CCS/MSP430F6736: spi USCI_A1 module problem

Part Number: MSP430F6736

Tool/software: Code Composer Studio

Hi ,

i have a custom board with a controller and an ultrasonic sensor(MAX35101),the interface between those are by spi.i'm using(spi A1)A1 module .my configuration shown below.

/////////////////////////initialisation///////////////////////////////////////////////

P8SEL&=~BIT6; //CS PIN
P8DIR|=BIT6;
P8OUT|=BIT6; //INTIALLY CS PIN HIGH
P1SEL|=BIT4|BIT5; // SECONDARY PERIPHERAL SELECT
P2SEL|=BIT4;

UCA1CTL1 |=UCSWRST;
UCA1CTL0 =0XA9;
UCA1CTL1|= UCSSEL_2; // SMCLK
UCA1BR0 = 0x02; // /2
UCA1BR1 =0x00;
UCA1MCTLW = 0;
P2DIR |=BIT4;
P1DIR |=BIT5;
P1DIR &=~BIT4;

UCA1CTL1 &= ~UCSWRST;

/////////////////////////////////////////////////////////////////////////////////////////////////

if i send an 8 bit register value to max35101 i can see only one clock (i probed mosi miso sck cs pins using logic analyzer  ).for testing the clock i write the below code

while(1){
P8OUT|=BIT6;
__delay_cycles(10000);
P8OUT&=~BIT6;

UCA1TXBUF = 0x38;                           // Send over SPI to Slave
while (!(UCA1IFG&UCTXIFG)); 

P8OUT|=BIT6;
}

but i can see only one pulse  in clock line foreach chip select low time .can any one explain how this happened?.(i checked the pins by toggling they looks fine).