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+.. highlight:: cpp
+
+.. _jtag:
+
+JTAG
+====
+
+.. FIXME [0.1.0] Updated adapter schematic, better information
+
+JTAG is an interface for low-level debugging of digital devices. It
+gives instruction by instruction control over the microprocessor and
+allows data to be read and written to arbitrary memory and register
+locations. It is typically used with a debugging tool like `gdb
+<http://www.gnu.org/software/gdb/>`_ when hacking low level routines
+and hardware peripherals (we use it when working on :ref:`libmaple
+<libmaple>`) or to flash a new bootloader.
+
+Note that the STM32 on the Maple has a built-in low level serial
+debugger which could also be used to flash bootloaders, and
+:ref:`lang-assert` allows basic debugging over a USART serial channel.
+We expect only fairly advanced users to use this feature.
+
+.. contents:: Contents
+   :local:
+
+Wiring Diagram
+--------------
+
+.. figure:: /_static/img/jtag-wiring.png
+   :align: center
+   :alt: JTAG wiring diagram
+   :width: 7.4in
+   :target: _images/jtag-wiring.png
+
+   JTAG wiring diagram (`large version <_images/jtag-wiring.png>`_)
+   to connect a standard 20-pin ARM JTAG device to the 8-pin JTAG port
+   on the Maple.
+
+The Maple has holes for a 8-pin JTAG header, but that header is not
+soldered on.  To use JTAG, simply solder on standard 0.1" pitch male
+header pins (either the exact 4 by 2 block, or two 4-pin pieces of
+straight breakaway header).
+
+Compatible Devices
+------------------
+
+We have had good experience with the `Olimex ARM-USB-OCD
+<http://www.olimex.com/dev/arm-usb-ocd.html>`_ device, which costs
+about €55 plus shipping (as of April 2011).
+
+Function Reference
+------------------
+
+You can disable or enable the JTAG and Serial Wire debugging ports in
+software using the ``disableDebugPorts()`` and ``enableDebugPorts()``
+functions.
+
+* :ref:`lang-disabledebugports`
+* :ref:`lang-enabledebugports`
+
+Recommended Reading
+-------------------
+
+* `Wikipedia Article on Joint Test Action Group (JTAG)
+  <http://en.wikipedia.org/wiki/Joint_Test_Action_Group>`_
+
+* `STM32, GDB, OpenOCD How To
+  <http://fun-tech.se/stm32/OpenOCD/gdb.php>`_
+
+* `LeafLabs Wiki JTAG How To
+  <http://wiki.leaflabs.com/index.php?title=Maple_JTAG_How_To>`_
+
+* `LeafLabs forum thread on JTAG
+  <http://forums.leaflabs.com/topic.php?id=536>`_
+
+* ST documentation:
+
+  * Reference Manual `RM0008
+    <http://www.st.com/stonline/products/literature/rm/13902.pdf>`_
+    (PDF), Chapter 31, "Debug support", and Chapter 9,
+    "General-purpose and alternate function I/Os".