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问题如下：
Ti EVM DM642采用flash为AMD29LV033C，大小：4M Bytes，8位数据线，22地址线，接于DSP的CE1空间
1、块擦除函数
/* The Flash Erase function uses
* the AMD algorithm to erase the
* entire chip.
*/
void EraseFlash(void)
{
int i;
/* Code to erase AMD29LV033C
* 32MBit (4MK X 8) Flash Memory
*/
*FLASH_PAGE = 0;
*(volatile char *)FLASH_START = (char)FLASH_KEY1;
*(volatile char *)FLASH_START = (char)FLASH_KEY2;
*(volatile char *)FLASH_START = (char)FLASH_KEY4;
*(volatile char *)FLASH_START = (char)FLASH_KEY1;
*(volatile char *)FLASH_START = (char)FLASH_KEY2;
*(volatile char *)FLASH_START = (char)FLASH_KEY5;
/* Wait until erase is done */
while(GetFlashVal(FLASH_START) != 0xff);
/* Put the Flash in normal mode */
*(volatile char *)FLASH_START = (char)0xf0;
/* Mark all sectors as erased */
for (i = 0; i < FLASH_SECTORS; i++)
erasetable[i] = 1;
return;
}
2、！！！！！！！！
写入函数
/* Burns flash data, starting at flashnext.
* This embodies the burning algorithm for the
* AMD29LV033C flash memory used on DM642 EVM
*/
#define FLASH_PAGE ((volatile unsigned char *)0x90080018)
void BurnFlash(u8 *data, u16 nBytes)
{
u16 timeout;
u8 c;
volatile u8 *pdata;
/* Put the Flash in normal mode */
*(volatile char *)FLASH_START = (char)0xf0;
flash_erase((u32)flashnext, (u32)nBytes);
while(nBytes--)
{
/* Prep AMD
* 32MBit (4M x 8) Flash Memory
* for writing a byte.
*/
*FLASH_PAGE = (u8)(((u32)flashnext & 0x380000) >> 19);
*(volatile char *)FLASH_START = (char)FLASH_KEY1;
*(volatile char *)FLASH_START = (char)FLASH_KEY2;
*(volatile char *)FLASH_START = (char)FLASH_KEY3;
pdata = (volatile u8 *)((u32)flashnext & 0xffc7ffff);
*pdata = *data;
/* Spin here 'til programming completes
*/
c = *data++;
timeout = 0;
do timeout += 1;
while(*pdata != c && timeout < (u16)0xffff);
flashnext++;
}
/* Put the Flash in normal mode */
*(volatile char *)FLASH_START = (char)0xf0;
}
非常迷惑这里写函数中：
pdata = (volatile u8 *)((u32)flashnext & 0xffc7ffff);
这里想把pdata 指向flashnext（扇区首地址，例如0x90000000），然后循环写某个大小。为何传地址给指针pdata 时，flashnext 要和0xffc7ffff进行与操作？还有*FLASH_PAGE = (u8)(((u32)flashnext & 0x380000) >> 19);意义何在？
解答如下：
原因是EVM板的flash地址线连接，比较特殊：
A0 -A18：直接连接到DSP的地址线；
A19-A21：连接到FPGA内部的页地址寄存器。
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