使用STM32H750 QSPI W25Q64作为外部FLASH，映射后读0X90010000地址的数据读到的是0XFF的原因？

我使用STM32H750   QSPI  W25Q64 作为外部FLASH，使用非映射方式读写FLASH 正常，映射后，读0X90000000地址的数据也正常，但是读0X90010000 地址的数据读到的是0XFF，但是 用W25Qx_QSPI_FastRead 读 0X10000确是正常的，请问哪位大侠知道是怎么回事情
if(W25Qx_QSPI_Init()!=QSPI_OK){while(1);}
//      W25Qx_QSPI_Read(ucD,0x0,8);W25Qx_QSPI_FastRead( ucD[20],0x0000,8); W25Qx_QSPI_FastRead( ucD[30],0x10000,8);//      W25Qx_QSPI_Erase_Block(0);//      W25Qx_QSPI_Write(ucDat,0x0,8);//      W25Qx_QSPI_Read(ucD,0x0,8);W25Qx_QSPI_FastRead( ucD[38],0x10008,8);
if(QSPI_EnableMemoryMappedMode( hqspi)!= QSPI_OK){while(1);}
ucD[0] = *(unsigned char*)(0x8000000UL);ucD[11] =   [i](unsigned char)(0x90000000UL);ucD[12] =   [i](unsigned char)(0x90000001UL);ucD[13] =   [i](unsigned char)(0x90000002UL);ucD[14] =   [i](unsigned char)(0x90000003UL);
ucD[1] =   [i](unsigned char)(0x90010000UL);ucD[2] =   [i](unsigned char)(0x90010001UL);ucD[3] =   [i](unsigned char)(0x90010002UL);ucD[4] =   [i](unsigned char)(0x90010003UL);