MINDmaConfig Structure

Definition

#include <twl/mi.h>
  
  typedef struct _MINDmaConfig
  {
  	u32 intervalTimer;
  	u32 prescaler;
  	u32 blockWord;
  	u32 wordCount;
  }
  MINDmaConfig;

Members

The members of the MINDmaConfig structure are shown below.

Description

MINDmaConfig is a structure that specifies the DMA behavior used in new DMA operations.

There are many parameters that specify the behavior of the new DMA. Specifying all aspects of every behavior would cause the instruction length to be quite long, which in turn would be extremely troublesome. Consequently, the parts of these parameters that are unlikely to change during multiple DMA operations are gathered into the MINDmaConfig structure. By having applications refer to this structure during DMA operations, the burden on applications can be reduced.

Each of the four new DMAs contains a MINDmaConfig structure internally. During DMA operations, either of the following operations can be selected.

(1) Accessing the MINDmaConfig structure maintained internally
(2) Accessing the MINDmaConfig structure specified by the application

The functions that configure the internally maintained MINDmaConfig structure are the following:

The MI_InitNDmaConfig function, used to initialize the four internal structures
The MI_SetNDmaConfig function, used to copy the specified MINDmaConfig structure to an internal structure
The MI_SetNDmaInterval function, used to specify interval information for a particular internal structure
The MI_SetNDmaBlockWord function, used to specify BlockWord information for a particular internal structure
The MI_SetNDmaWordCount function, used to specify WordCount information for a particular internal structure

The functions that get the information in the internal MINDmaConfig structure are the following:

The MI_GetNDmaConfig function, used to copy an internal structure to a specified region of memory
The MI_GetNDmaIntervalTimer function, used to get the interval timer information for a particular internal structure
The MI_GetNDmaIntervalPrescaler function, used to get the interval prescalar information for a particular internal structure
The MI_GetNDmaBlockWord function, used to get the BlockWord information of a particular internal structure
The MI_GetNDmaWordCount function, used to get the WordCount information of a particular internal structure

The "interval information" mentioned in the set functions refers to the Interval Timer and Interval Prescaler information; both can be set simultaneously. For the get functions, two separate functions have been created to get these values individually.

The internal structure will be initialized using the OS_Init function, so the application doesn't have to handle the initialization at first. Call this function if it's necessary.

If you want to perform a new DMA operation using different parameters than the default settings, but you don't want to change the internal structure, perform the following procedure: (1) copy over the MINDmaConfig structure, (2) overwrite the members of the MINDmaConfig structure, (3) specify that structure and perform the new DMA operation.

If you want to change the actual value within the library's internal structure, either (1) copy MINDmaConfig and overwrite the necessary portions, then set the library to the structure, or (2) overwrite the necessary parameters directly using functions such as MI_SetNDmaInterval().

(Example) Copy the new DMA1 settings, overwrite the interval information (that is, the Interval Timer and Interval Prescaler information), and set that as the config [structure] for the new DMA1 [channel].


MINDmaConfig config;

//---- get config
MI_GetNDmaConfig( 1, &config );

//---- change config values
config.intervalTimer = 0x100;
config.prescaler = MI_NDMA_INTERVAL_PS_16;

//---- set config
MI_SetNDmaConfig( 1, &config );



See Also

MI_InitNDmaConfig
MI_SetNDmaConfig


Revision History

2008/01/22 Initial version.

CONFIDENTIAL