求助：定时器DMA操作IO口

我前段时间做了一个UART的DMA传输，非常简单。
rUCON0 = rUCON0 & 0xff3 | 0x8;
    
    /****** DMA0 Initialize *****/

    rDISRC0 = (U32)(SEND_ADDR);
    rDISRCC0 = (0<<1)|(0<<0); //Src=AHB,Increment
    
    rDIDST0 = (U32)UTXH0;  // Tx FIFO address
    rDIDSTC0 = (1<<1)|(1<<0); //Dst=APB,Fixed;
    
    rDCON0 = (0<<31)|(0<<30)|(1<<29)|(0<<28)|(0 << 27) | (1 << 24) | (1 << 23) | (1 << 22) | (0 << 20) | (50);
        //handshake,Sync=APB,IntEn,   unit,   single,     dst=UART0,  HwReqMode,  NoAutoReload,Halfword,
    
    rDMASKTRIG0 = (1<<1);     //DMA0En

但是后来我改成了Timer的DMA操作IO口，就发生了问题。
//**********    Set Timer1    ***********************//
        rGPBCON &= ~0xf;            //set GPB0 GPB1 as tout0, pwm output
        rGPBCON |= 0x8;    
        rTCFG0 &= ~0xff;
        rTCFG0 |= 0;            //prescaler = 0+1
        rTCFG1 &= ~0xf;
        rTCFG1 &= (0<<4);            //mux = 1/2 ,timer1
        rTCFG1 &= ~(0x7<<20);
        rTCFG1 |= (0x2<<20);                                             //DMA 模式
        rTCNTB1 = 1000;
        rTCMPB1 = rTCNTB1>>1;    // 50%
        rTCON |= (0xb<<8);            //disable deadzone, auto-reload, inv-off, update TCNTB0&TCMPB0, start timer 1
        rTCON |= (0xf<<8);            //disable deadzone, auto-reload, inv-off, update TCNTB0&TCMPB0, start timer 1
        rTCON &= ~(2<<8);            //clear manual update bit
    //    while(rTCNTO3>0);
        rTCON |= 0;            //clear manual update bit
定时器是有波形
    pISR_DMA0=(U32)Dma0Done;//DMA0的中断服务程序
rr:         Uart_Printf("DMA is enter!\n");
    Tx = (U32 *)0x30000000;
    for(i = 0;i < 0x8; i++)
        * Tx++ = ((i % 2)<<1);
    Tx = (U32 *)0x30000000;
    rDISRC0=(U32)Tx;
    rDISRCC0=(0<<1)|(0<<0); // inc,AHB目的为AHB,increased
    rDIDST0 =(U32) 0x56000034;//GPDDAT Adress
    rDIDSTC0=(1<<1)|(1<<0); // inc,AHB源来自于APB,fixed
    rDCON0=(0<<31)|(1<<30)|(1<<29)|(1<<28)|(1<<27)|(3<<24)|(0<<23)|(0<<22)|(1<<21)|(0<<20)|8;
    ClearPending(BIT_DMA0);
    rDMASKTRIG0 = (1<<1);         //DMA0En
//******************************************************//
    while(DMA_END == 0);
    Uart_Printf("DMA is Over!\n");
//    rINTMSK |= (0x1<<11);            // Close timer 1
//    rDMASKTRIG0 = (1<<2);     //DMA0En
    DMA_END = 0;
                     goto rr;
发现DMA根本就没有执行。
static void __irq Dma0Done(void)
{
//    Tx=(unsigned int *)0x30000000;
    ClearPending(BIT_DMA0);
    DMA_END = 1;
    //rDISRC0 =(int) Tx;
}

请高手帮助。万分感谢！