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oharboe 6d3bed69dc Uwe Hermann: 14 years ago
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README Uwe Hermann: 14 years ago
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Free and Open On-Chip Debugging, In-System Programming
and Boundary-Scan Testing
Copyright (c) 2004-2007 Dominic Rath

The debugger uses an IEEE 1149-1 compliant JTAG TAP bus master to access on-chip
debug functionality available on ARM7 and ARM9 based microcontrollers /
system-on-chip solutions.

User interaction is realized through a telnet command line interface and a gdb
(The GNU Debugger) remote protocol server.

1. JTAG hardware

Currently, OpenOCD supports the following JTAG interfaces:

- Parallel port wigglers. These devices connect to a PC's parallel port,
providing direct access to the JTAG lines. The OpenOCD contains descriptions
of a few Wiggler layouts, including the original 'Wiggler' design. Other
layouts (i.e. mapping of parallel port pins to JTAG lines) can be added easily.
Typical Wiggler speeds are around 12kByte/s code download to an ARM7's RAM.

The list of supported parallel port devices includes:

* Macraigor Wiggler JTAG cable
* Gateworks GW16012 JTAG programmer
* Xilinx DLC5 JTAG parallel cable III
* Ka-Ro TRITON starterkit II JTAG cable
* Lattice parallel port JTAG cable
* ST FlashLINK programming cable

- The Amontec JTAG Accelerator. This is a configuration for Amontec's Chameleon
dongle, a parallel port interface based on a Xilinx CoolRunner CPLD. It uses
the IEEE1284 EPP parallel port specification, providing many times the
performance achievable with wiggler-style devices. Additional information is
available on
Typical JTAG Accelerator speeds are around 120-160kByte/s to an ARM7's RAM.

- FTDI FT2232 based USB devices. The FT2232 (but not FT232 or FT245) features a
multi-protocol synchronous serial engine (MPSSE) that can be used to run the
serial JTAG protocol. There are several implemenations of FT2232 based devices:

The USBJTAG was designed by Prof. Hubert Hoegl to provide a high-speed USB
interface for use with the OpenOCD. Schematics are available at the USBJTAG
website, and a homebrew device can easily be built using the FTDI evaluation
module DLP2232M.

* OOCD-Link:
Similar to the USBJTAG, this design comes with free schematics, too.

* Amontec JTAGkey:
The Amontec JTAGkey offers support for a wide variety of target voltages from
1.4V to 5V. It also allows the JTAG lines and reset signals to be tri-stated,
allowing easy interfacing with a wide variety of targets.

* Amontec JTAGkey-Tiny:
The Amontec JTAGkey offers support for a wide variety of target voltages from
2.8V to 5V. It also allows the reset signals to be tri-stated, allowing easy
interfacing with a wide variety of targets.

* Olimex ARM-USB-OCD:
The Olimex ARM-USB-OCD offers support for a wide vriety of target voltages from
2.0V to 5V. It also allows targets to be powered from the ARM-USB-OCD and
features and additional RS232 UART.

* eVerve Signalyzer:
The Signalyzer offers support for a wide variety of target voltages from 1.2V to
5.5V. A second connector provides access to a TTL level UART.

* TinCanTools 'Flyswatter' USB JTAG programmer.

* Turtelizer 2:
Another USB JTAG programmer, with freely available schematics. It supports
target voltages from 1.65V to 5.5V.

* Hitex STR9-comSTICK:
A STR912FW44x microcontroller "board" with USB and JTAG functionality.

* Luminary Micro development board evb_lm3s811 JTAG interface.

The ASIX PRESTO is a USB JTAG programmer for a wide range of components, e.g.
microcontrollers, serial EEPROM and Flash memory chips, CPLDs and others.

* usbprog:
The usbprog is a freely programmable USB adapter, which can (among other
things) use a firmware which turns it into a JTAG programmer/debugger.

All FT2232 based devices may be accessed using either FTDI's proprietary FTD2XX
library ( or using an open-source replacement from, also included
with many Linux distributions.

2. Supported cores

This version of openocd supports the following ARM7/9 cores:

- ARM7TDMI(-s)
- ARM920t
- ARM922t
- ARM926ej-s
- ARM966e
- Cortex-M3

Support for Intel XScale CPUs is also included:

- PXA25x
- PXA27x
- IXP42x

And support for the Marvell Feroceon CPU core as found in the
Orion SoC family is included as well.

3. Host platforms

OpenOCD was originally developed on x86-Linux, but has since then been ported
to run on Windows/Cygwin, native Windows with MinGW, FreeBSD, IA64-Linux,
AMD64-Linux, Alpha-Linux, ARM-Linux, and PowerPC OS-X.

4. Documentation

Documentation for the OpenOCD is hosted in the Berlios OpenFacts Wiki at

There is also and openocd(1) manpage, the 'openocd --help' output and
an OpenOCD info page (type 'info openocd').

5. Licensing

OpenOCD is licensed under the terms of the GNU General Public License, see the
file COPYING for details.