UART transmission using DMA?

Hi all,

I'm attending to write a program which communication with PC via UART connection on MSP430F5151

I ran some examples such as echo, Its work well.

In order to make data transmission more easily, I'm trying to use DMA.

So, I wrote some code.

After initialzing  for DMA with following info;

+ Channel 0

+ Trigger  source : UCA0TXIF

When send data request occurs, I will resize DMA size, then send directly first byte with UCA0TXBUF

After that enable DMA with DMAEN bit.

I also enable DMA interrupt for checking last bit is transferred.

My source code is here :

main.c 

char verStr[] = { "Hello World\r\n" };

volatile UINT dmaLength = 12;

volatile UINT hasData= 0;

..

Init_UART();

..

{

while(1)

{

    if (hasData == 1)

    {

      hasData = 0;

    changeDMASizeAndSend();

   }

 }

}

void changeDMASizeAndSend()
{

    DMA0SZ = --dmaLength;

   if (dmaLength <= 1) dmaLength = 12;
    UCA0TXBUF = verStr[0];
    DMA0CTL |= DMAEN;
}

// UCA0RX interrupt

#pragma vector=USCI_A0_VECTOR
__interrupt void USCI_A0_ISR (void)

{

 switch(__even_in_range(UCA0IV,4))
      {
      case 0:break;                             // Vector 0 - no interrupt
      case 2:                                   // Vector 2 - RXIFG
          hasData  = 1;
        break;
      case 4:
          break;                             // Vector 4 - TXIFG
      default: break;
      }

}

// DMA interrupt

#pragma vector=DMA_VECTOR
__interrupt void DMA_ISR (void)
{
     DMA0CTL &= ~DMAEN;
}

But It's not work. My thinking is wrong? Pls help me.