Texas Instruments MSP430x4xx - Manual (Page 303)

USART Registers: SPI Mode
15-17 USART Peripheral Interface, SPI Mode
UxBR0, USART Baud Rate Control Register 0
7 6 5 4 3 2 1 0
2 7 2 6 2 5 2 4 2 3 2 2 2 1 2 0
rw rw rw rw rw rw rw rw
UxBR1, USART Baud Rate Control Register 1
7 6 5 4 3 2 1 0
2 15 2 14 2 13 2 12 2 11 2 10 2 9 2 8
rw rw rw rw rw rw rw rw
UxBRx The baud-rate generator uses the content of {UxBR1+UxBR0} to set the
baud rate. Unpredictable SPI operation occurs if UxBR < 2.
UxMCTL, USART Modulation Control Register
7 6 5 4 3 2 1 0
m7 m6 m5 m4 m3 m2 m1 m0
rw rw rw rw rw rw rw rw
UxMCTLx Bits
7−0 The modulation control register is not used for SPI mode and should be set
to 000h.