1. Computer System Laboratory
Lab3 SW Emulator

2. Experimental Goal
Understand the basic process of bootloader & download this trivial bootloader to target board by Domingo
Lab3
2019/4/26

3. Environment Host System Build System Target System Software
Windows XP/Ubuntu 8.04
Build System
Ubuntu 8.04
Target System
XScale PXA270
Software
Bootloader source code
Makefile & linker script
Test program
Microtime Domingo IDE
You can download all the source codes from
RSWiki CSL Course Software
Lab3
2019/4/26

4. Equipment –PXA270
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2019/4/26

5. Introduction to ARM
The ARM processor design is based on RISC principles
Load-store architecture
Fixed-length 32-bit instructions
3-address instruction formats
The ARM processor has 37 registers, each of these registers is 32 bit wide
31 general-purpose registers & 6 status registers
The ARM processor has 7 processor modes
They are User, FIQ, IRQ, Supervisor, Abort, Undefined & System mode
Mode changes can be made by writing directly to CPSR (explain later), or can be caused by exception arising
The modes other than User mode are known as privileged modes
The privileged modes other than System mode are known as exception modes
Lab3
2019/4/26

6. Banked Registers
The ARM processor has a different register bank for each processor mode, as shown in picture below
Each column of picture shows which registers are visible in the indicated processor mode
Banked registers are registers which are visible in particular processor mode
Lab3
2019/4/26

7. Banked Registers (Cont.)
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8. Program Status Registers
The ARM processor uses Current Program Status Register (CPSR) to monitor and control internal operations
The bits at the bottom of the CPSR control the processor mode, instruction set (‘ T ’) & interrupt enables (‘ I ’ & ‘ F ’) and write to these bits in User mode are ignored
Each exception mode has a Saved Program Status Register (SPSR), that is used to preserve the value of the CPSR when the associated exception occurs
Lab3
2019/4/26

9. Exceptions The ARM processor has 7 exception types
The picture below shows the types of exception and the processor mode that is used to process each type
When exception arises, execution is forced from a fixed memory address corresponding to the type of exception
The fixed address are called the exception vectors
Lab3
2019/4/26

10. Misc.
On reset, the ARM processor starts up in Supervisor (SVC) mode, in ARM state, with IRQ and FIQ disabled, and then the processor fetches and executes code from 0x
The Thumb instruction set is designed to allow better code density than ARM instruction set, we do not discuss it here
There are many ARM software development tools on the market, such as ADS, RVDS, IAR EWARM & Keil MDK-ARM, but they are not free
Recommended Reference Books
ARM Architecture Reference Manual
ARM System-on-Chip Architecture 2/e
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2019/4/26

11. Exception Vectors Code
The instruction at each exception vector will usually contain a branch to the exception handler
All GNU assembler directives have names that begin with a period (‘ . ’), they behave similarly to preprocessor directives in the C programming language
.section "Vect"
_reset_entry:
b Reset_Handler
b Undefined_Handler
b SWI_Handler
b Prefetch_Handler
b Abort_Handler
b IRQ_Handler
b FIQ_Handler
Lab3
2019/4/26

12. Initialization Code
There are some tasks should be accomplished before calling C main function
Initialize the memory system
Initialize the stack pointers
Copy the content of the initialized data section to specified address
Reserve spaces for unitialized data section in RAM
Tips
init.s does not perform memory system initialization
Use Domingo’s peripheral configuration manager instead for memory system initialization
Need to use Domingo for running and debugging foo.c
Lab3
2019/4/26

13. Linker Script
The main purpose of the linker script is to control the memory layout of the executable
Please refer to the website below
According to our linker script (i.e. foo.ld), the executable should be downloaded to memory at 0xa
Now, we can compile trivial bootloader
Just download codes from RSWiki and make (check Lab1’s arm-elf toolchain path in PATH)
The resulting foo.bin is the executable we want
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2019/4/26

14. File Transfer
If you did not create Build System, you need to switch to Windows to download bootloader using Domingo
Use one of the following methods to transfer executable
Install EXT2IFS,
By R217 workstation
By USB, , or else
Lab3
2019/4/26

15. Hardware Setup Connect target board and ICE via JTAG
Connect RS232 null cable and parallel cable to your PC
Connect Ethernet cable to your PC
Connect target board and ICE via JTAG
Lab3
2019/4/26

16. Introduction to Domingo
Domingo is an integrated development environment developed by Microtime Computer Inc.
Domingo adopts visual project management which integrates with editor, compiler and debugger let you manage project just from a single environment
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17. Connect with Domingo Step1 : power on the board
Step2 : install Domingo IDE in Windows
Step3 : start Domingo and choose No Project
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18. Connect with Domingo (Cont.)
Step4 : import creator_pxa270.pcm and click OK
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19. Download Executable to Board
Step1 : click Debug  Load Module
Step2 : load foo.bin (load address 0xa )
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2019/4/26

20. Download Executable to Board (Cont.)
Step3 : change the PC value in registers
Step4 : click Debug  Free Go
You will see LED lighting
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2019/4/26