Joint Test Action
Joint Test Action Group (JTAG) is the common name for what was later standardized as the IEEE 1149.1 Standard Test Access Port and Boundary-Scan Architecture. It was initially devised for testing printed circuit boards using boundary scan and is still widely used for this application.
Today JTAG is also widely used for ICdebug ports. In the embedded processor market, essentially all modern processors support JTAG when they have enough pins. Embedded systems development relies on debuggers talking to chips with JTAG to perform operations like single stepping and breakpointing. Digital electronics products such as cell phones or a wireless access point generally have no other debug or test interfaces
