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关于skyeye,它是一个极好的嵌入式模拟软件

		  HelloForSkyeye
			
			Version: 0.0.1
			Author: SU Hang
			Date:   2004-08-28

Introduction:
	To the freshmen of skyeye and embedded system development, besides 
reading books, it would be better to have a simple example to exercise. 
"Hello world" program is often the first one we learn at the beginning of 
learning a language or tool. Therefore, I tried to use the least codes to 
print "hello world" on skyeye with reference to ucos-ii codes. Please note: 
"HelloForSkyeye" is different from the existed "helloworld" program on skyeye. 
It needs not operation system. It isn't an application. It sends characters 
to UART directly. "HelloForSkyeye" has a few lines of codes and little value 
for practice. It is only written as exercise. 

Compilation and Run:
	"HelloForSkyeye" is developed on Redhat9.0 and Skyeye0.7.4. Before 
compilation, please ensure skyeye and arm-elf-tools have been installed.

1.	Download HelloForSkyeye.tar to your home directory on linux.
2.	tar -xf HelloForSkyeye.tar
3.	cd HelloForSkyeye
4.	make
5.	skyeye hello 
6.	tar sim
7.	load
8.	run

After these steps, you should see the following results:
***************************************************************
**** ****
**** SkyEye Simulator Ver 0.7.4 with GDB 5.3 Interface ****
**** ****
***************************************************************
GNU gdb 5.3
Copyright 2002 Free Software Foundation, Inc.
GDB 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.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This SkyEye was configured as "--host=i686-pc-linux-gnu --target=arm-elf"...
(no debugging symbols found)...
(SkyEye) tar s
cpu info: armv3, arm7tdmi, 41007700, fff8ff00, 0 
mach info: name at91, mach_init addr 0x813dae4
log_info: log is off.
log_info:log file is /tmp/sk1.log, fd is 0x829e0e0
log_info: log start clock 0
log_info: log end clock 200000
SKYEYE: use arm7100 mmu ops
Connected to the simulator.
(SkyEye) load 
Loading section .text, size 0x98 vma 0x1000000
Loading section .data, size 0x1000 vma 0x1002000
Start address 0x1000000
Transfer rate: 33984 bits in <1 sec.
(SkyEye) run
Starting program: /home/shang/HelloForSkyeye/hello 
helloworldhelloworldhelloworldhelloworldhelloworldhelloworldhelloworldhelloworld
helloworldhelloworldhelloworldhelloworldhelloworldhelloworldhelloworldhelloworld    

Source Files:
	After using command 'make clean' to delete binary files, you will find 
there are only five source files in "HelloForSkyeye". They are hello.c, hello.lds, 
makefile, skyeye.conf and start.S. I shall introduce them one by one.

makefile:		
	As the input file of 'make', makefile describes how to compile the whole 
"HelloForSkyeye" project. Some compilation parameters are strange, such as -mapcs,
-march. You can find their meaning in "as.info->Machine Dependencies->ARM-Dependent
->ARM Options"

start.S:
	Initial assemble codes are placed in this file to make irq mode with all irqs 
disabled,  set sp_irq and call "hello" fuction to print "helloworld" string. You may 
find the syntax of comments, constants and symbols is different from what described 
in textbook about ARM. Don't worry about it, because the GNU assembler has a 
machine-independent syntax. You can refer to the Syntax chapter of as.info to get more 
information.

hello.c:	
	This is a common C source file which has only one function "hello". The "Hello" 
function output the "helloworld" string to UART. On AT91, the base address of UART0 is 
0xfffd0000 and the offset of US_THR is 0x1c so that when we write character to 0xfffd001c 
address, it means send character to UART. And skyeye will print the character to the 
screen. 

hello.lds	
	This is ld script file in which program entry and every place of section are 
regulated. The script chapter of ld.info describes the syntax of lds file. We also can 
use command "objdump -x" to check the binary file.

skyeye.conf	Configure file of skyeye.