in the high-impedance state. B-to-A data flow is similar to A-to-B data flow but uses the OEBA\, LEBA, and CLKBA inputs.

In the test mode, the normal operation of the SCOPE^TM universal 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 performs boundary-scan test operations according to the protocol described in IEEE Std 1149.1-1990.

Four dedicated test pins are used to 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.

Active bus-hold circuitry is provided to hold unused or floating data inputs at a valid logic level.

The B-port outputs of 'LVTH182512, which are designed to source or sink up to 12 mA, include equivalent 25- series resistors to reduce overshoot and undershoot.

The SN54LVTH18512 and SN54LVTH182512 are characterized for operation over the full military temperature range of -55°C to 125°C. The SN74LVTH18512 and SN74LVTH182512 are characterized for operation from -40°C to 85°C.

Products containing the "SN74LVTH182512" keyword are: SN74LVTH182512DGGR , SN74LVTH182512DGGRG4

• Members of the Texas Instruments SCOPE^TM Family of Testability Products
• Members of the Texas Instruments Widebus^TM Family
• State-of-the-Art 3.3-V ABT Design Supports Mixed-Mode Signal Operation (5-V Input and Output Voltages With 3.3-V V_CC)
• Support Unregulated Battery Operation Down to 2.7 V
• UBT^TM (Universal Bus Transceiver) Combines D-Type Latches and D-Type Flip-Flops for Operation in Transparent, Latched, or Clocked Mode
• Bus Hold on Data Inputs Eliminates the Need for External Pullup/Pulldown Resistors
• B-Port Outputs of 'LVTH182512 Devices Have Equivalent 25- Series Resistors, So No External Resistors Are Required
• Compatible With the IEEE Std 1149.1-1990 (JTAG) Test Access Port and Boundary-Scan Architecture
• SCOPE^TM Instruction Set
  • IEEE Std 1149.1-1990 Required Instructions and Optional CLAMP and HIGHZ
  • Parallel-Signature Analysis at Inputs
  • Pseudo-Random Pattern Generation From Outputs
  • Sample Inputs/Toggle Outputs
  • Binary Count From Outputs
  • Device Identification
  • Even-Parity Opcodes
• Package Options Include 64-Pin Plastic Thin Shrink Small Outline (DGG) and 64-Pin Ceramic Dual Flat (HKC) Packages Using 0.5-mm Center-to-Center Spacings

SCOPE, Widebus, and UBT are trademarks of Texas Instruments Incorporated.