The maximum clock frequency for the MSP430F1111AIDW is 8 MHz, but it can be overclocked up to 16 MHz with reduced voltage and temperature range.
To use an external crystal oscillator, connect the crystal to the XIN and XOUT pins, and configure the UCSCTL6 register to select the external crystal oscillator as the clock source.
The minimum voltage required for the MSP430F1111AIDW to operate is 1.8V, but it can operate down to 1.6V with reduced performance and functionality.
To use the built-in UART module, configure the UCAxCTL0 and UCAxCTL1 registers to set the baud rate, data bits, and stop bits, and use the UCAxTXBUF and UCAxRXBUF registers to transmit and receive data.
No, the MSP430F1111AIDW is not 5V tolerant and should only be used with a power supply between 1.8V and 3.6V.