Flash erase/program 检查方法

  注意:读本篇文章要对flash的操作有些基础知识，或者要找份datasheet来看看。
 
  有两种方法Data polling 和Toggle bit

1. Data Polling
   在erase/program cmd写下去之后，Q7位会变成data取反(因为erase后是0xff，所以这时Q7=0),然后直到erase/program操作结束，Q7才会 变成实际的data。也就是flash进入普通的read模式。所以我们在写driver时，是可以使用 erase: while(*addr==0xff); program: while(*addr==data); 这样的方法来等待操作结束的。
2. Toggle Bit
   在erase/program cmd写下去之后, Q6位在连续的两次读操作中，读出的数据会相反，直到erase/program操作结束.参考这样一段代码

int FlashDataToggle( void ) {    volatile FLASH_DEF u1, u2; /* hold values read from any address offset within                            the Flash Memory */    volatile FLASH_DEF * pFA;    while( 1 ) /* TimeOut!: If, for some reason, the hardware fails then this                   loop may not exit. Use a timer function to implement a timeout                   from the loop. */    {       /* Step 1: Read DQ6 (into a word) */       pFA = FLASH_CAST(FLASH_ADRS); /* Read DQ6 from the Flash (any address) */       u1 = *pFA;       /* Step 2: Read DQ5 and DQ6 (into another word) */       u2 = *pFA; //FlashRead( ANY_ADDR ); /* Read DQ5 and DQ6 from the Flash (any       /* Step 3: If DQ6 did not toggle between the two reads then return                  FLASH_SUCCESS */       if( (u1&0x40) == (u2&0x40) ) /* DQ6 == NO Toggle */          return FLASH_SUCCESS;       /* Step 4: Else if DQ5 is zero then operation is not yet complete */       if( (u2&0x20) == 0x00 )          continue;       /* Step 5: Else (DQ5 == 1), read DQ6 again */       u1 = *pFA; //FlashRead( ANY_ADDR ); /* Read DQ6 from the Flash (any address) */       u2 = *pFA; //FlashRead( ANY_ADDR ); /* Read DQ6 from the Flash (any address) */       /* Step 6: If DQ6 did not toggle between the last two reads then                  return FLASH_SUCCESS */       if( (u2&0x40) == (u1&0x40) ) /* DQ6 == NO Toggle */          return FLASH_SUCCESS;       /* Step 7: Else return FLASH_TOGGLE_FAIL */       else { /* DQ6 == Toggle here means fail */          return FLASH_TOGGLE_FAIL;       }    } /* end of while loop */ }

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