What does JTAG mean in IEEE

JTAG, or Joint Test Action Group, is an industry-standard interface that provides access to an integrated circuit’s internal testing and debugging features. It is used for on-chip debugging, remote system bringup, and boundary scan test. With JTAG you can test the design functionality of digital systems before they are built, as well as diagnose and repair faults that occur during manufacture or operation.

By using JTAG, it is possible to detect flaws in logic circuits before boards are even fabricated. This saves time and money in the development process because errors can be quickly identified and corrected without having to resort to costly board revisions. Additionally, the use of JTAG enables system designers to easily make changes in their designs with the ability to quickly verify logic functions by running tests from a remote computer.

The basic principle behind JTAG technology is simple; it consists of a communications interface connected between the device being tested and a controller circuitry which drives specific test patterns into selected pins within the target device. These patterns include various sequences of clock pulses, data bits, control signals and other information required for testing or programming an IC's behavior or debugging its operation. The controller analyzes responses from the device and provides feedback on its current state or condition accordingly.

The original Joint Test Action Group (JTAG) standards were developed in 1985 by representatives from four companies; Intel Corporation (USA), Motorola Semiconductor Products Sector (USA), Philips Semiconductors (The Netherlands), Digital Equipment Corporation (USA). The goal was to standardize how tests could be managed across a multitude of IC technologies so that automated test equipment could be used on various integrated circuits manufactured by different vendors.

Most types of Integrated Circuits (IC’s) benefit from using this system but some more than others; devices with complex logic including microcontrollers such as ARM processors are best served by Having access to all pins along with support for I/O pin multiplexing and memory mapping support makes them ideal candidates for debugger connections via this protocol.

Broadly speaking, there are five main application areas where this technology has become indispensable; debuggers / emulators, board bringup & simulation aids, production & manufacturing test systems, functional / performance benchmarking against known standards, emulation systems. Generally speaking if you need reliable access into a chip then activating this interface can provide you with enough access to accurately navigate your way around all its components and functions.

Boundary Scan enables testing at the board level not just at component level with minimal external hardware. It uses IEEE 1149.1 1-Wire Serial Bus scheme embedded inside chips which enable register based I/O controls over dedicated test points allowing very limited number of external testers attached directly onto these taken via short cables linked only within handful inches outside each chip.