嵌入式系統設計-第7章-DMA資料快速搬移－youboook的部落格

第7章

大量資料的快速搬移─DMA

7.1 STM32 DMA簡介

DMA，又稱Direct Memory Access。主要功能為對記憶體坐直接存取的動作而不用透過CPU，透過硬體使得記憶體與I/O設備建立一條直接傳送資料的通道，藉此使CPU的效率大為提高。

使用DMA，對CPU而言有兩個很大的好處：

1. 使用DMA，能使CPU的使用效率提升。
2. 使用DMA操作記憶體，比使用CPU操作記憶體還要快速。

STM32最多有兩個DMA的控制器，(DMA2僅存在於大容量的產品當中)，DMA1有7個通道，每個通道專門用來管理來自於一個或多個外部設備的請求。此外還有一個仲裁器來協調各個DMA請求的優先權。

STM32的DMA有以下的特性：

每個通道都直接連接到DMA，每個通道都支援軟體觸發，這些功能透過軟體來設定。
在七個請求通知的優先權，須通過軟體進行設定，一共有四級，假如在相等優先權時，則由硬體決定優先權。
可獨立設置來源位置與目的位置的資料傳輸寬度(8bits、16bits、32bits)，兩邊的資料寬度必須相等。
支援Circular buffer
每個通道都有三個旗標(DMA半傳輸、DMA傳輸完成、DMA傳輸錯誤)。
支援記憶體對記憶體的傳輸
支援外部設備對記憶體與記憶體對外部設備的傳輸
FLASH、SRAM、外部SRAM、APB1APB2和AHB均可當作DMA操作的來源位置或目的位置。
可傳輸的最大數目為65535。

而SIOC(STM32F103C8T6)只有一個DMA控制器，DMA1，下面我們就針對DMA1進行介紹。

從外部周邊(TIMx、ADC、SPIx、I2Cx和USARTx)產生的DMA請求，須通過OR邏輯閘輸入至DMA控制器，這表示同時只能有一個外部請求可被執行。

DMA1通道一覽表與DMA Request Mapping：

外部	通道1	通道2	通道3	通道4	通道5	通道6	通道7
ADC	ADC1
SPI		SPI1_RX	SPI1_TX	SPI2_RX	SPI2_TX
USART		USART3_TX	USART3_RX	USART1_TX	USART1_RX	USART2_RX	USART2_TX
I2C				I2C2_TX	I2C2_RX	I2C1_TX	I2C1_RX
TIM1		TIM1_CH1	TIM1_CH2	TIM1_TX4 TIM1_TRIG TIM1_COM	TIM1_UP	TIM1_CH3
TIM2	TIM2_CH3	TIM2_UP			TIM2_CH1		TIM2_CH2 TIM2_CH4
TIM3		TIM3_CH3	TIM3_CH4 TIM3_UP			TIM3_CH1 TIM3_TRIG
TIM4	TIM4_CH1			TIM4_CH2	TIM4_CH3		TIM4_UP

7.2 DMA Registers

本章節將逐一介紹在使用DMA時，會使用到的暫存器

Register	Description
ISR	紀錄DMA 中斷狀態的暫存器
IFCR	計錄DMA 清除中斷的暫存器
CCRx	紀錄DMA Channelx 設定的暫存器
CNDTRx	紀錄DMA Channelx待傳輸資料筆數的暫存器
CPARx	儲存DMA Channelx 周邊記憶體位置的暫存器
CMARx	儲存DMA Channelx 主記憶體位置的暫存器

DMA Register Mapping

7.3 DMA Standard Driver Library

本章節將介紹使用者在撰寫程式時，會使用到的函式。

Function name	Description
DMA_DeInit
DMA_Init	初始 DMAy Channelx
DMA_StructInit	填入 DMA_InitStruct 參數
DMA_Cmd	Enables or disables the specified DMAy Channelx.
DMA_ITConfig	Enables or disables the specified DMAy Channelx interrupts.
DMA_GetCurrDataCounter	回傳 DMAy當下的剩餘資料個數
DMA_ClearFlag	清除 DMAy Channelx pending flags.
DMA_GetITStatus	確認 DMAy Channelx的中斷旗標有沒有被觸發
DMA_ClearITPendingBit	清除 DMAy Channelx interrupt pending bits.

DMA_DeInit function

Function name	DMA_DeInit
Function prototype	void DMA_DeInit(DMA_Channel_TypeDef* DMAy_Channelx)
Behavior description	Resets the DMAy Channelx registers to their default reset values.
Input parameter	DMAy_Channelx: where y selects the DMA (y = 1 for DMA1, y = 2 for DMA2) and x selects the DMA Channel (x = 1 to 7 for DMA1 or x = 1 to5 for DMA2).
Output parameter	None
Return parameter	None
Required preconditions	None
Called functions	RCC_AHBPeriphClockCmd().

Example:

/* Deinitialize the DMA1 Channel2 */

DMA_DeInit(DMA1_Channel2);

DMA_Init function

Function name	DMA_Init
Function prototype	void DMA_Init(DMA_Channel_TypeDef* DMAy_Channelx,DMA_InitTypeDef* DMA_InitStruct)
Behavior description	Initializes the DMAy Channelx according to the parameters specified in the DMA_InitStruct.
Function name	DMA_Init
Input parameter1	DMAy_Channelx: where y selects the DMA (y = 1 for DMA1, y = 2 for DMA2) and x selects the DMA Channel (x = 1 to 7 for DMA1 or x = 1 to 5 for DMA2).
Input parameter2	DMA_InitStruct: pointer to a DMA_InitTypeDef structure that contains the configuration information for the specified DMAy Channelx. Refer to DMA_InitTypeDef structure for more details on the allowed values for this parameter.
Output parameter	None
Return parameter	None
Required preconditions	None
Required preconditions	None

DMA_InitTypeDef structure

The DMA_InitTypeDef structure is defined in the stm32f10x_dma.h file:

typedef struct

{

u32 DMA_PeripheralBaseAddr;

u32 DMA_MemoryBaseAddr;

u32 DMA_DIR;

u32 DMA_BufferSize;

u32 DMA_PeripheralInc;

u32 DMA_MemoryInc;

u32 DMA_PeripheralDataSize;

u32 DMA_MemoryDataSize;

u32 DMA_Mode;

u32 DMA_Priority;

u32 DMA_M2M;

} DMA_InitTypeDef;

DMA_PeripheralBaseAddr

紀錄DMA周邊記憶體起始位置。

DMA_MemoryBaseAddr

紀錄DMA主記憶體起始位置。

DMA_DIR

設定DMA要將周邊記憶體視為來源端或是目的端。

DMA_DIR	Description
DMA_DIR_PeripheralDST	將周邊視為目的端
DMA_DIR_PeripheralSRC	將周邊視為來源端

DMA_BufferSize

此欄位定義DMA傳送的buffer大小，此大小必須想等於DMA_PeripheralDataSize或DMA_MemoryDataSize。

DMA_PeripheralInc

此欄位將設定DMA操作周邊時，是否要啟用累加器。

DMA_PeripheralInc	Description
DMA_PeripheralInc_Enable	Current peripheral register incremented
DMA_PeripheralInc_Disable	Current peripheral register unchanged

DMA_MemoryInc

此欄位將設定DMA操作主記憶體時，是否要啟用累加器。

DMA_MemoryInc	Description
DMA_MemoryInc_Enable	Current memory register incremented
DMA_MemoryInc_Disable	Current memory register unchanged

DMA_PeripheralDataSize

此欄位設定來自周邊的資料寬度。

DMA_PeripheralDataSize	Description
DMA_PeripheralDataSize_Byte	Data width = 8bits
DMA_PeripheralDataSize_HalfWord	Data width = 16bits
DMA_PeripheralDataSize_Word	Data width = 32bits

DMA_MemoryDataSize

此欄位設定來自主記憶體的資料寬度。

DMA_MemoryDataSize	Description
DMA_MemoryDataSize_Byte	Data width = 8bits
DMA_MemoryDataSize_HalfWord	Data width = 16bits
DMA_MemoryDataSize_Word	Data width = 32bits

DMA_Mode

此欄位設定DMA的運作模式。

DMA_Mode	Description
DMA_Mode_Circular	Circular buffer mode is used
DMA_Mode_Normal	Normal buffer mode is used

在DMA_Mode_Circular模式下，不能使用memory-to-memory轉移。

DMA_Priority

此欄位設定軟體的優先權。

DMA_Priority	Description
DMA_Priority_VeryHigh	DMAy Channelx has a very high priority
DMA_Priority_High	DMAy Channelx has a high priority
DMA_Priority_Medium	DMAy Channelx has a medium priority
DMA_Priority_Low	DMAy Channelx has a low priority

DMA_M2M

此欄位設定memory-to-memory轉移是否要被啟用。

DMA_M2M	Description
DMA_M2M_Enable	DMAy Channelx configured for memory-to-memory transfer
DMA_M2M_Enable	DMAy Channelx not configured for memory-to memory transfer

Example:

/* Initialize the DMA1 Channel1 according to the DMA_InitStructure members */

DMA_InitTypeDef DMA_InitStructure;

DMA_InitStructure.DMA_PeripheralBaseAddr = 0x40005400;

DMA_InitStructure.DMA_MemoryBaseAddr = 0x20000100;

DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;

DMA_InitStructure.DMA_BufferSize = 256;

DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;

DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;

DMA_InitStructure.DMA_PeripheralDataSize =

DMA_PeripheralDataSize_HalfWord;

DMA_InitStructure.DMA_MemoryDataSize =

DMA_MemoryDataSize_HalfWord;

DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;

DMA_InitStructure.DMA_Priority = DMA_Priority_Medium;

DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;

DMA_Init(DMA1_Channel1, &DMA_InitStructure);

DMA_StructInit function

Function name	DMA_StructInit
Function prototype	Void DMA_StructInit(DMA_InitTypeDef* DMA_InitStruct)
Behavior description	Fills each DMA_InitStruct member with its default value.
Input parameter	DMA_InitStruct: pointer to the DMA_InitTypeDef structure to be initialized
Output parameter	None
Return parameter	None
Required preconditions	None
Called functions	None

DMA_initStruct default values

Member	Default value
DMA_PeripheralBaseAddr	0
DMA_MemoryBaseAddr	0
DMA_DIR	DMA_DIR_PeripheralSRC
DMA_BufferSize	0
DMA_PeripheralInc	DMA_PeripheralInc_Disable
DMA_MemoryInc	DMA_MemoryInc_Disable
DMA_PeripheralDataSize	DMA_PeripheralDataSize_Byte
DMA_MemoryDataSize	DMA_MemoryDataSize_Byte
DMA_Mode	DMA_Mode_Normal
DMA_Priority	DMA_Priority_Low
DMA_M2M	DMA_M2M_Disable

Example:

/* Initialize a DMA_InitTypeDef structure */

DMA_InitTypeDef DMA_InitStructure;

DMA_StructInit(&DMA_InitStructure);

DMA_Cmd function

Function name	DMA_Cmd
Function prototype	void DMA_Cmd(DMA_Channel_TypeDef* DMAy_Channelx,FunctionalState NewState)
Behavior description	Enables or disables the specified DMAy Channelx.
Input parameter1	DMAy_Channelx: where y selects the DMA (y = 1 for DMA1, y = 2 for DMA2) and x selects the DMA Channel (x = 1 to 7 for DMA1 or x = 1 to 5 for DMA2).
Input parameter2	NewState: new state of the DMAy Channelx. This parameter can be: ENABLE or DISABLE
Output parameter	None
Return parameter	None
Required preconditions	None
Called functions	None

Example:

/* Enable DMA1 Channel7 */

DMA_Cmd(DMA1_Channel7, ENABLE);

DMA_ITConfig function

Function name	DMA_ITConfig
Function prototype	void DMA_ITConfig(DMA_Channel_TypeDef* DMAy_Channelx, u32 DMA_IT, FunctionalState NewState)
Behavior description	Enables or disables the specified DMAy Channelx interrupts.
Input parameter1	DMAy_Channelx: where y selects the DMA (y = 1 for DMA1, y = 2 for DMA2) and x selects the DMA Channel (x = 1 to 7 for DMA1 or x = 1 to 5 for DMA2).
Input parameter2	DMA_IT: specifies the DMAy Channelx interrupt sources to be enabled or disabled. More than one interrupt can be selected using the “\|” operator.Refer to DMA_IT for more details on the allowed values for this parameter.
Input parameter3	NewState: new state of the specified DMAy Channelx interrupts.This parameter can be: ENABLE or DISABLE.
Output parameter	None
Return parameter	None
Required preconditions	None
Called functions	None

DMA_IT

此函數用來設置DMA的三個中斷

DMA_IT	Description
DMA_IT_TC	Transfer complete interrupt mask
DMA_IT_HT	Half transfer interrupt mask
DMA_IT_TE	Transfer error interrupt mask

Example:

/* Enable DMA1 Channel5 complete transfer interrupt */

DMA_ITConfig(DMA1_Channel5, DMA_IT_TC, ENABLE);

DMA_GetCurrDataCounter function

Function name	DMA_GetCurrDataCounter
Function prototype	u16 DMA_GetCurrDataCounter(DMA_Channel_TypeDef* DMAy_Channelx)
Behavior description	Returns the number of remaining data units in the current DMAy Channelx transfer.
Input parameter	DMAy_Channelx: where y selects the DMA (y = 1 for DMA1, y = 2 for DMA2) and x selects the DMA Channel (x = 1 to 7 for DMA1 or x = 1 to 5 for DMA2).
Output parameter	None
Return parameter	The number of remaining data units in the current DMAy Channelx transfer.
Required preconditions	None
Called functions	None

Example:

/* Get the number of remaining data units in the current DMA1 Channel2 transfer */

u16 CurrDataCount;

CurrDataCount = DMA_GetCurrDataCounter(DMA1_Channel2);

DMA_GetFlagStatus function

Function name	DMA_GetFlagStatus
Function prototype	FlagStatus DMA_GetFlagStatus(u32 DMA_FLAG)
Behavior description	Checks whether the specified DMAy Channelx flag is set or not.
Input parameter	DMA_FLAG: specifies the flag to check.Refer to DMA_FLAG for more details on the allowed values for this parameter.
Output parameter	None
Return parameter	New state of DMA_FLAG (SET or RESET).
Required preconditions	None
Called functions	None

DMA_FLAG

DMA_FLAG	Description
DMA1_FLAG_GL1	DMA1 Channel1 global flag
DMA1_FLAG_TC1	DMA1 Channel1 transfer complete flag
DMA1_FLAG_HT1	DMA1 Channel1 half transfer flag
DMA1_FLAG_TE1	DMA1 Channel1 transfer error flag
DMA1_FLAG_GL2	DMA1 Channel2 global flag
DMA1_FLAG_TC2	DMA1 Channel2 transfer complete flag
DMA1_FLAG_HT2	DMA1 Channel2 half transfer flag
DMA1_FLAG_TE2	DMA1 Channel2 transfer error flag
DMA1_FLAG_GL3	DMA1 Channel3 global flag
DMA1_FLAG_TC3	DMA1 Channel3 transfer complete flag
DMA1_FLAG_HT3	DMA1 Channel3 half transfer flag
DMA1_FLAG_TE3	DMA1 Channel3 transfer error flag
DMA1_FLAG_GL4	DMA1 Channel4 global flag
DMA1_FLAG_TC4	DMA1 Channel4 transfer complete flag
DMA1_FLAG_HT4	DMA1 Channel4 half transfer flag
DMA1_FLAG_TE4	DMA1 Channel4 transfer error flag
DMA1_FLAG_GL5	DMA1 Channel5 global flag
DMA1_FLAG_TC5	DMA1 Channel5 transfer complete flag
DMA1_FLAG_HT5	DMA1 Channel5 half transfer flag
DMA1_FLAG_TE5	DMA1 Channel5 transfer error flag
DMA1_FLAG_GL6	DMA1 Channel6 global flag
DMA1_FLAG_TC6	DMA1 Channel6 transfer complete flag
DMA1_FLAG_HT6	DMA1 Channel6 half transfer flag
DMA1_FLAG_TE6	DMA1 Channel6 transfer error flag
DMA1_FLAG_GL7	DMA1 Channel7 global flag
DMA1_FLAG_TC7	DMA1 Channel7 transfer complete flag
DMA1_FLAG_HT7	DMA1 Channel7 half transfer flag
DMA1_FLAG_TE7	DMA1 Channel7 transfer error flag

Example:

/* Test if the DMA1 Channel6 half transfer interrupt flag is set or not */

FlagStatus Status;

Status = DMA_GetFlagStatus(DMA1_FLAG_HT6);

DMA_ClearFlag function

Function name	DMA_ClearFlag
Function prototype	void DMA_ClearFlag(u32 DMA_FLAG)
Behavior description	Clears the DMAy Channelx's pending flags.
Input parameter	DMA_FLAG: flag to be cleared. More than one flag can be cleared using the “\|” operator. Refer to DMA_FLAG for more details on the allowed values for this parameter. The user can select more than one flag, by ‘ORing’ them.
Output parameter	None
Return parameter	None
Required preconditions	None
Called functions	None

Example:

/* Clear the DMA1 Channel3 transfer error interrupt pending bit */

DMA_ClearFlag(DMA1_FLAG_TE3);

DMA_GetITStatus function

Function name	DMA_GetITStatus
Function prototype	ITStatus DMA_GetITStatus(u32 DMA_IT)
Behavior description	Checks whether the specified DMAy Channelx interrupt has occurred or not.
Input parameter	DMA_IT: DMAy Channelx interrupt source to check. Refer to DMA_IT for more details on the allowed values for this parameter.
Output parameter	None
Return parameter	The new state of DMA_IT (SET or RESET).
Required preconditions	None
Called functions	None

DMA_IT

DMA_FLAG	Description
DMA1_IT_GL1	DMA1 Channel1 global interrupt
DMA1_IT_TC1	DMA1 Channel1 transfer complete interrupt
DMA1_IT_HT1	DMA1 Channel1 half transfer interrupt
DMA1_IT_TE1	DMA1 Channel1 transfer error interrupt
DMA1_IT_GL2	DMA1 Channel2 global interrupt
DMA1_IT_TC2	DMA1 Channel2 transfer complete interrupt
DMA1_IT_HT2	DMA1 Channel2 half transfer interrupt
DMA1_IT_TE2	DMA1 Channel2 transfer error interrupt
DMA1_IT_GL3	DMA1 Channel3 global interrupt
DMA1_IT_TC3	DMA1 Channel3 transfer complete interrupt
DMA1_IT_HT3	DMA1 Channel3 half transfer interrupt
DMA1_IT_TE3	DMA1 Channel3 transfer error interrupt
DMA1_IT_GL4	DMA1 Channel4 global interrupt
DMA1_IT_TC4	DMA1 Channel4 transfer complete interrupt
DMA1_IT_HT4	DMA1 Channel4 half transfer interrupt
DMA1_IT_TE4	DMA1 Channel4 transfer error interrupt
DMA1_IT_GL5	DMA1 Channel5 global interrupt
DMA1_IT_TC5	DMA1 Channel5 transfer complete interrupt
DMA1_IT_HT5	DMA1 Channel5 half transfer interrupt
DMA1_IT_TE5	DMA1 Channel5 transfer error interrupt
DMA1_IT_GL6	DMA1 Channel6 global interrupt
DMA1_IT_TC6	DMA1 Channel6 transfer complete interrupt
DMA1_IT_HT6	DMA1 Channel6 half transfer interrupt
DMA1_IT_TE6	DMA1 Channel6 transfer error interrupt
DMA1_IT_GL7	DMA1 Channel7 global interrupt
DMA1_IT_TC7	DMA1 Channel7 transfer complete interrupt
DMA1_IT_HT7	DMA1 Channel7 half transfer interrupt
DMA1_IT_TE7	DMA1 Channel7 transfer error interrupt

Example:

/* Test if the DMA1 Channel7 transfer complete interrupt has occurred or not */

ITStatus Status;

Status = DMA_GetITStatus(DMA1_IT_TC7);

DMA_ClearITPendingBit function

Function name	DMA_ClearITPending Bit
Function prototype	void DMA_ClearITPendingBit(u32 DMA_IT)
Behavior description	Clears the DMAy Channelx’s interrupt pending bits.
Input parameter	DMA_IT: DMAy Channelx interrupt pending bit to clear.More than one interrupt can be cleared using the “\|” operator. Refer to DMA_IT for more details on the allowed values for this parameter.
Output parameter	None
Return parameter	None
Required preconditions	None
Called functions	None

Example:

/* Clear the DMA1 Channel5 global interrupt pending bit */

DMA_ClearITPendingBit(DMA1_IT_GL5);

7.4 立即演練

實驗1：Polling DMA

實驗說明：利用Polling的方式使用DMA搬移記憶體資料。

Grafcet：

此實驗的重點，就是何謂「Polling」機制？所謂Polling就是輪詢的意思就是指CPU不斷的去檢查、查看。以範例的程式碼為例：

while (1)

{

/* Wait the end of transmission */

printf("\r\nWait the end of transmission...");

while (DMA_GetFlagStatus(DMA1_FLAG_TC6) == RESET);

printf("\r\nDMA1_FLAG_TC6:%d",DMA_GetFlagStatus(DMA1_FLAG_TC6));

printf("\r\nDMA1 Channel6 Received Data:");

/* Check if the transmitted and received data are equal */

Buffercmp(SRC_Const_Buffer, DST_Buffer, BufferSize);

DMA_ClearFlag(DMA1_FLAG_TC6);

}

這段敘述就是一個典型的Polling的例子。DMA1_FLAG_TC6是確認DMA是否已搬完資料的旗標，為RESET時表示尚未搬完；為SET時表示已搬完。當CPU執行這段程式碼，一旦DMA_GetFlagStatus(DMA1_FLAG_TC6) == RESET條件成立，即DMA尚未搬完資料，程式將不斷執行此空迴圈，而CPU也會不斷地去檢查while當中的條件是否成立。

在此實驗當中，雖然CPU並沒有提升使用效率，因為CPU大部分的時間還是花在Polling的動作。但是因為有使用到DMA，在做記憶體存取資料的速度，還是比一般用for迴圈速度還要來的快！

其餘重要的DMA設定部分如：

void RCC_Configuration(void)

{

/* Enable peripheral clocks ------------------------------------------------*/

/* Enable DMA1 clock */

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

}

void DMA_Configuration(void)

{ /* DMA1 channel6 configuration */

DMA_InitTypeDef DMA_InitStructure;

DMA_DeInit(DMA1_Channel6);

DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)SRC_Const_Buffer;

DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)DST_Buffer;

DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;

DMA_InitStructure.DMA_BufferSize = BufferSize;

DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Enable;

DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;

DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word;

DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Word;

DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;

DMA_InitStructure.DMA_Priority = DMA_Priority_High;

DMA_InitStructure.DMA_M2M = DMA_M2M_Enable;

DMA_Init(DMA1_Channel6, &DMA_InitStructure);

}

實驗2：Interrupt DMA

實驗說明：利用Interrupt的方式使用DMA搬移記憶體資料。

Grafcet：

Interrupt機制最大不同於Polling就是，DMA完成工作時，將會主動告知CPU，而CPU就無須用Polling的方式，大大增進了效率。

讀者可以發現，在main.c的程式碼中，不同於上一實驗，已經少了while (DMA_GetFlagStatus(DMA1_FLAG_TC6) == RESET)的敘述，取而代之的是在stm32f10x_it中的void DMA1_Channel6_IRQHandler(void)敘述：

void DMA1_Channel6_IRQHandler(void)

{

/* Test on DMA1 Channel6 Transfer Complete interrupt */

if(DMA_GetITStatus(DMA1_IT_TC6))

{

printf("\r\nDMA1_FLAG_TC6:%d",DMA_GetFlagStatus(DMA1_FLAG_TC6));

DMA_ClearITPendingBit(DMA1_IT_TC6);

printf("\r\n DMA1 Channel6 Interrupt Received data:");

Buffercmp(SRC_Const_Buffer, DST_Buffer, BufferSize);

}

此敘述就是在描述當DMA的工作完成，即啟動Interrupt通知CPU。

開啟Interrupt設定部分如：

void NVIC_Configuration(void)

{

NVIC_InitTypeDef NVIC_InitStructure;

NVIC_SetVectorTable(0x08003000,0x0);

/* Enable DMA1 channel6 IRQ Channel */

NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel6_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

}

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