[求助]BF518基于描述符的DMA传输问题

最近在用BF518这款DSP做网络传输，其中用到基于描述符的DMA传输，输出采用DMA2通道。
//以太网帧头格式
ADI_ETHER_FRAME_BUFFER dma12={
                                16,                                                                
                                {0xff,0xff,0xff,0xff,0xff,0xff},
                                {0x00,0x24,0x8c,0xf8,0x05,0xb4},
                                {0x0800}
                                     };
//DMA描述符                                                        
DMA_DESCRIPTOR dma2={NULL,&dma12,0x758b,16};

*pDMA2_NEXT_DESC_PTR=&dma2;
*pDMA2_X_COUNT=16;
*pDMA2_X_MODIFY=4;
register_handler(ik_ivg11, EMAC_TX_ISR);
*pSIC_IMASK0 |= 0x40000000;
*pSIC_IAR3 &= 0xf0f0ffff;
*pSIC_IAR3 |=(4<<24);
*pIMASK |=(1<<11);
*pDMA2_CONFIG=0x758b;
*pEMAC_OPMODE |=0x10000;

我是这样编程的，可是查询DMA2_IRQ_STATUS寄存器的最后一位，始终是1，没有改变过，并且我的产生中断函数
EX_INTERRUPT_HANDLER(EMAC_TX_ISR)
{
        printf("TX is completed\n");
}也没有执行，请问这是怎么回事？

还是自己回答吧，是要先使能EMAC,再使能DMA2传输，即*pDMA2_CONFIG=0x758b;
*pEMAC_OPMODE |=0x10000;这两句需要把位置换一下就OK了