ARM·存儲器配置
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sdram_elf:
Disassembly of section .text:
30000000 <_start>:
30000000: eb000005 bl 3000001c
30000004: eb000010 bl 3000004c
30000008: eb000007 bl 3000002c
3000000c: e59ff090 ldr pc, [pc, #144] ; 300000a4
30000010 :
30000010: e3a0d30d mov sp, #872415232 ; 0x34000000
30000014: eb000035 bl 300000f0
30000018 :
30000018: eafffffe b 30000018
3000001c :
3000001c: e3a01453 mov r1, #1392508928 ; 0x53000000
30000020: e3a02000 mov r2, #0 ; 0x0
30000024: e5812000 str r2, [r1]
30000028: e1a0f00e mov pc, lr
3000002c :
3000002c: e3a01000 mov r1, #0 ; 0x0
30000030: e3a02203 mov r2, #805306368 ; 0x30000000
30000034: e3a03a01 mov r3, #4096 ; 0x1000
30000038: e4914004 ldr r4, [r1], #4
3000003c: e4824004 str r4, [r2], #4
30000040: e1510003 cmp r1, r3
30000044: 1afffffb bne 30000038
30000048: e1a0f00e mov pc, lr
3000004c :
3000004c: e3a01312 mov r1, #1207959552 ; 0x48000000
30000050: e28f2018 add r2, pc, #24 ; 0x18
30000054: e1a00000 nop (mov r0,r0)
30000058: e2813034 add r3, r1, #52 ; 0x34
3000005c: e4924004 ldr r4, [r2], #4
30000060: e4814004 str r4, [r1], #4
30000064: e1510003 cmp r1, r3
30000068: 1afffffb bne 3000005c
3000006c: e1a0f00e mov pc, lr
30000070 :
30000070: 22011110 .word 0x22011110
30000074: 00000700 .word 0x00000700
30000078: 00000700 .word 0x00000700
3000007c: 00000700 .word 0x00000700
30000080: 00000700 .word 0x00000700
30000084: 00000700 .word 0x00000700
30000088: 00000700 .word 0x00000700
3000008c: 00018005 .word 0x00018005
30000090: 00018005 .word 0x00018005
30000094: 008c07a3 .word 0x008c07a3
30000098: 000000b1 .word 0x000000b1
3000009c: 00000030 .word 0x00000030
300000a0: 00000030 .word 0x00000030
300000a4: 30000010 .word 0x30000010
300000a8: e1a00000 .word 0xe1a00000
300000ac: e1a00000 .word 0xe1a00000
300000b0 :
300000b0: e52db004 push {fp} ; (str fp, [sp, #-4]!)
300000b4: e28db000 add fp, sp, #0 ; 0x0
300000b8: e24dd00c sub sp, sp, #12 ; 0xc
300000bc: e50b0008 str r0, [fp, #-8]
300000c0: e51b2008 ldr r2, [fp, #-8]
300000c4: e3520000 cmp r2, #0 ; 0x0
300000c8: 03a03000 moveq r3, #0 ; 0x0
300000cc: 13a03001 movne r3, #1 ; 0x1
300000d0: e20310ff and r1, r3, #255 ; 0xff
300000d4: e2423001 sub r3, r2, #1 ; 0x1
300000d8: e50b3008 str r3, [fp, #-8]
300000dc: e3510000 cmp r1, #0 ; 0x0
300000e0: 1afffff6 bne 300000c0
300000e4: e28bd000 add sp, fp, #0 ; 0x0
300000e8: e8bd0800 pop {fp}
300000ec: e12fff1e bx lr
300000f0 :
300000f0: e92d4800 push {fp, lr}
300000f4: e28db004 add fp, sp, #4 ; 0x4
300000f8: e3a02456 mov r2, #1442840576 ; 0x56000000
300000fc: e2822010 add r2, r2, #16 ; 0x10
30000100: e3a03456 mov r3, #1442840576 ; 0x56000000
30000104: e2833010 add r3, r3, #16 ; 0x10
30000108: e5933000 ldr r3, [r3]
3000010c: e3c33bff bic r3, r3, #261120 ; 0x3fc00
30000110: e5823000 str r3, [r2]
30000114: e3a02456 mov r2, #1442840576 ; 0x56000000
30000118: e2822010 add r2, r2, #16 ; 0x10
3000011c: e3a03456 mov r3, #1442840576 ; 0x56000000
30000120: e2833010 add r3, r3, #16 ; 0x10
30000124: e5933000 ldr r3, [r3]
30000128: e3833b55 orr r3, r3, #87040 ; 0x15400
3000012c: e5823000 str r3, [r2]
30000130: e3a02456 mov r2, #1442840576 ; 0x56000000
30000134: e2822014 add r2, r2, #20 ; 0x14
30000138: e3a03456 mov r3, #1442840576 ; 0x56000000
3000013c: e2833014 add r3, r3, #20 ; 0x14
30000140: e5933000 ldr r3, [r3]
30000144: e3833e1e orr r3, r3, #480 ; 0x1e0
30000148: e5823000 str r3, [r2]
3000014c: e3a02456 mov r2, #1442840576 ; 0x56000000
30000150: e2822014 add r2, r2, #20 ; 0x14
30000154: e3a03456 mov r3, #1442840576 ; 0x56000000
30000158: e2833014 add r3, r3, #20 ; 0x14
3000015c: e5933000 ldr r3, [r3]
30000160: e3c33020 bic r3, r3, #32 ; 0x20
30000164: e5823000 str r3, [r2]
30000168: e3a00064 mov r0, #100 ; 0x64
3000016c: ebffffcf bl 300000b0
30000170: eafffff5 b 3000014c
Disassembly of section .comment:
00000000 <.comment>:
Disassembly of section .ARM.attributes:
00000000 <.ARM.attributes>:
1）首先我們明確這段程序所處的位置，它位于NAND FLASH 的首地址處，也就是0x0000 0000處。當我們從NAND FLASH啟動時，會自動把前面4K的代碼復制到SRAM中運行。
這里，我就遇到了一個讓我困惑了很久的問題：這條代碼的運行地址是0x3000 0000，那么它怎么能在0x0000 0000處運行呢？
答：這就是我們上面補充知識說的位置無關(guān)碼，
bl
這3條指令仍然可以執(zhí)行，且完成對SDRAM的初始化
2）既然完成了對SDRAM的初始化，也就是說SDRAM現(xiàn)在已經(jīng)可以幫助內(nèi)存處理信息了，這時我們的指令是
ldr pc, =on_sdram
這就是我們的位置相關(guān)碼，也就是從SRAM中跳到了SDRAM中繼續(xù)執(zhí)行，完成了操作；
【關(guān)于實驗操作】
友善視頻中用的是oflash，但是我們現(xiàn)在有更強大的minitool工具，所以我這里就用minitool進行下載，但是幾次調(diào)試都失敗了，原因如下（圖是借用的2451的，不用在意這些細節(jié)，自動替換成2440）
【這是我前面燒寫失敗的下載方法】
至于錯誤原因，我暫時不知道
【下面是正確的燒寫姿勢。。?！?img onload="if(this.width>620)this.width=620;" onclick="window.open(this.src)" style="cursor:pointer" name="image_operate_66461417679849543" real_src="http://editerupload.eepw.com.cn/fetch/20161101/320994_2_1.jpg" src="http://editerupload.eepw.com.cn/fetch/20161101/320994_2_1.jpg" />
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