首次运行时出现假中断触发

大家好！我在PIC24FJ256GB606设备上工作在中断驱动的UART上。我的代码工作正常，除非UART接收中断第一次被错误触发：例如，主例程是：ISR是：初始化：请参阅附上的图像并考虑如下，1）微控制器在这一点上不需要接收任何东西。我试图运行相同的代码离开RX线打开，我得到了同样的结果。2）这个代码工作正常，如果我禁用接收中断IEC1BITS。U2RXYE＝0；



      以下为原文

    Hi Everyone! I am working on interrupt driven UART on PIC24FJ256GB606 device. My code works just fine except UART receive interrupt gets falsely  triggered for the first time: e.g.
main routine is :
int main(){

System_init();
uart_init();

// UART2_PPS
  RPINR19bits.U2RXR= 21;
  RPOR13bits.RP26R = 5;
  
  TRISGbits.TRISG6 = 1;
  TRISGbits.TRISG7 = 0;
  
        uart_puts("n**********************************************");
        uart_puts("nMy project ");
        uart_puts("n x");
        uart_puts("n x");
        uart_puts("n"__DATE__);
        uart_puts("n**********************************************");
return -1;
}
}

ISR is:
void __attribute__ ( ( interrupt, no_auto_psv ) ) _U2RXInterrupt( void )
{

        IFS1bits.U2RXIF = 0;
        uart_puts("False Trigger");
        __delay_ms(1000);
}

Initialization is:
int uart_init()
{
    int status = -1;
        size_t i;
   
        
   // STSEL 1; IREN disabled; PDSEL 8N; UARTEN enabled; RTSMD disabled; USIDL disabled; WAKE disabled; ABAUD disabled; LPBACK disabled; BRGH enabled; URXINV disabled; UEN TX_RX;
   U2MODE = 0x8008;
   // OERR NO_ERROR_cleared; URXISEL RX_ONE_CHAR; UTXBRK COMPLETED; UTXEN disabled; ADDEN disabled; UTXISEL0 TX_ONE_CHAR; UTXINV disabled;
   U2STA = 0x0000;
   // U2TXREG 0;
   U2TXREG = 0x0000;
   // BaudRate = 9600; Frequency = 4000000 Hz; U2BRG 103;
   U2BRG = 0x0067;
   // ADMADDR 0; ADMMASK 0;
   U2ADMD = 0x0000;
  
            rb_attr_t attr = {sizeof(_rbmem[0]), ARRAY_SIZE(_rbmem), _rbmem};
            if (ring_buffer_init(&_rbd, &attr) == 0) {
            U2MODEbits.UARTEN = 1; // And turn the peripheral on
            U2STAbits.UTXEN = 1; //UART2 Transmit Enable
            IFS1bits.U2RXIF = 0; //_U2RXIF = 0;
            IEC1bits.U2RXIE = 1; //_U2RXIE = 1;
                status = 0;
            }
        
    return status;
}

please see the image attached and consider following,
1) microcontroller is not expected to receive anything at this point. i tried to run the same code leaving rx line open i got the same result.
2) This code works just fine if i disable the receive interrupt  IEC1bits.U2RXIE = 0;

   Attached Image(s)