UCR1_ATDMAEN
ucr1 |= UCR1_RXDMAEN | UCR1_TXDMAEN | UCR1_ATDMAEN;
ucr1 &= ~(UCR1_RXDMAEN | UCR1_TXDMAEN | UCR1_ATDMAEN);
UCR1_ATDMAEN | UCR1_SNDBRK);
ucr1 |= UCR1_RXDMAEN | UCR1_ATDMAEN;
ucr1 &= ~(UCR1_RXDMAEN | UCR1_ATDMAEN);