Nirav,
I'm suspecting that you UART RX FIFO is being overrun when you use the instrumented libraries. Can you try switching back to the instrumented UART library, changing the CPU freq back to 80Mhz, and reconfiguring the FIFO trigger level afterthe call to UART_open(). Note, you need to #include some header files for this.
#include <inc/hw_memmap.h> #include <inc/hw_ints.h> #include <inc/hw_types.h> #include <driverlib/uart.h> UART_open(...); UARTFIFOLevelSet(UART0_BASE, UART_FIFO_TX1_8, UART_FIFO_RX1_8);I'd like to know if we allow the hardware to trigger an UART RX interrupt sooner (with less data in the FIFO) if it would help avoiding dropped incoming UART data. The UART driver sets it to 7/8 full to reduce the number of interrupts generated, but that might not be a good configuration at your baudrate.