Echo a received character, RX ISR used. Normal mode is LPM0. // USART1 RX interrupt triggers TX Echo. // Baud rate divider with 1048576hz = 1048576/38400 = ~27.31 (01Bh|03h) // ACLK = LFXT1 = 32768Hz, MCLK = SMCLK = default DCO = 32 x ACLK = 1048576Hz // //* An external watch crystal between XIN & XOUT is required for ACLK