The hardware USART module in the MSP430 is a state machine whose
state has to be RESET every time a new USART configuration is
defined. This can be achieved by a set/reset sequence of the SWRST
bit in the UCTL register by firmware.
The SWRST bit is set by default on power on reset(POR). If the USART
module parameters are defined for the first time by configuring
the control registers after POR, configuring the UCTL register should
be the last in the sequence such that the SWRST is reset to start
the state machine with the defined settings. This can be achieved
with a MOV.B #000X XXX0B,&UCTL in assembly language and UCTL = 0b000X XXX0
in C language. Please refer the device User`s guide and code examples
for more details.
If the USART module is re-configured in firmware then a set/reset
sequence of the SWRST bit must be done after re-configuration, to
re-start the USART state machine with the new configuration.