interesting
/
riscv-openocd
mirror of https://github.com/riscv/riscv-openocd.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

David Brownell <david-b@pacbell.net>: 

Rework the TAP creation documentation.

 - Try to use "TAP" not "tap" everywhere; it's an acronym.

 - Update the associated "target config files" section:
     * reference the "TAP Creation" chapter for details
     * simplify:  reference interesting multi-tap config files
     * let's not forget CPU configuration (*before* workspace setup)
     * streamline it a bit
     * move that workspace-vs-mmu issue to a better location

 - Clean up TAP creation doc mess
     * switch to @deffn
     * (re)organize the remaining stuff
     * reference the "Config File Guidelines" chapter

 - Tweak the "Target Configuration" chapter
     * rename as "CPU configuration"; unconfuse vs. target/*.cfg
     * bring out that it's not just there for GDB
     * move TAP events to the TAP chapter, where they belong (bugfix)


git-svn-id: svn://svn.berlios.de/openocd/trunk@2013 b42882b7-edfa-0310-969c-e2dbd0fdcd60
This commit is contained in:
zwelch 2009-06-03 00:56:50 +00:00
parent 4ecf2c7dd8
commit 5ca513a097
1 changed files with 294 additions and 256 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

550
doc/openocd.texi
View File

@ -69,8 +69,8 @@ Free Documentation License''.
* Daemon Configuration:: Daemon Configuration
* Interface - Dongle Configuration:: Interface - Dongle Configuration
* Reset Configuration:: Reset Configuration
* Tap Creation:: Tap Creation
* Target Configuration:: Target Configuration
* TAP Creation:: TAP Creation
* CPU Configuration:: CPU Configuration
* Flash Commands:: Flash Commands
* NAND Flash Commands:: NAND Flash Commands
* General Commands:: General Commands
@ -111,7 +111,10 @@ in-system programming and boundary-scan testing for embedded target
devices.
@b{JTAG:} OpenOCD uses a ``hardware interface dongle'' to communicate
with the JTAG (IEEE 1149.1) compliant taps on your target board.
with the JTAG (IEEE 1149.1) compliant TAPs on your target board.
A @dfn{TAP} is a ``Test Access Port'', a module which processes
special instructions and data. TAPs are daisy-chained within and
between chips and boards.
@b{Dongles:} OpenOCD currently supports many types of hardware dongles: USB
based, parallel port based, and other standalone boxes that run
@ -835,9 +838,12 @@ sequence to enable that external flash or SDRAM should be found in the
board file. Boards may also contain multiple targets, i.e.: Two CPUs, or
a CPU and an FPGA or CPLD.
@item @b{target}
@* Think chip. The ``target'' directory represents a JTAG tap (or
chip) OpenOCD should control, not a board. Two common types of targets
@* Think chip. The ``target'' directory represents the JTAG TAPs
on a chip
which OpenOCD should control, not a board. Two common types of targets
are ARM chips and FPGA or CPLD chips.
When a chip has multiple TAPs (maybe it has both ARM and DSP cores),
the target config file defines all of them.
@end itemize
@b{If needed...} The user in their ``openocd.cfg'' file or the board
@ -902,9 +908,9 @@ In summary the target files should contain
@enumerate
@item Set defaults
@item Create taps
@item Add TAPs to the scan chain
@item Add CPU targets
@item Reset configuration
@item Work areas
@item CPU/Chip/CPU-Core specific features
@item On-Chip flash
@end enumerate
@ -1002,7 +1008,6 @@ used at will within a ?TARGET? configuration file.
# these names still work!
network.cpu configure ... params
video.cpu configure ... params
@end example
@subsection Default Value Boiler Plate Code
@ -1028,72 +1033,62 @@ if @{ [info exists CPUTAPID ] @} @{
@} else @{
set _CPUTAPID 0x3f0f0f0f
@}
@end example
@subsection Creating Taps
After the ``defaults'' are choosen [see above] the taps are created.
@subsection Adding TAPs to the Scan Chain
After the ``defaults'' are set up,
add the TAPs on each chip to the JTAG scan chain.
@xref{TAP Creation}, and the naming convention
for taps.
@b{SIMPLE example:} such as an Atmel AT91SAM7X256
In the simplest case the chip has only one TAP,
probably for a CPU or FPGA.
The config file for the Atmel AT91SAM7X256
looks (in part) like this:
@example
# for an ARM7TDMI.
set _TARGETNAME [format "%s.cpu" $_CHIPNAME]
jtag newtap $_CHIPNAME cpu -irlen 4 -ircapture 0x1 -irmask 0xf \
-expected-id $_CPUTAPID
@end example
@b{COMPLEX example:}
A board with two such at91sam7 chips would be able
to source such a config file twice, with different
values for @code{CHIPNAME} and @code{CPUTAPID}, so
it adds a different TAP each time.
This is an SNIP/example for an STR912 - which has 3 internal taps. Key features shown:
There are more complex examples too, with chips that have
multiple TAPs. Ones worth looking at include:
@enumerate
@item @b{Unform tap names} - See: Tap Naming Convention
@item @b{_TARGETNAME} is created at the end where used.
@end enumerate
@itemize
@item @file{target/omap3530.cfg} -- with a disabled ARM, and a JRC
(there's a DSP too, which is not listed)
@item @file{target/str912.cfg} -- with flash, CPU, and boundary scan
@item @file{target/ti_dm355.cfg} -- with ETM, ARM, and JRC (this JRC
is not currently used)
@end itemize
@subsection Add CPU targets
After adding a TAP for a CPU, you should set it up so that
GDB and other commands can use it.
@xref{CPU Configuration}.
For the at91sam7 example above, the command can look like this:
@example
if @{ [info exists FLASHTAPID ] @} @{
set _FLASHTAPID $FLASHTAPID
@} else @{
set _FLASHTAPID 0x25966041
@}
jtag newtap $_CHIPNAME flash -irlen 8 -ircapture 0x1 -irmask 0x1 \
-expected-id $_FLASHTAPID
if @{ [info exists CPUTAPID ] @} @{
set _CPUTAPID $CPUTAPID
@} else @{
set _CPUTAPID 0x25966041
@}
jtag newtap $_CHIPNAME cpu -irlen 4 -ircapture 0xf -irmask 0xe \
-expected-id $_CPUTAPID
if @{ [info exists BSTAPID ] @} @{
set _BSTAPID $BSTAPID
@} else @{
set _BSTAPID 0x1457f041
@}
jtag newtap $_CHIPNAME bs -irlen 5 -ircapture 0x1 -irmask 0x1 \
-expected-id $_BSTAPID
set _TARGETNAME [format "%s.cpu" $_CHIPNAME]
target create $_TARGETNAME arm7tdmi -chain-position $_TARGETNAME
@end example
@b{Tap Naming Convention}
Work areas are small RAM areas associated with CPU targets.
They are used by OpenOCD to speed up downloads,
and to download small snippets of code to program flash chips.
If the chip includes a form of ``on-chip-ram'' - and many do - define
a work area if you can.
Again using the at91sam7 as an example, this can look like:
See the command ``jtag newtap'' for detail, but in brief the names you should use are:
@itemize @bullet
@item @b{tap}
@item @b{cpu}
@item @b{flash}
@item @b{bs}
@item @b{etb}
@item @b{jrc}
@item @b{unknownN} - it happens :-(
@end itemize
@example
$_TARGETNAME configure -work-area-phys 0x00200000 \
-work-area-size 0x4000 -work-area-backup 0
@end example
@subsection Reset Configuration
@ -1101,17 +1096,6 @@ Some chips have specific ways the TRST and SRST signals are
managed. If these are @b{CHIP SPECIFIC} they go here, if they are
@b{BOARD SPECIFIC} they go in the board file.
@subsection Work Areas
Work areas are small RAM areas used by OpenOCD to speed up downloads,
and to download small snippets of code to program flash chips.
If the chip includes a form of ``on-chip-ram'' - and many do - define
a reasonable work area and use the ``backup'' option.
@b{PROBLEMS:} On more complex chips, this ``work area'' may become
inaccessible if/when the application code enables or disables the MMU.
@subsection ARM Core Specific Hacks
If the chip has a DCC, enable it. If the chip is an ARM9 with some
@ -1800,208 +1784,273 @@ powerup and pressing a reset button.
@end deffn
@node Tap Creation
@chapter Tap Creation
@cindex tap creation
@cindex tap configuration
@node TAP Creation
@chapter TAP Creation
@cindex TAP creation
@cindex TAP configuration
In order for OpenOCD to control a target, a JTAG tap must be
defined/created.
@emph{Test Access Ports} (TAPs) are the core of JTAG.
TAPs serve many roles, including:
Commands to create taps are normally found in a configuration file and
are not normally typed by a human.
When a tap is created a @b{dotted.name} is created for the tap. Other
commands use that dotted.name to manipulate or refer to the tap.
Tap Uses:
@itemize @bullet
@item @b{Debug Target} A tap can be used by a GDB debug target
@item @b{Flash Programing} Some chips program the flash directly via JTAG,
instead of indirectly by making a CPU do it.
@item @b{Boundry Scan} Some chips support boundary scan.
@item @b{Debug Target} A CPU TAP can be used as a GDB debug target
@item @b{Flash Programing} Some chips program the flash directly via JTAG.
Others do it indirectly, making a CPU do it.
@item @b{Program Download} Using the same CPU support GDB uses,
you can initialize a DRAM controller, download code to DRAM, and then
start running that code.
@item @b{Boundary Scan} Most chips support boundary scan, which
helps test for board assembly problems like solder bridges
and missing connections
@end itemize
OpenOCD must know about the active TAPs on your board(s).
Setting up the TAPs is the core task of your configuration files.
Once those TAPs are set up, you can pass their names to code
which sets up CPUs and exports them as GDB targets,
probes flash memory, performs low-level JTAG operations, and more.
@anchor{jtag newtap}
@section jtag newtap
@b{@t{jtag newtap CHIPNAME TAPNAME configparams ....}}
@cindex jtag newtap
@cindex tap
@cindex tap order
@cindex tap geometry
@section Scan Chains
OpenOCD uses a JTAG adapter (interface) to talk to your board,
which has a daisy chain of TAPs.
That daisy chain is called a @dfn{scan chain}.
Simple configurations may have a single TAP in the scan chain,
perhaps for a microcontroller.
Complex configurations might have a dozen or more TAPs:
several in one chip, more in the next, and connecting
to other boards with their own chips and TAPs.
Unfortunately those TAPs can't always be autoconfigured,
because not all devices provide good support for that.
(JTAG doesn't require supporting IDCODE instructions.)
The configuration mechanism currently supported by OpenOCD
requires explicit configuration of all TAP devices using
@command{jtag newtap} commands.
One like this would create a tap named @code{chip1.cpu}:
@comment START options
@itemize @bullet
@item @b{CHIPNAME}
@* is a symbolic name of the chip.
@item @b{TAPNAME}
@* is a symbol name of a tap present on the chip.
@item @b{Required configparams}
@* Every tap has 3 required configparams, and several ``optional
parameters'', the required parameters are:
@comment START REQUIRED
@itemize @bullet
@item @b{-irlen NUMBER} - the length in bits of the instruction register, mostly 4 or 5 bits.
@item @b{-ircapture NUMBER} - the IDCODE capture command, usually 0x01.
@item @b{-irmask NUMBER} - the corresponding mask for the IR register. For
some devices, there are bits in the IR that aren't used. This lets you mask
them off when doing comparisons. In general, this should just be all ones for
the size of the IR.
@comment END REQUIRED
@end itemize
An example of a FOOBAR Tap
@example
jtag newtap foobar tap -irlen 7 -ircapture 0x42 -irmask 0x55
jtag newtap chip1 cpu -irlen 7 -ircapture 0x01 -irmask 0x55
@end example
Creates the tap ``foobar.tap'' with the instruction register (IR) is 7
bits long, during Capture-IR 0x42 is loaded into the IR, and bits
[6,4,2,0] are checked.
@item @b{Optional configparams}
@comment START Optional
@itemize @bullet
@item @b{-expected-id NUMBER}
@* By default it is zero. If non-zero represents the
expected tap ID used when the JTAG chain is examined. Repeat
the option as many times as required if multiple id's can be
expected. See below.
@item @b{-disable}
@item @b{-enable}
@* By default not specified the tap is enabled. Some chips have a
JTAG route controller (JRC) that is used to enable and/or disable
specific JTAG taps. You can later enable or disable any JTAG tap via
the command @b{jtag tapenable DOTTED.NAME} or @b{jtag tapdisable
DOTTED.NAME}
@comment END Optional
@end itemize
Each target configuration file lists the TAPs provided
by a given chip.
Board configuration files combine all the targets on a board,
and so forth.
Note that @emph{the order in which TAPs are created is very important.}
It must match the order in the JTAG scan chain, both inside
a single chip and between them.
@comment END OPTIONS
@end itemize
@b{Notes:}
@comment START NOTES
@itemize @bullet
@item @b{Technically}
@* newtap is a sub command of the ``jtag'' command
@item @b{Big Picture Background}
@*GDB Talks to OpenOCD using the GDB protocol via
TCP/IP. OpenOCD then uses the JTAG interface (the dongle) to
control the JTAG chain on your board. Your board has one or more chips
in a @i{daisy chain configuration}. Each chip may have one or more
JTAG taps. GDB ends up talking via OpenOCD to one of the taps.
@item @b{NAME Rules}
@*Names follow ``C'' symbol name rules (start with alpha ...)
@item @b{TAPNAME - Conventions}
@itemize @bullet
@item @b{tap} - should be used only FPGA or CPLD like devices with a single tap.
@item @b{cpu} - the main CPU of the chip, alternatively @b{foo.arm} and @b{foo.dsp}
@item @b{flash} - if the chip has a flash tap, example: str912.flash
@item @b{bs} - for boundary scan if this is a seperate tap.
@item @b{etb} - for an embedded trace buffer (example: an ARM ETB11)
@item @b{jrc} - for JTAG route controller (example: OMAP3530 found on Beagleboards)
@item @b{unknownN} - where N is a number if you have no idea what the tap is for
@item @b{Other names} - Freescale IMX31 has a SDMA (smart dma) with a JTAG tap, that tap should be called the ``sdma'' tap.
@item @b{When in doubt} - use the chip maker's name in their data sheet.
@end itemize
@item @b{DOTTED.NAME}
@* @b{CHIPNAME}.@b{TAPNAME} creates the tap name, aka: the
@b{Dotted.Name} is the @b{CHIPNAME} and @b{TAPNAME} combined with a
dot (period); for example: @b{xilinx.tap}, @b{str912.flash},
@b{omap3530.jrc}, or @b{stm32.cpu} The @b{dotted.name} is used in
numerous other places to refer to various taps.
@item @b{ORDER}
@* The order this command appears via the config files is
important.
@item @b{Multi Tap Example}
@* This example is based on the ST Microsystems STR912. See the ST
document titled: @b{STR91xFAxxx, Section 3.15 Jtag Interface, Page:
For example, the ST Microsystems STR912 chip has
three separate TAPs@footnote{See the ST
document titled: @emph{STR91xFAxxx, Section 3.15 Jtag Interface, Page:
28/102, Figure 3: JTAG chaining inside the STR91xFA}.
@url{http://eu.st.com/stonline/products/literature/ds/13495.pdf}
@*@b{checked: 28/nov/2008}
The diagram shows that the TDO pin connects to the flash tap, flash TDI
connects to the CPU debug tap, CPU TDI connects to the boundary scan
tap which then connects to the TDI pin.
Checked: 28-Nov-2008}.
To configure those taps, @file{target/str912.cfg}
includes commands something like this:
@example
# The order is...
# create tap: 'str912.flash'
jtag newtap str912 flash ... params ...
# create tap: 'str912.cpu'
jtag newtap str912 cpu ... params ...
# create tap: 'str912.bs'
jtag newtap str912 bs ... params ...
jtag newtap str912 flash ... params ...
jtag newtap str912 cpu ... params ...
jtag newtap str912 bs ... params ...
@end example
@item @b{Note: Deprecated} - Index Numbers
@* Prior to 28/nov/2008, JTAG taps where numbered from 0..N this
feature is still present, however its use is highly discouraged and
should not be counted upon. Update all of your scripts to use
TAP names rather than numbers.
@item @b{Multiple chips}
@* If your board has multiple chips, you should be
able to @b{source} two configuration files, in the proper order, and
have the taps created in the proper order.
@comment END NOTES
@end itemize
@comment at command level
Actual config files use a variable instead of literals like
@option{str912}, to support more than one chip of each type.
@xref{Config File Guidelines}.
@section Enable/Disable Taps
@b{Note:} These commands are intended to be used as a machine/script
interface. Humans might find the ``scan_chain'' command more helpful
when querying the state of the JTAG taps.
@section TAP Names
@b{By default, all taps are enabled}
When a TAP objects is created with @command{jtag newtap},
a @dfn{dotted.name} is created for the TAP, combining the
name of a module (usually a chip) and a label for the TAP.
For example: @code{xilinx.tap}, @code{str912.flash},
@code{omap3530.jrc}, @code{dm6446.dsp}, or @code{stm32.cpu}.
Many other commands use that dotted.name to manipulate or
refer to the TAP. For example, CPU configuration uses the
name, as does declaration of NAND or NOR flash banks.
The components of a dotted name should follow ``C'' symbol
name rules: start with an alphabetic character, then numbers
and underscores are OK; while others (including dots!) are not.
@quotation Tip
In older code, JTAG TAPs were numbered from 0..N.
This feature is still present.
However its use is highly discouraged, and
should not be counted upon.
Update all of your scripts to use TAP names rather than numbers.
Using TAP numbers in target configuration scripts prevents
reusing on boards with multiple targets.
@end quotation
@anchor{TAP Creation Commands}
@section TAP Creation Commands
@c shouldn't this be(come) a {Config Command}?
@anchor{jtag newtap}
@deffn Command {jtag newtap} chipname tapname configparams...
Creates a new TAP with the dotted name @var{chipname}.@var{tapname},
and configured according to the various @var{configparams}.
The @var{chipname} is a symbolic name for the chip.
Conventionally target config files use @code{$_CHIPNAME},
defaulting to the model name given by the chip vendor but
overridable.
@cindex TAP naming convention
The @var{tapname} reflects the role of that TAP,
and should follow this convention:
@itemize @bullet
@item @b{jtag tapenable} @var{DOTTED.NAME}
@item @b{jtag tapdisable} @var{DOTTED.NAME}
@item @b{jtag tapisenabled} @var{DOTTED.NAME}
@item @code{bs} -- For boundary scan if this is a seperate TAP;
@item @code{cpu} -- The main CPU of the chip, alternatively
@code{arm} and @code{dsp} on chips with both ARM and DSP CPUs,
@code{arm1} and @code{arm2} on chips two ARMs, and so forth;
@item @code{etb} -- For an embedded trace buffer (example: an ARM ETB11);
@item @code{flash} -- If the chip has a flash TAP, like the str912;
@item @code{jrc} -- For JTAG route controller (example: the ICEpick modules
on many Texas Instruments chips, like the OMAP3530 on Beagleboards);
@item @code{tap} -- Should be used only FPGA or CPLD like devices
with a single TAP;
@item @code{unknownN} -- If you have no idea what the TAP is for (N is a number);
@item @emph{when in doubt} -- Use the chip maker's name in their data sheet.
For example, the Freescale IMX31 has a SDMA (Smart DMA) with
a JTAG TAP; that TAP should be named @code{sdma}.
@end itemize
@cindex tap enable
@cindex tap disable
@cindex JRC
@cindex route controller
These commands are used when your target has a JTAG route controller
that effectively adds or removes a tap from the JTAG chain in a
non-standard way.
The ``standard way'' to remove a tap would be to place the tap in
bypass mode. But with the advent of modern chips, this is not always a
good solution. Some taps operate slowly, others operate fast, and
there are other JTAG clock synchronisation problems one must face. To
solve that problem, the JTAG route controller was introduced. Rather
than ``bypass'' the tap, the tap is completely removed from the
circuit and skipped.
From OpenOCD's point of view, a JTAG tap is in one of 3 states:
Every TAP requires at least the following @var{configparams}:
@itemize @bullet
@item @b{Enabled - Not In ByPass} and has a variable bit length
@item @b{Enabled - In ByPass} and has a length of exactly 1 bit.
@item @b{Disabled} and has a length of ZERO and is removed from the circuit.
@item @code{-ircapture} @var{NUMBER}
@*The IDCODE capture command, such as 0x01.
@item @code{-irlen} @var{NUMBER}
@*The length in bits of the
instruction register, such as 4 or 5 bits.
@item @code{-irmask} @var{NUMBER}
@*A mask for the IR register.
For some devices, there are bits in the IR that aren't used.
This lets OpenOCD mask them off when doing IDCODE comparisons.
In general, this should just be all ones for the size of the IR.
@end itemize
The IEEE JTAG definition has no concept of a ``disabled'' tap.
@b{Historical note:} this feature was added 28/nov/2008
A TAP may also provide optional @var{configparams}:
@b{jtag tapisenabled DOTTED.NAME}
@itemize @bullet
@item @code{-disable} (or @code{-enable})
@*Use the @code{-disable} paramater to flag a TAP which is not
linked in to the scan chain when it is declared.
You may use @code{-enable} to highlight the default state
(the TAP is linked in).
@xref{Enabling and Disabling TAPs}.
@item @code{-expected-id} @var{number}
@*A non-zero value represents the expected 32-bit IDCODE
found when the JTAG chain is examined.
These codes are not required by all JTAG devices.
@emph{Repeat the option} as many times as required if more than one
ID code could appear (for example, multiple versions).
@end itemize
@end deffn
This command returns 1 if the named tap is currently enabled, 0 if not.
This command exists so that scripts that manipulate a JRC (like the
OMAP3530 has) can determine if OpenOCD thinks a tap is presently
enabled or disabled.
@c @deffn Command {jtag arp_init-reset}
@c ... more or less "init" ?
@page
@node Target Configuration
@chapter Target Configuration
@anchor{Enabling and Disabling TAPs}
@section Enabling and Disabling TAPs
@cindex TAP events
In some systems, a @dfn{JTAG Route Controller} (JRC)
is used to enable and/or disable specific JTAG TAPs.
Many ARM based chips from Texas Instruments include
an ``ICEpick'' module, which is a JRC.
Such chips include DaVinci and OMAP3 processors.
A given TAP may not be visible until the JRC has been
told to link it into the scan chain; and if the JRC
has been told to unlink that TAP, it will no longer
be visible.
Such routers address problems that JTAG ``bypass mode''
ignores, such as:
@itemize
@item The scan chain can only go as fast as its slowest TAP.
@item Having many TAPs slows instruction scans, since all
TAPs receive new instructions.
@item TAPs in the scan chain must be powered up, which wastes
power and prevents debugging some power management mechanisms.
@end itemize
The IEEE 1149.1 JTAG standard has no concept of a ``disabled'' tap,
as implied by the existence of JTAG routers.
However, the upcoming IEEE 1149.7 framework (layered on top of JTAG)
does include a kind of JTAG router functionality.
@c (a) currently the event handlers don't seem to be able to
@c fail in a way that could lead to no-change-of-state.
@c (b) eventually non-event configuration should be possible,
@c in which case some this documentation must move.
@deffn Command {jtag cget} dotted.name @option{-event} name
@deffnx Command {jtag configure} dotted.name @option{-event} name string
At this writing this mechanism is used only for event handling,
and the only two events relate to TAP enabling and disabling.
The @code{configure} subcommand assigns an event handler,
a TCL string which is evaluated when the event is triggered.
The @code{cget} subcommand returns that handler.
The two possible values for an event @var{name}
are @option{tap-disable} and @option{tap-enable}.
So for example, when defining a TAP for a CPU connected to
a JTAG router, you should define TAP event handlers using
code that looks something like this:
@example
jtag configure CHIP.cpu -event tap-enable @{
echo "Enabling CPU TAP"
... jtag operations using CHIP.jrc
@}
jtag configure CHIP.cpu -event tap-disable @{
echo "Disabling CPU TAP"
... jtag operations using CHIP.jrc
@}
@end example
@end deffn
@deffn Command {jtag tapdisable} dotted.name
@deffnx Command {jtag tapenable} dotted.name
@deffnx Command {jtag tapisenabled} dotted.name
These three commands all return the string "1" if the tap
specified by @var{dotted.name} is enabled,
and "0" if it is disbabled.
The @command{tapenable} variant first enables the tap
by sending it a @option{tap-enable} event.
The @command{tapdisable} variant first disables the tap
by sending it a @option{tap-disable} event.
@quotation Note
Humans will find the @command{scan_chain} command more helpful
than the script-oriented @command{tapisenabled}
for querying the state of the JTAG taps.
@end quotation
@end deffn
@node CPU Configuration
@chapter CPU Configuration
@cindex GDB target
This chapter discusses how to create a GDB debug target. Before
creating a ``target'' a JTAG tap DOTTED.NAME must exist first.
This chapter discusses how to create a GDB debug target for a CPU.
You can also access these targets without GDB
(@pxref{Architecture and Core Commands}) and, where relevant,
through various kinds of NAND and NOR flash commands.
Also, if you have multiple CPUs you can have multiple such targets.
Before creating a ``target'', you must have added its TAP to the scan chain.
When you've added that TAP, you will have a @code{dotted.name}
which is used to set up the CPU support.
The chip-specific configuration file will normally configure its CPU(s)
right after it adds all of the chip's TAPs to the scan chain.
@section targets [NAME]
@b{Note:} This command name is PLURAL - not singular.
@ -2067,7 +2116,7 @@ Example:
@section TARGETNAME (object) commands
@b{Use:} Once a target is created, an ``object name'' that represents the
target is created. By convention, the target name is identical to the
tap name. In a multiple target system, one can preceed many common
tap name. In a multiple target system, one can precede many common
commands with a specific target name and effect only that target.
@example
str912.cpu mww 0x1234 0x42
@ -2242,22 +2291,6 @@ multiplexing, and so on.
@* Success
@item @b{resumed}
@* Target has resumed
@item @b{tap-enable}
@* Executed by @b{jtag tapenable DOTTED.NAME} command. Example:
@example
jtag configure DOTTED.NAME -event tap-enable @{
puts "Enabling CPU"
...
@}
@end example
@item @b{tap-disable}
@*Executed by @b{jtag tapdisable DOTTED.NAME} command. Example:
@example
jtag configure DOTTED.NAME -event tap-disable @{
puts "Disabling CPU"
...
@}
@end example
@end itemize
@anchor{Target Create}
@ -2338,6 +2371,11 @@ Example:
@}
@end example
@b{PROBLEM:} On more complex chips, the work area can become
inaccessible when application code enables or disables the MMU.
For example, the MMU context used to acess the virtual address
will probably matter.
@section Target Variants
@itemize @bullet
@item @b{cortex_m3}