CC254x can not enter sleep mode after write UART data with BLE-stack 1.3

Hi

I am developing UART read/write with CC2541EM + smartRF05 + ble-stack-1.3 simpleBLEPeripheral

I modify simpleBLEPeripheral.c(static void performPeriodicTask( void )) as

static void performPeriodicTask( void )

{  

P1_0 = 1; //set LED_1 on

HalUARTWrite(SERIAL_APP_PORT, "123456789", 9);

 }

and hal_sleep.c(void halSleep( uint32 osal_timeout )) as

void halSleep( uint32 osal_timeout )

{

.

.

.

P1_0 = 0; //set LED_1 off

HAL_SLEEP_SET_POWER_MODE();

.

.

}

I can receive "123456789" with PC terminal tool, but LED_1 never turn off.

I try to implement same application with ble-stac-1.2.1 and LED_1 work correct.

Can anyone help me to fix this problem? thanks.