User's Guide: more init info, autoprobing, etc
Mention the autoprobing as a tool that may be useful when figuring out how to set up; and add a section showing how to use that mechanism (with an example). Strengthen the differences between config and run stage descriptions; add a section for the latter. Mention Dragonite. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
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David Brownell
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@ -725,6 +725,13 @@ than the target config file, as in the AT91SAM7X256 example.
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That's because there is no external memory (flash, DDR RAM), and
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the board differences are encapsulated by application code.
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@item Maybe you don't know yet what your board looks like to JTAG.
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Once you know the @file{interface.cfg} file to use, you may
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need help from OpenOCD to discover what's on the board.
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Once you find the TAPs, you can just search for appropriate
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configuration files ... or write your own, from the bottom up.
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@xref{Autoprobing}.
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@item You can often reuse some standard config files but
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need to write a few new ones, probably a @file{board.cfg} file.
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You will be using commands described later in this User's Guide,
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@ -1533,6 +1540,8 @@ may access or activate TAPs.
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After it leaves this stage, configuration commands may no
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longer be issued.
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@section Entering the Run Stage
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The first thing OpenOCD does after leaving the configuration
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stage is to verify that it can talk to the scan chain
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(list of TAPs) which has been configured.
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@ -1545,10 +1554,18 @@ Common errors include using an initial JTAG speed that's too
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fast, and not providing the right IDCODE values for the TAPs
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on the scan chain.
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Once OpenOCD has entered the run stage, a number of commands
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become available.
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A number of these relate to the debug targets you may have declared.
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For example, the @command{mww} command will not be available until
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a target has been successfuly instantiated.
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If you want to use those commands, you may need to force
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entry to the run stage.
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@deffn {Config Command} init
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This command terminates the configuration stage and
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enters the normal command mode. This can be useful to add commands to
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the startup scripts and commands such as resetting the target,
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enters the run stage. This helps when you need to have
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the startup scripts manage tasks such as resetting the target,
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programming flash, etc. To reset the CPU upon startup, add "init" and
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"reset" at the end of the config script or at the end of the OpenOCD
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command line using the @option{-c} command line switch.
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@ -2791,6 +2808,75 @@ for querying the state of the JTAG taps.
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@end quotation
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@end deffn
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@anchor{Autoprobing}
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@section Autoprobing
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@cindex autoprobe
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@cindex JTAG autoprobe
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TAP configuration is the first thing that needs to be done
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after interface and reset configuration. Sometimes it's
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hard finding out what TAPs exist, or how they are identified.
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Vendor documentation is not always easy to find and use.
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To help you get past such problems, OpenOCD has a limited
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@emph{autoprobing} ability to look at the scan chain, doing
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a @dfn{blind interrogation} and then reporting the TAPs it finds.
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To use this mechanism, start the OpenOCD server with only data
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that configures your JTAG interface, and arranges to come up
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with a slow clock (many devices don't support fast JTAG clocks
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right when they come out of reset).
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For example, your @file{openocd.cfg} file might have:
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@example
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source [find interface/olimex-arm-usb-tiny-h.cfg]
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reset_config trst_and_srst
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jtag_rclk 8
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@end example
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When you start the server without any TAPs configured, it will
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attempt to autoconfigure the TAPs. There are two parts to this:
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@enumerate
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@item @emph{TAP discovery} ...
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After a JTAG reset (sometimes a system reset may be needed too),
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each TAP's data registers will hold the contents of either the
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IDCODE or BYPASS register.
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If JTAG communication is working, OpenOCD will see each TAP,
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and report what @option{-expected-id} to use with it.
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@item @emph{IR Length discovery} ...
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Unfortunately JTAG does not provide a reliable way to find out
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the value of the @option{-irlen} parameter to use with a TAP
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that is discovered.
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If OpenOCD can discover the length of a TAP's instruction
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register, it will report it.
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Otherwise you may need to consult vendor documentation, such
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as chip data sheets or BSDL files.
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@end enumerate
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In many cases your board will have a simple scan chain with just
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a single device. Here's what OpenOCD reported with one board
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that's a bit more complex:
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@example
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clock speed 8 kHz
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There are no enabled taps. AUTO PROBING MIGHT NOT WORK!!
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AUTO auto0.tap - use "jtag newtap auto0 tap -expected-id 0x2b900f0f ..."
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AUTO auto1.tap - use "jtag newtap auto1 tap -expected-id 0x07926001 ..."
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AUTO auto2.tap - use "jtag newtap auto2 tap -expected-id 0x0b73b02f ..."
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AUTO auto0.tap - use "... -irlen 4"
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AUTO auto1.tap - use "... -irlen 4"
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AUTO auto2.tap - use "... -irlen 6"
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no gdb ports allocated as no target has been specified
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@end example
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Given that information, you should be able to either find some existing
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config files to use, or create your own. If you create your own, you
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would configure from the bottom up: first a @file{target.cfg} file
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with these TAPs, any targets associated with them, and any on-chip
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resources; then a @file{board.cfg} with off-chip resources, clocking,
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and so forth.
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@node CPU Configuration
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@chapter CPU Configuration
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@cindex GDB target
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@ -2923,15 +3009,15 @@ At this writing, the supported CPU types and variants are:
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@itemize @bullet
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@item @code{arm11} -- this is a generation of ARMv6 cores
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@item @code{arm720t} -- this is an ARMv4 core
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@item @code{arm720t} -- this is an ARMv4 core with an MMU
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@item @code{arm7tdmi} -- this is an ARMv4 core
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@item @code{arm920t} -- this is an ARMv5 core
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@item @code{arm926ejs} -- this is an ARMv5 core
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@item @code{arm920t} -- this is an ARMv5 core with an MMU
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@item @code{arm926ejs} -- this is an ARMv5 core with an MMU
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@item @code{arm966e} -- this is an ARMv5 core
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@item @code{arm9tdmi} -- this is an ARMv4 core
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@item @code{avr} -- implements Atmel's 8-bit AVR instruction set.
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(Support for this is preliminary and incomplete.)
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@item @code{cortex_a8} -- this is an ARMv7 core
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@item @code{cortex_a8} -- this is an ARMv7 core with an MMU
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@item @code{cortex_m3} -- this is an ARMv7 core, supporting only the
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compact Thumb2 instruction set. It supports one variant:
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@itemize @minus
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@ -2941,6 +3027,7 @@ SRST, to avoid a issue with clearing the debug registers.
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This is fixed in Fury Rev B, DustDevil Rev B, Tempest; these revisions will
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be detected and the normal reset behaviour used.
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@end itemize
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@item @code{dragonite} -- resembles arm966e
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@item @code{fa526} -- resembles arm920 (w/o Thumb)
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@item @code{feroceon} -- resembles arm926
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@item @code{mips_m4k} -- a MIPS core. This supports one variant:
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