Abstract: A method and built-in circuit are described for testing direct current (DC) parameters of the input and output pins of a circuit by testing the transition time interval for rising and falling voltage transitions. When the voltage transition is for an integrated circuit (IC) pin having a known capacitance, which can include off-chip capacitance, the magnitude and direction of current at the pin can be determined. The method enables testing an IC via a test access port (TAP) comprising a subset of the pins of the IC, for example in conformance with the IEEE 1149.1 boundary scan test standard. For sufficiently small current magnitudes, such as leakage current (IIL and IIH), the technique can use only on-chip circuitry to sample a pin voltage at time intervals after an output transition is generated at the pin, the time intervals pre-determined to be less than the transition time interval.

Abstract: A method of synthesizing a circuit employs a technology parameter extraction circuit which is synthesized with constraints and simulated to derive values of performance parameters, and then, based on the derived values, a predetermined high-level circuit description of a second circuit is modified and then synthesized using the same constraints. Optional steps include the creation and substitution of a sub-circuit model to permit correct simulation, or substitution of an alternative sub-circuit to synthesize a second circuit that cannot otherwise be synthesized directly.

Abstract: A method for at-speed testing high-performance digital systems and circuits having combinational logic and memory elements that may be both scannable and non-scannable is performed by enabling at least two clock pulses during a capture sequence following a shift sequence. The method provides for initialization of any non-scannable memory elements via the scannable memory elements at the beginning of the test before an at-speed test is performed. During initialization, control logic generates a signal to disable the generation of system clock pulses for capture. Instead, only one clock cycle derived from the test clock or a system clock is generated to initialize the non-scannable elements. The number of shift sequences required depends on the maximum number of non-scannable elements that must be traversed between two scannable memory elements. During the same initialization period, the output response analyzer is disabled since unknown data values will present in the stream of data shifted out.

Abstract: A method of testing an analog, or mixed analog and digital, circuit designed for operation at a clock frequency multiplexes a plurality of low frequency stimulus signals using a high frequency clock to produce a circuit input signal, applies the input signal to the circuit to obtain a circuit output signal; samples the circuit output signal synchronously with the high frequency clock at a frequency equal to the clock frequency divided by the number of the low frequency signals; stores the samples and measures properties of the signal samples to determine properties of the output signal of the circuit.

Abstract: A scan-testing method for circuits having tri-state bus drivers disables all drivers during scan intervals and enables at most one of the bus drivers during the capture interval. A driver select signal is generated for each bus driver and gated with a corresponding circuit functional enable signal to generate a driver enable signal. A driver is selected by loading a driver select code into memory elements during the scan-in sequence and decoding the driver select code to produce the driver select signals.

Abstract: A method of testing a circuit having two or more clock domains at respective domain test clock rates and under control of a main test clock signal, the circuit having core logic, a plurality of scannable memory elements, each having a clock input, an input connected to an output of the core logic and/or an output connected to an input to the core logic, and configurable in scan mode in which the memory elements are connected to define one or more scan chains in each domain and in normal mode in which the memory elements are connected to the core logic in normal operational mode, the method comprising configuring the memory elements in scan mode; concurrently clocking a test stimulus into each scan chain of each clock domain including, for each clock domain having a domain test clock signal which is synchronous with respect to the main test clock signal, clocking the test stimulus at a shift clock rate derived from the main test clock signal and, for each clock domain having a domain test clock signal which is

Abstract: A method of testing phase locked loops (PLL) and a testing circuit comprising the steps of applying a normal stimulus signal whose frequency is within the lock range of the PLL to the input of the PLL, substituting the normal input stimulus with an alternative signal derived from an internal feedback of the PLL, adding or deleting one or more cycles from the alternative signal and observing the response of the PLL to the alternative signal. Variations of the method allow for determining Gain-Bandwidth product, lock range, lock time, Bit Error Rate, Jitter and other parameters which can then be compared with predetermined values to determine whether the PLL is properly functional.

Abstract: A method is provided for producing a synthesizable RT-Level specification, having a testability enhancement from a starting RT-Level specification representative of a circuit to be designed, for input to a synthesis tool to generate a gate-level circuit. The method includes the steps of performing a testability analysis on a Directed Acyclic Graph by computing and propagating Testability Measures forward and backward through VHDL statements, identifying the bits of each signal and/or variable, and adding test point statements into the specification at the RT-Level to improve testability of the circuit to be designed. The computation of Controllability and Observability method is purely functional, and does not subsume the knowledge of a gate-level implementation of the circuit being analyzed.

Abstract: An improvement in a method of testing a digital circuit or system, having a plurality of scannable memory elements, in accordance with conventional BIST methods in which, at a reference clock, a test stimulus is shifted into the memory elements, the response of the elements is captured and the captured data is shifted out of the elements and analyzed, the improvement comprising controlling the average power consumption of the circuit during the test by suppressing clock pulses from the reference clock during phases of the test that do not require the maximum level of activity or in which the performance of the circuit is not to be evaluated; and, suppressing no clock pulses from the reference clock in phases of the test in which the performance of the circuit is to be evaluated, so that the conditions are substantially as those of normal mode of operation of the circuit.

Abstract: A method of testing the core logic in a digital system, the method having a sequence of test operations including a shift-in operation in which a test stimulus is shifted into scanable memory elements in the core logic, a capture operation in which data in the memory elements is captured, and a shift-out operation in which captured data is shifted out of the core logic for analysis, comprises the improvement of, for each the test operation, concurrently enabling the domain clock of each clock domain in the core logic at the beginning of each test operation, performing the test operation in each domain and disabling the domain clock at the end of each test operation in each domain. The method allows all of the clock domains, including signal paths which traverse domain boundaries and/or have multi-cycle paths to be tested concurrently and at their respective functional clock rate of each clock.

Abstract: A circuit and method is described whose objective is built-in self-test (BIST) for analog-to-digital converters (ADCS) and input logic gates of an integrated circuit. The technique converts the switching point voltage, or logic threshold, into a binary-encoded digital value which can be compared to upper and lower limits to decide pass or fail. Every clock cycle, the output of the ADC is compared to a digital output value, and if the output is larger than the reference a logic 0 is output, otherwise a logic 1. This series of ones and zeroes is fed back to an analog low pass filter connected to the ADC's input, and also to a digital averaging circuit which counts the number of ones in a constant interval. The number of ones is linearly proportional to the switching point voltage.

Abstract: A circuit and method is described which generates a high frequency clock signal whose frequency is accurate enough to be used for testing other circuitry, yet the circuit can be described using a hardware description language so that it is suitable for logic synthesis and automatic layout. The technique uses a plurality of programmable ring oscillators and means to select and enable one of the ring oscillators. The output frequency is measured relative to that of a lower frequency reference signal, and when the output frequency is incorrect, a different ring oscillator is selected or the present ring oscillator's frequency is changed. Circuitry is included to prevent glitches at the output of the clock generator when the frequency is changed, regardless of how the ring oscillators are constructed.

Abstract: A method and digital system for testing scannable memory and combinational networks. The scannable memory is configurable into several scan chains. Each chain may have a different effective clock rate, as determined by respective clock enable signals. The method and digital system allow scan testing of digital circuits that use a single operational clock rate and several functional clock enable signals to effect slower lock operating rates. The digital system includes memory elements having scan enable and clock enable inputs.

Abstract: A method of testing an integrated circuit having core logic with two or more clock domains and at least one signal path originating in one clock domain and terminating in an other clock domain, each signal path having a source control element in the one clock domain and an associated destination control element in the other clock domain, each the control element being a scannable memory element, the method comprising the steps of, for each the control element shifting a test stimulus into all scannable elements in the core logic; placing an associated source control element in a hold mode for a predetermined number of clock cycles prior to a capture operation so that the source control element holds its output constant during the predetermined number of clock cycles; performing a capture operation for capturing the data output in response to the test stimulus by the control element and by all other scannable elements which are not control elements; maintaining an associated source control element in a hold mo

Abstract: An interface allowing to transfer serial test data from a Test Access Port (TAP) to controllers located in several clock domains is described. The clock frequencies can be different from each other and do not need to be related in phase to each other or with the clock of the TAP. The interface is proven to work reliably as long as the clock frequencies used for the test controllers and registers is 3 times higher than the one of the TAP used to source the serial test data.

Abstract: A method and apparatus suitable for built in self test (BIST) of analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) embedded in a mixed-signal integrated circuit, and high precision converters. Deterministic test patterns, such as a binary count, are applied to the DAC, and via the DAC directly to the ADC or via an analog circuit to be tested in the test mode. The testing is performed digitally via the digital-analog-digital path, is compatible with conventional digital test, and requires minimal additional circuitry to implement. The output response of the ADC is accumulated into four or more signatures which individually represent a number of parameters including offset, gain, second harmonic distortion, third harmonic distortion, and differential non-linearity.