$40021000 constant RCC_CR
$40021004 constant RCC_CFGR
$40021008 constant RCC_CIR
$4002100C constant RCC_APB2RSTR
$40021010 constant RCC_APB1RSTR
$40021014 constant RCC_AHBENR
$40021018 constant RCC_APB2ENR
$4002101C constant RCC_APB1ENR
$40021020 constant RCC_BDCR
$40021024 constant RCC_CSR