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User's Guide: more semihosting info 

List it in the concept index, in the section about target software
changes a project might want to consider, and in the section about
debug messaging.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
This commit is contained in:
David Brownell 2009-12-04 10:11:31 -08:00
parent 146e841fc9
commit acd6d33994
1 changed files with 21 additions and 2 deletions
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doc/openocd.texi
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@ -873,6 +873,20 @@ handling issues like:
@itemize @bullet
@item @b{ARM Semihosting}...
@cindex ARM semihosting
When linked with a special runtime library provided with many
toolchains@footnote{See chapter 8 "Semihosting" in
@uref{http://infocenter.arm.com/help/topic/com.arm.doc.dui0203i/DUI0203I_rvct_developer_guide.pdf,
ARM DUI 0203I}, the "RealView Compilation Tools Developer Guide".
The CodeSourcery EABI toolchain also includes a semihosting library.},
your target code can use I/O facilities on the debug host. That library
provides a small set of system calls which are handled by OpenOCD.
It can let the debugger provide your system console and a file system,
helping with early debugging or providing a more capable environment
for sometimes-complex tasks like installing system firmware onto
NAND or SPI flash.
@item @b{ARM Wait-For-Interrupt}...
Many ARM chips synchronize the JTAG clock using the core clock.
Low power states which stop that core clock thus prevent JTAG access.
@ -5675,6 +5689,7 @@ speeds, like the 32kHz startup clock of an AT91RM9200.
@end deffn
@deffn Command {arm7_9 semihosting} [@option{enable}|@option{disable}]
@cindex ARM semihosting
Display status of semihosting, after optionally changing that status.
Semihosting allows for code executing on an ARM target to use the
@ -6049,8 +6064,12 @@ This finishes by listing the current vector catch configuration.
@cindex tracing
@cindex libdcc
@cindex DCC
OpenOCD can process certain requests from target software. Currently
@command{target_request debugmsgs}
OpenOCD can process certain requests from target software, when
the target uses appropriate libraries.
The most powerful mechanism is semihosting, but there is also
a lighter weight mechanism using only the DCC channel.
Currently @command{target_request debugmsgs}
is supported only for @option{arm7_9} and @option{cortex_m3} cores.
These messages are received as part of target polling, so
you need to have @command{poll on} active to receive them.