嵌入式学习笔记2—S3C2440的内存初始化

本文基于国嵌的视频教程，总结一下ARM内存体系架构。

由S3C2440的datasheet可以看出，该芯片具有27根地址总线，则2^27=134217728bits=131072Kb=128Mb。总共有8根片选总线，所以最大可扩展内存为8*128=1024Mb=1GB地址空间。从外部看即有8个memory banks。ARM核访问内存地址则主要是通过存储控制器去访问内存空间。





具体初始化代码如下：

#define mem_contrl 0x48000000
init_sdram:
	ldr  r0,=mem_contrl  @first register address
	add  r3,r0,#4*13     @final register address,every register's length is 4 byte,
			     @total has 13 registers
	adrl r1,mem_data     @"adrl" load long address,r1 save data list first address 

0:
	ldr r2,[r1],#4  @"#4"(decimalism) next loop [r1]=[r1]+4
	str r2,[r0],#4
	cmp r0,r3       @r0 and r3 compare 
	bne 0b 		@judge:if not equal,then turn to 0 . "b" means turn to before
	mov pc,lr
mem_data:
	.long 0x22000000  @.long indicate it's length
	.long 0x00000700
	.long 0x00000700
	.long 0x00000700
	.long 0x00000700
	.long 0x00000700
	.long 0x00000700
	.long 0x00018001
	.long 0x00018001
	.long 0x008c04f5
	.long 0x000000b1
	.long 0x00000030
	.long 0x00000030

关于寄存器的取值和地址详见S3C2440的datasheet或者参考国嵌的视频教程。