Cisco Technology, Inc.

Sang Hyeon Baeg

Sung Soo Chung

Hongshin Jun

A boundary scan test system including a transmitter and a receiver. The system performs DC and AC boundary scan testing of the interconnections between devices. The system addresses fault masking that can occur during testing. Of concern are AC coupled interconnections while providing IEEE 1149.1 DC test compatibility. The test receiver includes an input test buffer and an interface mechanism. The input test buffer has a built-in null detection capability. The interface mechanism includes a technology mapper, one or more detectors, and an integrator. The receiver provides at least partial, if not complete, coverage for at least one of five fault syndromes that can result from single defect conditions in the system.

Test buffer design and interface mechanism for differential receiver AC/DC boundary scan test

An AC boundary scan cell is disclosed. For one embodiment the AC boundary scan cell includes a first multiplexer, a second multiplexer, a first data shift register, a second data register, an XOR logic gate, and a third multiplexer. For one such embodiment the AC boundary scan cell includes an SDI line, an SDO line, a TDI line, a TDO line, a ShiftDR signal input line, an AC_Pattern_Clock or ClockDR signal input line, an UpdateDR signal input line, and a Mode signal input line. The AC boundary scan cell also includes an AC_Pattern_Source signal input line and an AC_Test signal input line. For one such embodiment, each line is coupled to receive the corresponding signal from the boundary scan logic.

AC coupled line testing using boundary scan test methodology

Testing AC coupled interconnects using boundary scan test methodology. Specially designed AC boundary scan cells and boundary scan logic are used. These are compatible with IEEE Standard 1149.1 testing. An AC_EXTEST method is used to determine the reliability of the AC coupled interconnections. The method includes preloading the test stimulus, initiating the AC_EXTEST instruction, executing the instruction, transferring the instruction results, and evaluating the results. During the test, the TAP controllers of both the driving and receiving ICs are held in the Run-Test/Idle state for the time required to complete execution of the instruction. During this time, the driving IC is applying the AC test stimulus to the interconnections and the receiving IC is sampling the signal. The test may be repeated with different test data and may be run together with a DC EXTEST method to determine the reliability of both the AC and the DC coupled interconnections independently.

Programmable test pattern driver and capture mechanisms for boundary scan cluster or functional block testing. A boundary scan test system includes at least one device under test. The device may include a Test Access Port (TAP) controller, a plurality of output AC boundary scan cells (BSCs), and a plurality of input AC BSCs. The device may further include a programmable AC_Pattern_Source signal generator configured to produce AC signal patterns that selectively remain unchanged for at least one cycle before and after an original capture cycle location, a programmable AC_Sync signal generator configured to independently control the AC_Sync signal to lead or lag an original cycle location at full cycle increments, a programmable phase controller configured to independently control either the rising or falling edge aligned AC_Pattern_Clock signal or AC_Counter_Clock signal, and an AC_Test_Clock signal switcher configured to selectively utilize one of a plurality of clock signals including a TCK signal.

Growing community of inventors

Cupertino, CA, United States of America

Sang Hyeon Baeg