使用ADS时候有uboot功能的启动代码

;**************************************************************
;
;    This an simple implementation of  bootloader for S3C4510B
;    Hope it is useful to you.
;
;    Duyunhai use this program to UART0
;
;    Enjoy it!
;
;**************************************************************

LOOPNUM        EQU        0x02

AREA    Init, CODE, READONLY
CODE32
GET snds.s

ENTRY

start

;Part 1
;***************************************************************
;disable interrupts in CPU and switch to SVC32 mode

MRS    r0, cpsr
BIC    r0, r0, #MASK_MODE
ORR    r0, r0, #MODE_SVC32
ORR     r0, r0, #I_BIT
ORR     r0, r0, #F_BIT
MSR    cpsr_c, r0

LDR    r2, =ARM7_INTMASK             ;R2->interrupt controller
MVN    r1, #0                         ;&FFFFFFFF
STR    r1, [r2]                     ;disable all interrupt soucres

LDR    r2, =ARM7_INTPEND             ;R2->interrupt pend register.
MVN    r1, #0                         ;&FFFFFFFF
STR    r1, [r2]                     ;clear all interrupt flags.

;Part 2
;****************************************************************

LDR    r0, =ARM7_SYSCFG
LDR    r1, =0x87ffffA0                ;config SYSCFG
STR    r1, [r0]                     ;Cache & WB disabled

;Part 3
;***************************************************************
;    Import some important variables for later use

IMPORT |Image$$RO$$Base|
IMPORT |Image$$RO$$Limit|
IMPORT |Image$$RW$$Base|
IMPORT |Image$$RW$$Limit|
IMPORT |Image$$ZI$$Base|
IMPORT |Image$$ZI$$Limit|

;Part 4
;****************************************************************
;Initalize the memory as followa:
;    FLASH            @ 0  ~ 2 M
;    SDRAM            @ 2  ~ 18M

LDR    r1, =rEXTDBWTH                 ;EXTDBWTH
LDR    r2, =rROMCON0                  ;ROMCON0    @ 0M ~ 2M
LDR    r3, =rROMCON1                ;ROMCON1    @ DISABLED
LDR    r4, =rROMCON2                ;ROMCON1    @ DISABLED
LDR    r5, =rROMCON3                ;ROMCON1    @ DISABLED
LDR    r6, =rROMCON4                ;ROMCON1    @ DISABLED
LDR    r7, =rROMCON5                ;ROMCON1    @ DISABLED
LDR    r8, =rSDRAMCON0                ;SDRAMCON0     @ 2M ~ 18M
LDR    r9, =rSDRAMCON1                ;SDRAMCON1     @ DISABLED
LDR    r10,=rSDRAMCON2                ;SDRAMCON2     @ DISABLED
LDR    r11,=rSDRAMCON3                ;SDRAMCON3     @ DISABLED
LDR    r12,=rSREFEXTCON

LDR    r0, =ARM7_EXTDBWTH
STMIA    r0, {r1-r12}

;Part 5
;***************************************************************
;Self copy from FLASH to SDRAM

LDR        r0, =|Image$$RO$$Base|
LDR        r1, =|Image$$RO$$Limit|
LDR        r2, =|Image$$RW$$Base|
LDR        r3, =|Image$$RW$$Limit|

SUB         r1, r1, r0
SUB        r3, r3, r2
ADD        r1, r1, r3

LDR        r2, =0x200000   ;@2M

COPY
LDR        r3, [r0], #4
STR        r3, [r2], #4
SUBS        r1, r1,   #4
BNE        COPY

;Part 6
****************************************************************
;Remap the memory
;     FLASH    @ 16 ~ 18M
;     SDRAM    @ 0  ~ 16M

LDR    r1, =rEXTDBWTH_R             ;EXTDBWTH
LDR    r2, =rROMCON0_R              ;ROMCON0    @ 16M ~ 18M
LDR    r3, =rROMCON1_R                ;ROMCON1    @ DISABLED
LDR    r4, =rROMCON2_R                ;ROMCON2    @ DISABLED
LDR    r5, =rROMCON3_R                ;ROMCON3    @ DISABLED
LDR    r6, =rROMCON4_R                ;ROMCON4    @ DISABLED
LDR    r7, =rROMCON5_R                ;ROMCON4    @ DISABLED
LDR    r8, =rSDRAMCON0_R            ;SDRAMCON0     @ 0M ~ 16M
LDR    r9, =rSDRAMCON1_R            ;SDRAMCON1     @ DISABLED
LDR    r10,=rSDRAMCON2_R            ;SDRAMCON2     @ DISABLED
LDR    r11,=rSDRAMCON3_R            ;SDRAMCON3     @ DISABLED
LDR    r12,=rSREFEXTCON_R

LDR    r0, =ARM7_EXTDBWTH
STMIA    r0, {r1-r12}            ;注意这一句之后就是存储控制其重映射了
;但是MCU中PC的值没有变，所以依然是从
;这里开始执行，但是“这里”已经不是FLASH
;里面了，而是SDRAM中

;Part 7
;*****************************************************************
; Copy RW & ZI to SDRAM

LDR r0, =|Image$$RO$$Limit|
LDR r1, =|Image$$RW$$Base|
LDR r3, =|Image$$ZI$$Base|

CMP r0, r1
BEQ %1

0     CMP r1, r3                         ; Copy init data
LDRCC r2, [r0], #4
STRCC r2, [r1], #4
BCC %0

1     LDR r1, =|Image$$ZI$$Limit|     ; Top of zero init segment
MOV r2, #0

2     CMP r3, r1                         ; Zero init
STRCC r2, [r3], #4
BCC %2

;Part 8 这部分才是真正的执行code，前面的都是linker添加的类似uboot的代码
;*********************************************************************
;Use the UART0 to tranmit some byte

;;------------------------------------
;;    SerialComm program
;;------------------------------------

;;    ARM7_ULCON0 (UART0s Line control Register) Initializatin
;
;    [1:0] Word length per frame (WL)
;        00 = 5 bits 01 = 6 bits
;        10 = 7 bits 11 = 8 bits
;    [2] Number of Stop bits at the end of frame (STB)
;        0 = One stop bit per frame
;        1 = Two stop bits per frame
;    [5:3] Parity mode (PMD)
;        0xx = No parity
;        100 = Odd parity
;        101 = Even parity
;        110 = Parity forced/ checked as 1.
;        111 = Parity forced/checked as 0.
;    [6] Serial clock selection (SC)
;        0 = Internal (MCLK)
;        1 = External (UCLK)
;    [7] Infra-red mode selection (IR)
;        0 = Normal mode operation
;;        1 = Infra-red Tx/Rx mode

LDR    R1,=ARM7_ULCON0
LDR    R0,=0x03    ;8 bit ,one stop,no parity,MCLK,Normal mode
STR    R0,[R1]

;     ARM7_UCON0 (UART0s control Register) Initializatin

LDR    R1,=ARM7_UCON0
LDR    R0,=0x09    ;no receive interrupt,interrupt Tx mode,no DSR
STR    R0,[R1]

;;     ARM7_UBRDIV0 (UART0s baud rate divisor Register)
;
;    BRGOUT = (MCLK2 or UCLK)/(CNT0 + 1)/(16^CNT1)/16
;
;    When MCLK=50MHz(MCLK2=MCLK/2)
;            Baudrate=9600:    UBRDIV0=0xA20
;;            Baudrate=19200:    UBRDIV0=0x500

LDR    R1,=ARM7_UBRDIV0
LDR    R0,=0x500    ;When MCLK=50MHz, Baudrate=19200
STR    R0,[R1]

;     Transmit the message from UART0 of S3C4510B to DCE

LDR    R7,=LOOPNUM

LOOP
LDR    R1,=LINE1
BL    PrintLine

LDR    R1,=LINE2
BL    PrintLine

LDR    R1,=LINE3
BL    PrintLine

LDR    R1,=LINE4
BL    PrintLine

LDR    R1,=LINE5
BL    PrintLine

SUBS    R7,R7,#1
BNE    LOOP

STOP
;        MOV     r0, #0x18       ; angel_SWIreason_ReportException
;        LDR     r1, =0x20026    ; ADP_Stopped_ApplicationExit
;        SWI     0x123456        ; Angel semihosting ARM SWI

NOP
B    STOP

;Subroute----PrintLine

PrintLine

MOV    R4,LR
MOV    R5,R1

Line
LDRB    R2,[R5],#1
AND        R1,R2,#&FF
TST        R1,#&FF
MOVEQ    PC,R4

BL        PrintByte
NOP
MOV        R0,R0
NOP
B        Line

PrintByte
LDR        R3,=ARM7_USTAT0    ;Query the TBE bit,if bit=0,waiting...
LDR        R6,[R3]
TST        R6,#&40
BEQ        PrintByte        ;TBE=0

LDR        R3,=ARM7_UTXBUF0    ;TBE=1,and write data to UTXBUF0 and transmit
STR        R2,[R3]
MOV        PC,LR

AREA PRINTLINEOUT,DATA,READWRITE        ;这是RW data

LINE1    DCB        &A,&D,"***************************************",0
LINE2    DCB     &A,&D,"  hello world,i am qrsgate2004 in ARM ",0
LINE3    DCB     &A,&D,"  These is the Serial IO test program!",0
LINE4    DCB     &A,&D,"          Let us go on!!",0
LINE5    DCB        &A,&D,"***************************************",&A,&D,&A,&D,0

END