2.126 Extensible DMA Controller (XDMAC)

Using The Library

The XDMA controller requires a source address, destination address and transfer count to initiate the transfer. It transfers data on each DMA trigger and decrements the transfer count. The DMA generates completion interrupt to notify the CPU at the end of the DMA transfer.

The user can use either the callback mechanism or the polling mechanism to determine DMA completion.

• With polling, the application will need to continuously poll to check if the DMA has completed the transfer.

• With callback, the registered callback function will be called when the transfer is completed. This means the application do not have to poll continuously.

Callback method

This following example demonstrates a DMA transfer with callback.

#define USART1_TRANSMIT_ADDRESS     (&USART1_REGS->US_THR)

uint8_t txBuffer[] = "Hello World!";

void XDMAC_Callback(XDMAC_TRANSFER_EVENT status, uintptr_t context)
{
      if(status == XDMAC_TRANSFER_COMPLETE)
      {
           // Transfer is completed.
      }
}

 int main ( void )
{
      SYS_Initialize ( NULL );

      XDMAC_ChannelCallbackRegister(XDMAC_CHANNEL_0, XDMAC_Callback, 0);

      XDMAC_ChannelTransfer(XDMAC_CHANNEL_0, txBuffer, (const void *)USART1_TRANSMIT_ADDRESS, sizeof(txBuffer));

}

Polling method

The following example demonstrates a DMA transfer with polling.

#define USART1_TRANSMIT_ADDRESS     (&USART1_REGS->US_THR)

uint8_t txBuffer[] = "Hello World!";

int main ( void )
{
      SYS_Initialize ( NULL );

      XDMAC_ChannelTransfer(XDMAC_CHANNEL_0, txBuffer, (const void *)USART1_TRANSMIT_ADDRESS, sizeof(txBuffer));

      while(XDMAC_ChannelIsBusy(XDMAC_CHANNEL_0));
}

Library Interface

Extensible DMA Controller peripheral library provides the following interfaces:

Functions

Data types and constants