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From: Jan Halla
Subject: (no subject)
Date: Tue, 2 Dec 2008 17:56:33 +0100
User-agent: Mutt/1.5.13 (2006-08-11)

* Overview::                    Overview
* Hardware::                    POD, Pins, Power
* Driver::                      The Driver
* Library::                     A Library for Applications

* Testing::                     Is BDM working

* GDB::                         Building and using GDB

* Server::                      BDM Server

@c Following blank line required for remaining bug in makeinfo conds/menus

* Reporting Bugs::              Reporting Bugs
* Index::                       Index
@end menu
@end ifinfo

@c ---------------------------------------
@node Overview, Build System, Top, Top
@chapter Overview

@cindex what is this?

Welcome to Background Debug Mode (BDM) support for GDB. BDM is emulator
or debugger support in a range of Motorola processors. This package
deals with the CPU32, and Coldfire family of processors. PowerPC
processors are not supported by this package. 

CPU32 processors were the first processors to appear with BDM
support. The Coldfire family's BDM module is similar to the CPU32 family
of processors. The CPU32 has the BDM module integrated into the
processor core. The Coldfire is more modular. The debug module is
separate to the core.

BDM is not JTAG debugging although a serial bug is used. JTAG is a
standard and operates differently to BDM. BDM uses high level commands
to control the device. You do not need to clock in and out a loop of

BDM is accessed on the procesor via a three wire serial bus. The signals
are a clock, data in and data out. Various other support signals
exists. This are used to place the processor into BDM, break the
prcessor, or monitor the status of a running processor.

The CPU32 standard BDM connector is not the same as the Coldfire
connector. You need separate plug on modules for each processor
family. Check the POD you use matches the processors voltage and clock
speed. This is import for Coldfire users.

Coldfire BDM has support for realtime trace. This package does not
support realtime trace.

Coldfire BDM can operate in a limited manner while the processor is
running. The BDM module being separate from the procesor core allows
this feature.


Gunta Magna contributes here is a bit of history of how GDB and BDM
came to light due to mutual support.

Somewhere in 1994/1995 Gunta Magna wrote (with the help of Michael
Schraut, at that time a student at lpr.e-technik.tu-muenchen) a first
version of the m68k Linux BDM device driver. This driver heavily based
on the work of Scott Howard (address@hidden), who wrote BD32, a DOS
tool to access 683xx controllers via BDM. He made the driver available
in source form, so I could use them.  Scott is currently maintainer of
the crossgcc mailing list (http://www.objsw.com/CrossGCC/).

Additionally Gunta Magna wrote a BDM backend for gdb-4.13. (Note: Eric
credits M.Schraut falsly as the author of the GDB patches in the header
files. This went through until Chris Johns's version for Coldfire).

The driver was only for BDM interfaces compatilble to AN1230, aka as PD
interfaces. Scott supported also the ICD compatible interface, but due to
lack of equipment at that time Gunta Magna did not include that.

Eric Norum used those sources to port it to NextStep. He did not like
my way of interfacing driver and application, and designed a new
interface. He also introduced an abstraction layer, enabling other
applications than gdb to take advantage of the BDM driver. He also added
support for 68360, which is different in detail from the 68332 version
(MBAR support).

In 1996, Gunta Magna upgraded his driver to ICD by a compile time
option, and fixed some errors. He also upgraded the gdb backend to
gdb-4.16, introducing Eric's idea of the abstraction layer. Sources for
that can be found at the ftp server of lpr.e-technik.tu-muechen.de

In 1997 Eric went Linux and ported his NextStep driver to Linux. He
also wrote/ported his NextStep gdb backend, incorporating some of the
ideas (and bugs) introduced in Gunta's 4.16-version. He also published a
schematic stemming from the Motorola customer center here in Munich
(bd32new) (See below).

In 1997 I upgraded my driver to simultaneously support ICD and PD
interfaces. The selection is made by accessing different minor numbers.
This version has been handed out to several testers (including Chris
Johns), but has never been officially released.

Chris Johns used Eric's driver and added Coldfire support.

@c ---------------------------------------
@node Build System, Layout, Overview, Top
@chapter POD, Pins, Power

@cindex hardware

Various means exist to access a BDM port on a processor. This driver
provides support for various host operating system, and adapator boards.

The driver support the IDC hardware. A circuit abd PAL equations are
provided in the package.

The Coldfire support is via the P&E standard interface. You can find
information about these adaptor from the P&E web site.

<more on CPU32 hardware>


The Coldfire has a 26pin header. The expanded connector is for the
realtime trace. These signals are the PST or processor status
signals. Four of these signals provide provide the status of the
processor in realtime. 

The 5206 and 5206e processor share the PST signals with the parallel
port on Coldfire. Anr application that uses the Coldfire's parallel
port, cannot relying on the PST for the realtime status of the
processor. The P&E module provides a processor halted signal to the PC's
parallel port based on the PST signals. The P&E Windows driver and DLL
use this signal. Using this software with the P&E interface and a 5206
variant of Coldfire requires the parallel port to left for the PST
signals. The PST signals on the 5307 processor are not shared. They are
free to be used for debugging.

This driver does not require the use of the PST signals. The parallel
port on the 5206 processor can be used as a parallel port.

The 5206 and 5206e differ in Vcc voltage. The 5206 is a 5.0V processor
while the 5206e is a 3.3V processor. You need to check your POD can
handle your processors voltage. The 5206e can operate at 54MHz. The 5307
operate at 70MHz. The processor clock is carried up the BDM cable to the
POD. You need to insure the PLD on the POD is fast enough and the cable
from the target to the POD is not too long. If the cable is too long or
the PLD marginal the processor clock could be dragged out of shape
causing various problems which can be hard to find.

Various people have reported problems when using the driver with 5307
processors. Building the driver with the Makefile define @code{USE_PST}
causes the problem to go away. The error is 

@c ---------------------------------------
@node Build System, Layout, Overview, Top
@chapter The Driver

@cindex driver

Various means exist to access a BDM port on a processor. This driver
provides support for various host operating system, and adapator boards.

The code which accesses the pod is 

The driver supports different host operating systems.

@c ---------------------------------------
@node Layout, Configurations, Build System, Top
@chapter A Library for Applications

@cindex Library

The library provides an interface to the driver for user
applications. GDB currently requires this library to build. Future
release may have the library moved into the GDB patch allowing the BDM
code reside in the GDB source tree.

The library also contains the client code for talking to the BDM server.

@c ---------------------------------------
@node Layout, Configurations, Build System, Top
@chapter Testing

@cindex Testing

The driver should be tested with the `chk' program. It provides a
reasonable test of the software, driver and hardware path to the target.

@c ---------------------------------------
@node Layout, Configurations, Build System, Top
@chapter GDB

@cindex GDB

This section covers building GDB and contains some info about using GDB
with BDM.

@c ---------------------------------------
@node Layout, Configurations, Build System, Top
@chapter Server

@cindex Server

This section covers building and installing the GDB server.

Currently only a Unix version exists. It should operate on any platform
the driver can be built for.

The BDM server operates from inetd. You need to add the following line
to @file(/etc/services} :


bdm       6543/tcp                    # BDM server

@end smallexample

The port number @code{6543} was a random selection. If for any reason it
is a bad or taken number, please let me know.

In the file @file{/etc/inetd.con} add the following line :


bdm     stream  tcp     nowait  cjohns  /usr/local/sbin//bdmd bdmd

@end smallexample

I am running this server as me. If the BDM devices have global
read/write enabled, then it should be ok to use the user @code{nobody},
or something similar as the user.

The server has not been checked for security holes. If the 

@c ---------------------------------------
@node Reporting Bugs
@chapter Reporting Bugs
@cindex bugs in @code{MRB}
@cindex reporting bugs in @code{MRB}

Your bug reports play an essential role in making @code{MRB} reliable.

Reporting a bug may help you by bringing a solution to your problem, or
it may not.  But in any case the principal function of a bug report is
to help the entire community by making the next version of @code{MRB}
work better.  Bug reports are your contribution to the maintenance of

In order for a bug report to serve its purpose, you must include the
information that enables us to fix the bug.

* Bug Criteria::                Have you found a bug?
* Bug Reporting::               How to report bugs
@end menu

@c ---------------------------------------
@node Bug Criteria
@section Have you found a bug?
@cindex bug criteria

If you are not sure whether you have found a bug, here are some guidelines:

@itemize @bullet
If the you select a particular configuration and @code{MRB} does not
build. It should build if the configuration parameter selection make
sense. For example building the networking code without configuring a
network driver.

The standard targets which are contained in MRB do not run.

A new release of the GNU tools can break the current code.

Your suggestions for improvement of @code{MRB} are welcome.
@end itemize

@c ---------------------------------------
@node Bug Reporting
@section How to report bugs
@cindex bug reports
@cindex @code{MRB} bugs, reporting

The fundamental principle of reporting bugs usefully is this:
@strong{report all the facts}. If you are not sure whether to state a
fact or leave it out, state it!

Often people omit facts because they think they know what causes the
problem and assume that some details do not matter. Play it safe and
give a specific, complete example. That is the easiest thing for you to
do, and the most helpful.

Keep in mind that the purpose of a bug report is to enable us to fix the
bug if it is new to us. Therefore, always write your bug reports on the
assumption that the bug has not been reported previously.

Sometimes people give a few sketchy facts and ask, ``Does this ring a
bell?''  Those bug reports are useless, and we urge everyone to
@emph{refuse to respond to them} except to chide the sender to report
bugs properly.

To enable us to fix the bug, you should include all these things:

@itemize @bullet
The version of @code{MRB}.

Without this, we will not know whether there is any point in looking for
the bug in the current version of @code{MRB}.

Any patches you may have applied to the @code{MRB} source.

The type of host machine you are using, and the operating system name
and version number.

What compiler (and its version) was used to compile @code{MRB}
--e.g. address@hidden''.

The target you are building. If this is a new target you are developing,
you may need to provide some details of the changes you have made.

A description of what behavior you observe that you believe is

If you wish to suggest changes to the @code{MRB} source, send us context
diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or
@samp{-p} option.  Always send diffs from the old file to the new file.
If you even discuss something in the @code{MRB} source, refer to it by
context, not by line number.

The line numbers in our development sources will not match those in your
sources.  Your line numbers would convey no useful information to us.
@end itemize

Here are some things that are not necessary:

@itemize @bullet
A patch for the bug.

A patch for the bug does help us if it is a good one.  But do not omit
the necessary information, such as the test case, on the assumption that
a patch is all we need.  We might see problems with your patch and decide
to fix the problem another way, or we might not understand it at all.

And if we cannot understand what bug you are trying to fix, or why your
patch should be an improvement, we will not install it.  A test case will
help us to understand.
@end itemize

@c ---------------------------------------
@node Index
@unnumbered Index

@printindex cp


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