UCR1_TXDMAEN
ucr1 |= UCR1_RXDMAEN | UCR1_TXDMAEN | UCR1_ATDMAEN;
ucr1 &= ~(UCR1_RXDMAEN | UCR1_TXDMAEN | UCR1_ATDMAEN);
ucr1 &= ~UCR1_TXDMAEN;
ucr1 |= UCR1_TXDMAEN;
ucr1 &= ~UCR1_TXDMAEN;
ucr1 |= UCR1_TXDMAEN;
ucr1 &= ~UCR1_TXDMAEN;