原创 stm32 fsmc数据地址线的关系

      stm32的fsmc接口设置的资料很少，所以现在对各个寄存器的具体应用还不是很明白，最近写了一个程序是把以前8位数据线读写sram的程序，改为16位数据线。有了一个小小的发现，现在把它写出来，希望大家来讨论一下。

      当改为16位数据线输出后，经过测量发现8位地址线整体往右移了一位，也就是说，比如程序里往地址为0101 1111内写入16位的数据。但测量8位地址线时就变成了0010 1111 。在此我对它的理解是，由于是拿着以前八位数据线，八位地址线访问的程序改的，以前是一个地址对应一个八位数据，现在一次可以传送16位数据，相当于以前传两次，所以这16位数据过来之后，应该放到相应的地址以及地址加一的位置上。这样相同的数据量传送的次数就比以前少了一半，以前需要1111 1111 次才能传完，现在需要0111 1111次就可以了。因为输出地址相应的往右一位，所以内部写地址时，最低位为0或1，输出的地址是相同的，所以在内部连续写地址时应该进行加2，就可以避免输出地址重复，至于内部怎么操作的我也不是很清楚，不明白。我把前后的程序贴出来，

八位数据线时的程序：

void FSMC_SRAM_Init(void)
{
  FSMC_NORSRAMInitTypeDef  FSMC_NORSRAMInitStructure;
  FSMC_NORSRAMTimingInitTypeDef  p;
 
/*-- FSMC Configuration ------------------------------------------------------*/
  p.FSMC_AddressSetupTime = 0;
  p.FSMC_AddressHoldTime = 0;
  p.FSMC_DataSetupTime = 2;
  p.FSMC_BusTurnAroundDuration = 0;
  p.FSMC_CLKDivision = 0;
  p.FSMC_DataLatency = 0;
  p.FSMC_AccessMode = FSMC_AccessMode_A;

  FSMC_NORSRAMInitStructure.FSMC_Bank = FSMC_Bank1_NORSRAM3;
  FSMC_NORSRAMInitStructure.FSMC_DataAddressMux = FSMC_DataAddressMux_Disable;
  FSMC_NORSRAMInitStructure.FSMC_MemoryType = FSMC_MemoryType_SRAM;
  FSMC_NORSRAMInitStructure.FSMC_MemoryDataWidth = FSMC_MemoryDataWidth_8b;
  FSMC_NORSRAMInitStructure.FSMC_BurstAccessMode = FSMC_BurstAccessMode_Disable;
  FSMC_NORSRAMInitStructure.FSMC_WaitSignalPolarity = FSMC_WaitSignalPolarity_Low;
  FSMC_NORSRAMInitStructure.FSMC_WrapMode = FSMC_WrapMode_Disable;
  FSMC_NORSRAMInitStructure.FSMC_WaitSignalActive = FSMC_WaitSignalActive_BeforeWaitState;
  FSMC_NORSRAMInitStructure.FSMC_WriteOperation = FSMC_WriteOperation_Enable;
  FSMC_NORSRAMInitStructure.FSMC_WaitSignal = FSMC_WaitSignal_Disable;
  FSMC_NORSRAMInitStructure.FSMC_ExtendedMode = FSMC_ExtendedMode_Disable;
  FSMC_NORSRAMInitStructure.FSMC_AsyncWait = FSMC_AsyncWait_Disable;
  FSMC_NORSRAMInitStructure.FSMC_WriteBurst = FSMC_WriteBurst_Disable;
  FSMC_NORSRAMInitStructure.FSMC_ReadWriteTimingStruct = &p;
  FSMC_NORSRAMInitStructure.FSMC_WriteTimingStruct = &p;

  FSMC_NORSRAMInit(&FSMC_NORSRAMInitStructure);

  /* Enable FSMC Bank1_SRAM Bank */
  FSMC_NORSRAMCmd(FSMC_Bank1_NORSRAM3, ENABLE); 
}

/*******************************************************************************
* Function Name  : FSMC_SRAM_WriteBuffer
* Description    : Writes a Half-word buffer to the FSMC SRAM memory.
* Input          : - pBuffer : pointer to buffer.
*                  - WriteAddr : SRAM memory internal address from which the data
*                    will be written.
*                  - NumHalfwordToWrite : number of half-words to write.
*                   
* Output         : None
* Return         : None
*******************************************************************************/
void FSMC_SRAM_WriteBuffer(u8* pBuffer, u8 WriteAddr, u32 NumHalfwordToWrite)
{

  for(; NumHalfwordToWrite != 0; NumHalfwordToWrite--) /* while there is data to write */
  {
    /* Transfer data to the memory */
    *(u16 *) (Bank1_SRAM3_ADDR + WriteAddr) = *pBuffer++;
   
    /* Increment the address*/  
   WriteAddr += 1;
  }  
}

16位数据线，8位地址线时:

void FSMC_SRAM_Init(void)
{
  FSMC_NORSRAMInitTypeDef  FSMC_NORSRAMInitStructure;
  FSMC_NORSRAMTimingInitTypeDef  p;

/*-- FSMC Configuration ------------------------------------------------------*/
  p.FSMC_AddressSetupTime = 0;
  p.FSMC_AddressHoldTime = 0;
  p.FSMC_DataSetupTime = 2;
  p.FSMC_BusTurnAroundDuration = 0;
  p.FSMC_CLKDivision = 0;
  p.FSMC_DataLatency = 0;
  p.FSMC_AccessMode = FSMC_AccessMode_A;

  FSMC_NORSRAMInitStructure.FSMC_Bank = FSMC_Bank1_NORSRAM3;
  FSMC_NORSRAMInitStructure.FSMC_DataAddressMux = FSMC_DataAddressMux_Disable;
  FSMC_NORSRAMInitStructure.FSMC_MemoryType = FSMC_MemoryType_SRAM;
  FSMC_NORSRAMInitStructure.FSMC_MemoryDataWidth = FSMC_MemoryDataWidth_16b;
  FSMC_NORSRAMInitStructure.FSMC_BurstAccessMode = FSMC_BurstAccessMode_Disable;
  FSMC_NORSRAMInitStructure.FSMC_WaitSignalPolarity = FSMC_WaitSignalPolarity_Low;
  FSMC_NORSRAMInitStructure.FSMC_WrapMode = FSMC_WrapMode_Disable;
  FSMC_NORSRAMInitStructure.FSMC_WaitSignalActive = FSMC_WaitSignalActive_BeforeWaitState;
  FSMC_NORSRAMInitStructure.FSMC_WriteOperation = FSMC_WriteOperation_Enable;
  FSMC_NORSRAMInitStructure.FSMC_WaitSignal = FSMC_WaitSignal_Disable;
  FSMC_NORSRAMInitStructure.FSMC_ExtendedMode = FSMC_ExtendedMode_Disable;
  FSMC_NORSRAMInitStructure.FSMC_AsyncWait = FSMC_AsyncWait_Disable;
  FSMC_NORSRAMInitStructure.FSMC_WriteBurst = FSMC_WriteBurst_Disable;
  FSMC_NORSRAMInitStructure.FSMC_ReadWriteTimingStruct = &p;
  FSMC_NORSRAMInitStructure.FSMC_WriteTimingStruct = &p;

  FSMC_NORSRAMInit(&FSMC_NORSRAMInitStructure);

  /* Enable FSMC Bank1_SRAM Bank */
  FSMC_NORSRAMCmd(FSMC_Bank1_NORSRAM3, ENABLE); 
}

/*******************************************************************************
* Function Name  : FSMC_SRAM_WriteBuffer
* Description    : Writes a Half-word buffer to the FSMC SRAM memory.
* Input          : - pBuffer : pointer to buffer.
*                  - WriteAddr : SRAM memory internal address from which the data
*                    will be written.
*                  - NumHalfwordToWrite : number of half-words to write.
*                   
* Output         : None
* Return         : None
*******************************************************************************/
void FSMC_SRAM_WriteBuffer(u16* pBuffer, u8 WriteAddr, u32 NumHalfwordToWrite)
{
  for(; NumHalfwordToWrite != 0; NumHalfwordToWrite--) /* while there is data to write */
  {
    /* Transfer data to the memory */
    *(u16 *) (Bank1_SRAM3_ADDR + WriteAddr) = *pBuffer++;
   
    /* Increment the address*/  
   WriteAddr += 2;
  }  
}