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JTAG basics... Help me!

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Jul 20, 2009
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jtag basics

Hi guys,

I need to clarify some things from JTAG basics.

What is JTAG?

What is the use of JTAG connection in flashing tools like MSP430 FET?

What are the types of JTAG interfaces with reference to the above question ?

Looking forward for ur reply.
Thanks & regards

what is jtag

JTAG along with its apt software (eg IAR) is a programmer and debugger tool that is used to burn the code to the micorcontroller. It is powered with USB and has a 20 pin connector.

I hope it was useful.


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Thanks for the help ankita.

Can u elaborate some more on that?
I would like to know abt the internal working of JTAG

Basically, JTAG is a loading and debugging tool.
It can be RS232 or USB connected.

It takes in the Asynchronous data from the PC and converts to synchronous data. The clock rate is at the microcontroller rate ur using.
During loading microcontroller internal oscillator is used. This is the reason why even though ur external oscillator is not running ur program gets loaded.

JTAG basically uses another microcontroller. Every manufacturer has their own JTAGS which include microcontroller of their own make. That is the min reason why JTAGS are not universal.

If u can observe the pin outs of microcontroller which are connected to JTAG interface, we have CLK, DATA, RST.
RST will be applied which leads the controller to execute bootloader section and from then on program gets loaded.


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JTAG (named after its developers, Joint Test Action Group) was a test procedure that has morphed into a full blown IEEE specification that defines a "Boundry-Scan" test methodology. Hardware is added inside the part (as with MSP430) to allow access to its internal workings (the JTAG interface). Outside the part another interface is required to connect JTAG to a PC (as with a JTAG programmer).
A program run on the PC then allows access to inside the part for testing, troubleshooting, and programming.

There's an excellent tutorial on the subject at:

HI All

I need to control JTAG using Pattern Generator . Can somebody help me ????

Thanks in advance

Ateet Omer said:
HI All

I need to control JTAG using Pattern Generator . Can somebody help me ????

Thanks in advance

Maybe JTV can help you! Please google "SiliconAid JTV", Hope to help you!

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