I2C interrupt problem

Other Parts Discussed in Thread: MOTORWARE

I have written a simple I2C slave interface for the F28027F and it seems to be working as expected, but there is one remaining problem.  When I add the I2C stuff into motorware lab1 it runs for a while then hangs (seems to be holding scl low).  This locks up the bus until there is a reset.  When I reduce the overhead of mainISR the problem goes away.  

This is is what I have found causes the problem:

I get the I2C_IntSrc_Slave_Addr (7) interrupt, if it is a read command I also immediately get the I2C_IntSrc_Tx_Rdy (5).  Normally this isn't a problem. If mainISR is executing at this time it seems that one of the interrupts is missed and the I2C module locks up.  I have verified this behavior by timing the ISRs with a logic analyzer.

I am not using FIFOs, which I imagine could mitigate the problem.  I use the I2C_IntSrc_Slave_Addr interrupt to setup to clear some array indices and set I2CDXR to the first value (if I do this on the I2C_IntSrc_Tx_Rdy interrupt the first byte sent uses the previous value of I2CDXR), I could probably do this on a stop interrupt just as well.  I could also implement some sort of timeout check as well. I mainly just want to understand what the problem is in this case.

Init Code:

void HAL_setupI2C(HAL_Handle handle)	
{
	HAL_Obj *obj = (HAL_Obj *)handle;
	//I2C_Obj *I2CARegs=(I2C_Obj *)obj->I2CaHandle;
	   // Initialize I2C
	/*   I2CARegs->I2CSAR = 0x0050;        // Slave address - EEPROM control code
	   I2CARegs->I2COAR =1;

	   // I2CCLK = SYSCLK/(I2CPSC+1)

	   I2CARegs->I2CPSC = 6;       // Prescaler - need 7-12 Mhz on module clk
	   I2CARegs->I2CCLKL = 20;           // NOTE: must be non zero
	   I2CARegs->I2CCLKH = 20;            // NOTE: must be non zero
	   I2CARegs->I2CIER = (1<<6)|(1<<4)|(1<<3);      // Enable SCD & ARDY interrupts

	   I2CARegs->I2CMDR = 0x0020;    // Take I2C out of reset*/
	                                    // Stop I2C when suspended
	   //PIE_enableInt(PIE_Handle pieHandle, const PIE_GroupNumber_e group, const PIE_InterruptSource_e intSource)*/

	I2C_setSlaveAddress(obj->I2CaHandle, 0x0001);
	I2C_setupClock(obj->I2CaHandle, 6, 20,20);
	I2C_enableInt(obj->I2CaHandle,I2C_IntEn_Rx_Rdy|I2C_IntEn_Tx_Rdy|I2C_IntEn_Slave_Addr);
	I2C_setSlave(obj->I2CaHandle);
	I2C_enable(obj->I2CaHandle);

}

void HAL_enableI2CInt(HAL_Handle handle)
{
	  HAL_Obj *obj = (HAL_Obj *)handle;

	  PIE_enableInt(obj->pieHandle,PIE_GroupNumber_8,PIE_InterruptSource_I2CA1 );
	  CPU_enableInt(obj->cpuHandle,CPU_IntNumber_8);
}

Isr code:

interrupt void i2c_int1a_isr(void)     // I2C-A
{

   // Read interrupt source
	halHandle->gpioHandle->AIOTOGGLE=(1<<2);
	int IntSource;
   IntSource = (int)I2C_getIntSource(halHandle->I2CaHandle);

   //GPIO_toggle(myGpio, GPIO_Number_1);
   // Interrupt source = stop condition detected
   /*if(IntSource == I2C_SCD_ISRC)
   {

   }  // end of stop condition detected
	*/


	if(IntSource==I2C_IntSrc_Slave_Addr)
	   {
		   RxPointer=0;
		   TxPointer=0;
		   //GPIO_toggle(myGpio, GPIO_Number_2);
		   //I2caRegs.I2CDXR=StatusPacket[0];
	   }
	if(IntSource==I2C_IntSrc_Rx_Rdy)
	   {

		   if(RxPointer<sizeof(RxPacket))
			   RxPacket[RxPointer]=I2C_getData(halHandle->I2CaHandle);
		   if(RxPointer==1)
			   RxLength=RxPacket[RxPointer];
		   if(RxPointer==(RxLength+3))
		   {
			   memcpy((void*)DecodeBuffer,(void*)RxPacket,sizeof(DecodeBuffer));
			   DecodePacket=1;
		   }
		   RxPointer++;

	   }
	if(IntSource==I2C_IntSrc_Tx_Rdy)
	   {
		   if(TxPointer<(sizeof(StatusPacket)-1))
				   TxPointer++;
		   /*if(TxPointer==0)
			   GPIO_setLow(myGpio, GPIO_Number_3);
		   else
			   GPIO_setHigh(myGpio,GPIO_Number_3);*/
		   I2C_putData(halHandle->I2CaHandle,StatusPacket[TxPointer]);
	   }


   // Enable future I2C (PIE Group 8) interrupts
   //PieCtrlRegs.PIEACK.all = PIEACK_GROUP8;
	PIE_clearInt(halHandle->pieHandle,PIE_GroupNumber_8);
	//halHandle->gpioHandle->AIOCLEAR=(1<<2);
}