TMS320F28035: when as slave device, one interrupt sequence error happen

{
    // Initialize I2C-A:
    EALLOW;
    SysCtrlRegs.PCLKCR0.bit.I2CAENCLK = 1;     // I2C

    GpioCtrlRegs.GPBPUD.bit.GPIO32 = 0;    // Enable pull-up for GPIO32 (SDAA)
    GpioCtrlRegs.GPBPUD.bit.GPIO33 = 0;    // Enable pull-up for GPIO33 (SCLA)

    GpioCtrlRegs.GPBQSEL1.bit.GPIO32 = 3;  // Asynch input GPIO32 (SDAA)
    GpioCtrlRegs.GPBQSEL1.bit.GPIO33 = 3;  // Asynch input GPIO33 (SCLA)

    GpioCtrlRegs.GPBMUX1.bit.GPIO32 = 1;   // Configure GPIO32 for SDAA operation
    GpioCtrlRegs.GPBMUX1.bit.GPIO33 = 1;   // Configure GPIO33 for SCLA operation
    EDIS;

    I2caRegs.I2CMDR.bit.IRS = 0;            //I2C Reset bit.
    I2caRegs.I2CMDR.bit.MST = 0;            //@NOTE: 0=slave mode; 1=master mode.
    I2caRegs.I2CMDR.bit.XA  = 0;            //@NOTE: 0=7bit address; 1=10bit address.
    I2caRegs.I2CMDR.bit.BC  = 0x00;         //@NOTE: 0=8 bits per data byte
    I2caRegs.I2CMDR.bit.NACKMOD = 0;        //I2C Reset bit.
    I2caRegs.I2CEMDR.bit.BCM  = 0x00;

    I2C_SetPMbusAddress(SLAVE_ADDRESS_INIT);

    I2caRegs.I2CIER.bit.AAS = 1;            //Addressed as slave interrupt enable 1h (R/W) = Interrupt request enabled
    I2caRegs.I2CIER.bit.SCD = 1;            //Stop condition detected interrupt enable 1h (R/W) = Interrupt request enabled
                                            //this for non-PEC check
    I2caRegs.I2CIER.bit.RRDY = 1;           //receive ready
    I2caRegs.I2CIER.bit.XRDY = 1;           //transmit ready

    I2caRegs.I2CSAR = 0x0000;       // The next address.
    I2caRegs.I2CPSC.bit.IPSC = 5;   // Prescaler - need 7-12 Mhz on module clk (60/6 = 10MHz)
                                    // module clock frequency = I2C input clock frequency/(IPSC + 1)

    // 10MHz/(45+5 + 45 +5) = 100K
    I2caRegs.I2CCLKL = 45;          // NOTE: must be non zero
    I2caRegs.I2CCLKH = 45;          // NOTE: must be non zero

    I2caRegs.I2CMDR.bit.IRS = 1;            //I2C Reset bit.  Take I2C out of reset

    I2caRegs.I2CFFTX.all = 0x0000;  // Enable FIFO mode and TXFIFO
    I2caRegs.I2CFFRX.all = 0x0000;  // Enable RXFIFO, clear RXFFINT,
}

initial as I2C slave device.

enable 4 type interrupt

    I2caRegs.I2CIER.bit.AAS = 1;            //Addressed as slave interrupt enable 1h (R/W) = Interrupt request enabled
    I2caRegs.I2CIER.bit.SCD = 1;            //Stop condition detected interrupt enable 1h (R/W) = Interrupt request enabled
                                            //this for non-PEC check
    I2caRegs.I2CIER.bit.RRDY = 1;           //receive ready
    I2caRegs.I2CIER.bit.XRDY = 1;           //transmit ready

ISR code

{
    Uint16 u16IntSrcReg;
//    static Uint16 i = 0;
//    static Uint16 j = 0;

    u16IntSrcReg = (Uint16)I2caRegs.I2CISRC.bit.INTCODE;

	switch(u16IntSrcReg)
	{
		case 0x01:
			//Arbitration lost
		break;	
		case 0x02:
			//No-acknowledgment condition detected
		break;	
		case 0x03:
			//Registers ready to be accessed
		break;	
		case 0x04:
		    //while(I2caRegs.I2CFFRX.bit.RXFFST < 4)  {};
		    j= 0;
		    if(I2caRegs.I2CSTR.bit.SDIR == 1)
		    {
		        //
		    }
		    else//slave read data
		    {

                RxData[i] = I2caRegs.I2CDRR;
                command = RxData[0];
                if(i>=6)
                {
                    i=0;
                }
                else
                {
                    i++;
                    if((command_type == 1)&&(command == 0x99))//command length =1
                    {
                        i=0;
                    }
                }
		    }


		break;	
		case 0x05://Transmit data ready

            if(command == 0x99)
            {
                //while(!I2C_xrdy());

                //while(I2caRegs.I2CSTR.bit.XRDY != 1) {};// 1 = Data transferred tp the core TX register after shifting data
                if(j>=7)
                {
                    I2caRegs.I2CDXR = 0xFF;
                }
                else
                {
                    I2caRegs.I2CDXR = Array[j];
                }
                j++;
            }
            else
            {
                I2caRegs.I2CDXR = 0xFF;
            }


		break;	
		case 0x06:
			//Stop condition detected
		break;		
		case 0x07:
			//Addressed as slave
			if(I2caRegs.I2CSTR.bit.SDIR == 1)  //means address read
			{
			    //address read
			    I2C_bIsSlaveAddressRead();
			}
			else
			{
			    //I2caRegs.I2CIER.bit.XRDY = 0;//address write
			    //I2caRegs.I2CMDR.bit.TRX = 0;
			    I2C_bIsSlaveAddressWrite();
			    //i=0;

			}
		break;			
		default:
			//error happen
		break;
	}	


    PieCtrlRegs.PIEACK.all = PIEACK_GROUP8;   //release other interrupt
}

when I add test pin in the code, get below waveform.

channel 3: toggle when XRDY happen    channel4: toggle when AAS happen.

question: why AAS happen before than XRDY? if I need to exchange it, how to config the I2C module?  thanks!