How about JTAG (How JTAG work)

JTAG stands for Joint Test Action Group and it is a standard to test integrated circuit (IC) connections. Suppose on a board, you have used integrated circuit and similar devices where each IC has hundreds of pins, it becomes very essential to examine connections and confirm the operation. For this purpose, you need a small tool called JTAG. Therefore, JTAG can be defined as a process to test connections on PCBs that are applied at the level of integrated circuit. JTAG is very useful for testing such connections and there are quite a few reasons for that. Using the customary in-circuit testers, it is quite tough to test the intricate circuits. These testers are unable to access BGA devices and small components and the physical space required by these devises also plays a limitation factor. On top of that, board testing has become quite expensive and all these factors ensure that JTAG is the best solution to triumph over the intricacies related with physical in-circuit testers.There is no need to use any physical probes for testing interconnects amid a board’s built-in circuits. This is definitely a great plus for using JTAG, as there is no need for any added personalized testing tool.

How JTAG works
If you have a JTAG enabled device with a boundary-scan cell for every pin, you can test the interconnects between integrated circuits easily. A boundary-scan cell is capable of reading and setting data of all the pins. With the device, you can connect the boundary-scan cells and start to transfer the data serially into the cells. Scan chain or scan path controls this process of serial shifting of data and this is the major functionality of JTAG interface.

JTAG interface
Generally, huge number of test vectors is required to initialize the entire devices. If you are using JTAG, there is no such need. The three major benefits of using JTAG devices are bigger diagnostic competence and higher test coverage, shorter time for testing, and minimum cost of equipments. This is not all, JTAG is also very useful in the electronics industry. JTAG has great usage in the filed of programming and debugging. Several FLASH memories, microcontrollers, FPGAs and comparable devices can be programmed by using the JTAG interface. Same interface can be used for the debugging purpose as well. Therefore, JTAG interface is a boon to the electronics industry. Even though plenty of variations abound with the JTAG header on the board, it is not a complex process. Any JTAG interface is compatible with the standard JTAG signals and boundary-scan software.

JTAG connectors for games
You can also use JTAG connector to play Xbox 360. Playing game is loved by almost everyone as it is one of the best pass-time activities and stress buster. You can choose from a diverse selection of games, but the problem could be high price factor. You can make use of JTAG connector and play full games without playing full money. The JTAG cable can establish connection with USB or any parallel port of your computer for excellent connectivity and access.

Below is the video introduce about JTAG boundary scan

This article is only the introduction of JTAG , if you want to study in deep about jtag , please visit the following urls…

The Role of JTAG in system debug & test throughout the embedded system development lifecycle
JTAG tutorial from Corelis
JTAG tutorial in PDF format from Amontec

Thank you very much

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What is jtag and how about arm jtag.

Today the story is about JTAG for arm microcontroller.

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 –>



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

R-link from Raisonance

U-link from KEIL

U-link from KEIL

J-link from IAR

J-link from IAR

OpenOCD Jtag

OpenOCD Jtag

Thank you so much.

Good ARM usb openOCD jtag debugger and programmer

Today I write an article about the JTAG for ARM.It is an open-source JTAG or openOCD. The article below is the introduction of the good JTAG I found from www.sparkfun.com website (It was made from OLIMEX).

ARM USB openOCD JTAG is a device that used for debugging the ARM series microcontroller, it also can be used as the programmer too. This ARM USB openOCD JTAG is combined with RS232 virtual COM port and power supply adapter. This item allow you to debug your ARM boards with full featured virtual RS232 port with all modem signals on it. It also have a power jack that can provide the tree range voltage that is  5V , 9V and 12V DC via jumper selection. It include the CD that contain the software neccessary to perform the ARM development and debugging with this USB openOCD such as

– Eclipse IDE using Yagarto and Codesourcery as toolchains.

– ARM USB openOCD driver for Windows.

– Various ARM sample project (include source code) that can use the ARM USB openOCD as the debugger and programmer.

– A good documents and instruction about how to use this ARM USB openOCD with Eclipse IDE .

– Other utilities software that can be used to integrate with the ARM development IDE and can work together with ARM USB openOCD (such as CYGWIN GNU  C/C++ compiler,  GNUARM GNU C/C++ compiler).

– OpenOCD for JTAG debugging software.

(*almost the software list above is open-source)

– This item can be used with the CrossWorks for ARM development IDE too. Please visit the Olimex website for more information about how to use it with CrossWorks for ARM.

For more information about its hardware specifications, you can visit the two links below.



For the person who develop ARM project on an open-source platform, This JTAG would be suitable for you.


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