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請問各位大佬們 怎么理解這兩段單片機(jī)代碼
/*-------------------------------------------------------------------------------------------------
Function Name : uint8 Get4ByteFromFlash(uint8 xdata *BlockStartAddr)
Description : 從目標(biāo)FLASH扇區(qū)讀取4字節(jié)最新寫入的數(shù)據(jù)
Input : uint8 xdata *BlockStartAddr：目標(biāo)FLASH扇區(qū)
Output : 讀出的數(shù)據(jù)
-------------------------------------------------------------------------------------------------*/
uint32 Get4ByteFromFlash(uint8 xdata *BlockStartAddr)
{
uint8 xdata *FlashStartAddr = BlockStartAddr;
uint8 i;
uint32 tempofFlashData;
for(i=0;i<32;i++)
{
tempofFlashData = *(uint32 code *)(FlashStartAddr + 4*i);
if(tempofFlashData==0)
{
if(i!=0)
{
tempofFlashData = *(uint32 code *)(FlashStartAddr + 4*(i-1));
return tempofFlashData;
}
else
{
return 0;
}
}
else
{
if(i==31)
{
return tempofFlashData;
}
}
}
return 0;
}
/*-------------------------------------------------------------------------------------------------
Function Name : void Write4Byte2Flash(uint8 xdata *BlockStartAddr,uint32 NewData2Flash)
Description : 寫入4個(gè)字節(jié)到FLASH
Input : uint8 xdata *BlockStartAddr：目標(biāo)FLASH地址 NewData2Flash：被寫入數(shù)據(jù)
Output : 無
-------------------------------------------------------------------------------------------------*/
#if 1
void Write4Byte2Flash(uint8 xdata *BlockStartAddr,uint32 NewData2Flash)
{
uint8 xdata *FlashStartAddr = BlockStartAddr;
uint32 tempofFlashData=0;
uint32 tempofNewFlashData=0;
uint8 i;
FLASHUsingStatus=1; //FLASH正在使用
tempofNewFlashData = NewData2Flash;
for(i=0;i<32;i++)
{
tempofFlashData = *(uint32 code *)(FlashStartAddr+4*i);
if(tempofFlashData==0)
{
tempofFlashData = (tempofNewFlashData>>24)&0x000000ff;
Flash_Sector_Write((FlashStartAddr+4*i),(uint8)tempofFlashData);
_nop_();
tempofFlashData = (tempofNewFlashData>>16)&0x000000ff;
Flash_Sector_Write((FlashStartAddr+4*i+1),(uint8)tempofFlashData);
_nop_();
tempofFlashData = (tempofNewFlashData>>8)&0x000000ff;
Flash_Sector_Write((FlashStartAddr+4*i+2),(uint8)tempofFlashData);
_nop_();
tempofFlashData = tempofNewFlashData&0x000000ff;
Flash_Sector_Write((FlashStartAddr+4*i+3),(uint8)tempofFlashData);
_nop_();
break;
}
else
{
if(i==31)
{
Flash_Sector_Erase(FlashStartAddr);
_nop_();
tempofFlashData = (tempofNewFlashData>>24)&0x000000ff;
Flash_Sector_Write((FlashStartAddr),(uint8)tempofFlashData);
_nop_();
tempofFlashData = (tempofNewFlashData>>16)&0x000000ff;
Flash_Sector_Write((FlashStartAddr+1),(uint8)tempofFlashData);
_nop_();
tempofFlashData = (tempofNewFlashData>>8)&0x000000ff;
Flash_Sector_Write((FlashStartAddr+2),(uint8)tempofFlashData);
_nop_();
tempofFlashData = tempofNewFlashData&0x000000ff;
Flash_Sector_Write((FlashStartAddr+3),(uint8)tempofFlashData);
_nop_();
}
}
}
FLASHUsingStatus=0; //FLASH空閑
} |
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