Error in RM0490 Rev. 4 Section 6.2.6
Status bits in the RCC internal clock source calibration register (RCC_ICSCR) indicate which clock(s) is (are) ready and which clock is currently used as a system clock.
Should be the following:
Status bits in the RCC clock control register (RCC_CR) indicate which clock(s) is (are) ready.
Status bits in the RCC clock configuration register (RCC_CFGR) indicate which clock is currently used as a system clock.
