JTAG - Joint Test Action Group
A standard (see "IEEE Standard 1149.1") that defines how to control the
pins of
JTAG compliant devices.
Here:
An on-chip debug interface supported by a special hardware port on
some processors. It allows to take full control over the
CPU with
minimal external hardware, in many cases eliminationg the need for
expensive tools like In-Circuit-Emulators.
