what is jtag?

Answer 1

JTAG, an acronym for Joint Test Action Group, is the usual name used for the IEEE 1149.1 standard entitled Standard Test Access Port and Boundary-Scan Architecture for test access ports used for testing printed circuit boards using boundary scan.

JTAG was standardized in 1990 as the IEEE Std. 1149.1-1990. In 1994, a supplement that contains a description of the boundary scan description language (BSDL) was added. Since then, this standard has been adopted by electronics companies all over the world. Boundary-scan is nowadays mostly synonymous with JTAG.

While designed for printed circuit boards, it is nowadays primarily used for testing sub-blocks of integrated circuits, and is also useful as a mechanism for debugging embedded systems, providing a convenient "back door" into the system. When used as a debugging tool, an in-circuit emulator which in turn uses JTAG as the transport mechanism enables a programmer to access an on-chip debug module which is integrated into the CPU via JTAG. The debug module enables the programmer to debug the software of an embedded system

Answer 2

Hello,

Basically, JTAG is standard for microcontrollers and processors to use for in-circuit debugging and run-time analysis on the hardware (by allowing to 'peek' into the memory and interface regions of the unit on the fly, or even modify the contents of memory). Can be also used to program/read devices which support this standard.

See more here:

http://en.wikipedia.org/wiki/JTAG

Regards

Answer 3

JTAG is a serial interface which is commonly used to program FPGA's and PROMs. Instead of having to use a PROM blower to load your programs into a prom you can use the JTAG interface and load it from a PC.