Jtag is an important equipment use for programming (flash) and debugging
various microcontroller series.This story is about jtag for arm microcontroller.
Nowadays normally used jtag is divided in to two interfaces. One is parallel and the
other one is USB.These two kinds of jtag have and advantage and dis-advantage that is
the USB-jtag is faster and it can connect to almost PC of today but of course it is
more expensive than parallel jtag.Parallel-jtag is an old format jtag but it can still
be used upon now with the PC that have a parallel port.

Arm jtag is also can be divided in to two group (USB and parallel).On the
market Arm jtag has a various name that is J-link , U-link , R-link.Thease kinds of
jtag is categorized depend upon the IDE that use for debugging and programming
your current arm microcontroller.As an example , suppose that you use IAR Embedded
Workbench for debugging you LPC2378 development board , in this case you much use
the J-link that is supported by IAR Embedded Workbench.The X-link that I mentioned
above is jtag that is not open-source and was invented by the microcontroller software
tools company. Arm jtag has an open source too. It is call OpenOCD.OpenOCD is one kind
of jtag that can be used to flash and debugging arm microcontroller with the free
software development tool such as Eclipse.OpenOCD also have USB or paraller interface.
To setup the IDE used for OpenOCD must integrate many tools together. Such as Eclipse as
the main IDE, arm-gcc compiler ,arm-gcc  linker and the gdb server. To read more about
OpenOCD please visit –>

http://openocd.berlios.de/web/

http://www.yagarto.de/

To select which Arm jtag that is suitable for you is based on the software IDE and
software programming and debugging tools you use to develop that arm project.But the normally Arm jtag
selection is as follow

IAR Embedded Workbench for ARM -> use J-link.
Keil MDK-ARM  , Keil uVision for ARM (ARM RealView)  -> use U-link.
Ride7  IDE  from raisonance -> use R-link (Normally used for STMicroelectronics microcontroller series) .
Open source IDE -> use OpenOCD jtag.

Below is some pictures of these various kinds of Arm jtag.

R-link from Raisonance

U-link from KEIL

J-link from IAR

OpenOCD Jtag

Thank you so much.

Related posts:

1. Good ARM usb openOCD jtag debugger and programmer
2. How about JTAG (How JTAG work)
3. NXP Cortex-M0