IEEE 1149.1, also known as the Joint Test Action Group (JTAG) standard, is a technical standard for testing and debugging electronic circuits. It provides a method for accessing and controlling the internal components of a device through a serial communication interface. This allows engineers to perform boundary-scan testing, which helps identify faults in integrated circuits and printed circuit boards. The standard defines a set of test access ports and protocols that enable the testing of interconnections between chips on a board without physical probes. By using IEEE 1149.1, manufacturers can improve the reliability of their products and reduce the time and cost associated with testing and debugging electronic systems.