GNUPro® Toolkit
GNUPro Toolkit Reference for eCos
Matsushita MN10300
eCos 1.2.1
April 1999
Table of Contents

Copyright Ó 1999 CYGNUS SOLUTIONS, Inc. All rights reserved.
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Part #: 300-400-1010048-1.2.1
Table of Contents

Introduction Tool naming conventions
Toolkit features Processor version(s)
Targets Supported
Hosts Supported
Object file format GNUPro on Windows NT Windows environment settings
Case Sensitivity GNUPro on Redhat Linux Reference Compiler MN10300-specific command-line options
Preprocessor symbols
MN10300-specific attributes New compiler and linker features Initialization prioritization
Selective linking ABI Summary Data types sizes and alignments
Register allocation
Register usage:
Switches
The Stack Frame
Argument Passing
Function Return Values Assembler MN10300-specific command-line options
Syntax
Special characters
Register names
Addressing modes
Floating point
Opcodes
Synthetic Instructions Linker MN10300-specific command-line options Debugger MN10300-specific command-line options
Debugging programs with multiple threads Simulator Features
MN10300-specific command-line options
Using the simulator
Simulator exceptions within GDB
CygMon, the simulator, and thread-aware debugging Appendix A: CygMon (Cygnus ROM Monitor) Installing and building CygMon Installing CygMon Source
Building CygMon CygMon command list baud
break
disassemble
dump
go
help
load
memory
port
register
reset
step
terminal
transfer
unbreak
usage
version CygMon command editing
Debugging CygMon Appendix B: MN10300-specific Assembler Error Messages

Appendix C: Bibliography

Introduction

The GNUPro Toolkit for eCos is a complete solution for C and C++ development for the Matsushita MN10300. The tools include the compiler, assembler, linker, simulator and interactive debugger. Simulator, linker and debugger support is also included for the MN10300 Series evaluation board. In addition to this manual, please read Getting started with eCos. Tool naming conventions

Cross-development tools in the Cygnus GNUPro Toolkit normally have names that reflect the target processor and the object file format output by the tools (for example ELF). This makes it possible to install more than one set of tools in the same binary directory, including both native and cross-development tools.

The complete tool name is a three-part hyphenated string. The first part indicates the processor or processor family (mn10300). The second part indicates the file format output by the tool (elf). The third part is the generic tool name (gcc). For example, the GCC compiler for the Matsushita MN10300 is,
mn10300-elf-gcc.

The MN10300 package includes the following supported tools:

Tool Description | Tool Name
GCC compiler | mn10300-elf-gcc
C++ compiler | mn10300-elf-c++
GAS assembler | mn10300-elf-as
GLD linker | mn10300-elf-ld
Standalone simulator | mn10300-elf-run
Binary Utilities | mn10300-elf-ar mn10300-elf-nm mn10300-elf-objcopy mn10300-elf-objdump mn10300-elf-ranlib mn10300-elf-size mn10300-elf-strings mn10300-elf-strip
GDB debugger | mn10300-elf-gdb

The binaries for a Windows NT hosted toolchain are installed with an .exe suffix. However, the .exe suffix does not need to be specified when running the executable. Toolkit features

The following describes MN10300-specific features of the GNUPro Toolkit. Processor version(s) Matsushita MN10300 family, incorporating the MN10300 and MN103002. These parts are also sold under the Panasonic or Pana-X brand name. Wherever Matsushita or 10300 are used in this document, Panasonic or Pana-X should be considered identical. Targets Supported GNUPro Instruction Set Simulator with architectural extensions to support eCos execution

MN10300 Series evaluation board.

Both targets run in little-endian mode.

Hosts Supported

CPU | Operating System | Vendor
x86 | Windows NT 4.0 | Microsoft
x86 | Redhat Linux 5.x | Redhat

Object file format The MN10300 tools support the ELF object file format. Refer to Chapter 4, System V Application Binary Interface (Prentice Hall, 1990.). Use ld (refer to Using LD in GNUPro Utilities) or objcopy (refer to The GNU Binary Utilities in GNUPro Utilities) to produce S-records.

GNUPro on Windows NT

Windows environment settings The Windows NT hosted toolchain requires the following environmental settings to function properly. Assume the release is installed in:

C:\cygnus\gnupro\i386-cygwin32\mn10300-elf\ecos-98r1p6
SET PROOT=C:\cygnus\gnupro\i386-cygwin32\mn10300-elf\ecos-98r1p6
SET PATH=%PROOT%\H-i386-cygwin32\bin;%PATH%
SET INFOPATH=%PROOT%\info
REM Set TMPDIR to point to a ramdisk if you have one
SET TMPDIR=C:\TEMP For the Sourceware release of eCos, ensure that the Cygwin B20.1 tools are also installed. Assuming these are installed in their default location in
C:\cygnus\cygwin-b20 then add the environmental setting
: SET PATH=C:\cygnus\cygwin-b20\H-i586-cygwin32\bin;%PATH%
If you are using the eCos Developers Kit CD release (not included in the sourceware release), a working environment can be established by using the following shortcut from the Windows Start menu:
Programs->Cygnus eCos->eCos Development Environment. This will bring up a window running bash, and your Windows environment will be automatically set up. Case Sensitivity The following strings are case sensitive under Windows NT:

- command line options
- assembler labels
- linker script commands
- section names

The following strings are not case sensitive under Windows NT:

- gdb commands
- assembler instructions and register names

Case sensitivity for Windows NT is dependent on system configuration. By default, file names under Windows NT are not case sensitive.

GNUPro on Redhat Linux

The GNUPro Tools for Redhat Linux are supplied in a ZIP format file. Detailed instructions for installation can be found on the eCos sourceware site:
http://sourceware.cygnus.com/ecos/
Assuming the sources for the tools were installed in
/usr/cygnus/ecosSWtools-990319/src
By following the instructions in the Installation Guide, you should eventually have the tools installed in
/usr/cygnus/ecosSWtools-990319/H-i386-pc-linux-gnu/bin
In which case, we recommend you have the following settings in your appropriate shell startup script.

For Bourne shell compatible shells:
PROOT=/usr/cygnus/ecosSWtools-990319
PATH=$PROOT/H-i386-pc-linux-gnu/bin:$PATH
INFOPATH=$PROOT/info:${INFOPATH-/usr/local/info:/usr/info}
MANPATH=$PROOT/man:${MANPATH-/usr/local/man:/usr/man}
export PATH INFOPATH MANPATH
For C-shell compatible shells:
setenv PROOT /usr/cygnus/ecosSWtools-990319

if ( "$?MANPATH" == "0" ) then
setenv MANPATH "/usr/local/man:/usr/man"
endif

if ( "$?INFOPATH" == "0" ) then
setenv INFOPATH "/usr/local/info:/usr/info"
endif

setenv MANPATH $PROOT/man:$MANPATH
setenv INFOPATH $PROOT/info:$INFOPATH
set path = ( $PROOT/H-i386-pc-linux-gnu/bin $path )

Reference

Compiler

This section describes MN10300-specific features of the GNUPro Compiler. MN10300-specific command-line options For a list of available generic compiler options, see "GNU CC Command Options" in Using GNU CC in GNUPro Compiler Tools. In addition, the following MN10300-specific command-line options are supported:

-mmult-bug Generate code to work around bugs in the mn10300 multiply instruction. This is the default. -mno-mult-bug Do not generate code to work around bugs in the mn10300 multiply instruction.

Preprocessor symbols By default, the compiler defines the preprocessor symbols __MN10300__ and __mn10300__. MN10300-specific attributes There are no MN10300-specific attributes. See "Declaring Attributes of Functions" and "Specifying Attributes of Variables" in "Extensions to the C Language Family" in Using GNU CC in GNUPro Compiler Tools for more information.

New compiler and linker features

The GNUPro compiler and linker have been improved by Cygnus to provide even more benefits for customers developing for embedded targets. These features are guaranteed order of initialization at startup, and selective linking. Initialization prioritization In C++, you can define static and global objects with constructors, or initialize static and global variables from a function. This means that the constructors or functions are run before the rest of your program starts. However, when you have these objects spread over multiple files the C++ standard does not specify the order in which they are initialized, and for all practical purposes the order is random. For an embedded system, this can be a problem, as you may want to ensure that a static scheduler object is initialized before static threads can attach to it, or that devices are initialized before they are used. GNUPro solves this problem by allowing you to define a priority when the static or global is declared. The following example shows the syntax:

static object_t myobj __attribute__((init_priority (30000) ));

The syntax is slightly different if the object takes any arguments to its constructor:

static object_t myobj __attribute__((init_priority (30000) )) = object_t(arg1, arg2);

The numeric priority can be from 1 to 65535, with 1 being the highest priority, and 65535 being the lowest. The default priority for objects without this attribute is 65535. Constructors with a higher priority are guaranteed execution before constructors with lower priority.

In all cases, you must provide the argument -finit-priority to the compiler on its command-line for it to recognize this attribute when you are compiling your C++ source files.

If you are using eCos, be warned that eCos uses initialization priorities internally. Ensure you choose an appropriate priority level so that other eCos subsystems will have initialized before you refer to them in your own constructor.

Selective linking When writing C and C++ code, it is sometimes natural to include more than one function in a source file. For example in C++, it is common to have all methods for a particular class contained in the same C++ source file. However, there is a drawback that, conventionally, if you use just one of these functions, then all the functions defined in that file also get included in the final executable image. For an embedded system, this can substantially and unnecessarily increase the size of the final image stored in ROM, or loaded into RAM when debugging.

The GNUPro C and C++ compilers can now optionally remove these unnecessary functions from the final image. They also ensure that any shared global data is removed that is only referenced by functions that are removed. This can be done by including the options -ffunction-sections and -fdata-sections on the command-line, when you invoke the C or C++ compiler. The -ffunction-sections option removes unnecessary functions, and the -fdata-sections option removes unnecessary data.

In addition, when classes define virtual methods in C++, it is possible to remove any unused methods from the final image by passing the option -fvtable-gc to the C++ compiler on its command-line.

In all cases, you must also supply a command-line option when linking. If invoking the linker ld directly, use --gc-sections on its command-line; alternatively, if you are using the preferred method of linking your executable, using the form
gcc -o <program name> <file1>.o <file2>.o, then also pass the option -Wl,--gc-sections on the compiler command-line, for example:
gcc -o prog f1.o f2.o -Wl,--gc-sections

ABI Summary

This section describes the MN10300 Application Binary Interface. Data types sizes and alignments

This table describes the size and alignment of the data types:

Type | Size (bytes) | Alignment (bytes)
char | 1 byte | 1 byte
short | 2 bytes | 2 bytes
int | 4 bytes | 4 bytes
long | 4 bytes | 4 bytes
long long | 8 bytes | 8 bytes
float | 4 bytes | 4 bytes
double | 8 bytes | 8 bytes
long double | 8 bytes | 8 bytes
pointer | 4 bytes | 4 bytes

- The stack is kept 4-byte aligned.
- Structures and unions have the same alignment as their most strictly aligned component.

Register allocation

The compiler allocates registers in the following order:
d0, d1, a0, a1, d2, d3, a2, a3

Register usage:

This table describes register usage:

Type | Registers | Notes
volatile | d0, d1, a0, a1 |
saved | d2, d3, a2, a3 |
special purpose | sp, ccr, mdr, lar, lir | (1) (2)
frame pointer | a3 (if needed) | (3)

Table notes:

1. The compiler does not generate code that uses ccr, lar or lir.
2. mdr is only used for integer division and modulo operations.
3. a3 is the frame pointer in functions that need a frame pointer; otherwise it is an allocatable register.

Switches

There are no switches that effect the ABI or calling conventions. There are two switches that control a particular aspect of code generation. See MN10300-specific command-line options.
The Stack Frame

The following describes the MN10300 stack frame.

- The stack grows downwards from high addresses to low addresses.
- A leaf function need not allocate a stack frame if it does not need one.
- A frame pointer need not be allocated.
- The stack pointer shall always be aligned to 4 byte boundaries.

Stack frames for functions that take a fixed number of arguments look like this:

Note:
FP points to the same location as SP.

Stack frames for functions that take a variable number of arguments look like:

Argument Passing

d0 and d1 are used for passing the first two argument words, any additional argument words are passed on the stack.

Any argument, more than 8 bytes in size, is passed by invisible reference. The callee is responsible for copying the argument if the callee modifies the argument.

Function Return Values

a0 is used to return pointer values

d0 and d1 are used for returning other scalars and structures less than or equal to 8 bytes in length.

If a function returns a structure that is greater than 8 bytes in length, then the caller is responsible for passing in a pointer to the callee which specifies a location for the callee to store the return value. This pointer is passed as the first argument word before any of the functions declared parameters.

Assembler

This section describes MN10300-specific features of the GNUPro Assembler. MN10300-specific command-line options For a list of available generic assembler options, see "Command-Line Options" in Using AS in GNUPro Utilities. There are no MN10300 specific assembler command-line options. Syntax The MN10300 syntax is based on the syntax in Matsushitas MN10300 Architecture Manual.

The assembler does not support "user defined instructions" nor does it support synthesized instructions (pseudo instructions, which correspond to two or more actual machine instructions).

Special characters The MN10300 assembler supports ; (semi-colon) and # (pound). Both characters are line comment characters when used in column zero. The semi-colon may also be used to start a comment anywhere within a line. Register names These are the register names supported for the MN10300: d0, d1, d2, d3, a0, a1, a2, a3, sp, mdr, ccr, lir, lar.

Addressing modes

The following describes MN10300 assembler addressing modes:

Register Direct:
Dm/Dn
Am/An
Immediate value:
imm8/regs
imm16
imm32
imm40
imm48
Register Indirect:
(Am)/(An)
Register indirect with displacement
(d8,Am)/(d8,An) | d8 is sign extended
(d16,Am)/(d16,An) | d16 is sign extended
(d32,Am)/(d32,An) |
(d8,pc) | d8 is sign extended
(d16,pc) | d16 is sign extended
(d32,pc) |
(d8,sp) | d8 is sign extended
(d16,sp) | d16 is sign extended
(d32,sp) |
Absolute:
(abs16) | abs16 is zero extended
(abs32) |
Register indirect with index
(Di,Am)/(Di,An)

The subscripts m, n, and i indicate source, destination and index respectively. The values of m, n and i' are from 0 to 3.

For detailed information, see MN10300 Series Instruction Manual.

Floating point Although the MN10300 has no hardware floating point, the .float and .double directives generate IEEE-format floating-point values for compatibility with other development tools. Opcodes For detailed information on the MN10300 machine instruction set, see MN10300 Series Instruction Manual. The GNU Assembler (GAS) implements all the standard MN10300 opcodes. Synthetic Instructions The assembler does not support "user defined instructions" nor does it support synthesized instructions (pseudo instructions, which correspond to two or more actual machine instructions).

Linker

eCos generates linker scripts appropriate for the exact eCos configuration you have chosen. Instructions on how to use this linker script are provided in the manual Getting Started with eCos. MN10300-specific command-line options For a list of available generic linker options, refer to "ld command line options" in Using LD in GNUPro Utilities. There are no MN10300-specific command-line linker options.

Debugger

This section describes MN10300-specific features of the GNUPro Debugger.
For debugging examples, see chapter "Run an eCos test case" in Getting Started with eCos

There are two ways for GDB to talk to an MN10300 target. Each target requires that the program be compiled with a target specific linker script.

1. Simulator:
To build eCos for the simulator you may either configure it to build for the standard evaluation board with ROM startup, or for the minimal simulator with RAM startup. Linking your program against the eCos libtarget.a library, and with the target.ld linker script will produce the correct final executable that should be loaded into the simulator.

Note:
Loading binaries into the simulator that were built for the standard evaluation board with RAM startup will not work.

To activate the simulator in GDB, follow the instructions in the Simulator section later in this document.

2. Remote target board:
To load your program onto the standard evaluation board, build eCos for the hardware with RAM startup. Provided the board is fitted with CygMon ROMs, or GDB loader stub ROMs, you may connect to the target board in GDB using the command

target remote <devicename>

where <devicename> will be a serial device such as com2 (Windows NT) or /dev/ttyS1 (Linux). Then load the code onto the target board by typing load. After being downloaded, the program can be executed.

Note:
When using the remote target, GDB does not accept the run command. However, since downloading the program has the side effect of setting the PC to the start address, you can start your program by typing continue (the letter c works as a shortcut for the continue command). MN10300-specific command-line options For the available generic debugger options, see Debugging with GDB in GNUPro Debugging Tools. There are no MN10300-specific debugger command-line options.

Debugging programs with multiple threads

Programs with multiple threads can be debugged using either the graphic user interface to GDB, GDBTk or the GDB command line interface. The following describes how to debug multiple threads using the GDB command line.

In some operating systems, such as eCos, a single program may have more than one thread of execution. The precise semantics of threads differ from one operating system to another, but in general the threads of a single program are akin to multiple processes, except that they share one address space (that is, they can all examine and modify the same variables). On the other hand, each thread has its own registers and execution stack, and perhaps private memory.

GDB provides the following functions for debugging multi-thread programs

- thread threadno, a command to switch among threads
- info threads, a command to inquire about existing threads
- thread apply [threadno][all] args , a command to apply a command to a list of threads
- thread-specific breakpoints

The GDB thread-debugging facility allows you to observe all threads while your program runs, but whenever GDB takes control, one thread in particular is always the focus of debugging. This thread is called the current thread. Debugging commands show program information from the perspective of the current thread.
For debugging purposes, GDB associates its own thread number, always a single integer, with each thread in your program.

info threads Display a summary of all threads currently in your program. GDB displays for each thread (in the following order):

1. The thread number assigned by GDB.
2. The target systems thread I.D.
3. The current stack frame summary for that thread.

An asterisk * to the left of the GDB thread number indicates the current thread. Use the following example for clarity. (gdb) info threads
* 2 thread 2 breakme ()
at /eCos/packages/kernel/v1_2_1/tests/thread_gdb.c:91
Name: controller, State: running, Priority: 0, More: <none>
1 thread 1 Cyg_HardwareThread::thread_entry (thread=0x1111aaa2)
at /eCos/packages/kernel/v1_2_1/src/common/thread.cxx:68
Name: Idle Thread, State: running, Priority: 31, More: <none>
thread <threadno> Make thread number <threadno>the current thread. The command argument, <threadno>, is the internal GDB thread number, as shown in the first field of the info threads display. GDB responds by displaying the system identifier of the thread you selected, and its current stack frame summary, as in the following output.
(gdb) thread 2
[Switching to thread 2]
#0 change_state (id=0, newstate=0 '\000')
at /eCos/kernel/current/tests/bin_sem2.cxx:93
93 if (PHILO_LOOPS == state_changes++)
Current language: auto; currently c++
thread apply [<threadno>][<all>] <args> The thread apply command allows you to apply a command to one or more threads. Specify the numbers of the threads that you want affected with the command argument <threadno>, where <threadno> is the internal GDB thread number, as shown in the first field of the info threads display. To apply a command to all threads, use thread apply all args.
Whenever GDB stops your program, due to a breakpoint or a signal, it automatically selects the thread where that breakpoint or signal happened.

When your program has multiple threads, you can choose whether to set breakpoints on all threads, or on a particular thread.
break <linespec> thread <threadno> If <linespec> specifies source lines, then there are several ways of writing them. Use the qualifier thread <threadno> with a breakpoint command to specify that you only want GDB to stop the program when a particular thread reaches this breakpoint. <threadno> is one of the numeric thread identifiers assigned by GDB, shown in the first column of the info threads display.

If you do not specify thread <threadno> when you set a breakpoint, the breakpoint applies to all threads of your program.

You can use the thread qualifier on conditional breakpoints as well; in this case, place thread <threadno> before the breakpoint condition, as the following example shows.
(gdb) break frik.c:13 thread 28 if bartab > lim
Whenever your program stops under GDB for any reason, all threads of execution stop; not just the current thread. This allows you to examine the overall state of the program, including switching between threads, without worrying that things may change.

Conversely, whenever you restart the program, all threads start executing. This is true even when single stepping with commands like step or next. In particular, GDB cannot single-step all threads in lockstep. Since thread scheduling is up to your debugging targets operating system (not controlled by GDB), other threads may execute more than one statement while the current thread completes a single step. In general other threads stop in the middle of a statement, rather than at a clean statement boundary, when the program stops.

You might even find your program stopped in another thread after continuing or even single stepping. This happens whenever some other thread runs into a breakpoint, a signal, or an exception before the first thread completes whatever you requested.

SET SCHEDULER-LOCKING
For targets that support it, GDB has a new command that helps to debug
multi-threaded programs. The set scheduler-locking [on off step] command allows the GDB user to exert some control over how threads are scheduled while debugging.

Normally GDB does not attempt to interfere with thread scheduling. This means that in the default mode (scheduler-locking off), the current thread may be scheduled out, and a different thread may begin running, at any time (as determined by the native scheduler). For instance, you may give a GDB command such as step or finish, and when the command completes, you may be looking at a different thread.

If you set the scheduler-locking mode to step, then GDB will try to interfere with the native scheduler just enough to prevent another thread from popping up while you debug. Other threads may get to run sometimes, but whenever a command such as step or finish completes, you should be looking at the same thread that was running before the command. Of course, if another thread gets to run and hits a breakpoint, GDB will still switch you to that thread (so if you dont want that to happen, then disable your breakpoints).

For even greater (and more intrusive) control over the thread scheduler, GDB provides the mode scheduler-locking on. In this mode, the native scheduler is completely locked, and no thread may run except the current one. Obviously this will radically change the behavior of your program, and may lead to deadlock or other unpleasant consequences, so use it with caution.

Syntax:

set scheduler-locking [off on step] Set mode for locking scheduler during target execution. off No locking (threads may preempt at any time). on Full locking (no thread except the current thread may run). step The scheduler is locked during every single-step operation. In this mode, no other thread may run during a step command. However, other threads may run while stepping over a function call (next).

Simulator

The GNUPro simulator allows execution of a program compiled for the MN10300 target CPU on any supported host computer. It includes a simulator module for the target CPU instruction set, memory, and may also include simulated peripheral devices such as serial I/O and timers. Altogether, these features allow developers to test their MN10300 programs, without need for an actual board with that CPU.

The MN10300 simulator is not designed to match timing characteristics of its target board. For example, the CPU module uses a single clock cycle for all instructions, its memory is infinitely fast, and its simulated serial I/O is infinitely fast. Furthermore, a number of obscure or inapplicable functions were omitted from the simulated peripherals. The simulator is just complex and accurate enough to run eCos programs.

Features
The GNUPro simulator supports the following registers:

Volatile registers: d0, d1, a0, a1

Saved registers: d2, d3, a2, a3

Special purpose registers: sp, pc, ccr, mdr, lar, lir

Memory is 4mb starting at location 0x48000000. The stack starts at the highest memory address and works downward. The heap starts at the lowest address after the text, data and bss.

MN10300-specific command-line options
The following general options, are supported by the simulator:

--board=BOARD Specifies that the simulator be tailored to a model of a specified hardware board. For the mn10300, the --board=stdeval1 option will add support for several peripherals on the evaluation board, including the mn103002 on-board interrupt controller, timers, and serial I/O modules. The boards actual RAM & ROM memory layouts are matched by the simulator. --profile [on|off] This option creates a file called gmon.out that contains profiling information. This file can be used as input to gprof, the GNU profiler. --sockser-addr=HOSTNAME:PORT Specifies that the simulation of the primary serial I/O peripherals should send data to and from a TCP/IP socket rather than to and from the simulator console. The TCP/IP sockets listening address is specified by the argument. HOSTNAME should refer to an IP address of the host, and PORT should be an unused port number between 1024 and 65535. You may use any terminal program that connects to TCP/IP sockets, such as telnet, kermit, or socket, to interact directly with the simulated program. You can also use gdbs target remote HOSTNAME:PORT command to connect, if the simulator is running a program equipped with a gdb stub. --trace=[on|off] This creates a file called trace.din that contains tracing information. Use the --tracefile switch (discussed below) to change the name of the output file. C:\> mn10300-elf-run --trace hello
Hello, world!
3 + 4 = 7

Here are the first 10 lines of the file produced by the above run:

2 a0040004 ; width 4 ; load instruction
2 a0040008 ; width 4 ; load instruction
2 a004000c ; width 4 ; load instruction
2 a0040010 ; width 4 ; load instruction
2 a0040014 ; width 4 ; load instruction
2 a0040018 ; width 4 ; load instruction
2 a004001c ; width 4 ; load instruction
2 a0040020 ; width 4 ; load instruction
2 a0040024 ; width 4 ; load instruction
2 a0040028 ; width 4 ; load instruction

--tracefile <file> This changes the name of the file to which trace information will be written.

C:\> mn10300-elf-run --trace --tracefile=trace.out hello
Placing trace information into file "trace.out"
Hello, world!
3 + 4 = 7

Using the simulator

An eCos program is normally built with a particular "download method" in mind, that is, the means by which the program is to be ultimately loaded into the target hardware. With some special considerations, the simulator is able to run programs built for any of these methods. Use the configuration options in eCoss Hardware Abstraction Layer (HAL) package to support the different download methods. The following table summarizes the ways in which an eCos image can be prepared for different types of download.

HAL configuration, for various download methods

Download method | HAL configuration
Burn hardware ROM | ROM startup
Download to ROM emulator | ROM startup
Download to board with CygMon | RAM startup
Download to simulator without CygMon | ROM startup
Download to simulator with CygMon | RAM startup
Download to simulator, ignoring devices | SIM configuration

CAUTION: An application configured for RAM startup cannot be run directly on the simulator: it will fail during startup. You can only download it to the simulator if you are already running CygMon in the simulator, as described below.
The simulator-specific configuration does not include device drivers or watchdog devices that the simulator would otherwise have to emulate.

In most circumstances, you should not download to simulator ignoring devices. If you use this download method, the binaries built with this configuration will not run on the target board; they can only run on the simulator. Likewise, binaries built to run on the target board will not run on the simulator.

In some cases, you may want to use a simulator specific configuration to try to work around problems with the device drivers or with the simulator itself.

Simulator clocks and timers sometimes appear to be running very slowly, even when there are apparently no active threads. Delays that should only be in seconds can run to minutes. These delays occur because the eCos kernel idle thread is running intensively, and the simulator emulates it faithfully. With the SIM configuration, however, the eCos kernel realizes it is in a simulated environment, and can therefore adjust the clock settings to be more realistic.

Simulator exceptions within GDB

If you invoke the simulator within GDB, using the target sim command, you may encounter some ambiguities when processing signals and exceptions. When an exception is raised in the simulator, GDB does not known whether the simulated program is intended to handle the exception, or if GDB is intended to handle it.

For example, suppose you are debugging a ROM monitor in the simulator invoked from GDB (well call this GDB1), and you have downloaded an application to it from a second GDB session (which we will call GDB2). The second GDB session, GDB2, would simply consider the simulated target as a remote target and nothing more. Now suppose that in GDB2 you set a breakpoint in the program. The breakpoint will be physically set in GDB1. So when the breakpoint is reached, instead of the breakpoint being handled by the ROM monitor as if it was a real target, the breakpoint will be interpreted by GDB1 as if you had asked GDB1 to set a breakpoint in the ROM monitor code. This may not be your desired intention. To solve this, you can tell GDB1 not to process breakpoints itself, but to let the simulated target process them.

To do this, use the following command:
handle SIGxxxx pass nostop noprint
where SIGxxxx is one of the signals listed by GDB when you use the
info handle command to the GDB console prompt.

For example the command handle SIGTRAP pass nostop noprint tells GDB to not stop the simulated target at a breakpoint, or even to print that it has been stopped. Instead, the command tells GDB to pass the information back to the program. You can modify the command to use with other signals and exceptions.

Note: if you use the aforementioned command, you will no longer be able to set breakpoints in the ROM monitor code (as in the example). You may be able to work around this problem by using conditional breakpoints. Please consult the GDB manual on how to use conditional-breakpoints.

The ambiguities discussed in this section are not a problem when you are using the standalone simulator. In such a case, the standalone simulator is the only target program that can handle the exception

CygMon, the simulator, and thread-aware debugging

The simulator does not support thread-aware debugging. However, CygMon does support it. To obtain this functionality in the simulator, run CygMon under the simulator, and interact with it as if it were actually running on the real hardware.

While this approach offers the desired functionality, it is has a few disadvantages. The simulator is not only slow to execute code compared with real hardware, but simulation of the ROM monitor also slows the downloading of code to approximately the speed of a serial port. In addition, since the simulator must run continuously to execute CygMon, it can interfere with the performance of GDB. If there is insufficient memory for both programs to be in memory together, there may also be delays due to memory paging.

This technique uses TCP/IP for communication between the simulator and GDB, so you must ensure that the TCP/IP protocol stack is installed on your machine.

To run CygMon in the simulator, type the following command at the command line:

mn10300-elf-run --board=stdeval1 --sockser-addr=localhost:XXXX cygmon.rom

Where XXXX, is an unused TCP port number on your computer. A value of 1234 usually works, but any number between 1024 and 65535, which does not result in an error will do. The executable, cygmon.rom can be found in the directory, loaders/mn10300-stdeval1 within the eCos installation.

This has started the simulator running CygMon. To make use of it you must run a separate GDB session and connect to it.

If you run GDB in command-line mode, you can attach it to the simulated CygMon with the following command:
(gdb) target remote localhost:XXXX

Where XXXX is the port number given in the call to the simulator. GDB should connect to the simulator and talk to the version of CygMon running in it in exactly the same way as if it were talking to CygMon running on the real hardware.

If you are running the GDBTk then, in the Target Settings dialog, select Remote/TCP in the Target edit field. Type localhost into the Host edit field, and put the value chosen for the port number in the Port entry.

You should use executables configured to run on the target board with RAM startup, and not executables configured for the simulator.

If the performance of the two programs on a single machine is too slow, it is possible to use two machines: one to run the simulator and one to run GDB. These machines must be connected together on a TCP/IP network. Run the simulator on one machine, but supply the name of the machine in place of localhost in the --sockser-addr option. When running GDB on the other machine, replace localhost with the name of the machine running the simulator.

Appendix A: CygMon (Cygnus ROM Monitor)

CygMon is a ROM monitor designed to be portable across a large number of embedded systems. It is also completely compatible with existing GDB protocols, thus allowing the use of a standard ROM monitor with existing GNU tools across a wide range of embedded platforms.

CygMon has basic program handling and debugging commands, programs can be loaded into memory and run, and the contents of memory can be viewed. There are several more advanced options that can be included at compile time, such as a disassembler (this of course increases the code size significantly).

Since CygMon contains a GDB remote stub, full debugging can be done from a host running GDB to a target running CygMon. Switching between CygMon monitor mode and GDB stub mode is designed to be transparent to the user, since CygMon can detect when GDB is communicating with the target and switch into stub mode. When GDB stops communicating with the target normally, it sends a termination packet which lets the stub know when to switch to the CygMon monitor mode.

The command parser was written specifically for CygMon, to provide necessary functionality in limited space. All commands consist of words followed by arguments separated by spaces. Abbreviations of command names may be used. Any unique subset of a command name is recognized as being that command, so du is recognized to be the dump command. The user is prompted to resolve any ambiguities. Generally, a command with some or all of its arguments empty will either assume a default-set of arguments or return the status of the operation controlled by the command.

CygMon includes an API, which allows user programs, running under it, to use system calls for various functions. The available system calls allow access to the serial ports and on-board timer functions, if they are available.

Installing and building CygMon

This section explains to owners of the eCos Development Kit how to install the CygMon source, and build the CygMon ROM monitor program under the Windows NT operating system.

For users of the Sourceware release of eCos, instructions can be found at

http://sourceware.cygnus.com/ecos/

Installing CygMon Source By selecting the appropriate component, the eCos installer will install the CygMon source code, and we recommend you do so. When installed the sources would then be found in:

C:\Program Files\Cygnus Solutions\eCos\ecos-98r1p6\cygmon-src

If you choose to install the sources to a different location, the cygmon-src directory will be located at ecos-98r1p6\cygmon-src relative to the specified location. Please note that due to the configuration and build tools being used, the sources must be installed in a directory hierarchy that uses only alphanumeric, dash or underscore characters in the directory names.

Building CygMon
From the Start Menu, select:

Programs->Cygnus eCos->eCos Development Environment

This will bring up a window running bash.

Mount the sources such that the full path to the CygMon sources uses only alphanumeric, dash or underscore characters:
mount C:/Program\ Files/Cygnus\ Solutions/eCos /ecos
In addition, you must mount the bin directory for the unsupported tools as /bin:
mount C:/cygnus/gnupro/i386-cygwin32/i386-cygwin32/\
unsupported-98r1p2/H-i386-cygwin32/bin /bin
You should now be able to configure and build CygMon as follows:
mkdir /ecos/ecos-98r1p6/objdir
cd /ecos/ecos-98r1p6/objdir
../cygmon-src/configure --host=i386-cygwin32 --target=mn10300-elf
make -w
When complete, you will have CygMon images built in:
mn10300-elf/cygmon/eval
The images are:
cygmon.img
Is the ROM-resident version of CygMon in binary format.

cygmon.rom
Is the ELF executable of the ROM-resident version of CygMon. It is used in the standalone simulator for thread-aware debugging.

cygmon.sre
Is the ROM-resident version of CygMon in S-Record format.

If you want to read the source code, here are the names of the files in the cygmon and libstub directories, specific to this version of CygMon.

File names | Descriptions
Generic Parts
libstub/generic-stub.c | Generic remote debug stub
libstub/relocate.c | Segment relocation while booting ROMS
cygmon/bsp/monitor.c | Detailed vector table management
cygmon/bsp/monitor_cmd.c | Cygmon command interpreter
cygmon/bsp/ledit.c | CygMon line editor
Processor Specific Parts
libstub/mn10300/mn10300.mk | Makefile common to all MN10300 variants
libstub/mn10300/mn10300-stub.c | Specific to MN10300, gdb stub support
cygmon/mn10300/mn10300.mon.c | Specific to MN10300, CygMon support
Board Specific Parts
libstub/mn10300/eval.mk | Makefile specific to MN10300 EVB
libstub/mn10300/mn10300-lib.c | Support for MN10300 EVB
cygmon/mn10300/mn10300.mon.ld | CygMon linker script for EVB

CygMon command list

This is a list of all the commands that can be typed at the CygMon command prompt. Arguments in [brackets] are optional, arguments without brackets are required. Note that all commands can be invoked by typing enough of the command name to uniquely specify the command. Some commands have aliases, which are single letter abbreviations for commands which do not have unique first letters. Aliases for all commands are shown in the help screens. baud Usage: baud speed

The baud command sets the speed of the active serial port. It takes one argument, which specifies the speed to which the port will be set.

Example: baud 9600

Sets the speed of the active port to 9600 baud.

break Usage: break [location]

The break command displays and sets breakpoints in memory. It takes zero or one argument. With zero arguments, it displays a list of all currently set breakpoints. With one argument it sets a new breakpoint at the specified location.

Example: break 4ff5

Sets a breakpoint at address 4ff5.

disassemble Usage: disassemble [location]

The disassemble command disassembles the contents of memory. Because of the way breakpoints are handled, all instructions are shown and breakpoints are not visible in the disassembled code. The disassemble command takes zero or one argument. When called with zero arguments, it starts disassembling from the current (user program) pc. When called with a location, it starts disassembling from the specified location. When called after a previous call and with no arguments, it disassembles the next area of memory after the one previously disassembled.

Example: disassemble 45667000

Displays disassembled code starting at location 45667000.

dump Usage: dump location

The dump command shows a region of 16 bytes around the specified location, aligned to 16 bytes. Thus, dump 65 would show all bytes from 60 through 6f.

Example: dump 44f5

Displays 16 bytes starting with 44f0 and ending with 44ff.

go Usage: go [location]

The go command starts user program execution. It can take zero or one argument. If no argument is provided, go starts execution at the current pc. If an argument is specified, go sets the pc to that location, and then starts execution at that location.

Example: go 40020000

Sets the pc to 40020000, and starts program execution.

help Usage: help [command]

The help command without arguments shows a list of all available commands with a short description of each one. With a command name as an argument it shows usage for the command and a paragraph describing the command. Usage is shown as command name followed by names of extensions or arguments.

Arguments in [brackets] are optional, plain text arguments are required. Note that all commands can be invoked by typing enough of the command name to uniquely specify the command. Some commands have aliases, which are
one-letter abbreviations for commands which do not have unique first letters. Aliases for all commands are shown in the help screen, which displays commands in the format:

command name: (alias, if any) description of command

Example: help foo

Shows the help screen for the command foo.

load Usage: load

The load command switches the monitor into a state where it takes all input as s-records and stores them in memory. The monitor exits this mode when a termination record is hit, or certain errors (such as an invalid s-record) cause the load to fail.

memory Usage: memory[.size] location [value]

The memory command is used to view and modify single locations in memory. It can take a size extension, which follows the command name or partial command name without a space, and is a period, followed by the number of bits to be viewed or modified. Options are 8, 16, 32, and 64. Without a size extension, the memory command defaults to displaying or changing 8 bits at a time.

The memory command can take one or two arguments, independent of whether a size extension is specified. With one argument, it displays the contents of the specified location. With two arguments, it replaces the contents of the specified location with the specified value.

Example: memory.8 45f6b2 57

Places the 8-bit value 57 at the location 45f6b2.

port Usage: port [port number]

The port command allows control over the serial port being used by the monitor. It takes zero or one argument. Called with zero arguments it displays the port currently in use by the monitor. Called with one argument it switches the port in use by the monitor to the one specified. It then prints out a message on the new port to confirm the switch.

Example: port 1

Switches the port in use by the monitor to port 1.

register Usage: register [register name] [value]

The register command allows the viewing and manipulation of register contents. It can take zero, one, or two arguments. When called with zero arguments, the register command displays the values of all registers. When called with only the register name argument, it displays the contents of the specified register. When called with both a register name and a value, it places that value into the specified register.

Example: register g1 1f

Places the value 1f in the register g1.

reset Usage: reset

The reset command resets the board.

step Usage: step [location]

The step command causes one instruction of the user program to execute, then returns control to the monitor. It can take zero or one argument. If no argument is provided, step executes one instruction at the current pc. If a location is specified, step executes one instruction at the specified location.

Example: step

Executes one instruction at the current pc.

terminal Usage: terminal type

The terminal command sets the type of the current terminal to that specified in the type argument. The only available terminal types are vt100 and dumb. This is used by the line editor to determine how to update the terminal display.

Example: terminal dumb

Sets the type of the current terminal to a dumb terminal.

transfer Usage: transfer

The transfer or $ function transfers control to the gdb stub. This function does not actually need to be called by the user, as connecting to the board with gdb will call it automatically. The transfer command takes no arguments. The $ command does not wait for a return, but executes immediately. A telnet setup in line mode will require a return when executed by the user, as the host computer does not pass any characters to the monitor until a return is pressed. Disconnecting from the board in gdb automatically returns control to the monitor.

unbreak Usage: unbreak location

The unbreak command removes breakpoints from memory. It takes one argument, the location to remove the breakpoint from.

Example: unbreak 4ff5

Removes a previously set breakpoint at memory location 4ff5.

usage Usage: usage

Shows the amount of memory being used by the monitor, broken down by category. Despite its name, it has nothing to do with the usage of any other command.

version Usage: version

The version command displays the version of the monitor.

CygMon command editing

CygMon has a line-editing interface. If you type the wrong thing, you can correct it. Position the cursor back, delete the wrong characters and entry the right ones. The user can recover previous commands and edit them or simply re-execute them.

These are common EMACS and X text editing escape sequences. Here are the keys for editing.

Keystroke | Command
CR \n | Execute the currently displayed command
ctl-a | Move to Beginning of line
ctl-e | End of line
ctl-f | Forward char
ctl-b | Backward char
ctl-k | Delete to end of line
ctl-y | Yank Character (undelete)
ctl-d | Delete current character
ctl-p | Edit previous command
ctl-u | Erase Line
ctl-n | Edit next command

Debugging CygMon

The CygMon directories build two binaries. One is a ROM image. The other is a downloadable program, which can be run under the supervision of the previous monitor. The downloaded CygMon will be using the serial connection. GDB can be used to talk to the downloaded CygMon. Once the downloaded CygMon has initialized to the point of installing the exception handler, the original ROM monitor will no longer support debugging. At that point CygMon can be used to download and run additional programs. It is important to watch your memory layouts carefully.

When developing and debugging CygMon, it is convenient to run CygMon itself as a downloadable application. There are some modifications that the developer may want to make temporarily, to debug CygMon. Reconfigure CygMon so it does not patch the exception handler. Have your test program call breakpoint explicitly. This combination disables CygMon in some serious ways, but many essential features remain functional and debuggable. Breakpoints can be administered, memory accesses can be tested, or registers fetched. You can debug the serial driver. But, you cannot resume execution, single step or test if a breakpoint has been hit. You can force CygMon through its context-save and context-restore. This is the plan; get all the basics working and verified, and then restore the exception patching capability.

Appendix B: MN10300-specific Assembler Error Messages

Error: Unrecognized opcode This instruction is misspelled or there is a syntax error somewhere.
Warning: operand out of range An immediate value was specified that is too large for the instruction

Appendix C: Bibliography

MN10300 Series Instruction Manual
(Version 1.03, Matsushita Electronics Corporation, November, 1996)

MN103000 LSI Users Manual
(1st Edition, Matsushita Electronics Corporation, November, 1996)

32-bit Microcontroller MN103002A LSI Manual
(Version 3.0, Matsushita Electronics Corporation)

Getting Started with eCos version 1.2.1
(Sunnyvale: Cygnus Solutions, 1999)

eCos User's Guide version 1.2.1
(Sunnyvale: Cygnus Solutions, 1999)

eCos Reference Manual version 1.2.1
(Sunnyvale: Cygnus Solutions, 1999)

Getting Started with GNUPro Toolkit
(Sunnyvale: Cygnus Solutions, 1999)

GNUPro Compiler Tools
(Sunnyvale: Cygnus Solutions, 1999)

GNUPro Debugging Tools
(Sunnyvale: Cygnus Solutions, 1999)

GNUPro Libraries
(Sunnyvale: Cygnus Solutions, 1999)

GNUPro Utilities
(Sunnyvale: Cygnus Solutions, 1999)

GNUPro Advanced Topics
(Sunnyvale: Cygnus Solutions, 1999)

GNUPro Tools for Embedded Systems
(Sunnyvale: Cygnus Solutions, 1999)

System V Application Binary Interface
(Prentice Hall, 1990)