The maximum clock frequency of the MSP430F5437IPN is 18 MHz.
To use an external crystal oscillator, connect the crystal to the XIN and XOUT pins, and configure the UCS (Universal Clock System) module to use the external crystal oscillator as the clock source.
The maximum current consumption of the MSP430F5437IPN is approximately 2.1 mA at 18 MHz and 3.3V supply voltage.
To use the built-in UART module, configure the UART module using the UCAxCTL0 and UCAxCTL1 registers, and use the UART transmit and receive functions provided in the MSP430F5437IPN driver library.
No, the MSP430F5437IPN is not 5V tolerant and should only be used with a power supply voltage between 1.8V and 3.6V.
MSP430F5437IPN datasheet
by Texas Instruments
