Direct Memory Access

DMA (Direct Memory Access) transfers can be used to copy a block of memory from one location to another and/or to fill a block of memory with a given value in hardware. All DMA function in HEL Library use the general purpose channel (channel 3). More...

Functions

• void hel_DmaCopy16 (void *pDest, const void *pSrc, u32 SizeIn16BitWords)

  Copy memory using DMA Channel 3 in 16BIT mode.
  

• void hel_DmaCopy32 (void *pDest, const void *pSrc, u32 SizeIn32BitWords)

  Copy memory using DMA Channel 3 in 32BIT mode.
  

• void hel_DmaSet16 (void *pDest, volatile u16 SrcValue, u32 SizeIn16BitWords)

  Fills a block of memory with a specified value using Channel 3 in 16BIT mode.
  

• void hel_DmaSet32 (void *pDest, volatile u32 SrcValue, u32 SizeIn32BitWords)

  Fills a block of memory with a specified value using Channel 3 in 32BIT mode.
  

• void hel_DmaSet8 (void *pDest, u8 SrcValue, u32 SizeInBytes)

  Fills a block of memory with a specified value using DMA Channel 3.
  

• void hel_DmaZeroMemory (void *pDest, u32 SizeInBytes)

  Fills a block of memory with zeros using DMA Channel 3.
  

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Detailed Description

DMA (Direct Memory Access) transfers can be used to copy a block of memory from one location to another and/or to fill a block of memory with a given value in hardware. All DMA function in HEL Library use the general purpose channel (channel 3).

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Function Documentation

void hel_DmaCopy16	(	void *	pDest,
		const void *	pSrc,
		u32	SizeIn16BitWords
	)

Copy memory using DMA Channel 3 in 16BIT mode.

The hel_DmaCopy16 function copies a block of memory from one location to another using DMA Channel 3 in 16BIT mode.

Parameters:

[in]	pDest	Pointer to copy destination
[in]	pSrc	Pointer to block to copy
[in]	SizeIn16BitWords	Size 16BIT Words of block to copy

See also:

hel_DmaCopy32

void hel_DmaCopy32	(	void *	pDest,
		const void *	pSrc,
		u32	SizeIn32BitWords
	)

Copy memory using DMA Channel 3 in 32BIT mode.

The hel_DmaCopy32 function copies a block of memory from one location to another using DMA Channel 3 in 32BIT mode.

Parameters:

[in]	pDest	Pointer to copy destination
[in]	pSrc	Pointer to block to copy
[in]	SizeIn32BitWords	Size 32BIT Words of block to copy

See also:

hel_DmaCopy16

void hel_DmaSet16	(	void *	pDest,
		volatile u16	SrcValue,
		u32	SizeIn16BitWords
	)

Fills a block of memory with a specified value using Channel 3 in 16BIT mode.

The hel_DmaSet16 function fills a block of memory with a specified value using DMA Channel 3 in 16bit mode.

Parameters:

[in]	pDest	Pointer to block to fill
[in]	SrcValue	The 16bit value with which to fill
[in]	SizeIn16BitWords	Size in 16bit words of block to fill

Note:

The destination address specified by pDest must be multiply 2.

See also:

hel_DmaSet8, hel_DmaSet32

void hel_DmaSet32	(	void *	pDest,
		volatile u32	SrcValue,
		u32	SizeIn32BitWords
	)

Fills a block of memory with a specified value using Channel 3 in 32BIT mode.

The hel_DmaSet32 function fills a block of memory with a specified value using DMA Channel 3 in 32bit mode.

Parameters:

[in]	pDest	Pointer to block to fill
[in]	SrcValue	The 32bit value with which to fill
[in]	SizeIn32BitWords	Size in 32bit words of block to fill

Note:

The destination address specified by pDest must be multiply 4.

See also:

hel_DmaSet8, hel_DmaSet16

void hel_DmaSet8	(	void *	pDest,
		u8	SrcValue,
		u32	SizeInBytes
	)

Fills a block of memory with a specified value using DMA Channel 3.

The hel_DmaSet8 function fills a block of memory with a specified value using DMA Channel 3.

Parameters:

[in]	pDest	Pointer to block to fill
[in]	SrcValue	The byte value with which to fill
[in]	SizeInBytes	Size in bytes of block to fill

Note:

The Game Boy Advance hardware does not provide support to perform 8bit DMA transfers in hardware. The hel_DmaSet8 functions emulates this by using the 16bit mode and writes the first and/or last byte in software. Because some memory alignment checks have to be done, before actually starting the DMA transfer, this function is kinda slower than a pure 16bit transfer due to the setup code.

See also:

hel_DmaSet16, hel_DmaSet32

void hel_DmaZeroMemory	(	void *	pDest,
		u32	SizeInBytes
	)

Fills a block of memory with zeros using DMA Channel 3.

The hel_DmaZeroMemory function fills a block of memory with zeros using DMA Channel 3.

Parameters:

[in]	pDest	Pointer to block to fill with zeros
[in]	SizeInBytes	Size in bytes of block to fill with zeros

Note:

This function uses hel_DmaSet8 to zeroise a block of memory. Zeroising a block of memory, using Direct Memory Access, which is only a few bytes in size brings no advantage though.

See also:

hel_DmaSet8

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