Equivalence checking between SLM and RTL using machine learning techniques

Deep State Sequence-based (DSS) equivalence checking and path-based equivalence checking have been successfully applied for verification of digital designs between System Level Model (SLM) and Register Transfer Level (RTL). The DSS-based equivalence checking method can validate designs without mapping information, but the query size for each DSS is large compared with path-based verification. The query size for path-based methods is small, but the number of comparisons is large. In this work, we combine the advantages of DSS-based methods and path-based methods. We use DSS-based methods to find the corresponding paths and use cut-points like in path-based methods to split the DSS to reduce the query size. Finite State Machine with Datapath (FSMD) is used to represent the SLM and RTL models. Experimental results demonstrate that our method can effectively validate the designs and reduce the query size for DSS-based equivalence checking method.

A formal verification method for checking correctness of code motion techniques is presented in this article. Finite State Machine with Datapath (FSMD) models have been used to represent the input and the output behaviors of each synthesis step. The method introduces cutpoints in one FSMD, visualizes its computations as concatenation of paths from cutpoints to cutpoints, and then identifies equivalent finite path segments in the other FSMD; the process is then repeated with the FSMDs interchanged. Unlike many other reported techniques, the method is capable of verifying both uniform and nonuniform code motion techniques. It has been underlined in this work that for nonuniform code motions, identifying equivalent path segments involves model checking of some data-flow properties. Our method automatically identifies the situations where such properties are needed to be checked during equivalence checking, generates the appropriate properties, and invokes the model checking tool NuSMV to verify them. The correctness and the complexity of the method have been dealt with. Experimental results demonstrate the effectiveness of the method.

This paper describes a formal method for checking the equivalence between the finite state machine with datapath (FSMD) model of the high-level behavioural specification and the FSMD model of the behaviour transformed by the scheduler. The method consists in introducing cutpoints in one FSMD, visualizing its computations as concatenation of paths from cutpoints to cutpoints and finally, identifying equivalent finite path segments in the other FSMD; the process is then repeated with the FSMDs interchanged. The method is strong enough to accommodate merging of the segments in the original behaviour by the typical scheduler such as DLS, a feature very common in scheduling but not captured by many works reported in the literature. It also handles arithmetic transformations

The rapidly increasing complexities of hardware designs are forcing design methodologies and tools to move to the Electronic System Level (ESL), a higher abstraction level with better productivity than the state-of-the-art Register Transfer Level (RTL). Behavioral synthesis, which automatically synthesizes ESL behavioral specifications to RTL implementations, plays a central role in this transition. However, since behavioral synthesis is a complex and error-prone translation process, the lack of designers' confidence in its correctness becomes a major barrier to its wide adoption. Therefore, techniques for establishing equivalence between an ESL specification and its synthesized RTL implementation are critical to bring behavioral synthesis into practice. The major research challenge to equivalence checking for behavioral synthesis is the significant semantic gap between ESL and RTL. The semantics of ESL involve untimed, sequential execution; however, the semantics of RTL involve timed, concurrent execution. We propose a sequential equivalence checking (SEC) framework for certifying a behavioral synthesis flow, which exploits information on successive intermediate design representations produced by the synthesis flow to bridge the semantic gap. In particular, the intermediate design representation after scheduling and pipelining transformations permits effective correspondence of internal operations between this design representation and the synthesized RTL implementation, enabling scalable, compositional equivalence checking. Certifications of loop and function pipelining transformations are possible by a combination of theorem proving and SEC through exploiting pipeline generation information from the synthesis flow (e.g., the iteration interval of a generated pipeline). The complexity brought by bubbles in function pipelines is creatively reduced by symbolically encoding all possible bubble insertions in one pipelined design representation. The result of this dissertation is a robust, practical, and scalable framework for certifying RTL designs synthesized from ESL specifications. We have validated the robustness, practicality, and scalability of our approach on industrial-scale ESL designs that result in tens of thousands of lines of RTL implementations.

Much effort in register transfer level (RTL) design has been devoted to developing types of tools. However, given the highly complex nature, and lack of control on RTL design, push-button type synthesis is not accepted by many designers. Interactive design with assistance of algorithms and tools can be more effective if it provides control to the steps of synthesis. In this paper, we propose an interactive RTL design environment which enables designers to control the design steps and to integrate hardware components into a system. Our design environment is targeting a generic RTL processor architecture and supporting pipelining, multicycling, and chaining. Tasks in the RTL design process include clock definition, component allocation, scheduling, binding, and validation. In our interactive environment, the user can control the design process at every stage, observe the effects of design decisions, and manually override synthesis decisions at will. We present a set of experimental results that demonstrate the benefits of our approach. Our combination of automated tools and interactive control by the designer results in quickly generated RTL designs with better performance than fully-automatic results, comparable to fully manually optimized designs.

Background: In recent years, the rising demand for high-performance radar systems in aeronautics, astronautics, national defense, and civil communication has driven the widespread application of phased-array technology. The design of beam controllers, the core of phased-array systems, faces many challenges. Traditional implementation schemes are usually based on application-specific integrated circuits (ASIC) or discrete components, which have a long development cycle, poor flexibility, and limited adaptability. Field-programmable gate arrays (FPGA), with their high parallelism, reconfigurability, and powerful signal processing capabilities, offer a new way to implement phased-array control systems. But FPGA design has traditionally relied on register transfer level (RTL) description, which is inefficient and struggles to keep up with the rapid iteration of complex algorithms. With the development of high-level synthesis (HLS) technology, it has become possible to develop FPGAs using high-level languages such as C/C++. However, improving development efficiency while ensuring hardware performance remains a key issue in the design of phased-array beam controllers. Materials and Methods: This study employs an HLS - RTL co - design method to build a phased - array beam controller. This approach combines the strengths of HLS's efficient algorithm implementation and RTL's precise hardware interface control. The system architecture consists of three parts: the host - machine control layer, FPGA processing layer, and phase - control output layer. In the FPGA processing layer, the core beam - forming algorithm is implemented via HLS. Based on phased - array principles, this algorithm converts target angles to wave vectors and calculates phase - compensation values for each element in an 8×8 array. Pipelining and parallel processing techniques are used in the HLS design to optimize algorithm throughput and latency. The phase - control output layer, designed with RTL, repackages 64 calculated phase values and distributes them to 16 physical phase - shifter chips. Each phase - shifter manages four elements and receives control data through an SPI interface. Results: The proposed FPGA-based phased-array beam controller design in this paper has successfully achieved high - speed, high - precision beam control. By using the HLS - RTL co - design method, it has solved the problem of low algorithm implementation efficiency in traditional FPGA development and ensured the high performance and reliability of hardware interfaces. Experimental results indicate that the system meets or surpasses design targets on key performance indicators. Its end - to - end latency is kept within 130μs, it supports an angle update rate of over 5,000 times per second, and can satisfy the requirements for tracking highly dynamic targets in practical applications. Conclusion: The major contributions of this research are as follows: presenting an HLS - RTL co - design methodology for complex FPGA system development; designing an efficient phased - array beam - forming algorithm and its hardware implementation; and developing a flexible and scalable phased - array control system architecture that supports different array configurations. These findings are highly significant for beamforming technologies in phased - array radar and 5G communication systems, as well as for other FPGA applications requiring high - speed signal processing.

Application-specific systems are increasingly being deployed on reconfigurable computing platforms such as the field-programmable gate array (FPGA). These systems can integrate many disparate computing elements, and often contain soft processors hosting application components. Soft processors are sequential, synchronous devices with low computational density, and are not capable of exploiting the concurrency available on the FPGA. We present a method for increasing the computational density of application-specific systems by eliminating soft processors within these systems. This method eliminates soft processors by replacing programs that would be hosted on soft processors with custom, self-contained, circuitizable finite-state machine with datapath (FSMD) components that are automatically generated. We show that FS-MDs produced using this method eliminate the computational overhead associated with fetching and decoding instructions. We further show that this method, when applied to interrupt-driven programs, can produce concurrent FSMDs that arbitrate for shared datapath resources. We discuss how these FSMDs are capable of leveraging the spatial computational capabilities of the FPGA and are therefore more aptly suited for deployment within application-specific systems. We show that these FSMDs eliminate overhead associated with interrupt context switching, decrease interrupt servicing latencies, and eliminate interrupt livelock. We discuss implications and limitations of this method, and describe a prototype that implements the method for programs targeted for the Intel 8051.

Existing C-to-FPGA high-level synthesis (HLS) tools are good at exploiting instruction-level and loop-level parallelism, but not efficient at exploiting task-level parallelism (or requires extensive manual re-write). In this paper, we present an automated flow and architecture template to map task-level data-model (coarse-grain task graphs) onto FPGAs. We automatically generate multiple communicating FSMDs (finite-state machine with datapath) based on the architecture template to manage the required synchronization and communication. The key architectural components in our approach include a progress table that traces task execution, an automatic memory duplication scheme that enables a larger parallelism and provides isolation between different tasks, and a memory lifetime analysis and reuse scheme to reduce the on-chip memory consumption. Through data-flow driven execution, the presented flow can reduce the total latency by 30%, with moderate area overhead, when compared with the RTL implementation using a single hierarchical FSMD generated by a state-of-art HLS tool.

Equivalence checking is an integral part of the formal verification of ASIC to ensure that the constructed design flow meets the specifications. State-of-the-art techniques and heuristics are available for combinational equivalence checking restricted to binary netlists and do not work for netlists containing and propagating the “X” value. To accommodate the X-value, a 3-valued formal analysis has to be done which is computationally exponentially harder than its binary counterpart and can be a capacity challenge for the verification tool. X-value propagation becomes crucial for applications including low power equivalence checking under power shutoff and comparing a Register Transfer Level (RTL) design to a synthesized netlist. This paper introduces an algorithm for X-value equivalence checking using Binary Decision Diagrams (BDD) for combinational circuits. It extends the functionality of pre-existing formal verification tools available for binary netlists, to X-value netlists by introducing new variables to the BDD. The Colorado University Decision Diagram (CUDD) package has been used for BDD manipulation.

Today, the most common abstraction level for manual design capture is at the so called register transfer level. At this level, all synchronous registers, latches and the combinational logic between the sequential elements are described in a hardware description language such as Verilog or VHDL. The description is then transformed into logic gate implementations based on a technology specific cell library, a procedure known as logic synthesis. This allows a designer to handle more complex design because detailed manual analysis need not be made at the logic gate level that is more tedious and error prone. Register transfer level is certainly not the only starting point for automated hardware synthesis. The analysis and synthesis of digital circuits are still being pushed toward even higher level of abstraction for manual manipulation. For example, macro block level specification and synthesis has been practiced in some design areas. The register transfer and macro block level design methodologies are part of the architecture and system level techniques to be discussed in this chapter.

According to Moore's Law, number of transistors on chip doubles in every next two years, So the complexity of the circuit increases. So it needs to be careful in designing and verification. Register Transfer Level (RTL) designing and its verification is also most important part of circuit design. The intent behind verification is to check that design meets all system specification and requirements or not. It is important to verify RTL before simulation and synthesis the design because It save clock cycle and time of simulation. This paper is focused on the RTL verification tool, Such as HAL linting and Spyglass RTL signoff tool. This type of RTL verification is used to find bugs and error in design before synthesis. It is easy to debug RTL design and pinpoint the problem and their solution. It is important to identify design issues as early as possible before synthesis RTL design.

Transaction-level modeling is used in hardware design for describing designs at a higher level compared to the register-transfer level (RTL) (e.g. Cai and Gajski in CODES+ISSS '03: proceedings of the 1st IEEE/ACM/IFIP international conference on Hardware/software codesign and system synthesis, pp. 19---24, 2003; Chen et al. in FMCAD '07: proceedings of the formal methods in computer aided design, pp. 53---61, 2007; Mahajan et al. in MEMOCODE '07: proceedings of the 5th IEEE/ACM international conference on formal methods and models for codesign, pp. 123---132, 2007; Swan in DAC '06: proceedings of the 43rd annual conference on design automation, pp. 90---92, 2006). Each transaction represents a unit of work, which is also a useful unit for design verification. In such models, there are many properties of interest which involve interactions between multiple transactions. Examples of this are ordering relationships in sequential processing and hazard checking in pipelined circuits. Writing such properties on the RTL design requires significant expertise in understanding the higher-level computation being done in a given RTL design and possible instrumentation of the RTL to express the property of interest. This is a barrier to the easy use of such properties in RTL designs. In this paper, we consider specification of interaction properties at the transaction-level and the subsequent encoding of the property and the transaction-level model as a finite-state system for model checking. We discuss how the encoded finite-state system can be automatically generated from the specification of the property and the transaction-level model, and illustrate this through simple examples.

This paper presents a formal method for equivalence checking between the descriptions before and after scheduling in high-level synthesis (HLS). Both descriptions are represented by finite state machine with datapaths (FSMDs) and are then characterized through finite sets of paths. The main target of our proposed method is to verify scheduling employing code transformations-such as speculation and common subexpression extraction (CSE), across basic block (BB) boundaries-which have not been properly addressed in the past. Nevertheless, our method can verify typical BB-based and path-based scheduling as well. The experimental results demonstrate that the proposed method can indeed outperform an existing state-of-the-art equivalence checking algorithm.

In this paper, we propose a new testability analysis method for Register-Transfer Level (RTL) descriptions. The proposed method is based on the idea of testability analysis in terms of data-flow and control structure which can be extracted from RTL designs. We analyze testability of RTL descriptions with more testability measures than those of conventional gate-level testability, so that the method provides information for design for testability (DFT). We have implemented the presented method and experimental results show that we can reduce circuit cost for test and achieve highly testable circuits by DFT using our RTL testability analysis.

Design for testability (DFT) is introduced to reduce the complexity of testing integrated circuit and help improve fault coverage. However, conventional DFT with additional 2-to-1 multiplexer (MUX) might add an increasing amount of delay and area overhead. Therefore, register transfer level (RTL) scan design is introduced to overcome this problem. This paper aims to present the development of an ASIC with RTL scan design by using multiple scan paths instead of the conventional technique, which is gate-level (GL) scan insertion to insert scan cells. This method inserts multiple scan cells by utilizing the existing multiplexer and operational units in order to reduce area overhead and delay. Besides, multiple scan paths are implemented instead of a single scan chain to reduce the complexity of the testing process, where a single scan chain has long test application times due to the high number of clock cycles for the scan chain process. RTL design is also modified by adding an extra gate for multiple scan chain insertion. The graph is derived in order to analyse the connection between registers such that the multiple scan paths can be determined accordingly. Synopsys tool is used for synthesized, placement and routing and performing automatic test pattern generation while static timing analysis is used to verify the results of the setup slack time for ASIC design. The simulation result shows that multiple scan paths insertion at RTL level has an area overhead and slack time of about 3.79% and 0.44ns less compared to multiple scan paths insertion at GL for a finite impulse response circuit with comparable high fault coverage and small delay. A comparison of the performance metrics such as area, setup slack time, and fault coverage of the multiple scan chain is done between the RTL scan and GL scan.