ldr r0,=0x30000000
0
stmia r0!,{r1-r8}
subs r9,r9,#32
bne ?% B0?
;Clear SDRAM End
1
;Initializestacks
bl InitStacks
;------------------------------------------------------------------------------------------------
;===========================================================
;OM0是flash选择开关，OM0接地时从nand 启动，悬空时（核心板上有上拉电阻）从nor启动
;OM1在核心板上，始终是接地,为0
;OM1：OM0取值：00 nandflash mode
; 01 16bit nor
; 10 32bit nor
; 11 test mode
;详见：s3c2440 用户手册 5.memory controller 一节
;ands指令，加s表示结果影响cpsr寄存器的值
ldr r0, =BWSCON ;BWSCON总线宽度&等待控制寄存器
ldr r0, [r0]
ands r0, r0, #6 ;OM[1:0]!= 0, NOR FLash boot
bne copy_proc_beg ;do not read nand flash
adr r0, ResetEntry ;OM[1:0] == 0, NAND FLash boot
cmp r0, #0 ;ifuse Multi-ice,
bne copy_proc_beg ;donot read nand flash for boot
;nop
;===========================================================
;把nand中的数据，拷贝到ram中
nand_boot_beg
[ {TRUE}
bl RdNF2SDRAM
]
ldr pc, =copy_proc_beg
;===========================================================
;这里的一段代码时对内存数据的初始化，涉及代码段，数据段，bss段等
;因对这里的变量设置等有异议，暂时未全面分析，但是基本原理想通，就是一个比较地址，复制数据的过程
copy_proc_beg
adr r0, ResetEntry
ldr r2, BaseOfROM
cmp r0, r2
ldreq r0, TopOfROM
beq InitRam
ldrr3, TopOfROM
0
ldmia r0!, {r4-r7}
stmia r2!, {r4-r7}
cmp r2, r3
bcc % B0???
sub r2, r2, r3
sub r0, r0, r2
InitRam
ldr r2, BaseOfBSS
ldr r3, BaseOfZero
0
cmp r2, r3
ldrcc r1, [r0], #4
strcc r1, [r2], #4
bcc % B0???
mov r0, #0
ldr r3, EndOfBSS
1
cmp r2, r3
strcc r0, [r2], #4
bcc % B1???
ldr pc, = % F2 ;gotocompiler address
2
; [CLKdiv_VAL>1 ; meansFclk:Hclk is not 1:1.
; bl MMU_SetAsyncBusMode
; |
; blMMU_SetFastBusMode ; default value.
; ]
;===========================================================
; Setup IRQ handler
; 把中断服务函数的总入口地址，赋给HandleIRQ地址（文件最低端定义）
ldr r0,=HandleIRQ ;Thisroutine is needed
ldr r1,=IsrIRQ ;ifthere is not subs pc,lr,#4 at 0x18, 0x1c
str r1,[r0]
[ :LNOT:THUMBCODE
bl Main ;Do not use main() because ......
b .
]
[ THUMBCODE ;for start-up code for Thumbmode
orr lr,pc,#1
bx lr
CODE16
bl Main ;Do not use main() because ......
b .
CODE32
]
;------------------------------------------------------------------------------------------------
;function initializing stacks
; 初始化栈空间（各个模式下的），为c函数运行做准备
InitStacks
;Donot use DRAM,such as stmfd,ldmfd......
;SVCstackis initialized before
;Undertoolkit ver 2.5, msr cpsr,r1 can be used instead of msr cpsr_cxsf,r1
mrs r0,cpsr
bic r0,r0,#MODEMASK
orr r1,r0,#UNDEFMODE|NOINT
msr cpsr_cxsf,r1 ;UndefMode
ldr sp,=UndefStack ; UndefStack=0x33FF_5C00
orr r1,r0,#ABORTMODE|NOINT
msr cpsr_cxsf,r1 ;AbortMode
ldr sp,=AbortStack ; AbortStack=0x33FF_6000
orr r1,r0,#IRQMODE|NOINT
msr cpsr_cxsf,r1 ;IRQMode
ldr sp,=IRQStack ;IRQStack=0x33FF_7000
orr r1,r0,#FIQMODE|NOINT
msr cpsr_cxsf,r1 ;FIQMode
ldr sp,=FIQStack ;FIQStack=0x33FF_8000
bic r0,r0,#MODEMASK|NOINT
orr r1,r0,#SVCMODE
msr cpsr_cxsf,r1 ;SVCMode
ldr sp,=SVCStack ;SVCStack=0x33FF_5800
;USERmode has not be initialized.
mov pc,lr
;TheLR register will not be valid if the current mode is not SVC mode.
LTORG
;------------------------------------------
