PIC32MX350: INT4 wird nie ausgelöst

    INT2Rbits.INT2R = 0x0000;   //RD9->EXT_INT:INT2;

    INT4Rbits.INT4R = 0x0003;   //RD11->EXT_INT:INT4;

    INT1Rbits.INT1R = 0x0004;   //RD8->EXT_INT:INT1;

    IPC4bits.INT4IP = 1;

    IPC4bits.INT4IS = 0;

    IPC1bits.INT1IP = 1;

    IPC1bits.INT1IS = 0;

    IPC2bits.INT2IP = 1;

    IPC2bits.INT2IS = 0;

    INTCONbits.MVEC = 1;

void __ISR(_EXTERNAL_4_VECTOR, IPL1AUTO) _EXTERNAL_4(void)

{

    //***User Area Begin->code: Ext INT 4***

    SYNCIsr();

    //***User Area End->code: Ext INT 4***

    EX_INT4_InterruptFlagClear();

}