Lpc2000

Jayasooriah wrote:

>Dominic, I do not think this is the threat the designers were defending.
>  
>
>>You can't access the JTAG port while the device is in reset, because the 
>>LPCs keep the test logic in reset, too.
>>    
>>
>
>I am curious if this is stated anywhere or if you determined this by 
>experiment.  Note, besides ETM chain, there is also a processor chain that 
>can be accessed.
>
>  
>
Understandably, Philips does not go into detail as to how JTAG operates, 
this is an IEEE spec now and documents are available elsewhere. JTAG is 
very very well documented: Joint Test / Action Group.  JTAG is not a 
"secret" but was created in response to a growing problem in the ATE 
(Auto Test Engineering) and software development arena in dealing with 
more complex processors.

This link would get you started into understanding JTAG:
http://klabs.org/richcontent/old_news/old_news_7/old_news_7.htm

TomW



-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
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