RCC PLL1 fractional divider register
PLL1FRACN | Fractional part of the multiplication factor for PLL1 VCO This bitfield is set and reset by software to control the fractional part of the VCO multiplication factor. It can be written at any time, allowing dynamic fine-tuning of the PLL1 VCO. VCO output frequency = Fref1_ck x (PLL1N + (PLL1FRACN / 213)), with: PLL1N must be between 4 and 512. PLL1FRACN can be between 0 and 213- 1. The input frequency Fref1_ck must be between 4 and 16 MHz. To change the FRACN value on-the-fly even if the PLL is enabled, the application must proceed as�follows: Set PLL1FRACEN = 0. Write the new fractional value into PLL1FRACN. Set PLL1FRACEN = 1. |