CCS/DAC102S085: The DAC_B of DAC102S085 is shify.

Tool/software: Code Composer Studio

Hi, 

When I was writing to DAC102S085, for example I write a word 0x5E1C to set DAC_B to output a voltage, the value is shifty, not stable. 

Next is my program and waveform.

Please help me how can I resolve it.

#include <msp430.h>

unsigned char RXData = 0;
unsigned char TXData;

int main(void)
{
WDTCTL = WDTPW | WDTHOLD;

P1SEL0 |= BIT5 | BIT6 | BIT7; // set 3-SPI pin as second function
P1DIR |= BIT1;
P1OUT |= BIT1;

UCA0CTLW0 |= UCSWRST; // **Put state machine in reset**
UCA0CTLW0 |= UCMST|UCSYNC|UCMSB|UCCKPL|UCCKPH; // 3-pin, 8-bit SPI master
// Clock polarity high, MSB
UCA0CTLW0 |= UCSSEL__ACLK; // Select ACLK
UCA0BR0 = 0x02; // BRCLK = ACLK/2
UCA0BR1 = 0; //
UCA0MCTLW = 0; // No modulation
UCA0CTLW0 &= ~UCSWRST; // **Initialize USCI state machine**
UCA0IE |= UCRXIE; // Enable USCI_A0 RX interrupt

PM5CTL0 &= ~LOCKLPM5; // Disable the GPIO power-on default high-impedance mode
// to activate previously configured port settings

while(1)
{

P1OUT &= ~ BIT1;
UCA0IE |= UCTXIE;
__bis_SR_register(LPM0_bits | GIE); // enable global interrupts, enter LPM0
TXData = 0x1C;

UCA0IE |= UCTXIE; // Enable TX interrupt
__bis_SR_register(LPM0_bits | GIE); // enable global interrupts, enter LPM0
TXData = 0x5E;
__delay_cycles(100);

P1OUT |= BIT1;
__delay_cycles(60);

}

}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=USCI_A0_VECTOR
__interrupt void USCI_A0_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(USCI_A0_VECTOR))) USCI_A0_ISR (void)
#else
#error Compiler not supported!
#endif
{
switch(__even_in_range(UCA0IV,USCI_SPI_UCTXIFG))
{
case USCI_NONE: break; // Vector 0 - no interrupt
case USCI_SPI_UCRXIFG:
RXData = UCA0RXBUF;
UCA0IFG &= ~UCRXIFG;
__bic_SR_register_on_exit(LPM0_bits);// Wake up to setup next TX
break;
case USCI_SPI_UCTXIFG:
UCA0TXBUF = TXData; // Transmit characters

UCA0IE &= ~UCTXIE;
break;
default: break;
}