UART_DM_ISR
volatile uint32_t * UART_DM_ISR = (uint32_t *)(UART_BASE + 0x14);
while (((*UART_DM_ISR & UART_DM_TX_READY) == 0) && --limit) {
while ((uart_getreg(bas, UART_DM_ISR) & UART_DM_TX_READY) == 0