Circuit Emulation With Four-State X-Propagation Semantics
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Solution Overview
Problem
Conventional emulation methods for identifying unpredictable behavior in digital systems, particularly in advanced processes like 22 nanometers and below, are inefficient due to the time-consuming process of locating and debugging unknown states in billions of logic circuits, leading to improper logic operations.
Innovation Solution
The implementation of a four-state semantic representation for digital signals in emulation environments, where a signal's state is indicated using two bits to distinguish between known and unknown states, allowing for rapid propagation and identification of improper operations through conversion of Boolean logic operators, flip flops, latches, and memory circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binary state representation is used for digital signals in emulation, then the emulation can be performed using standard digital logic circuits, but identifying unknown operations becomes time-consuming requiring millions of emulation cycles
Solution Approach 1:
The patent changes the parameter representation of digital signals from conventional binary (2 states: 0 and 1) to four-state semantic (4 states: 0, 1, X, and high-impedance Z). This parameter expansion allows the emulation system to explicitly represent unknown states and high-impedance states, enabling rapid identification of improper operations without requiring millions of emulation cycles. The four-state representation is achieved by using two bits per signal (strong bit and weak bit) to encode the four possible states.
Solution Approach 2:
The patent introduces an additional dimension to signal representation by adding the high-impedance state (Z) beyond the traditional three-state logic (0, 1, X). This dimensional expansion allows the emulation system to distinguish between unknown states (X) and high-impedance states (Z), which have different implications for circuit behavior. The two-bit encoding scheme (strong bit, weak bit) provides the necessary degrees of freedom to represent all four states uniquely.
2Productivity
If four-state semantic representation is implemented to rapidly identify unknown operations, then debugging efficiency improves significantly, but the device complexity increases due to additional circuit requirements
Solution Approach 1:
The patent uses copying by creating a semantic representation model that mirrors the physical circuit behavior. Instead of modifying physical circuits to detect unknown states, the patent creates a four-state semantic copy of the circuit logic that propagates state information explicitly. This semantic copying allows the emulation system to identify improper operations rapidly without adding physical detection circuitry to the actual device under test.
Solution Approach 2:
The patent introduces an intermediary layer between the physical circuit and the analysis system. The four-state semantic representation acts as an intermediary that translates physical circuit states into a richer state space that explicitly captures unknown and high-impedance conditions. This intermediary semantic layer enables efficient debugging by providing explicit state information without requiring direct modification of the physical circuit.
3Quantity of substance
If conventional binary representation is used, then hardware resource costs are lower, but locating sources of unknown states requires performing a large number of digital logic operations
Solution Approach 1:
The patent applies preliminary action by pre-defining the four-state semantic representation and the rules for state propagation before emulation begins. The two-bit encoding scheme and the logic for propagating strong and weak bits through circuits are established in advance. This preliminary setup enables the emulation system to rapidly locate unknown state sources during execution without requiring additional computational overhead for state representation, as the framework is already in place.
Data Source
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AI summary
Embodiments relate to the emulation of circuits, and representation of unknown states of signals. A disclosed system (and method and computer program product) includes an emulation environment to convert a digital signal of a DUT in a form capable of representing an unknown state. In addition, the disclosed system converts digital logic circuits such as Boolean logic, flip flops, latches, and memory circuits to be operable with signals having unknown states. Thus, an unknown state of a signal is indicated and propagated through digital logic circuits represented in a disclosed semantic to enable prompt detection of improper operation of the DUT, for example, due to power shut down or inadequate initialization.