求助：msp430下通过dma方式读写FLASH

我通过DMA方式访问flash读写数据，采用中断的方式可以读写，当采用dma方式，没反应，附代码，

void UCSI_SPIB0_Init(void)
{
 P2SEL  |= BIT1+BIT2+BIT3;    //select B0 is SPI interface
 P2DIR  |= BIT0;

 P5DIR  |= BIT6;        //close write protect
 P5OUT  |= BIT6;

 UCB0CTL1 |= UCSWRST;       //software reset
 //2 edge,polarity is high,MSB,8bit,master mode,
 UCB0CTL0 |= UCCKPL+UCMSB+UCMST+UCMODE_0+UCSYNC;
 UCB0CTL1 |= UCSSEL_2;
 UCB0BR0  |= 0x04;
 UCB0CTL1 &=~UCSWRST;

 P2OUT &=~BIT0;                              //打开片选
 P5OUT |= BIT6;                              //关闭写保护

}

void SPI_B0_DMA_Config(void)
{
 //DMA0 is spi_flash Tx
 DMACTL0 |= DMA1TSEL_18 + DMA0TSEL_0;   //触发源选择DMA channel 0 transfer select 0: USCIB0 transmit
 __data16_write_addr((unsigned short) &DMA0SA,(unsigned long) SPI_S_buf); //SRC地址指针
 __data16_write_addr((unsigned short) &DMA0DA,(unsigned long) &UCB0TXBUF); //DST地址指针SPI_D_buf
 DMA0SZ  = 4;
 DMA0CTL |= DMADT_1 + DMASRCINCR_3 +  DMASBDB + DMAEN + DMALEVEL; //Single transfer, inc src, byte, enable
                 //DMADSTINCR_3+
 //DAM1 is spi_flash_Rx
 __data16_write_addr((unsigned short) &DMA1SA,(unsigned long) &UCB0RXBUF);//SPI_S_buf
 __data16_write_addr((unsigned short) &DMA1DA,(unsigned long) SPI_R_buf);
 DMA1SZ  = 5;
 DMA1CTL |= DMADT_1 + DMADSTINCR_3 + DMASBDB + DMAEN  ;//+ DMAIE + DMAIFG+ DMASRCINCR_3

}

void DMA_Triggle(void)
{
 //DMA0CTL |= DMAEN;

 //UCB0TXBUF = 0xAA;
 //DMA1CTL |= DMAREQ;
 DMA0CTL |= DMAREQ;
}

是哪里的问题 ，谢谢！