How to do a good job in FPGA quality control and testing？

With the explosive development of digital and intelligent equipment, FPGA products with higher reliability and integration have successfully replaced the traditional stacked electronic component design method and applied it to equipment design by relying on their own custom programming design, repeatability revision and other characteristics. In the future electronic information field, the trend of hardware equipment software design is irreversible. It can be said that as long as there is hardware, there will inevitably be the presence of FPGA. In this issue's Expert Interview column, Qi Yue, Deputy Director of Testing Technology for Radio and Television Measurement Software, is invited to deeply analyze FPGA quality control and testing, helping enterprises improve FPGA testing efficiency and design quality

What are the main application areas of FPGA software?

FPGA, also known as Field Programmable Gate Array, translates to Field Programmable Gate Array in Chinese. It is an integrated chip mainly composed of digital circuits and belongs to one of the programmable devices. FPGA emerged as a semi custom circuit in the field of ASIC (Application Specific Integrated Circuit), with the ability to reprogram infinitely. By reconfiguring prefabricated gate circuits, flip flops, and programmable wiring resources, it can achieve any logic function, greatly improving the flexibility of integrated circuits. It not only solves the lack of flexibility in custom circuits, but also overcomes the disadvantage of small gate circuit capacity in original programmable devices.

Therefore, the application direction of FPGA is very extensive. In terms of application fields, FPGA has been widely used in many fields such as high-speed communication, data processing, industrial control, special equipment, and aerospace.

Why evaluate FPGA software?

According to the requirements for the testing and identification of a certain product by the relevant unit, FPGA should be included in the software list for management and included in the scope of software testing requirements assessment. Key or important FPGAs should undergo targeted testing such as code rule inspection, functional simulation, and timing verification.. So according to the above documents, all FPGA software in the equipment must undergo internal testingthird-party evaluationappraisal evaluation.

What are the challenges facing FPGA software testing?

FPGA software includes programs, documents, and data generated from design, as well as related software and hardware features. FPGA software testing needs to consider comprehensive coverage of software code correctness, software hardware interface coordination, timing, and other aspects. FPGA can work stably and reliably, and not only does its function need to meet the requirements, but also its timing and safety indicators need to meet the requirements.

Different FPGA chip manufacturers, operating voltage and temperature conditions can result in significant differences in FPGA timing, often leading to errors during FPGA execution. Therefore, FPGA testing needs to verify not only the software characteristics of the FPGA, but also whether the hardware characteristics of the FPGA chip, as well as the impact of voltage and temperature on timing and other environmental characteristics, meet the requirements. Therefore, FPGA software testing includes comprehensive testing of FPGA software characteristics, hardware characteristics, and environmental characteristics.

What are the contents and processes of FPGA software testing?

The FPGA development process is complex, and from front-end design code to final generation of configuration bitstream files, there is a possibility of introducing design defects. Therefore, in the field of safety critical, the independent evaluation process of FPGA software covers various key nodes generated by RTL code into bitstream files, and various methods are used at different levels to confirm software functionality, interfaces, timing, and performance.

The main testing methods include encoding rule check, cross clock check, functional simulation, gate level simulation, timing simulation, power consumption analysis, logic equivalence check, etc. The testing process mainly includes

1. Conduct testing requirement analysis based on software requirements to ensure 100% coverage of software requirements during testing.
2. Conduct encoding rule checks and functional simulation tests on RTL level code to verify the correctness of FPGA front-end design.
3. Conduct logical equivalence testing on the gate level netlist files after logical synthesis to verify the reliability and consistency of logical synthesis.
4. Conduct static timing analysis and timing simulation testing on the wiring network table after layout and routing, to verify whether the timing path of FPGA backend design converges.
5. Conduct board level physical testing on the target device after burning and downloading to verify the correctness of FPGA device functionality.
6. Use professional tools to check the consistency between the FPGA front-end hardware description design and the back-end sequential circuit logic.

How to improve the efficiency and accuracy of FPGA testing?

1. Using automated testing tools Automated testing tools can significantly improve testing efficiency and reduce human error.
2. Optimize testing strategy Based on the specific application scenarios and specification requirements of FPGA, develop targeted testing strategies to improve the effectiveness and accuracy of testing.
3. Strengthen on board testing On board testing can better simulate actual working conditions and help identify potential problems.
4. Strengthen reliability assessment By improving the accelerated aging test method and introducing more stress factors in practical work scenarios, the accuracy of reliability assessment can be improved.
5. Strengthen simulation testing adopt more accurate simulation models and more comprehensive scene coverage to improve the effectiveness of simulation testing.

How to improve the quality and reliability of FPGA software design?

FPGA quality improvement is a system engineering that covers the entire process of design, validation, implementation, and testing. Below, we will introduce several key links in detail

1. Quality assurance during the design phase

Modular design Adopting a modular design approach helps improve code readability and reusability, and simplifies later maintenance. Each module should have a clear functional definition and follow good design principles.

Resource optimization Reasonably allocate logical resources, memory resources, and wiring resources based on specific application requirements, reduce power consumption and improve performance through algorithm optimization and architecture selection.

RTL Design Specification Write HDL code in accordance with industry standards and best practices to ensure consistent code style and ease of understanding by comprehensive tools, avoiding potential timing issues.

2. Strengthen the verification process

Functional simulation Conduct detailed functional simulation verification in the early stages to ensure that the design meets specification requirements and covers all possible states and boundary conditions.

Formal verification Using formal methods to verify the correctness of the design, including equivalence checks, attribute checks, and model checks, to reduce problems introduced due to traditional simulation omissions.

Static Timing Analysis (STA) Strictly perform STA after layout and routing to ensure that the design meets the specified timing constraints and prevent functional failures caused by clock skew and delay mismatch.

3. Enhanced reliability design

Redundancy technology use the third mock examination Redundancy (TMR), Error Correction Code (ECC) or other fault tolerance mechanisms to improve the anti error capability of the system.

Built in Self Test (BIST) Integrated self-test circuit that can detect hardware failures during operation, enhancing the on-site reliability of the product.

Soft Error Protection Adopt appropriate Soft Error Rate (SER) protection strategies for radiation effects and other non permanent faults.

4. Hardware implementation and signature

Integration and optimization Select high-performance comprehensive tools and adjust their parameters to obtain the optimal layout and routing results, while considering resource utilization, speed, and power.

Physical Design Verification Conduct a comprehensive physical design verification on the completed layout and routing design, including DRC (Design Rule Check) and LVS (Layout Versus Schematic), to ensure that the design meets process requirements.

In summary, improving the quality of FPGA design involves many aspects, and it is necessary to combine advanced design concepts, rigorous verification methods, and scientific testing methods throughout the entire development cycle in order to ultimately create highly reliable FPGA products.