Omega Engineering OME-PIO-D96 manual Initialhigh, activelow Interrupt source, Countl++

2.5.3Initial_high, active_low Interrupt source

If the P2C0 is an initial_high, active_low signal, the interrupt service routine should use INV0 to invert or not to invert the P2C0 for high_pulse generation as follows: (Refer to DEMO4.C)

Initial set:

	now_int_state=1;		/* initial state for P2C0			*/
	outportb(wBase+0x2a,0);		/* select the inverted P2C0 */
void interrupt irq_service()
{				/* now P2C0 is changed to LOW				*/(a)
if (now_int_state==1)
{				/* --> INT_CHAN_0=!P2C0=HIGH now				*/
	COUNT_L++;			/* find a LOW_pulse (P2C0)				*/
	If((inport(wBase+7)&1)==0)/* the P2C0 is still fixed in LOW							*/
{				/*	Æ need to generate a high_pulse			*/
	outportb(wBase+0x2a,1);/*				INV0 select the non-inverted input			*/(b)
				/*	INT_CHAN_0=P2C0=LOW -->			*/
	now_int_state=0;			/*	INT_CHAN_0 generate a high_pulse			*/
				/* now P2C0=LOW				*/
}				/* now P2C0=HIGH				*/
	else now_int_state=1;
}				/* don’t have to generate high_pulse				*/
				/* now P2C0 is changed to HIGH				*/(c)
else
{				/* --> INT_CHAN_0=P2C0=HIGH now				*/
	COUNT_H++;			/* find a HIGH_pulse (P2C0)				*/
	If((inport(wBase+7)&1)==1)/* the P2C0 is still fixed in HIGH							*/
{				/* need to generate a high_pulse				*/
	outportb(wBase+0x2a,0);/* INV0 select the inverted input */(d)
				/* INT_CHAN_0=!P2C0=LOW -->				*/
	now_int_state=1;			/* INT_CHAN_0 generate a high_pulse				*/
				/* now P2C0=HIGH				*/
}				/* now P2C0=LOW				*/
	else now_int_state=0;
}				/* don’t have to generate high_pulse				*/
if (wIrq>=8) outportb(A2_8259,0x20);
outportb(A1_8259,0x20);
}
		(a)	(b)			(c)	(d)
	P2C0

INV0

INT_CHAN_0

OME-PIO-D96 User Manual (Ver.1.1, Mar/2003) ---- 12