Mentor Graphics Corporation

Other

Thomas Hans Rinderknecht

Wu-Tung Cheng

Manish Sharma

Janusz Rajski

Nilanjan Mukherjee

Mark A Kassab

Arnold M Frisch

Nagesh Tamarapalli

Friedrich Hapke

Christopher John Hill

Liyang Lai

Michael Wittke

Randy Klingenberg

Mohamed Dessouky

Sascha Ochsenknecht

Subramanian Mahadevan

Christopher Hill

Methods and devices for using high-speed serial links for scan testing are disclosed. The methods can work with any scheme of scan data compression or with uncompressed scan testing. The protocol and hardware to support high speed data transfer reside on both the tester and the device under test. Control data may be transferred along with scan data or be partially generated on chip. Clock signals for testing may be generated on chip as well. In various implementations, the SerDes (Serializer/Deserializer) may be shared with other applications. The Aurora Protocol may be used to transport industry standard protocols. To compensate for effects of asynchronous operation of a conventional high-speed serial link, buffers may be used. The high-speed serial interface may use a data conversion block to drive test cores.

Scan test application through high-speed serial input/outputs

On-chip high speed clock control techniques for testing circuits with multiple clock systems are disclosed. The techniques allow certain (e.g. compatible) high speed clocks to be activated with predefined waveforms during a capture period of a logic test, based on a clock control signal. The clock control signal may be supplied via a JTAG control port or via a scan chain load port. The clock control signal may also be generated by a BIST controller. The techniques may ensure glitch-free transitions from slow speed clocks during a shift period to fast speed clocks during a capture period.

High speed clock control

Techniques are disclosed for reducing the set of initial candidates in signature based diagnosis methodology. These techniques are based on a unique way of making optimum use of information from logic back-cone tracing along with equations that describe the test response compactor.

Performance of signature-based diagnosis for logic BIST

In embodiments of the disclosed technology, diagnosis of a circuit is performed using compactor signatures (a technique referred to herein as 'signature-based diagnosis'). Signature-based diagnosis typically does not require a test step that bypasses the compactor. Compactor signatures can be read from a compactor on a per-pattern basis, and an expected signature can be loaded into a compactor while an actual signature is being read from the compactor. Error functions can be used to describe relationships between errors in scan cell values and per-pattern compactor signatures, and the functions can be used to help generate a list of fault candidates in a circuit design.

Direct fault diagnostics using per-pattern compactor signatures

A built-in self-test (BIST) circuit is disclosed that allows high fault coverage. Additionally, a method is disclosed for implementing the BIST circuit. In one aspect, the BIST circuit includes a plurality of scan chains that receive test patterns used in testing the integrated circuit. A pseudo random pattern generator provides test patterns to the scan chains. Weight select logic is positioned between the scan chains and the pseudo random pattern generator and controls the weightings of the test patterns that are loaded in the scan chains. In another aspect, the weight select logic can switch the weightings of the test patterns on a per-scan-cell basis. Thus, as the scan chains are loading, the weight select logic can effectively switch between test patterns being loaded into the scan chains.

Built-in self-test of integrated circuits using selectable weighting of test patterns

A method and apparatus for testing an integrated circuit using built-in self-test (BIST) techniques is described. In one aspect, a BIST circuit comprises a scan monitor with hold logic and a signature generation element. The hold logic is operable to suspend signature generation in the signature generation element at any desired point in the test sequence. In some embodiments, the hold logic comprises a scan-loadable signature hold flip-flop which allows the logic BIST controller to be restarted from any selected pattern within a pattern range and to run to any subsequent pattern. The BIST session can be run incrementally, testing and reporting intermediate MISR signatures. External automatic testing equipment can suspend signature generation at selected times during a BIST session to prevent tainting of the signature generation element. The hold logic also may comprise a rotating hold ring to suspend signature generation during predetermined shift cycles.

Restartable logic BIST controller

Various new and non-obvious apparatus and methods for testing an integrated circuit are disclosed. In one exemplary embodiment, a control point is selected in an integrated circuit design. Scan cells in the integrated circuit design are identified that can be loaded with a set of fixed values in order to propagate a desired test value to the control point. The integrated circuit design is modified to include circuit components configured to load the scan cells in the integrated circuit design with the set of fixed values during a test phase. The one or more scan cells may be identified by justifying the control point to the scan cells, thereby determining values that the scan cells must output in order to drive the control point to the desired test value. Computer-readable media comprising computer-executable instructions for causing a computer to perform any of the disclosed methods or computer-readable design information for any of the disclosed apparatus are also disclosed.

Using constrained scan cells to test integrated circuits

A built-in-self-test (BIST) circuit is discussed for selecting tristate nets with substantially uniform distribution using a tristate testing control device (TTCD). The circuit allows the deterministic testing of tristate nets in the context of pseudo-random BIST. A feedback shift register is described that activates a single tristate or set of tristate at a time in order to avoid bus contention. Another TTCD embodiment uses a counter and decoder. A test mode switching unit (TMSU) coupled between the TTCD and the tristate net selects test or functional mode for tristate enables. Parallel multiplexers are discussed as one embodiment of a TMSU. Another TMSU embodiment describes even better test coverage. A method, which may be performed on a distributed computer system, is discussed for identifying tristate nets within a net-list and adding a TTCD and a TMSU to the net-list.

Uniform testing of tristate nets in logic BIST

A jitter measurement system measures timing variations or &ldquo;jitter&rdquo; in a periodic signal waveform as provided, for example, by a phase-locked loop (PLL). In one implementation, the jitter measurement system includes a period gate generator that generates a gate signal with the instantaneous period of output signal waveform F,generated by the PLL. The gate signal includes a leading edge and a trailing edge and is delivered to a pair of triggered oscillators that provide respective oscillator output signals with substantially matched frequencies. The oscillators are triggered at the respective leading and trailing edges of the gate signal. The oscillator output signals are delivered to respective oscillation counters and to a coincidence detector. The oscillation counters count the periods of the respective oscillator output signals from when they are triggered until the coincidence detector detects coincidence between the signals (e.g., coincidence between the trailing edges of the signals). A period measurement of the output signal waveform F,is determined from the counts obtained by the oscillation counters. Multiple such period measurements are obtained to provide information representing jitter in the output signal waveform F,.

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Tualatin, OR, United States of America

Thomas Hans Rinderknecht