USART_CR3_DEP
cr3 &= ~USART_CR3_DEP;
cr3 |= USART_CR3_DEP;
cr3 &= ~(USART_CR3_DEM | USART_CR3_DEP);
cr3 &= ~USART_CR3_DEP;
cr3 |= USART_CR3_DEP;
USART_CR3_DEM | USART_CR3_DEP);