Testability design, as a key concept in the field of modern electronic technology, plays a vital role in the development and production of integrated circuits. The aim is to improve the testability of electronic devices to detect and troubleshoot more effectively. This article will delve into the importance of design for testability and the approaches in different use cases, including boundary scan design, built-in self-test, IEEE 1149.1 structure and JTAG, memory built-in self-test (MBIST), and logic built-in self-test (LBIST).
Background on measurability design
In the field of modern electronic technology, integrated circuits have become the core components of various electronic devices, from smartphones to computers and car control systems. The increasing complexity and density of these integrated circuits makes testing and troubleshooting more challenging. The concept of design for testability was developed to make electronic devices easier to test and repair.
The goal of design for testability is to improve the testability of electronic devices to ensure that faults can be detected and troubleshot quickly and accurately during production and repair. This helps reduce manufacturing costs, improve product quality, and reduce repair time. Different use cases require different approaches to design for testability, and we'll explore each of these methods and how they work.
Boundary scan design
Boundary scan design is a testability design method that is primarily used to test the interconnect lines of printed circuit boards. In a boundary scan design, the designer adds a specialized scan link to the circuit to allow the test device to easily access each interconnect point. These scan links include shift registers that control and monitor signals in the circuit.
The boundary scan design works by serially shifting the test mode data to the scan link and then observing the output data to detect faults. This method is ideal for detecting short circuits, open circuits, and other interconnect faults in interconnect lines. Boundary scan design has become one of the standard methods for printed circuit board manufacturing because it can efficiently detect and troubleshoot interconnect issues.
IEEE 1149.1 structure and JTAG
IEEE 1149.1 is an electronic test standard that defines a test architecture that includes a test access port (TAP) controller and register bank. This standard, also known as JTAG (Joint Test Action Group), has become a key component of design for testability.
The TAP controller is responsible for managing the test access ports, which include the Test Clock (TCK), Test Mode Selection (TMS), Test Data Input (TDI), Test Data Output (TDO) and Test Reset (TRST). These ports allow the test device to communicate with the circuit to perform test operations.
The IEEE 1149.1 structure and the use of JTAG can greatly simplify the testing process and improve testing efficiency. They allow test equipment to easily access parts of a circuit by scanning the link, perform automated tests, and generate test reports. This method is particularly useful in the testing of complex circuits.
Memory Built-in Self-Test (MBIST)
Memory Built-in Self-Test (MBIST) is a testability design approach specifically designed to test memory cells, such as RAM and ROM. The self-testing structure built into the memory includes a test pattern generator and comparator, as well as fault detection logic.
MBIST works by generating a test vector using a pseudo-random stimulus generator, loading it into a memory cell, and then comparing the actual output to the desired output. Through the comparison process, a variety of different types of memory failures can be detected, including fixed faults, rollover faults, and coupling faults.
The MBIST method is efficient, automated, and reproducible, making it suitable for large-scale memory testing. It increases test speed and reliability while reducing reliance on automated test equipment.
Logic Built-in Self-Test (LBIST)
Logic built-in self-test (LBIST) is a testability design method used primarily to test digital logic circuits. The structure of LBIST includes a pseudo-random excitation generator and comparator, as well as fault detection logic. The LBIST method uses a pseudo-random stimulus generator to generate a test vector, load it into a logic circuit, and then compare the actual output with the desired output.
The advantage of LBIST is that it reduces the reliance on automated test equipment while increasing test speed and reliability. It is suitable for testing a wide range of digital logic circuits, from microprocessors to communication devices.
A summary of the measurability design
Design for testability is a key concept in the field of modern electronics, which plays an important role in the development and production of electronic devices. Different use cases require different approaches to design for testability, including boundary scan design, built-in self-test, IEEE 1149.1 structure and JTAG, memory built-in self-test (MBIST), and logic built-in self-test (LBIST).
These methods all contribute to improving the testability of electronic devices, which can reduce manufacturing costs, improve product quality, and reduce repair time. As technology continues to evolve, we can expect design for testability to play an increasingly important role in the field of electronics, providing better support for the reliability and performance of electronic devices.