Texas Instruments TNETE211, TNETE110A manual Loading and Unloading an Interrupt Service Routine ISR

Loading and Unloading an Interrupt Service Routine (ISR)

4.1 Loading and Unloading an Interrupt Service Routine (ISR)

Before the ThunderLAN controller can be allowed to generate an interrupt to the host, it is necessary to install code for the host to handle the interrupt. The driver also relies on other host services that are interrupt-driven, like getting notice of timer ticks for deadman timers. The driver calculates the pattern to write to the interrupt controller to acknowledge the interrupt from the controller, based on the actual hardware interrupt line assigned to the NIC's slot.

This sample program hooks into the software vector table. The host PC timer interrupt comes first, so that the program can time out operations that can hang the PC and can also provide time stamp information for operations.

nic.OldTimer = HwSetIntVector((BYTE)0x1C, TimerIsr);

The driver points to the next code to execute when the timer interrupt goes off and saves the value for program restart. nic.OldTimer is a storage place for this information reserved in a routine called NICEVN, which is allocated for each NIC; this instance is called nic. HwSetIntVector is a function that inserts the address of a function into the interrupt table at a particular location:

//HwSetIntVector() ± Set PC interrupt vector and return previous one

//±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±

//Parameters:

//	bIRQ	BYTE		Irq to set
//	lpFunc	void	(ISR *)()	interrupt function
//

//Return val:

//void (ISR *)() Returns previous contents of vector //±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±

static void (ISR *HwSetIntVector( BYTE bIRQ, void (ISR *lpFunc)() ))()

{

BYTE bINT;

void (ISR *lpOld)(); if( bIRQ < 8 )

bINT = 8 + bIRQ ; else if (bIRQ < 15)

bINT = (0x70±8) + bIRQ;

else

bINT = bIRQ;

lpOld = _dos_getvect( bINT ); _dos_setvect( bINT,lpFunc);

return( lpOld );

}

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