Lpc2000

Reading this note, I realize I need to be clearer: my debug environment
does experience intermittent periods of lucidity where everything does
work flawlessly.  I am just desperately trying to find cause and effect
on how to get into this mode and stay there reliably.
 
-----Original Message-----
From: James Dabbs [mailto:jdabbs@...] 
Sent: Wednesday, May 12, 2004 6:13 AM
To: lpc2000@yahoogroups.com
Subject: RE: [lpc2000] Secondary JTAG Mood Swing



Hugh,
 
I did read this; it was very helpful.  My debug process is very similar
to this except that my "initial load" is through UART0 using the ISP
features of the chip.  My code sets JTAG2 and then spins.
 
However, either (1) I am making some mistake that I do not realize, or
(2) there is some kind of intermittent hardware problem with the
secondary JTAG port or, (3) the secondary JTAG port does not work
reliably with the Nohau debugger.  For the most part, the debugger
cannot find the chip at all.  Finally, once it can see the chip, I *can*
download code through JTAG2.  But single-stepping or setting a
breakpoint and running causes nonsensical behavior as seen through the
debugger.  Also, I can not determine any logical cause-and-effect as to
how or when the debugger will be able to find the chip at all.  My
working assumption right now is that the JTAG2 interface is not being
reliably activiated.
 
-James

-----Original Message-----
From: Hugh O'Keeffe [mailto:hugh.okeeffe@...] 
Sent: Wednesday, May 12, 2004 4:08 AM
To: lpc2000@yahoogroups.com
Subject: RE: [lpc2000] Secondary JTAG Mood Swing


Hi James,
For the full scoop on the secondary debug port see our on-line faq at
<http://www.ashling.com/support/lpc2000/knowledge_base.html>
http://www.ashling.com/support/lpc2000/knowledge_base.html. Look for the
note titled "
<http://www.ashling.com/support/lpc2000/knowledge_base.html#> How do I
use the LPC201x secondary debug port? "
 
HTH,



Hugh @  <http://www.ashling.com/support/lpc2000/>
http://www.ashling.com/support/lpc2000/ 

-----Original Message-----
From: James Dabbs [mailto:jdabbs@...] 
Sent: 12 May 2004 04:59
To: lpc2000@yahoogroups.com
Subject: [lpc2000] Secondary JTAG Mood Swing


I am using the secondary JTAG port to debug my target (LPC2106 Target;
Nohau Debugger)  Initially, I flashed the part through the serial port
using ISP, loading some code that enabled the secondary JTAG port, then
started using the secondary port.  Sometimes this port works, sometimes
it doesn't, and this state seems to be 'sticky' in that it persists
beyond reset and power cycling.  I've read through a couple of threads
here on the subject, and see some mention that there may be a design
flaw in the secondary JTAG port.  I can find no mention of this beyond
this group, though.

SO..

1. Is there a flaw with this port that makes it unreliable in some way?

2. Is there more information beyond AN10255 that discusses how to use
the secondary JTAG port?

3. Are there limitations to the use of the secondary JTAG port?

Any help would be greatly appreciated.

Thanks,

James Dabbs, TGA






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