SCAN TEST DEVICE WITH 18-BIT TRANSCEIVERS AND REGISTERS

The SN54ABT18646 scan test device with 18-bit Bus Transceivers and Registers is a member of the Texas Instruments SCOPE 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, the SN54ABT18646 is an 18-bit Bus Transceiver and Register that allows for multiplexed transmission of data directly from the input bus or from the internal Registers It 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 Bus Transceivers and Registers Transceiver function is controlled by output-enable (OE) and direction (DIR) inputs. When OE is low, the transceiver is active and operates in the A-to-B direction when DIR is high or in the B-to-A direction when DIR is low. When OE is high, both the A and B outputs are in the high-impedance state, effectively isolating both buses. Data flow is controlled by Clock (CLKAB and CLKBA) and select (SAB and SBA) inputs. Data on the A bus is clocked into the associated Registers on the low-to-high transition of CLKAB. When SAB is low, real-time A data is selected for presentation to the B bus (transparent mode). When SAB is high, stored A data is selected for presentation to the B bus (registered mode). The function of the CLKBA and SBA inputs mirrors that of CLKAB and SAB, respectively. Figure 1 illustrates the four fundamental bus-management functions that CAN be performed with the ABT18646. In the test mode, the normal operation of the SCOPE Bus Transceivers and Registers 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. By Texas Instruments
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SN54ABT18646 Pinout, Pinouts
SN54ABT18646 pinout,Pin out
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