MSP430 2x to 5X Code Conversion

Hi,

the UCRXIE bit is part of the UCBxIE register on MSP430F5xx. Please refer to the family User's Guide http://www.ti.com/lit/pdf/slau208 chapter 36.4.10 "UCBxIE Register"

There’s more to change than just this register name.

On 2x family, RX and TX have separate interrupt vectors, shared between USCIA and USCIB. On 5x family, USCIA and USCIB both have their own interrupt vector, handling RX and TX. So the ISR handling needs a major rewrite too.
Not to mention the required changes in the clock system setup to get the expected baudrate.