query about JTAG

[Caleb]

 hello engineersgarge,

i went to the article JTAG disablin it is a very nice article about JTAG…

http://www.engineersgarage.com/embedded/avr-microcontroller-projects/disable-jtag-port

 

but how to enable it again… and when we have to disable the JTAG for a new IC why at all this provision is provided in AVR.. what is the use of JTAG….

 

one more query… i the link given above… in the code section

 

/*Now diable JTAG port*/

 

	MCUCSR|=(1<<JTD);		// sendig 1 to JTD
	MCUCSR|=(1<<JTD);

 

 

why this part is given twice… i wan’t able to try this because i already disabled the JTAG and i don’t know how to enable this….

[Amit Joshi]

 the above instrustion dosen’t make ur JTAG permanantly.

this will enable if u burn another program without above instrustion the JTAG will enable .

to permantly enable disable u have to confogure the fusebits.

[Caleb]

sir you mean to say if i include the code part in my code that will disable the JTAG for that that code and if i permanently want to disable the JTAG i have to follow the above method using cmd…

 

k sir i understood tht…

 

sir one more thing you told in your reply that we have to configure fusebits what are they… is JTAG is a part of fuse bits….

 

and sir how to enable my device JTAG again so that i can practice it one more time…..

 

thanks in advance for your reply….

[Amit Joshi]

if ur working on high frequency external clock the following fuse bit setting can be use for your Atmega16

 

to enable JTAG =0x89FF

to enable JTAG =0xC9FF

[Author]

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