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start.S
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/*
* 张旭写于 2018.12.27 9:42pm
*
* Asymptote的程序入口
*
*
*
*/
.equ MEM_CTL_BASE, 0x48000000
.equ CLKDIVN, 0x4C000014
.equ MPLLCON, 0x4C000004
#define S3C2440_MPLL_200MHZ ((0x5c<<12)|(0x01<<4)|(0x02))
#define S3C2440_MPLL_400MHZ ((0x5c<<12)|(0x01<<4)|(0x01))
.text
.global _start
/*****************************************************************************/
@程序入口
_start:
@ 0x00: 复位异常的向量地址
b Reset
@ 0x04: 未定义指令中止模式的向量地址
HandleUndef:
b HandleUndef
@ 0x08: 管理模式的向量地址（在用户模式下，可通过SWI指令进入该模式）
HandleSvc:
b HandleSvc
@ 0x0c: 指令预取中止异常的向量地址
HandlePrefetchAbort:
b HandlePrefetchAbort
@ 0x10: 数据访问中止异常的向量地址
HandleDataAbort:
b HandleDataAbort
@ 0x14: 保留
HandleNotUsed:
b HandleNotUsed
@ 0x18: 中断模式的向量地址
HandleIRQ:
b HandleIRQ
@ 0x1c: 快中断模式的向量地址
HandleFIQ:
b HandleFIQ
/*****************************************************************************/
@复位异常入口
Reset:
ldr sp, =4096 @重启默认进入SVC模式，此处设置SVC模式栈指针
bl disable_watch_dog
bl clock_init
bl sdram_init
bl nand_init @初始化 NAND Flash
@nand_read函数需要3个参数：
ldr r1, =0x30000000 @1.目标地址=0x30000000，这是SDRAM的起始地址
mov r0, #0 @2.源地址 = 0
mov r2, #(1024*20) @3.复制长度 = 20KB
bl nand_read @调用C函数nand_read
ldr pc, =on_sdram @跳到SDRAM中继续执行
on_sdram:
msr cpsr_c, #0xdf @进入系统模式
ldr sp, =0x34000000 @设置系统模式栈指针
@ ldr lr, =loop
ldr lr, =0x32000000
ldr pc, =main
loop:
b loop
/***************************************************************/
disable_watch_dog:
ldr r0, =0x53000000 @关闭看门狗
mov r1, #0
str r1, [r0]
mov pc, lr
clock_init:
ldr r0, =CLKDIVN
@ mov r1, #0x03 @1:2:4
mov r1, #0x05 @1:4:8
str r1, [r0]
mrc p15, 0, r1, c1, c0, 0
orr r1, r1, #0xc0000000
mcr p15, 0, r1, c1, c0, 0
ldr r0, =MPLLCON
@ ldr r1, =S3C2440_MPLL_200MHZ
ldr r1, =S3C2440_MPLL_400MHZ
str r1, [r0]
mov pc, lr
sdram_init:
mov r1, #MEM_CTL_BASE @r1存放存储控制器基地址
adrl r2, mem_cfg_val @
add r3, r1, #13*4 @r3存放存储控制器尾地址
1:
ldr r4, [r2], #4 @
str r4, [r1], #4
cmp r1, r3
bne 1b
mov pc, lr
.align 4
mem_cfg_val:
@ 存储控制器13个寄存器的设置值
@ .long 0x22011110 @ BWSCON
@ .long 0x00000700 @ BANKCON0
@ .long 0x00000700 @ BANKCON1
@ .long 0x00000700 @ BANKCON2
@ .long 0x00000700 @ BANKCON3
@ .long 0x00000700 @ BANKCON4
@ .long 0x00000700 @ BANKCON5
@ .long 0x00018005 @ BANKCON6
@ .long 0x00018005 @ BANKCON7
@ .long 0x008C07A3 @ REFRESH
@ .long 0x000000B1 @ BANKSIZE
@ .long 0x00000030 @ MRSRB6
@ .long 0x00000030 @ MRSRB7
.long 0x22011110 //BWSCON
.long 0x00000700 //BANKCON0
.long 0x00000700 //BANKCON1
.long 0x00000700 //BANKCON2
.long 0x00000700 //BANKCON3
.long 0x00000740 //BANKCON4
.long 0x00000700 //BANKCON5
.long 0x00018005 //BANKCON6
.long 0x00018005 //BANKCON7
.long 0x008C04F4 // REFRESH
.long 0x000000B1 //BANKSIZE
.long 0x00000030 //MRSRB6
.long 0x00000030 //MRSRB7