STM32的功能引脚重映射程序不能理解
void GPIO_PinRemapConfig(uint32_t GPIO_Remap, FunctionalState NewState){
uint32_t tmp = 0x00, tmp1 = 0x00, tmpreg = 0x00, tmpmask = 0x00;
/* Check the parameters */
assert_param(IS_GPIO_REMAP(GPIO_Remap));
assert_param(IS_FUNCTIONAL_STATE(NewState));
tmpreg = AFIO->MAPR;
tmpmask = (GPIO_Remap & DBGAFR_POSITION_MASK) >> 0x10;
tmp = GPIO_Remap & LSB_MASK;
if ((GPIO_Remap & (DBGAFR_LOCATION_MASK | DBGAFR_NUMBITS_MASK)) == (DBGAFR_LOCATION_MASK | DBGAFR_NUMBITS_MASK))
{
tmpreg &= DBGAFR_SWJCFG_MASK;
AFIO->MAPR &= DBGAFR_SWJCFG_MASK;
}
else if ((GPIO_Remap & DBGAFR_NUMBITS_MASK) == DBGAFR_NUMBITS_MASK)
{
tmp1 = ((uint32_t)0x03)0x15)*0x10));
tmpreg |= ~DBGAFR_SWJCFG_MASK;
}
if (NewState != DISABLE)
{
tmpreg |= (tmp > 0x15)*0x10));
}
AFIO->MAPR = tmpreg;
}//这人程序是开启can脚映射的，但是我不理解里面的俺码比如DBGAFR_LOCATION_MASK ，DBGAFR_NUMBITS_MASKDBGAFR_SWJCFG_MASK，这些掩码是根据什么算出来的？:o
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