How to set P3DIR for UCAxRXD, UCAxRTD pins on MSP430F249?

I need to enable the UCA1RXD and UCA1TXD functions on the P3.7 and P3.6 pins of an MSP430F249.  Clearly, I should set the bits 6 and 7 of P3SEL.

How should I set the P3DIR bits, though?  I ask because these pins also have SPI bus functions.  That is, their functions are listed as

    P3.7/UCA1RXD/UCA1SOMI

    P3.6/UCA1TXD/UCA1SIMO

I would think that we should bit 6 of P3DIR and clear bit 7, since TXD is an output function and RXD is an input function.  I've seen sample code, however, where both bits are set -- or even where P3DIR isn't specified at all.  I might be missing something here, so can someone give me a definitive answer?