Abstract: A net of an integrated circuit design is analyzed by unfolding paths on the receive side of an asynchronous boundary to facilitate modeling of the propagation of a metastable value from a receive latch to sinks of the net. The paths are unfolded by replicating combinational logic and wiring along the coincident portions to form non-intersecting, separate paths from the receive latch to two or more sinks. Common data or control inputs are provided for the gates in the replicated combinational logic. Driver logic may additionally be inserted along each replicated path, upstream of the combinational logic, to independently drive each of the sinks.

Abstract: A system and method for accurately modeling an asynchronous interface using expanded logic elements are provided. With the apparatus and method, the logic of an asynchronous interface is reduced to primitive logic elements. These primitive logic elements are expanded by the mechanisms of the present invention to take into consideration whether or not the primitive logic elements themselves may be experiencing a switching or glitch hazard and whether or not the inputs to the primitive logic elements may be based on a switching or glitch hazard from another primitive logic element in the asynchronous interface logic. These expanded logic elements are used in an integrated circuit design to replace the original primitive logic elements in the design. The asynchronous interface may then be simulated with the expanded logic elements providing outputs indicative of whether the actual data output of the expanded logic elements is deterministic or not.

Abstract: Asynchronous behavior of a circuit is modeled by modifying latches in a netlist to add an extra port to the latches, e.g., a single-port latch is transformed into a dual-port latch. Each input port has an enable line and a data input. The data input in the added port is a feedback line from the latch output, and the enable line in the added port is the logical NOR of all of the original enable lines. By adding this extra latch port in the higher-level model, it becomes possible to introduce assertion logic to ensure that one and only one latch port for a given latch is ever active during the same simulation cycle. The model can then be tested earlier in the design methodology prior to the availability of the post-synthesis netlist. The model can also be used in both simulation and formal or semi-formal verification.

Abstract: A method for modeling metastablilty decay in digital circuit devices includes identifying each latch at a receiving end of an asynchronous clock boundary, enumerating a latch depth for each latch within logical influence of each of the identified receive latches, and inserting fence logic immediately prior to the input of each latch at an enumerated depth, n, wherein n represents a latch depth at which an indeterminate metastable value received at the asynchronous boundary decays to a random logic value. The fence logic converts an identified indeterminate value to a random logic value, and any indeterminate value initially received is allowed to propagate up to the fence logic.

Abstract: Asynchronous behavior of a circuit is emulated by modifying a netlist to insert additional logic at a driving element such as a latch. The additional logic outputs one of (i) a present output from the driving element, (ii) a delayed output from the driving element, or (iii) a random value, which drives downstream logic. The output of the additional logic is selectively responsive to a user-controlled skew enable input. The invention allows for simpler data skew logic transformations which are applicable to both latches and primary inputs, with no dependencies on any clock net.

Abstract: Methods and arrangements to model an asynchronous interface are disclosed. Embodiments include transformations, code, state machines or other logic to generate a skew pattern for a semi-static or time-constrained, asynchronous interface and employ the skew pattern in data transfers during a time interval in which the asynchronous interface. Embodiments may then alter the skew pattern in at the expiration of the time interval. In many embodiments, changes to the skew pattern may be substantially non-deterministic. In other embodiments, changes to the skew pattern may follow a heuristic or other dynamic or pre-determined pattern.

Abstract: A system and method for unfolding/replicating logic paths to facilitate propagation delay modeling are provided. With the system and method, nets of an integrated circuit design are unfolded and logic of these nets is replicated such that each leg of a fanout can be driven independently from the signal source. In order to unfold the nets, the nets and logic are replicated in the netlist and connected to replicated source and endpoints. These new nets in the netlist may then be driven separately such that a different propagation delay along different nets from the same source may be simulated. In this way, a level of propagation delay may be abstracted into the modeling by driving or delaying each path separately. The transitioning value will then appear to have differing arrival times from the perspective of the sinks.

Abstract: A system and method for accurately modeling an asynchronous interface using expanded logic elements are provided. With the apparatus and method, the logic of an asynchronous interface is reduced to primitive logic elements. These primitive logic elements are expanded by the mechanisms of the present invention to take into consideration whether or not the primitive logic elements themselves may be experiencing a switching or glitch hazard and whether or not the inputs to the primitive logic elements may be based on a switching or glitch hazard from another primitive logic element in the asynchronous interface logic. These expanded logic elements are used in an integrated circuit design to replace the original primitive logic elements in the design. The asynchronous interface may then be simulated with the expanded logic elements providing outputs indicative of whether the actual data output of the expanded logic elements is deterministic or not.