SFUART_IRQ_ENABLE_TXWM
(ie & SFUART_IRQ_ENABLE_TXWM) != 0) {
ie &= ~(SFUART_IRQ_ENABLE_TXWM);
reg |= SFUART_IRQ_ENABLE_TXWM;
reg &= ~(SFUART_IRQ_ENABLE_TXWM | SFUART_IRQ_PENDING_RXQM);
reg |= SFUART_IRQ_ENABLE_TXWM | SFUART_IRQ_PENDING_RXQM;