USCI UCB1 in SPI mode - MSP430F249

Hi,

I'm trying to get the MSP430F249 UCB1 working in 3 pin SPI mode.

This is the code I'm using to initialize the Interface:

// SPI-Hardware initialisieren ////////////////////////////////////////////////

UCB1CTL1 = 1<<UCSWRST;    // SPI-Controller Reset

UCB1CTL1 |= UCSSEL_1;    // ACLK

UCB1CTL0  = UCCKPH + UCMSB + UCMST + UCSYNC + UCMODE_0;  // Phase und Polarität, MSB-First, Master

UCB1BR0   = 4;  // Prescaler 4 -> 0.9MHz

UCB1BR1   = 0;

P5SEL |= (1<<1)|(1<<2)|(1<<3);  // SPI-Leitungen aktivieren

UC1IE |= UCB1RXIE;

UCB1CTL1 &= ~UCSWRST;

In the ISR of UCB1 I'm just doing a dummy read;

//UART_ISR

#pragma vector=USCIAB1RX_VECTOR

__interrupt void SPIB1_RX (void)

{ rx_data=UCB1RXBUF; }

In the main-loop I'm trying to repeatedly send 0xAA (recognizeable pattern 10101010) using the following code:

while(1)

{

spi_adresse(1,0,0);  // set CS

while (!(UC1IFG & UCB1TXIFG));  // buffer ready?

UCB1TXBUF = 0xAA;      // send 0xAA, start transfer

while(UCB1STAT & UCBUSY); // transmission done?

spi_adresse(0,0,0);  // reset CS

}

this is how the data looks like on a logic-analyzer:

 As you can see the controller sends out 7 zeros on the first transmission then stops and resets chip-select. After it starts the second transmission it sends out the same data (not 0xAA) repeatedly. It hangs at "while(UCB1STAT & UCBUSY);".

Because of 7 and not 8 clocks at the first transmission I tried setting the UC7BIT in the UCB1CTL0-register. The controller then sends out only 6 bits at the first transmission. The behaviour after the second transmission is the same, it clocks out data forever.

I just built a second board but it has the exact same behavior, so it shouldn't be a defective µC.

I'm using CCS 5.1.

What am I doing wrong?

Andreas Wenzel