Introduction - If you have any usage issues, please Google them yourself
SPI master talks to SPI slave using 3-wire mode. Incrementing
data is sent by the master starting at 0x01. Received data is expected to
be same as the previous transmission TXData = RXData-1.
USCI RX ISR is used to handle communication with the CPU, normally in LPM0.
ACLK = ~32.768kHz, MCLK = SMCLK = DCO ~ 1MHz. BRCLK = ACLK/2.