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Sun May 29 19:39:03 CEST 2011

AT91SAM7 back channel

Are the DBGU ports/registers accessible through JTAG in monitor mode?

Data sheet SAM7S 12.6.1

* Find out what monitor mode does (as opposed to HALT mode) [1]

* What are COMMTX and COMMRX signals.  

I'm browsing [1] looking for monitor mode at 5.9 and I find debug
communication channel (DCC) at 5.8.  Maybe that's what I'm looking
for.

Googling for '"coprocessor 14" openocd' I get [2].  On the ARM side
it's just a MCR / MRC instruction.  On the host side it's scan chain
2.

Is this the same DCC as in "dcc downloads" ?  Indeed.  This mechanism
is already used; I've found some ARM code so it looks like it places
some code in RAM to handle the other side.  Cool.

It has some setup code in arm7_9_common.c and the bulk in
embeddedice.c (embeddedice_write_dcc)

So this _should_ definitely be workable.  How to go about it then?



[1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0210c/I901036.html
[2] http://openocd.berlios.de/doc/html/Architecture-and-Core-Commands.html




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