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How to configure the TM4C1290NCPDT MCU to use 32K crystal oscillator? After the current configuration, the crystal oscillator of 32K cannot vibrate normally.
Hi,
Please refer to the clock tree diagram and the device datasheet for the PLL description. You cannot use OSC_EXT32 as a source for PLL. You can only use either PIOSC (internal 16Mhz OSC) or a external MOSC as the source for the PLL. Also note that the system clock frequency you can get needs to be divisible by the VCO. In another word, if the VCO output is 240Mhz then you can only get 120Mhz, 60Mhz and etc. If you use VCO at 320Mhz as in SYSCTL_CFG_VCO_320 then you can get 80Mhz, 40Mhz and so on.
