读STM32F1的SD初始化代码碰到两个麻烦,有哪位老师可以回答?

zhangjw258

第一个问题:
在"SD_Error SD_GetCardInfo(SD_CardInfo *cardinfo)"函数中
................

   /*!< Byte 12 */
   tmp = (uint8_t)((CSD_Tab[3] & 0xFF000000) >> 24);
   cardinfo->SD_csd.WrProtectGrEnable = (tmp & 0x80) >> 7;
   cardinfo->SD_csd.ManDeflECC = (tmp & 0x60) >> 5;
   cardinfo->SD_csd.WrSpeedFact = (tmp & 0x1C) >> 2;
   cardinfo->SD_csd.MaxWrBlockLen = (tmp & 0x03) << 2;
   /*!< Byte 13 */
   tmp = (uint8_t)((CSD_Tab[3] & 0x00FF0000) >> 16);
   cardinfo->SD_csd.MaxWrBlockLen |= (tmp & 0xC0) >> 6;
   cardinfo->SD_csd.WriteBlockPaPartial = (tmp & 0x20) >> 5;
   cardinfo->SD_csd.Reserved3 = 0;
cardinfo->SD_csd.ContentProtectAppli = (tmp & 0x01);//关注这一句
  /*!< Byte 14 */
   tmp = (uint8_t)((CSD_Tab[3] & 0x0000FF00) >> 8);
   cardinfo->SD_csd.FileFormatGrouop = (tmp & 0x80) >> 7;
   cardinfo->SD_csd.CopyFlag = (tmp & 0x40) >> 6;
   cardinfo->SD_csd.PermWrProtect = (tmp & 0x20) >> 5;
   cardinfo->SD_csd.TempWrProtect = (tmp & 0x10) >> 4;
   cardinfo->SD_csd.FileFormat = (tmp & 0x0C) >> 2;
   cardinfo->SD_csd.ECC = (tmp & 0x03);
......................
" Byte 13 "已经用完了8位,(tmp & 0x01)又是什么?
[img][/img]
Reserved3 已经占5bits,这个字节已处理完,何来(tmp & 0x01).
有哪位老师能回答我?





第二个问题:
函数
static SD_Error FindSCR(uint16_t rca, uint32_t *pscr)
{
uint32_t tempscr[2] = {0, 0};
.............................
  *(pscr + 1) = ((tempscr[0] & SD_0TO7BITS) << 24) | ((tempscr[0] & SD_8TO15BITS) << 8) | ((tempscr[0] & SD_16TO23BITS) >> 8) | ((tempscr[0] & SD_24TO31BITS) >> 24);
  *(pscr) = ((tempscr[1] & SD_0TO7BITS) << 24) | ((tempscr[1] & SD_8TO15BITS) << 8) | ((tempscr[1] & SD_16TO23BITS) >> 8) | ((tempscr[1] & SD_24TO31BITS) >> 24);
.......................................
}
这两句又是什么操作?
scr 是调用函数的变量定义,
  uint32_t scr[2] = {0, 0};
.............
  errorstatus = FindSCR(RCA, scr);
.............
经过这样调用后,为什么把tempscrt和scr交叉赋值?为什么又要在赋值过程中将字节顺序也交换了?
请教在上,不胜感激.

zhangjw258

这个坛子这么冷了?