Lpc2000

Hi,
I use UART1 to make a rs485 with GPIO0.10 for the direction.
I've got a problem, when I look the transmission with an oscilloscope 
the sens go to level 0 just before the last character.
I do this :
("p" is a pointer to the string to transfer and "n" the number of 
characters)

do{
   while (!(U1LSR & 0x20)) watchdog(); 
   U1THR = *p++;
} while (--n);

while (!(U1LSR & 0x20)) watchdog(); //wait last character transmit 
					
IOCLR0=SENS; //SENS=Rxd --> rs485 in reception