DMA - Direct Memory Access

Files
file	otDMA.h
	Direct Memory Access Library for BF51x.
Modules
	Version History
	DMA - Code example
Enumerations
enum	dmaChannels { DMA_CH_0, DMA_CH_1 }
enum	dmaData { DMA_BYTE, DMA_WORD, DMA_DWORD }
Functions
void	DmaSetInterruptService (U8 chan, void(*pCallback)(void))
	Set callback for specified MDMA channel.
void	DmaEnableInterrupt (U8 chan, bool ena)
	Enable or disable the interrupt on end of trasfer for the specified MDMA channel.
void	DmaMove (U8 chan, void *src, void *dest, U32 len, U8 dataType)
	Move an amount of memory from src to dst.
void	DmaMoveToPort (U8 chan, void *src, void *port, U32 len, U8 dataType)
	Move an amount of memory from src to a memory mapped peripheral.
void	DmaMoveFromPort (U8 chan, void *port, void *dest, U32 len, U8 dataType)
	Move an amount of memory from a memory mapped peripheral to a buffer.

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Detailed Description

Direct memory access (DMA) is a feature of computer systems that allows certain hardware subsystems to access main system memory (random-access memory), independent of the central processing unit (CPU).
Without DMA, when the CPU is using programmed input/output, it is typically fully occupied for the entire duration of the read or write operation, and is thus unavailable to perform other work. With DMA, the CPU first initiates the transfer, then it does other operations while the transfer is in progress, and it finally receives an interrupt from the DMA controller (DMAC) when the operation is done.
This feature is useful at any time that the CPU cannot keep up with the rate of data transfer, or when the CPU needs to perform work while waiting for a relatively slow I/O data transfer.
Many hardware systems use DMA, including disk drive controllers, graphics cards, network cards and sound cards.
DMA is also used for intra-chip data transfer in multi-core processors.
Computers that have DMA channels can transfer data to and from devices with much less CPU overhead than computers without DMA channels.
Similarly, a processing element inside a multi-core processor can transfer data to and from its local memory without occupying its processor time,
allowing computation and data transfer to proceed in parallel.
DMA can also be used for "memory to memory" copying or moving of data within memory. From wikipedia: https://en.wikipedia.org/wiki/Direct_memory_access

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Enumeration Type Documentation

enum dmaChannels

Enumeration values: DMA_CH_0  MDMA channel 0. DMA_CH_1  MDMA channel 1.

enum dmaData

Enumeration values: DMA_BYTE  MDMA transfer byte. DMA_WORD  MDMA transfer word (16bit). DMA_DWORD  MDMA transfer double word (32bit).

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Function Documentation

void DmaEnableInterrupt (  U8  chan, bool  ena )

Parameters: chan  MDMA channel see dmaChannels ena  If true enable the interrupt

void DmaMove (  U8  chan, void *  src, void *  dest, U32  len, U8  dataType )

Parameters: chan  MDMA channel see dmaChannels src  Pointer to a source buffer dest  Pointer to a destination buffer where data will be copied len  Lenght of data dataType  Data type, see dmaData

void DmaMoveFromPort (  U8  chan, void *  port, void *  dest, U32  len, U8  dataType )

Parameters: chan  MDMA channel see dmaChannels port  Pointer to a memory mapped peripheral dest  Pointer to a destination buffer where data will be copied len  Lenght of data dataType  Data type, see dmaData

void DmaMoveToPort (  U8  chan, void *  src, void *  port, U32  len, U8  dataType )

Parameters: chan  MDMA channel see dmaChannels src  Pointer to a source buffer port  Pointer to a memory mapped peripheral len  Lenght of data dataType  Data type, see dmaData

void DmaSetInterruptService (  U8  chan, void(*)(void)  pCallback )

Parameters: chan  MDMA channel see dmaChannels pCallback  Pointer to a function executed at the end of DMA transfer

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