Hi Dumitru
I am very interested in your problem but unfortunately I don't have a
solution.
I did not have time to examine the code closely but I think there might be
trouble with the C18 compiler loading two ISR events high.

I have two ISRs in my current program that work fine if you load one high
and the other low but if you load both high I get strange undefined behavior
across my program.

I'm using an 18F6520 and a 6520 both devices give me the same trouble.
My guess is that these parts are close/ near the same family as the one you
are working on.
(I'm no expert I don't even live near an expert on PIC devices I have only
done three products in the last three years two in asm one in
C18..........................but they are working fine in the field)


I have asked Microchip to look at my ISR code but they can find nothing
wrong. 
They say it should work but all I know is that it doesn't.
It is very difficult for me to debug because like I said the darn things
work fine with only one loaded high.

I didn't really need to have both ISRS loaded high for this product that I'm
beta testing today but in the next version I will not be so lucky so I might
end up with a different device or hiring a smart guy to help me figger it
out. 
 
The thing that lept out at me was two things happening in the high priority
ISR. 
Could you try an experiment where you try loading one high and one low?
 
Phillip
Things should be as simple as possible but no simpler
 
 
 
Phillip Coiner
CTO, GPS Source, Inc.
 
 
Your source for quality GNSS Networking Solutions and Design Services, Now!

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Dumitru Stama
Sent: Monday, December 04, 2006 12:13 PM
To: piclist@mit.edu
Subject: [PIC] Problems with C18 interrupt code

Hi guys,
I have problems with the folowing piece of code. I modified the
original example from Microchip C18 which implements TIMER0 interrupt
and i added PORTB on-change interrupt. The code does only one thing :
it increments pulse_count.b1234 which is an unsigned long (this being
made inside ISR) when it detects a change from 0 to 1 on RB4 and in the
main loop sends the value to PORTC so i can see it.
I tested this code using Proteus VSM and it works well. I applied an
impulse train on RB4 and the programs acts as it shoul with only one
problem : after ~30 seconds it behaves erratically for a few moments and
starts to count again from 0 !
I disabled watchdog timer (even from VSM), i disabled LVP, i disabled
BOR, i disabled Stack overflow reset, no luck whatsoever.
Can anyone see if i am doing something wrong with the folowing piece
of code ? I have the .lst as well as .hex files if that might help. I
have been doing this for the last 10 hours and i feel like i am
loosing my mind.

Thank you for your understanding,

//--------------------------------------------------------------------------
--


#include <p18F252.h>
#pragma config OSC = XT, OSCS = OFF, PWRT = ON, BOR = OFF, WDT = OFF,
STVR = OFF, LVP = OFF, DEBUG = OFF

//--------------------------------------------------------------------------
--

void main (void);
void InterruptHandlerHigh (void);

union {
  struct  {
    unsigned Timeout:1;         //flag to indicate a TMR0 timeout
    unsigned None:7;
  } Bit;
  unsigned char Byte;
} Flags;

//=========================
union {
        struct {
                unsigned char B0;
                unsigned char B1;
                unsigned char B2;
                unsigned char B3;
                } byte;
                unsigned long b1234;
} pulse_count;


//=========================
union {
  struct {
    unsigned RB0:1;
    unsigned RB1:1;
    unsigned RB2:1;
    unsigned RB3:1;
    unsigned RB4:1;
    unsigned RB5:1;
    unsigned RB6:1;
    unsigned RB7:1;
        };
        unsigned char old_portb;
} old_portb_bits;

//--------------------------------------------------------------------------
--
// Main routine

void main () {
        Flags.Byte = 0;
        INTCON = 0x28; //disable global and enable TMR0 interrupt and RB
        INTCON2 = 0x85; //TMR0 high priority
        RCONbits.IPEN = 1; //enable priority levels
        TMR0H = 0; //clear timer and set TMR0H
        TMR0L = 0; //clear timer low byte and also updates high byte from
TMR0H
        T0CON = 0x88; //set up timer0 - no prescaler
        INTCONbits.GIEH = 1; //enable interrupts
        TRISB = 0x7E; //PORTB bits 0 and 7 are output, the rest are input
        TRISC = 0; //PORTC bits are output
        PORTC = 0;

        old_portb_bits.old_portb = 0;
        pulse_count.b1234 = 0;
        
        while (1) {
                PORTC = pulse_count.byte.B0;
        }
}

//--------------------------------------------------------------------------
--
// High priority interrupt vector

#pragma code InterruptVectorHigh = 0x08
void
InterruptVectorHigh (void)
{
  _asm
    goto InterruptHandlerHigh //jump to interrupt routine
  _endasm
}

//--------------------------------------------------------------------------
--
// High priority interrupt routine

#pragma code
#pragma interrupt InterruptHandlerHigh

void InterruptHandlerHigh () {

        if (INTCONbits.TMR0IF) {                                //check for
TMR0 overflow
                INTCONbits.TMR0IF = 0;                          //clear
interrupt flag
        }

        if (INTCONbits.RBIF) {
                PORTB = PORTB;
                INTCONbits.RBIF = 0;
                if (PORTBbits.RB4 == 1 && old_portb_bits.RB4 == 0) (unsigned
long)pulse_count.b1234++;
                old_portb_bits.old_portb = PORTB;
        }
}

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