RTOS: Util_constructClock of cc2640r2f

Tool/software:TI-RTOS

i config the clock and use the uart.

Util_constructClock(&loop_send_data,loop_send_data_callback ,4000, 4000, true,TIMEOUT_EVT);

static void loop_send_data_callback(UArg arg)
{
Event_post(sema, arg);
}

for(;;)

{

uint32_t events;

events = Event_pend(sema, Event_Id_NONE, TIMEOUT_EVT,
ICALL_TIMEOUT_FOREVER);

DEG_PRINTF(uart_test, "sema\n", strlen("sema\n"));(i redirect the uart output,this is ok )

}

but the clock only run one time. whats problem???

the same way in cc2640 is runing nice...    

what i can do ???