I have two mode. The run mode use radio CLK output + PLL is 48M. The VLPR mode use fast IRC 4M. When the two mode is exchange. I have to confige the UART baud because the system clock changed. This could happen when the UART is work. So I want to confige the UART clock static. When the mode change. The UART clock is not change. How can I do this? Thank you.