Texas Instruments MSP430x4xx - Manual (Page 280)

USART Registers: UART Mode
14-23 USART Peripheral Interface, UART Mode
UxTCTL, USART Transmit Control Register
7 6 5 4 3 2 1 0
Unused CKPL SSELx URXSE TXWAKE Unused TXEPT
rw−0 rw−0 rw−0 rw−0 rw−0 rw−0 rw−0 rw−1
Unused Bit 7 Unused
CKPL Bit 6 Clock polarity select
0
UCLKI = UCLK
1 UCLKI = inverted UCLK
SSELx Bits
5-4 Source select. These bits select the BRCLK source clock.
00
UCLKI
01 ACLK
10 SMCLK
11 SMCLK
URXSE Bit 3 UART receive start-edge. The bit enables the UART receive start-edge
feature.
0
Disabled
1 Enabled
TXWAKE Bit 2 Transmitter wake
0
Next frame transmitted is data
1 Next frame transmitted is an address
Unused Bit 1 Unused
TXEPT Bit 0 Transmitter empty flag
0
UART is transmitting data and/or data is waiting in UxTXBUF
1 Transmitter shift register and UxTXBUF are empty or SWRST=1