Universal JTAG library, server and tools
========================================
Kolja Waschk (Ed.)
$Id$

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== Copyright ==

Copyright 2007, 2018 Kolja Waschk and the respective authors.

Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License, Version 1.2 or any later version
published by the Free Software Foundation. A copy of the license is included in
the section entitled "GNU Free Documentation License".

//=========================================================================

== General ==

=== JTAG ===
// Contributed by Ralf Engels

JTAG basics can be found all over the Internet. This section should go into
some more details about working with JTAG. What hardware do you need, what is
the usage of JTAG, where do I get files. What file formats are available...

==== Introduction ====

JTAG (IEEE 1149.1) is a serial interface for testing devices with
integrated circuits. The problem that the JTAG interface was designed to solve
is checking if connections between ICs are OK. Therefore you can set and check
in- and outputs of ICs. In order to save pins and logic a very simple serial
design was invented.

* One pin serial input
* One pin serial output
* One pin clock
* One pin control

The control pin (together with clock) allows to switch device states. A state
machine inside each chip can be controlled, e.g. to reset the device.  This
control machine also allows to have two internal shift registers in each device
(although we only have on in- and one output-pin). The registers are called
instruction register (IR) and data register (DR).  The current UrJTAG tool
allows you to set the IR and set and get the DR. It doesn't allow you to
directly control the state machine (yet).

==== Interfaces ====

The simplest interface that you can build is like the Xilinx parallel cable
(also called DLC5). If your device works with a 5V or 3.3V supply voltage then
this device can even be built just with passive parts.  (picture missing here)
UrJTAG also supports a number of other interface adapters.

==== Additions ====

In the meantime the JTAG specification was used as a basis for programming
flash files and debugging processors.  UrJTAG supports programming a couple of
different flash devices. It also supports programming of non-flash devices via
SVF files.  UrJTAG does not support debugging yet. Other open source solutions
such as OpenOCD allow you to debug ARM processors with gdb.

==== BSDL and UrJTAG data files ====

The BSDL file format describes the JTAG interface for one IC.  It is a VHDL
syntax with the needed information (like pin-names, register lengths and
commands) that is usually created by the supplier. e.g. Xilinx BSDL files are
all included in their free web-pack (using file extension ".bsd").

UrJTAG uses a different file format internally. So in order to add a new device
to UrJTAG you need to convert those files and produce a directory structure.
Currently there are at least three tools available to do that; included with
UrJTAG is "bsdl2jtag". Please ask on the mailing list in case of problems with
that. Please also send proven working files back to this project. 

Starting with post-0.7 releases, UrJTAG contains a BSDL subsystem that
retrieves the descriptions for chips in the chain from BSDL files on the
fly. "bsdl2jtag" is in fact a wrapper that uses the BSDL subsystem to
convert the BSDL file.

==== SVF files ====

The SVF file format contains a number of high level commands to drive the JTAG
bus. For example you can shift the IR or DR and even check for the results.
The Xilinx Impact and Altera QuartusII tools allow you to write this file to
program devices.

The player has been developed according to the "Serial Vector Format
Specification", Revision E, 8 March 1999 issued by ASSET InterTech, Inc. The
full specification can be found at
http://www.asset-intertech.com/support/svf.pdf[].

UrJTAG features an "SVF player" that can read SVF files and perform the
described actions on the bus.

SVF parser and lexer are also copyright 2002, CDS at http://www-csd.ijs.si/[].
They have been reused from the "Experimental Boundary Scan" project at
http://ebsp.sourceforge.net/[].

==== JAM/STAPL files ====

Another format for describing actions over JTAG interfaces is STAPL, actually
standardized as JEDEC "JESD-71A". Compared to SVF, it looks more like an
actual programming language and features looping, conditional execution, and
more. STAPL is not yet supported by UrJTAG.

//------------------------------------------------------------------------

=== UrJTAG ===
// Written by K.Waschk

==== Introduction ====

UrJTAG is a software package which enables working with JTAG-aware (IEEE
1149.1) hardware devices (parts) and boards through a JTAG adapter.

This package has an open and modular architecture with the ability to write
miscellaneous extensions (like board testers, flash memory programmers, and so
on).

UrJTAG is free software, covered by the GNU General Public License,
and you are welcome to change it and/or distribute copies of it under certain
conditions. There is absolutely no warranty for UrJTAG.  Please read
the COPYING file for more info.

WARNING: This software may damage your hardware!

Feedback and contributions are welcome.

==== About this document ====

This documentation is far from being complete. You're encouraged to amend and
supplement it and submit your changes in the Bugs or Enhancements tracker
at the UrJTAG website.

==== UrJTAG Website ====

The most current version of this documentation and UrJTAG source code
is always available from the project homepage at http://www.urjtag.org[].

==== The name "UrJTAG" ====

I (Kolja) favour short names, so I thought about adding only a few
letters to "JTAG". The prefix "Ur" in German means "ancestral", an "Ur-Vater"
is a forefather. UrJTAG shall become the forefather, the prototype for many
other JTAG tools. By mere chance the "Ur" is also another name for an aurochs,
an animal similar to the GNU...

==== Authors, contributors, ... thanks ====

A list of contributors is maintained in the file THANKS in the source
distribution. Special thanks go to Marcel Telka, who actually "invented" the
JTAG tools and wrote most of this basis of UrJTAG, and Arnim Laeuger for his
continuous support and development of SVF and BSDL subsystem and FT2232
drivers.

==== UrJTAG and openwince JTAG Tools ====

The JTAG Tools originally were developed by Marcel Telka as part of
the openwince project. Still a large portion of the source code is his work.
However, the last release of the JTAG tools was version 0.5.1 in 2003. After a
few years the development completely stalled. Every few months or so on the
project's mailing list someone asked about continuing, but a critical mass
wasn't reached before late 2007. A fork of the JTAG tools was created under the
wings of the UrJTAG project at Sourceforge.

//------------------------------------------------------------------------

=== System requirements ===
//Copied from original README

==== Supported host operating systems ====

JTAG Tools should run on all Unix like operating systems including MS Windows
with Cygwin installed. A precompiled version that runs on MS Windows without
Cygwin is available as a Windows installer executable.

==== Required software for running UrJTAG ====

Required only for MS Windows, unless you use the precompiled version:

 * current Cygwin net installation from http://cygwin.com[]
 * ioperm package (a part of the standard Cygwin net installation)

It may be necessary to run the command "ioperm -i" to install the IOPERM.SYS
driver in the system.

If UrJTAG was compiled to use the readline library, it has to be present on
the system as well. It's probably a standard part of your distribution.

More software is needed if you want to compile UrJTAG (which you probably want
because currently no pre-compiled binaries are available...).
See "Installation" below. 

==== Supported JTAG adapters/cables ====

See 'help cable' command for up-to-date info.

Parallel-port cables:

 * Arcom JTAG Cable
 * Altera ByteBlaster/ByteBlaster II/ByteBlasterMV Parallel Port Download Cable
 * Xilinx DLC5 JTAG Parallel Cable III
 * ETC EA253 JTAG Cable
 * ETC EI012 JTAG Cable
 * Ka-Ro TRITON (PXA255/250) JTAG Cable
 * Keith &amp; Koep JTAG Cable
 * Lattice Parallel Port JTAG Cable
 * Mpcbdm JTAG Cable
 * Macraigor Wiggler JTAG Cable

FT2232-based USB cables:

 * Amontec JTAGkey
 * Amontec JTAGkey-Tiny (supported as cable "JTAGkey")
 * KrisTech UsbScarab2 ARM JTAG http://www.kristech.eu/[]
 * Olimex ARM-USB-JTAG
 * Olimex ARM-USB-TINY
 * OOCDLink-s (experimental) http://www.joernonline.de/dw/doku.php?id=projects:oocdlink:2_oocdlinks[]
 * Other FT2232-based USB JTAG cables (experimental)
 * TinCanTools Flyswatter
 * Turtelizer 2 (experimental) http://www.ethernut.de/en/hardware/turtelizer/[]
 * USB to JTAG Interface (experimental)
 * http://www.hs-augsburg.de/~hhoegl/proj/usbjtag/usbjtag.html[]
 * Blackfin gnICE http://docs.blackfin.uclinux.org/doku.php?id=hw:jtag:gnice[]
 * Blackfin gnICE+ http://docs.blackfin.uclinux.org/doku.php?id=hw:jtag:gnice-plus[]
 * Xverve Signalyzer Tool (experimental)

Other USB cables:

 * Altera USB-Blaster and compatible http://www.ixo.de/info/usb_jtag[]
 * Segger/IAR J-Link / Atmel SAM-ICE (experimental, work in progress)
 * Xilinx Platform USB Cable / DLC9 (slow, experimental, work in progress - don't use)

Other cables:

 * Technologic Systems TS-7800 SoC GPIO builtin JTAG interface
 
==== JTAG-aware parts (chips) ====

The data/ directory of the UrJTAG installation has some more, but at
least the following are supported:

 * Altera EP1C20F400
 * Altera MAX7000 (w/ BSDL)
 * Altera EPM7128AETC100
 * Altera Cyclone I & II (w/ BSDL)
 * Analog Devices Blackfin (w/ BSDL)
   - BF504/BF506
   - BF512/BF514/BF516/BF518
   - BF522/BF523/BF524/BF525/BF526/BF527
   - BF531/BF532/BF533
   - BF538/BF539
   - BF534/BF536/BF537
   - BF542/BF544/BF547/BF548/BF549
   - BF561
   - BF592
 * Analog Devices Sharc-21065L
 * Atmel ATmega128 (partial support)
 * Atmel AT32AP7000 (partial support)
 * Broadcom BCM1250
 * Broadcom BCM3310 (partial support)
 * Broadcom BCM5421S
 * Broadcom BCM4712 (partial support)
 * DEC SA1100
 * Hitachi HD64465
 * Hitachi SH7727
 * Hitachi SH7729
 * IBM PowerPC 440GX
 * Intel IXP425
 * Intel SA1110
 * Intel PXA250/PXA255/PXA260/PXA261/PXA262/PXA263
 * Lattice LC4032V
 * Lattice M4A3-64/32
 * Lattice M4A3-256/192
 * Motorola MPC8245
 * Samsung S3C4510B
 * Sharp LH7A400
 * Toshiba TX4925/TX4926
 * Xilinx XC2C256-TQ144
 * Xilinx XCR3032XL-VQ44
 * Xilinx XCR3128XL-CS144
 * Xilinx XCR3128XL-VQ100
 * Xilinx XCR3256XL-FT256
 * Xilinx Spartan-IIE
 * Xilinx Spartan-3/E
 * Xilinx Spartan-3AN

==== Flash chips ====

NOTE: Not all chips are supported in every possible configuration, there may
be untested combinations of chip type, bus width, ...

 * Intel 28FxxxJ3A (28F320J3A, 28F640J3A, 28F128J3A)
 * Intel 28FxxxK3 (28F640K3, 28F128K3, 28F256K3)
 * Intel 28FxxxK18 (28F640K18, 28F128K18, 28F256K18)
 * AMD Am29LV64xD (Am29LV640D, Am29LV641D, Am29LV642D)
 * AMD Am29xx040B (Am29F040B, Am29LV040B)
 * Macronix MX29LV160, MX29LV320, MX29LV640

UrJTAG uses the multi-byte write mode if supported by the particular flash
device. The flash code will automatically switch to this algorithm if the
Device Geometry Definition reports that more than one memory location can be
written in a single step (refer to CFI details shown by 'detectflash'). Since
multiple locations are written in a burst-like manner with only one polling
sequence afterwards, the overall flashing performance increases by factor of
5-17.

In case you encounter any issues with the multi-byte write mode, run configure
with the '--disable-flash-multi-byte' option and re-compile to disable this
algorithm.

//------------------------------------------------------------------------

=== Compilation and installation ===

==== Installation of precompiled UrJTAG for Windows ====

By simply running UrJTAG-xxx.exe, the executable and data files will
be installed in your Windows program folder, usually some place like
C:\Program Files\UrJTAG. It comes ready with support for JTAG cables that are
directly attached to a parallel port. However, if you work with Windows Vista
and want access to the parallel port, a driver for it has to be installed
separately. It is available from

  http://www.highrez.co.uk/Downloads/InpOut32/

If you want to use UrJTAG with a JTAG cable attached to the USB port, 
actual cable drivers have to be installed beside UrJTAG itself. Usually,
the cable vendor will provide the drivers. For example, drivers for
Altera USB-Blaster come with their Quartus software. For FTDI-based
cables, you need an INF file describing the cable and FTDIBUS.SYS and
FTD2XX.DLL from FTDI (CDM drivers). If your cable shows up in the device
manager without any warning sign, UrJTAG probably is able to talk to it.

Finally, UrJTAG additionally needs libusb-win32 to talk to some USB cables that
are not based on FTDI chips (Xilinx Platform Cable USB, Segger J-Link). The
so-called libusb-win32 filter driver is available from the project's download
page at Sourceforge:

  http://libusb-win32.sourceforge.net/#downloads

==== Required software for compiling UrJTAG ====

To run autogen.sh, you need autoconf and automake, bison, pkg-config
and a recent flex.

The distributed source tarball contains source pregenerated with a current
flex version; flex therefore is only needed if you want to compile code
checked out from our Subversion repository.  Flex 2.5.4a as it comes with
most but the very latest Cygwin release cannot build the scanners for BSDL and
SVF. Building these files requires Flex 2.5.33 or newer. The configure script
will compare the available Flex version against these preconditions and enables
or disables the related features.

Furthermore, libtool should be available, and "devel" versions of the following
packages:

 * gettext
 * readline (not needed, but really eases interactive use)
 * ioperm (needed only for Cygwin)

==== Required libraries for USB support ====

For USB adapter support (including support for parallel port adapters attached
to USB-to-parallel converters), one or more additional libraries are required.

Many USB JTAG adapters and USB-to-parallel converters are based on chips
made by FTDI. To support these, either intra.net's "libftdi" or FTDI's 
"FTD2XX" library can be used.

On many modern Linux distributions, libftdi is available as a precompiled
package and can be installed using the distribution's package management system
(e.g. "apt-get libftdi-dev" for Debian and Ubuntu). If it isn't available or
you don't run Linux, you can get it from

 * http://www.intra2net.com/en/developer/libftdi/[]

Alternatively, you can use the FTD2XX library from the chip manufacturer FTDI.
It is available for Linux and Windows. There's more information about linking
to that library in a Cygwin environment below.

All other USB JTAG adapters can be supported only if libusb is installed.
There is a libusb-win32 variant that can be used in a Cygwin environment:

 * http://libusb.sourceforge.net[] (libusb)
 * http://libusb-win32.sourceforge.net[] (libusb for Windows)

For specific notes regarding the use of these libraries in a Cygwin
environment, see below.

==== Installing from source tar.gz ====

The installation follows the standard configure, make, make install scheme:

  tar xzvf urjtag-x.y.tar.gz
  cd urjtag-x.y
  ./configure
  make
  make install

==== Installing from Subversion repository ====

If you want to try the very newest version of UrJTAG...

  svn co http://urjtag.svn.sourceforge.net/svnroot/urjtag/trunk urjtag

  cd urjtag/jtag
  ./autogen.sh
  # ./configure done by autogen.sh; run it here with special options if needed
  make
  make install

==== Linking to FTD2XX.DLL in Cygwin environment ====

Before running configure, get the D2XX drivers from FTDI.

 * http://www.ftdichip.com/Drivers/D2XX.htm[] (FTDI FTD2XX library)

Unzip the archive into a directory of your choice (probably a choice
without spaces in the name is better) and afterwards run configure with the
"--with-ftd2xx" pointing to that directory, e.g.

  ./configure --with-ftd2xx="/cygdrive/c/temp/ftdi-cdm-drivers"

Configure should now report

  jtag is now configured for
    ...
    Detected libftd2xx   : yes


==== Using LibUSB-Win32 in Cygwin environment ====

Before running configure, install the LibUSB-Win32 "filter" driver from SF.

 * http://libusb-win32.sourceforge.net[]

Then point configure to the directory where LibUSB-Win32 was installed (it
might give problems if the path contains spaces, as "Program Files" does!):

  ./configure --with-libusb="/cygdrive/c/Programme/LibUSB-Win32/"

==== Compiling with MinGW ====

UrJTAG may be compiled into a Windows executable using the MinGW compiler
(http://www.mingw.org[]), or Cygwin GCC with the "-mno-cygwin" compiler flag.

This has the advantage over running in a Cygwin environment that you don't need
to install anything else but the jtag.exe (plus libraries like FTD2XX.dll or
InpOut32.DLL that are required for device access under Windows in any case).

However, because support for MinGW is quite new in UrJTAG, it may lack some
features (e.g. readline support) or run a little slower.

Because it seems to be easier to set up a Cygwin environment, we recommend 
using the Cygwin GCC with "-mno-cygwin" flag instead of using a MinGW setup:

  CFLAGS="-mno-cygwin -O2" ./configure --with-ftd2xx=/tmp/cdm-drivers --with-inpout32


It is even possible to cross-compile and build the executable on a Linux
host:

  ./configure --host=i586-mingw32msvc --with-ftd2xx=/tmp/cdm-drivers --with-inpout32
  make


The "--with-inpout32" switch tells UrJTAG to use the InpOut32.DLL for access to
parallel ports, because the Cygwin ioperm isn't available for MinGW. The InpOut32
library is available from logix4u.net:

  http://logix4u.net/Legacy_Ports/Parallel_Port/Inpout32.dll_for_Windows_98/2000/NT/XP.html

An version updated to work in Windows Vista and 64 bit Windows is available from highrez:

  http://www.highrez.co.uk/Downloads/InpOut32/

==== Driver tailoring ====

The configure script enables all default bus, cable and lowlevel drivers. You
can include and exclude specific drivers if required. For a list of parameters
run

  ./configure --help

to figure out the appropriate --enable-bus, --enable-cable, and --enable-lowlevel
options.


==== Building the BSDL subsystem ====

As mentioned above, building the BSDL lexer requires Flex 2.5.33 or newer. If
the detected Flex version is not recent enough, configure will disable the
BSDL subsystem. The detection result is summarized at the end of configure:

  jtag is now configured for
    ...
    Build BSDL subsystem : yes

Flex is only required when you're working on a check-out of the Subversion
repository. In this case Flex has to be called to transform bsdl_flex.l to
bsdl_flex.c. When you're compiling from released sources, the local Flex
version is not relevant since the output file of Flex is part of the
tarball. I.e. even if the local Flex fails the check, the BSDL subsystem is
enabled and will be compiled from the released C files.

//=========================================================================

== Usage ==

=== Quick start ===
// Contributed by Ralf Engels

==== Run the software ====

Connect your JTAG adapter between your PC and target device and turn
on your device.

To run UrJTAG type "jtag" and press Enter; jtag should start and
display some initial information. Output should end with a line like this:

  WARNING: UrJTAG may damage your hardware!
  Type "quit" to exit, "help" for help.

==== Configure the cable ====

Type "help cable" for a list of supported JTAG cables.

Type the "cable" command followed by the cable name and possibly further
arguments for cable configuration. Example:

  jtag> cable EA253 parallel 0x378
  Initializing ETC EA253 JTAG Cable on parallel port at 0x378

See the section about the "cable" command for details and USB support.

==== Detect parts on the JTAG chain ====

Type "detect" at the jtag command prompt:

  jtag> detect

Your output should look like this:

  IR length: 5
  Chain length: 1
  Device Id: 01011001001001100100000000010011
    Manufacturer: Intel
    Part:         PXA250
    Stepping:     C0
    Filename:     /usr/local/share/urjtag/intel/pxa250/pxa250c0

If you get empty output or an error message your JTAG adapter is not connected
properly, or your target board doesn't work, or it is turned off.

The "detect" command is required before all other commands.

==== Print current JTAG chain status ====

  jtag> print chain
   No. Manufacturer Part   Stepping Instruction Register
  ---------------------------------------------------------
     0 Intel        PXA250 C0       BYPASS      BR

==== Sample device pin status ====

  jtag> instruction SAMPLE/PRELOAD
  jtag> shift ir
  jtag> shift dr
  jtag> dr
  1000110010000010000110010111111111111111111001101110...
  jtag> print chain
   No. Manufacturer Part   Stepping Instruction    Register
  ------------------------------------------------------------
     0 Intel        PXA250 C0       SAMPLE/PRELOAD BSR
  jtag> get signal BOOT_SEL[0]
  BOOT_SEL[0] = 0
  jtag>

  Note: BSR is "Boundary Scan Register"

==== Burn flash connected to the part ====

  jtag> flashmem 0 brux.b
  0x00000000
  Note: Supported configuration is 2 x 16 bit only
  BOOT_SEL: Asynchronous 32-bit ROM

  2 x 16 bit CFI devices detected (QRY ok)!

  program:
  block 0 unlocked
  erasing block 0: 0
  addr: 0x00002854
  verify:
  addr: 0x00002854
  Done.
  jtag>

or:

  jtag> flashmem msbin xboot.bin
  Note: Supported configuration is 2 x 16 bit only
  BOOT_SEL: Asynchronous 32-bit ROM

  2 x 16 bit CFI devices detected (QRY ok)!

  block 0 unlocked
  erasing block 0: 0
  program:
  record: start = 0x00000000, len = 0x00000004, checksum = 0x000001EB
  record: start = 0x00000040, len = 0x00000008, checksum = 0x000001B0
  record: start = 0x00001000, len = 0x00002B30, checksum = 0x00122CAB
  record: start = 0x00004000, len = 0x00000160, checksum = 0x0000684B
  record: start = 0x00005000, len = 0x00000054, checksum = 0x000008EE
  record: start = 0x00005054, len = 0x00000030, checksum = 0x00000DA9
  record: start = 0x00000000, len = 0x00001000, checksum = 0x00000000

  verify:
  record: start = 0x00000000, len = 0x00000004, checksum = 0x000001EB
  record: start = 0x00000040, len = 0x00000008, checksum = 0x000001B0
  record: start = 0x00001000, len = 0x00002B30, checksum = 0x00122CAB
  record: start = 0x00004000, len = 0x00000160, checksum = 0x0000684B
  record: start = 0x00005000, len = 0x00000054, checksum = 0x000008EE
  record: start = 0x00005054, len = 0x00000030, checksum = 0x00000DA9
  record: start = 0x00000000, len = 0x00001000, checksum = 0x00000000

  Done.
  jtag>

==== Non-standard flash commands ====

Erasing and programming flash devices is covered by standard procedures
in UrJTAG. Apart from these, many flash chips implement a lot more
functionality via dedicated commands that vary from between manufacturers
and device families. UrJTAG can't cover them all natively.

It's however possible to send any command stream to the flash by using
the poke and peek commands. You just need to clarify two things:

 1. base address of the flash (BA) +
    it's the same that's used for detectflash
 2. data width, x8 or x16 +
    defined by the width of the bus where the flash is attached

Next look up the address/data pairs for the command in question. The data
sheet for your particular flash should document all commands in a table e.g.
If your flash is attached in x16 mode, the address must be shifted by one
position. Addresses in x8 mode are not affected.

The "Read Manufacturer ID" command in x16 mode would look like

  poke BA+(0x555*2) 0xaa 
  poke BA+(0x2aa*2) 0x55 
  poke BA+(0x555*2) 0x90 
  peek BA+(0x000*2)

Note that the calculations must be done beforehand. UrJTAG can't evaluate
expressions on the command line.

//------------------------------------------------------------------------

=== JTAG commands ===
// Various authors...

==== Overview ====

Following is a list of commands currently supported by jtag and some
example usage.

*bit*::         define new BSR bit
*bus*::         change active bus
*bsdl*::        manage BSDL files
*cable*::       select JTAG cable
*detect*::      detect parts on the JTAG chain
*detectflash*:: detect parameters of flash chips attached to a part
*discovery*::   discovery of unknown parts in the JTAG chain
*dr*::          display or set active data register for a part
*endian*::      set/print endianness for reading/writing binary files
*eraseflash*::  erase flash memory by number of blocks
*flashmem*::    burn flash memory with data from a file
*frequency*::   setup JTAG frequency
*get*::         get external signal value
*help*::        display this help
*include*::     include command sequence from external file
*initbus*::     initialize bus driver for active part
*instruction*:: change active instruction for a part or declare new instruction
*part*::        change active part for current JTAG chain
*peek*::        read a single word
*poke*::        write a single word
*print*::       display JTAG chain list/status
*quit*::        exit and terminate this session
*readmem*::     read content of the memory and write it to file
*register*::    define new data register for a part
*scan*::        detect changes on input pins of current part
*set*::         set external signal value
*shift*::       shift data/instruction registers through JTAG chain
*signal*::      define new signal for a part
*svf*::         execute SVF commands from file
*writemem*::    write content from file to memory

Some tools derived from the same openwince JTAG Tools code base as UrJTAG 
know additional commands, which are not supported in UrJTAG. See the section
about "Unsupported commands", below, about workarounds.

==== Basic commands ====

===== quit =====

This command closes the jtag console.

===== help =====

Without additional parameter it gives an overview of the available commands.
With a parameter you can get more information about any of the commands.
Example:

  jtag> help cable

Most cable drivers require some more details about the cable to start properly.
To learn about the details, use the "cable" command with the name of the cable
followed by the word "help". Example:

  jtag> cable wiggler help

===== include =====

Run commands from a named script file installed with UrJTAG or applies a BSDL
file to the active part. The directory prefix is added automatically
(e.g. /usr/share/urjtag/, depending on your installation), unless the file
name starts with a dot or slash.

For example, the following startup sequence configures the cable, chain, and
loads definitions and bus driver for a Samsung S3C4510B CPU to peek its memory
at 0x0:

  jtag> cable wiggler ppdev /dev/parport0
  jtag> detect
  jtag> include samsung/s3c4510b/s3c4510b
  jtag> peek 0x0000

If the file contains valid BSDL syntax, it will be converted to native
commands on the fly.

Optionally, a number X may be specified following the file name, to cause
an X times repetition of the command sequence from the file.

==== Chain management ====

===== cable =====

Sets and initializes the cable driver. This is usually the first command that
you are executing in a session. Example:

  jtag> cable EA253 parallel 0x378
  Initializing ETC EA253 JTAG Cable on parallel port at 0x378

For a parallel cable using the ppdev driver you would use this:

  jtag> cable DLC5 ppdev /dev/parport0

If you get an error, it may be that the parallel port kernel driver
was compiled as a module in your Linux kernel and wasn't loaded automatically.
Then you should try to load the ppdev driver manually (with root rights outside
the jtag shell):

  modprobe ppdev
  modprobe parport
  modprobe parport_pc

UrJTAG now also supports some USB cables. Unfortunately, there is no standard
for "JTAG over USB", so this support is limited to a few selected cables only.
For cables based on the FT2232 chip from FTDI, the cable command has to be
given cable name and optionally the driver name, USB Vendor, and Product ID of
the cable:

  jtag> cable ARM-USB-OCD vid=15ba pid=0003 driver=ftdi-mpsse

For all known cables, UrJTAG knows the VID and PID so you can just say

  jtag> cable ARM-USB-OCD

If your cable isn't detected automatically though it's listed as a known and
supported cable, feel free to report its VID and PID. It might be a different
revision and should be added to the known & tested list of cables.

As stated above, the driver name is not mandatory for the cable
command. UrJTAG will select the driver automatically based on UrJTAG's
configuration.  In case your system provides just one of libftdi or FTD2XX
the respective driver is selected. If both libraries are available, then
FTD2XX is selected. That's simply because FTD2XX showed some performance
advantages over libftdi in the past. You can still force libftdi with the
respective parameter.

WARNING: There's one quirk to consider when using FTDI's FTD2XX driver. It
connects to any known FTDI chip, randomly. I.e. if there's more than one FTDI
device connected to the host, chances are that the driver connects to the
wrong USB device. This might be an OEM USB-serial converter and you'll be
banging your head why there's no proper reading from the JTAG chain. Therefore
it's strongly recommended to specify the desc=xxx parameter for the cable
command if the ftd2xx driver is to be used. Set xxx to the product or serial
number descriptor string that are exhibited by the USB device.

===== detect =====

Detects devices on the chain. Example:

  jtag> detect
  IR length: 5
  Chain length: 1
  Device Id: 01011001001001100100000000010011
    Manufacturer: Intel
    Part:         PXA250
    Stepping:     C0
    Filename:     /usr/local/share/jtag/intel/pxa250/pxa250c0

During "detect", UrJTAG searches through the files in its database (usually in
/usr/share/urjtag) and optionally in the search path for BSDL files (see bsdl
command) to find a match for the manufacturer, revision and part number for the
IDCODE read from the part. However, not all parts identify themselves in a way
that is useful for "detect". For example, many chips with an ARM processor core
inside present an IDCODE that may be specific to the the particular core inside
the chip (e.g. ARM7TDMI), but doesn't tell about the actual manufacturer of
the chip. In such case, the data for the part has to be included manually. See
also the documentation for the "include" command.

===== print =====

Print a list of parts in the chain and the currently active instruction per part.
Further details of bus, signals and instructions can be obtained with dedicated
command options, see "help print".

===== initbus =====

Selects and initializes a bus of the currently selected part, e.g. the external
memory bus of a CPU. This is required in order to access chips that aren't
connected in the JTAG chain, but indirectly accessible through other chips
(e.g. CPU or programmable logic). 

Type "help initbus" to get a list of supported bus types. 
If you do not find a bus driver for your specific hardware, you might be lucky
enough to have EJTAG in your target (most MIPS-based CPUs do) and should try
the "ejtag" bus driver. In contrast to the method "via BSR", it uploads some
instructions to the CPU and triggers their execution to access the bus, and
should work with almost any EJTAG-capable chip (Note: JTAG isn't EJTAG):

  jtag> initbus ejtag

There's another option to support new chips "via BSR", the "prototype" bus
driver, which can be adapted to support your part with command parameters.
The only prerequisite for using this driver is knowledge of the names of the
signals that represent address bus, data bus, and enable signals, and that
address and data lines are numbered in order. 

For example, assume the signals are named in the BSDL description as follows:

 * Data bus: D0, D1, ... D31
 * Address bus: ADDR0, ADDR1, ... ADDR22
 * Output Enable: nOE
 * Write Enable: nWE 
 * Chip Select: nRCS0

The enable signals seem to be active low (indicated by the leading "n" in their
names). Further we assume the interesting connected part, some flash chip, is
only 16 bits wide even though the data bus width is 32 bits.  With this
information, you could use the following command (all on a single line!) to
access the bus:

  initbus prototype amsb=ADDR22 alsb=ADDR0 dmsb=D15 dlsb=D0
            ncs=nRCS0 nwe=nWE noe=nOE amode=x16

The "prototype" bus driver cannot deal with systems where address and data
bus are multiplexed on the same pins. If signals aren't numbered in the right
order or with gaps, you may get along by defining proper names as aliases for
the actual signals, with commands like "salias ADDR12 BSCGX44".

Most drivers work "via BSR", i.e. they directly access the pins of the device.
Because it isn't possible to efficiently address only particular pins but only
all at once, and data for all pins has to be transferred through JTAG for every
single change, this method isn't the fastest, but usually easiest to implement
and, well, sometimes it counts whether it works at all.

The "fjmem" (FPGA JTAG memory) bus driver attempts to address this issue by
moving control and observation away from BSR to a device-internal
register. For sure this is only possible on FPGAs where the designer can hook
additional logic to the JTAG chain. A core design plus examples for different
FPGA families is available in the extra/fjmem directory. Refer to the README
located there.

Some chips don't allow direct access to their pins via BSR at all. For these,
writing a new bus driver that utilizes a debug module to upload specific code
to access the bus is inevitable.

===== bus =====

It's possible to initialize more than one bus for part(s) within a chain. The
"bus" command allows to select the active bus for readmem, flashmem,
etc. operation.

==== Part definition commands ====

The following commands are also used in the data files to define a device (IC)
on the JTAG chain. It is not recommended to use these commands in an interactive
session. Instead you should produce a device definition file out of a .bsd file
using one of the supplied tools (or use the new BSDL subsystem, see below).

*bit*::         define new BSR bit
*instruction*:: change active instruction for a part or declare new instruction
*register*::    define new data register for a part
*signal*::      define new signal for a part

==== TAP control ====

The following commands can be used to directly manipulate and display the state
of the TAP controller(s) and registers in the chain:

*dr*::          display or set active data register for a part
*instruction*:: change active instruction for a part or declare new instruction
*get*::         get external signal value
*pod*::         low level direct access to POD signals like TRST; use with care
*scan*::        detect changes on input pins of current part
*set*::         set external signal value
*shift*::       shift data/instruction registers through JTAG chain

==== RAM/Flash access ====

These commands can be used if a part in the chain has memory connected to it
(or integrated). Before they can be used, a bus driver has to be selected and
initialized (see initbus command).

*detectflash*:: detect parameters of flash chips attached to a part
*endian*::      set/print endianness for reading/writing binary files
*eraseflash*::  erase flash memory by number of blocks
*flashmem*::    burn flash memory with data from a file
*peek*::        read a single word
*poke*::        write a single word
*readmem*::     read content of the memory and write it to file
*writemem*::    write content from file to memory

==== Highlevel commands ====

===== svf =====

The SVF player operates on a single part in the scan chain. Therefore, you
have to bring up the JTAG software, specify a cable and detect the scan
chain beforehand.

The player will establish a new instruction called "SIR" and a new register
called "SDR". They are used internally by the respective SVF commands and are
reassigned with new values as the player advances through the file. It is not
recommended to use them outside of the SVF player as their content is dynamic.

An example session:

  jtag> cable ppdev /dev/parport0 DLC5
  Initializing Xilinx DLC5 JTAG Parallel Cable III on ppdev port /dev/parport0
  jtag> detect
  IR length: 5
  Chain length: 1
  Device Id: 10010000101000100000000010010011
    Manufacturer: Xilinx
    Part:         XC2S300E-PQ208
    Stepping:     9
    Filename:     /usr/local/share/jtag/xilinx/xc2s300e-pq208/xc2s300e-pq208
  jtag> part <desired part of the scan chain>
  jtag> svf <SVF file for selected part>
  jtag> instruction BYPASS
  jtag> shift ir
  jtag> part <next part>
  jtag> svf <SVF file for selected part>
  jtag> instruction BYPASS
  jtag> shift ir

It is recommended to set the part's instruction register to BYPASS although
most SVF files do this at the end. By setting the instruction explicitely to
BYPASS the output of the print command will always show meaningful
information.

The SVF player will issue messages when situations arise that cannot be
handled. These messages are classified as warnings or errors depending on
whether the player can continue operation (warning) or not (error).
In case the TDO parameter of an SDR command leads to a mismatch the player
issues a warning and continues. If the player should abort in this case then
specify 'stop' at the svf command.

The absence of error or warning messages indicate that the SVF file was
executed without problems. To get a progress reporting while the player advances
through the SVF file, specify 'progress' at the svf command.

.Limitations and Deficiencies
*****************************
Several limitations exist for the SVF player.

The implementation of some SVF commands has deficiencies.

  - HIR, HDR commands not supported. +
    Their functionality should be covered by the part concept of UrJTAG.
  - PIO command not supported.
  - PIOMAP command not supported.
  - RUNTEST SCK not supported. +
    The maximum time constraint is not guaranteed.
  - TRST +
    Parameters Z and ABSENT are not supported.
  - TIR, TDR commands not supported. +
    Their functionality should be covered by the part concept of UrJTAG.

SVF files for programming flash-based devices might or might not work for a given
setup. This has been observed for Actel IGLOO devices where success and failure
depends on the actual clocking rate of the chosen cable.

The ref_freq=<...> option to the svf command allows to tweak the calculation
of 'RUNTEST xxx SEC' commands. For these commands, the SVF player needs to
calculate the equivalent number of clocks and per default it will use the
current cable clock frequency. This can be overridden with the ref_freq option
that specifies a fixed reference frequency for such calculations.
*****************************

===== bsdl =====

The 'bsdl' command is used to set up and test the underlying BSDL subsystem of
UrJTAG.

Whenever 'detect' encounters a new part, a configuration process is
started. This involves matching the retrieved IDCODE against the part
descriptions in /usr/share/urjtag as described above. However, before this
database is searched for a suitable description, the BSDL subsystem is started
and searches for a BSDL file that matches this device. If it finds a matching
file, traversal of the /usr/share/urjtag database is skipped. If not, then
this standard process follows.

To tell the BSDL subsytem where to look for BSDL files, the 'bsdl path
pathlist' command has to be issued prior to 'detect'. The contents of
'pathlist' must be a semicolon-separated list of directories where BSDL files
are located. This list is stored by 'bsdl path' and is used later on when
'detect' calls the BSDL subsystem.

IMPORTANT: The BSDL subsystem applies the first BSDL file that parses without
errors and that contains the correct IDCODE. Scanning the specified
directories happens in exactly the given order. Inside a directory however,
the order depends largely on your filesystem's behavior.

Further details of the 'bsdl' command:

  - bsdl path <path1>[;<path2>[;<pathN>]] +
    set paths for locating BSDL files
  - bsdl debug on|off +
    switches debug messages on or off
  - bsdl test [file] +
    reads file (if specified) or all files found via 'bsdl path' and
    prints a short status, an active part is not required
  - bsdl dump [file] +
    reads file (if specified) or all files found via 'bsdl path' and
    prints all configuration commands, an active part is not required

TIP: The 'bsdl dump file' command implements the same functionality as
bsdl2jtag.

==== Unsupported commands ====

===== script =====

Although it's still there, its functionality has been merged into the include
command. Please use "include" instead.

===== setdevice =====

This command was only there to support the SHARC 21065L processor,
which has no IDCODE and therefore can't be initialized correctly by
just running "detect". However, the proper initialization can be done
after "detect" by loading the proper declarations and bus driver manually:

  jtag> include analog/sharc21065l/sharc21065l

===== spiflashmem =====

The commands "spidetectflash", "spiflashmem", "spireadflash" and
"spieraseflash" only exist in a version of the JTAG tools copyrighted by
Intratrade Ltd., we just know about them from a posting on the net.

//========================================================================

== Internals ==

This section is only a placeholder for the information that will
be added soon...

=== Files ===

==== Source code Overview ====

doc/:: Documentation

data/:: Part descriptions (data files)

include/:: C header files

src/:: C source code

src/bsdl::  BSDL subsystem
src/bus::   Bus driver for various CPUs and other parts
src/cmd::   Implementation of the commands for the "jtag" shell
src/flash:: Flash detection and programming algorithms
src/jim::   JIM, the JTAG target simulator
src/lib::   Utility functions
src/part::  Functions for accessing specific parts in a chain
src/svf::   SVF player
src/tap::   Functions for accessing the chain in general

//------------------------------------------------------------------------

=== Drivers ===

 * Cable drivers
 * Link drivers
 * TAP drivers
 * Chain drivers
 * Bus drivers
 * Flash drivers
 * Commands

==== Cable-specific drivers (src/tap/cable) ====

Cable-specific drivers are those which are visible to the user through
the "jtag" command shell. They're listed in response to the "help cable"
command. Each driver has to provide the following functions:

 * connect(), init() - Initialization 
 * done(), cable_free(), disconnect() - Cleaning up
 * set_frequency() - set bitrate for shifting data through the chain
 * clock(), get_tdo(), transfer() - immediate JTAG activities
 * flush() - internally used to actually perform JTAG activities
 * help() - a help text to be displayed by the jtag command shell

=====  Initialization =====

After allocating a "cable_t" structure, a pointer to it and further
parameters (as strings) have to be passed first  to the selected cable's
connect() function. 

Following that, the init() function is called via cable_init(). If cable_init()
returns a zero value, all is fine and the cable is ready for use.

===== Cleaning up =====

There are two functions for actual cleanup:

 * done() is responsible for driving the hardware to a safe and consistent state.
 * cable_free() then can be used to clean up eventually extra allocated memory etc.

Both are usually called from chain_disconnect(). 

An additional mechanism allows to clean up if a disconnection was detected by
the low level driver (e.g. USB or parallel port driver). A cable has to provide
a disconnect() function for this purpose:

 1. Low level (e.g. parport) driver calls cable driver->disconnect()
 2. cable driver->disconnect() calls chain_disconnect()
 3. chain_disconnect() calls cable driver->done()
 4. chain_disconnect() then calls cable driver->cable_free()

After return from chain_disconnect() to cable driver->disconnect(), the cable_t
structure has been freed and must not be accessed anymore.

===== JTAG Activities =====

Currently the API provides five different functions for performing operations
at the JTAG interface on the low level signal level (using the four signals
TMS, TCK, TDI, and TDO).

 * clock(tms,tdi,n) takes values for TMS and TDI output as its parameters, ensures that actual cable signals are set accordingly, and does a 0-1 transition on TCK (n times)
 * get_tdo() returns the current value at the TDO input.
 * set_trst(x) sets the TRST signal and returns the current value.
 * get_trst() returns the current value of the TRST signal.

For many JTAG adapters, there's almost no delay when doing alternating clock()
and get_tdo(). Writing and reading happens immediately and the result is
available immediately as well. This is the case with most parallel port
adapters (but not when attached to USB-to-parallel adapters or USB docking
stations) and memory mapped IO (e.g. general purpose I/O pins of
microcontrollers).

But there are adapters, especially USB and Ethernet based adapters, which
exhibit a rather long delay between the initiation of reading a bit and the
delivery of the value of the bit. It is at least 1 millisecond with USB,
which would limit the transfer rate to 1 kHz.  One way to workaround this
is to transmit bits compacted into bytes and chunks of bytes, which is 
possible with the transfer() function.

 * transfer(in, out)

The transfer() function does a series of TCK pulses, with data for TDI read as
bytes from memory. The bytes are automatically serialized. TMS is set to zero
during transfer()s. Optionally, prior to each bit shifted out to the interface,
TDO input can be read into memory (deserialized into a byte array of the same
size as the input array).

It still doesn't yield much improvement if the operation consists of many read
and write transitions (e.g. repeatedly writing an instruction and some data
register values, then reading from the data register, as it is necessary for
memory access). For that reason, the above functions are also available in
variants that don't cause immediate activity, but rather schedule it for later.
In the API, they're visible as

 * cable_defer_clock()
 * cable_defer_get_tdo()
 * cable_defer_set_trst()
 * cable_defer_get_trst()
 * cable_defer_transfer()

These functions aren't implemented in the cable driver (but currently in
src/tap/cable.c).  The cable driver just has to provide a flush() function to
actually execute the queued activity in some cable-specific optimal way, and
to store the results of get_tdo() and transfer() activity. The caller later
can pick up the results using these functions (implemented in cable.c):

 * cable_get_tdo_late()
 * cable_get_trst_late()
 * cable_transfer_late()

As an example, consider the following sequence of activities:

 1. clock()
 2. get_tdo()
 3. clock()
 4. get_tdo()

If the result of the first get_tdo() isn't absolutely required before the
second clock(), the sequence can be optimized into the following sequence (if

 1. defer_clock()
 2. defer_clock()
 3. flush()
 4. get_tdo_late()
 5. get_tdo_late()

The next sections explain the queueing mechanism and its limits in detail.

===== When flushing occurs =====

The cable_flush() function is used to flush the queue towards the cable. It
takes one additional argument, "how_much", which may be one of

 * OPTIONALLY: The cable driver may flush if it's reasonable (e.g. if the
   queue has been filled so that some buffer limit for the cable interface
   is reached). It would be wise to flush early to keep the queue small, if
   there is no point in queueing up more items because the transfer to the
   cable would have to be split into smaller chunks anyway. This is used by
   UrJTAG immediately after adding items to the queue.

 * TO_OUTPUT: The cable driver should at least flush as much so that one 
   output becomes available in the output queue. If there's already something
   in the output queue, this should be interpreted similar to OPTIONALLY. This
   is used by UrJTAG immediately before it wants to use that output.

 * COMPLETELY: The cable driver has to flush the queue completely. This is
   used by UrJTAG immediately before actions that circumvent the queueing 
   such as calls to the legacy clock/get_tdo functions. It could also be
   used by application code to ensure that some action is actually done in
   time.

===== JTAG activity queueing =====

The source in src/tap/cable.c provides to important functions to access the
two queues "todo" (with activity to be done) and "done" (with results):

 * cable_add_queue_item
 * cable_get_queue_item

In src/tap/cable/generic.c you'll find two implementations of dequeueing 
algorithms, i.e. implementations of the flush() function. These could be used
by any new cable driver unless it provides a more sophisticated algorithm
itself:

 * generic_flush_one_by_one() simply calls the "classic" functions one after
   another. The performance of the cable driver using this implementation will
   be the same whether the immediate or defer variants of the functions are used.
 * generic_flush_using_transfer() tries to optimize as many clock() and
   get_tdo() by transforming them into calls to transfer() instead. This can
   give a slight advantage.

The generic implementations also serve as a template for new cable-specific
implementations. 

===== Generic implementations =====

As a reference and in many cases completely sufficient for new cables, take a
look at the code in src/tap/cable/generic.c, which contains generic routines,
suitable for parallel port based cables (and some for other types of cables as
well).

==== Link drivers ====

Link drivers like the "parport" driver collection provide the basis for
communication between cable driver and actual JTAG adapter. The openwince JTAG
tools supported only parallel port links with the "parport" drivers. UrJTAG
introduced support for USB links, but in the early releases the drivers for
these just mimic the parallel port links.

The basic functions provided by all link drivers are

 * connect(), to called from cable driver connect()
 * open(), to actually connect to the device during cable driver init()
 * close(), to disconnect from the device during cable driver done()
 * free(), to free all resources, called from cable driver free()

===== parport =====

Currently there are parport drivers for direct access to the parallel port on a
PC using I/O addresses (direct.c), and for using ppdev on Linux or ppi on FreeBSD.

In addition, there are "ftdi" and "ftd2xx" parport drivers that actually are for
communication with USB cables based on FTDI chips. They cannot be used for
connecting old parallel port cables through parallel to USB adapters with FTDI
chips, and probably soon will be rewritten as "usbconn" drivers instead.

All parport drivers present a common API for setting and reading signals.

===== usbconn =====

The usbconn drivers provide a common API to search for and connect with USB
devices. At the moment, there are drivers for libusd, libftdi and FTD2XX
(e.g. to communicate with FTDI chip based cables through libftdi and/or
FTD2XX, to communicate with Cypress FX2 using EZUSB.SYS or CyUSB.sys, and
more).

/////////////////////////////////////////////////////////////////////////////
arniml, 18-may-2008: Obsolete?
In contrast to the parport API, the usbconn drivers provide only the functions
for connecting, disconnecting, and for releasing ressources. The actual
communication must be implemented using the underlying library's functions,
e.g. usb_write from libusb, or ftdi_write from libftdi. Therefore, each driver
using usbconn usually only works together with one particular usbconn driver.
/////////////////////////////////////////////////////////////////////////////

==== Bus drivers ====

Bus drivers translate read and write operations on a bus into JTAG commands
and methods. A bus in this context is neither restricted to a processor bus,
nor to memory. Any system component that can be read from and written to could
be seen as attached to a bus. I.e. external or internal memory (RAM, ROM,
Flash) and peripherals connected to a processor or simply an FPGA with 1:1
connections.

The available bus drivers are listed in response to "help initbus". Each
driver has to provide the following functions:

 * bus_new() - Initialization
 * bus_free() - Cleaning up
 * bus_printinfo() - Short description
 * bus_prepare() - Preparation
 * bus_area() - Description of the bus geometry
 * bus_read_start() - Initiate reading
 * bus_read_next() - Read access
 * bus_read_end() - Finish reading
 * bus_read() - Atomic reading
 * bus_write() - Write access

IMPORTANT: Address parameters to the functions listed above specify always
byte locations, independent of the actual data width. The bus driver has to
adjust the address on its own if required.

===== Creation =====

Upon calling of its bus_new() function, the driver allocates a "bus_t"
structure and performs all required internal initializations.

===== Initialization =====

After creation of the new "bus_t" structure, the bus_init() function will
be called to give the driver the possibility to initialize it's internal
states or BSR bits as required. Such functionality has been split from
bus_new() since some drivers require to re-initialize during runtime.

===== Cleaning up =====

The driver is supposed to free all allocated memory (including its "bus_t"
structure). Additionally, it should set the device into a state that doesn't
prevent it from normal operation.

===== Short description =====

Prints a message describing the driver. This function is called by the "print"
command before it lists the areas covered by this bus driver.

===== Preparation =====

This function is called whenever a bus operation is initiated. The
driver should perform the required preparation steps so that
subsequent calls to the bus_read_* and bus_write functions can perform
their tasks properly.

E.g. a BSR bus driver would put the device into EXTEST mode to activate the
boundary scan register on the device pins.

===== Description of the bus geometry =====

At certain stages, the bus driver's bus_area() function is called by other
commands to query the bus geometry for a given address. The bus driver must
fill in the fields of a "bus_area_t" structure describing the geometry of the
area in which the specified address is located:

 * a short textual description of the area
 * start address of area
 * length of area in bytes
 * data width in bits

Queries with an address out of range must result in an area length of

  UINT64_C(0x100000000)

===== Initiate reading =====

Since the JTAG state machine defines a capture-shift-update sequence, it is
required to shift the address for a read prior to capturing the read
data. Therefore, the bus_read_start() function is called with the very first
address to read from. This enables the driver to shift the address into the
device before it can actually retrieve the read data for this address.

===== Read access =====

The bus_read_next() function fetches the read data from the device that has
been addressed by a previous call to bus_read_start() or
bus_read_next(). Again, this is due to the capture-shift-update sequence of
JTAG:

 1. capture read data from device pins
 2. shift new address
 3. update new address to device pins

IMPORTANT: The address parameter specifies the location of the 'following'
read access. It is not the address of the data returned by this function call.

===== Finish reading =====

Function "bus_read_end()" is called at the end of a read sequence. I.e. when
the higher level command determines that the last data portion is to be read
from the device. There is no new address and the function driver is supposed
to return the read data that was addressed previously.

===== Atomic reading =====

For ease of use, a bus driver has to supply a "bus_read()" function that
encapsulates reading data from a single address in an atomic operation. Bus
drivers typically build this function from "bus_read_start()" and a subsequent
"bus_read_end()".

===== Write access =====

This function writes one data element at the specified address. Since this
translates to a single JTAG operation (capture ignored, shift and update
address & data), there is no splitting as with the read functions.

=== Data file format ===
// By Marcel Telka

JTAG declarations files are located in directory "data". The files contains
common part specific JTAG information in parseable form, e.g.  list of the JTAG
commands, boundary scan register, list of JTAG registers, etc.

Syntax of the JTAG declaration file is defined in the following subsections.

==== General rules ====

JTAG declaration file is text file which consists of lines. Empty lines are
ignored. Text after first "#" on the line to the end of line is ignored. This
is useful for comments.  All other lines are significant.

Each significant line consists of tokens separated by whitespace. Whitespace
could be spaces and/or tabs.

==== Signal Definition ====

Signal definition line consists of word "signal" followed by whitespace and
signal name (without spaces in the name). Rest of the line should contain
whitespace separated list of pins of the part. This list is currently not used
for any purpose in JTAG Tools. It is intended for future use.  

==== Manufacturers List ====

The 'data/MANUFACTURERS' file is used to locate the manufacturer of a specific
device found in the JTAG chain.  If you get the error *Unknown manufacturer*
when attempting the 'detect' command, this is the file you need to update.

See the JEDEC document for more information:
JEDEC Solid State Technology Association, "Standard Manufacturer's
Identification Code", September 2001, Order Number: JEP106-K

===== Format =====

The first token is a bit string that matches bits 11-1 of the device's IDCODE.
We omit bit 0 because it should always be 1 (per the JEDEC standard).

The second token is the name of the directory under 'data/' to search for
specific part information.

The rest of the line is the human readable form of the manufacturer's name.

For example, we find this in 'data/MANUFACTURERS':

  00001100101	analog		Analog Devices, Inc.

The manufacturer's IDCODE is +000011001011+ (notice the last bit is stripped),
more part information can be found under 'data/analog/', and the human friendly
name is +Analog Devices, Inc.+.

==== Parts List ====

Every manufacturer subdirectory needs a 'PARTS' file.  This is used to look
up further information about a part such as the stepping and signal list.  If
you get the error *Unknown part* when attempting the 'detect' command, this is
the file you need to update.

===== Format =====

The first token is a bit string that matches bits 27-12 of the device's IDCODE.

The second token is the name of the directory under the manufacturer's 'data/'
directory to search for specific part information.

The rest of the line is the human readable form of the part's name.

For example, we find this in 'data/analog/PARTS':

  0010011111001000	bf537			BF537

The part's IDCODE is +0010011111001000+, more part information can be found
under 'data/analog/bf537/', and the human friendly name is +BF537+.

//------------------------------------------------------------------------

==== Stepping List ====

Every part subdirectory needs a 'STEPPINGS' file.  This is used to find the
file that contains information like the signals list.  If you get the error
*Unknown stepping* when attempting the 'detect' command, this is the file you
need to update.

===== Format =====

The first token is a bit string that matches bits 31-28 of the device's IDCODE.

The second token is the name of the file to load that contains information like
the signal list, extra instructions/registers, etc...  This file should be
placed alongside the 'STEPPINGS' file in the part-specific subdirectory.

The rest of the line is the human readable form of the part stepping's name.

For example, we find this in 'data/analog/bf537/STEPPINGS':

  0010	bf537		2

The part's stepping is +0010+, signal information can be found in the file
'data/analog/bf537/bf537', and the human friendly stepping name is +2+.

=== Development ===

==== Future Plans ====

- C API and library package
- Bindings for Python, Perl, ...
- TCP/IP access
- New cable drivers
- ...

==== How to contribute ====

 * Using Subversion
 * Create and submit a patch
 * Use SourceForge trackers

//========================================================================

== F.A.Q. ==

For a list of known problems in current versions, please also check the "Bugs"
tracker at the UrJTAG website!

Q. The documentation is incomplete. Where can I get more information?::
  A. Please ask in the "Using UrJTAG" Forum on http://urjtag.org[]

Q. My flash isn't detected or can't be programmed. What can I do?::
  A. Please record the output of the "detect" and "detectflash" commands and ask in the Forum. If possible, re-compile UrJTAG before with "--enable-jedec-exp" to get extra information.

Q. My CPU/FPGA/etc. chip isn't detected. What can I do?::
  A. First try to get hold of a "BSDL" description of the chip from the vendor, and specify where to find this file to UrJTAG using "bsdl path" before you "detect". Second, a bus driver has to be selected. Maybe "ejtag" or "prototype" work.

Q. When I type "cable parallel 0x378 DLC5" (in a Cygwin environment) I get "Unknown port driver: parallel"?::
  A. Please install the Cygwin ioperm package, and re-configure/compile.

Q. When I type "cable parallel 0x378 DLC5" (in a Cygwin environment) I get "Error: Cable initialization failed!".::
  A. Please install ioperm.sys driver using `ioperm -i` command.

Q. When running autogen.sh, I get "Can't exec "autopoint": No such file or directory"::
  A. You need the headers for gettext (e.g. Debian package "gettext-devel").

Q. When running autogen.sh, it complains about missing CVS::
  A. The easiest solution is to actually install CVS for this step, just to get around this error message.

Q. During compilation, I get "svf_bison.y: No such file or directory"::
  A. You need "bison".

Q. During compilation, I get "flex: can't open ... src/svf/svf_flex.l"::
  A. You need "flex"

Q. During compilation, I get "src/svf/svf_flex.l", line 27: unrecognized %option: bison-locations"::
  A. You need a newer version of flex. It should be 2.5.31 or newer;
    Unfortunately, Cygwin comes with only 2.5.4a. You may try to compile and
    install a newer version of flex from source to solve this. The distributed
    source tarball contains source pregenerated with a current flex version,
    you need flex yourself only to compile from fresh SVN checkouts.

Q. When running "make install", I get "Permission denied" errors::
  A. If you want to install into a system directory (the default /usr/local is one), you'll have to run "make install" as the  superuser, e.g. do "sudo make install".

Q. My BSDL file defines the bus DAT as bit_vector(15 downto 0), how should I access single elements?::
  A. BSDL syntax is an extension of the VHDL language. Array elements are indexed with
    parentheses: DAT(4) selects index number 4 of the DAT vector. Also refer to the "print
    signals" command.

Q. My board requires certain signals to be set to dedicated values before external memories can be accessed.::
  A. Most (if not all) BSR-based bus drivers allow for static configurations of
    pins that are controlled by BSR bits. Apply the required "set" commands before
    issueing the "initbus ..." command. These settings are preserved by all bus
    related commands if they don't collide with the signals required for bus operation.

Q. My USB pod seems slow.::
  A. USB-based JTAG pods suffer from a couple of intrinsic issues. Consider the
    following to get maximum performance:
    * Run UrJTAG on native linux. Cygwin and VMWare are reportedly slower.
    * Connect the pod via a high speed USB hub to a high speed USB host port.
      Even though the pod is a full speed device, it benefits from the shorter
      turn-around times between host and hub.

//========================================================================

== Licensing ==

=== Overview ===

Various licenses are used for the UrJTAG project. The GPL is used for most
of the code except for some include files, JIM, and cable driver source, where
a BSD or MIT license is used; this is noted in the file headers.

=== GNU Free Documentation License (FDL) ===
.........................................
include::fdl.txt[]
.........................................
=== GNU General Public License (GPL) ===
.........................................
include::gpl.txt[]
.........................................

