UART_DATA
bus_space_write_4(iot, ioh, UART_DATA, buf[loop]);
byte = bus_space_read_4(iot, ioh, UART_DATA);
(void) bus_space_read_4(iot, ioh, UART_DATA);
c = bus_space_read_4(iot, ioh, UART_DATA);
bus_space_write_4(iot, ioh, UART_DATA, c);