下面是一个External Port DMA的例子：

          while((*pDMAC0)&DMAS){asm("nop;");};    // DMA in progress

            *pDMAC0 = 0; //Disable External Port CH 0 DMA
            
            *pIIEP0 = Internal_buffer;   //Internal Memory Source
            *pEIEP0 = SDRAM_wbuffer;  //External Memory Destination
            *pIMEP0 = 1;    //Set up internal modify
            *pEMEP0 = 1;    //Set up external modify
            *pICEP0 = DMA_LEN;  //length of DMA
            *pECEP0 = DMA_LEN;
            
            printf("\nWrite DDR DMA start!\n");

            //Config and enable External Port CH 0 DMA

            *pDMAC0 = DEN|TRAN|DFLSH|INTIRT;    // write to external memory, Internal DMA Completion Interrupt in enabled.