JTAG (Joint Test Action Group)
JTAG (Joint Test Action Group) is a standard for testing and debugging integrated circuits (ICs) and electronic devices. Officially known as IEEE 1149.1, JTAG provides a way to test hardware components at the board and chip level without requiring physical probes.

How JTAG Works:
JTAG uses a Test Access Port (TAP) with four or five pins for communication. Devices connected via JTAG form a "scan chain," allowing a single interface to control and test multiple devices sequentially.

Key Features:

Boundary Scan Testing: Verifies connections between ICs on a PCB without requiring physical access to each pin.
In-System Programming (ISP): Allows firmware updates directly on the board.
Debugging: Enables developers to monitor and manipulate the state of a processor or microcontroller in real time.
JTAG is widely used in manufacturing for quality assurance, in embedded systems for debugging, and in FPGA/ASIC development for programming and testing. Its versatility has made it indispensable in hardware development and maintenance.