Texas Instruments MSP430x4xx - Manual (Page 288)

USART Introduction: SPI Mode
15-2 USART Peripheral Interface, SPI Mode
15.1 USART Introduction: SPI Mode
In synchronous mode, the USART connects the MSP430 to an external
system via three or four pins: SIMO, SOMI, UCLK, and STE. SPI mode is
selected when the SYNC bit is set and the I2C bit is cleared.
SPI mode features include:
- 7- or 8-bit data length
- 3-pin and 4-pin SPI operation
- Master or slave modes
- Independent transmit and receive shift registers
- Separate transmit and receive buffer registers
- Selectable UCLK polarity and phase control
- Programmable UCLK frequency in master mode
- Independent interrupt capability for receive and transmit
Figure 15−1 shows the USART when configured for SPI mode.