ARM的MMU问题，请高手指教

[thefuturelife]

extern char __ENTRY[];

void MMU_Init(void)
{
int i,j;
/*
这段程序不能实现当前堆栈和代码区域的重新映射，假如你
想让存储区域自由映射，需要你自己编写一个细致入微的MMU初始化代码
*/
//========================== IMPORTANT NOTE =========================
//The current stack and code area can't be re-mapped in this routine.
//If you want memory map mapped freely, your own sophiscated MMU
//initialization code is needed.
//===================================================================

MMU_DisableDCache();//禁止数据高速缓存
MMU_DisableICache();//禁止指令高速缓存

//要使用回写操作，一定要对DCache进行清除
//If write-back is used,the DCache should be cleared.
for(i=0;i<64;i++)
for(j=0;j<8;j++)
MMU_CleanInvalidateDCacheIndex((i<<26)|(j<<5));//使整个DCache的数据无效
MMU_InvalidateICache();//使无效整个指令Cache

#if 0
//To complete MMU_Init() fast, Icache may be turned on here.
//为了快速完成MMU_Init(), Icache在这打开。
MMU_EnableICache();
#endif

MMU_DisableMMU();//禁止MMU
MMU_InvalidateTLB();//使快表无效

//MMU_SetMTT(int vaddrStart,int vaddrEnd,int paddrStart,int attr)
//MMU_SetMTT(0x00000000,0x07f00000,0x00000000,RW_CNB); //bank0
MMU_SetMTT(0x00000000,0x03f00000,(int)__ENTRY,RW_CB); //bank0
MMU_SetMTT(0x04000000,0x07f00000,0,RW_NCNB); //bank0
MMU_SetMTT(0x08000000,0x0ff00000,0x08000000,RW_CNB); //bank1
MMU_SetMTT(0x10000000,0x17f00000,0x10000000,RW_NCNB); //bank2
MMU_SetMTT(0x18000000,0x1ff00000,0x18000000,RW_NCNB); //bank3
//MMU_SetMTT(0x20000000,0x27f00000,0x20000000,RW_CB); //bank4
MMU_SetMTT(0x20000000,0x27f00000,0x20000000,RW_CNB); //bank4 for STRATA Flash
MMU_SetMTT(0x28000000,0x2ff00000,0x28000000,RW_NCNB); //bank5
//30f00000->30100000, 31000000->30200000
MMU_SetMTT(0x30000000,0x30100000,0x30000000,RW_CB); //bank6-1
MMU_SetMTT(0x30200000,0x33e00000,0x30200000,RW_NCNB); //bank6-2
//
MMU_SetMTT(0x33f00000,0x33f00000,0x33f00000,RW_CB); //bank6-3
MMU_SetMTT(0x38000000,0x3ff00000,0x38000000,RW_NCNB); //bank7

MMU_SetMTT(0x40000000,0x47f00000,0x40000000,RW_NCNB); //SFR
MMU_SetMTT(0x48000000,0x5af00000,0x48000000,RW_NCNB); //SFR
MMU_SetMTT(0x5b000000,0x5b000000,0x5b000000,RW_NCNB); //SFR
MMU_SetMTT(0x5b100000,0xfff00000,0x5b100000,RW_FAULT);//not used


MMU_SetTTBase(_MMUTT_STARTADDRESS);//写转换表基地址到C2
MMU_SetDomain(0x55555550|DOMAIN1_ATTR|DOMAIN0_ATTR);
//DOMAIN1: no_access, DOMAIN0,2~15=client(AP is checked)
//写域访问控制位到C3
MMU_SetProcessId(0x0); //快速上下文切换,禁止? MVA="VA"
MMU_EnableAlignFault();//是否开启地址对齐检查功能

MMU_EnableMMU();//使能MMU
MMU_EnableICache();// 使能ICache

//DCache 必须要打开，当MMU打开时.
MMU_EnableDCache(); //DCache should be turned on after MMU is turned on.
}



这个函数中虚地址被映射为和实地址一样的，能不能映射成不一样的？
比如：MMU_SetMTT(0x40000000,0x47f00000,0xA0000000,RW_NCNB); //SFR这个样子好像不行。有没有高手指点，怎么实现，这样映射有什么问题？
如果有keil裸奔工程最好，请发一份给我。我的工程跑不了，总是跑飞，并且cache功能不明显。