Abstract: A programmed computer searches for functional defects in a description of a circuit undergoing functional verification in the following manner. The programmed computer simulates the functional behavior of the circuit in response to a test vector, automatically restores the state of the simulation without causing the simulation to pass through a reset state, and then simulates the functional behavior of the circuit in response to another test vector. A predetermined rule can be used to identify test vectors to be simulated, and the predetermined rule can depend upon a measure of functional verification, including the number of times during simulation when a first state transition is performed by a first-controller at the same time as a second state transition is performed by a second controller. During simulation of the test vectors, manually generated tests or automatically generated checkers can monitor portions of the circuit for defective behavior.

Abstract: The present invention describes a novel method and apparatus for sampling an input/output pin of an electronic device at high speeds, comprising the steps of: driving the device input/output pin through a series resistor with a middle voltage between the high and low voltages of the device; sampling and latching the voltage at the input/output pin; comparing the latched voltage at the device input/output pin with a high threshold voltage which is between the high voltage of the device and the middle voltage; comparing the latched voltage at the device input/output pin with a low threshold voltage which is between the low voltage of the device and the middle voltage; and using the results of the two comparisons to determine whether the device input/output pin is driving high, driving low, or in an input mode.

Abstract: A hardware interface generates and synchronizes precisely timed digital signals. The hardware interface receives data bits and associated timing information for application to a Hardware Modeling Element (HME). Preferably there are at least two modules, each including a clock generating circuit which has an input for receiving a master clock signal, a divider circuit for generating therefrom a plurality of evenly timed internal clock signals, wherein a first one of the internal clock signals rises at the same time as the master clock signal, and a phase adjusting circuit for receiving a feedback control signal for adjusting a phase delay in accordance with a sensed throughput delay. Each module also includes a timing multiplexer which receives the internal clock signals and each having a plurality of data channels, each having approximately the same throughput delay.