16F1827 interrupt hosed

[Macgman2000]

This is very strange. I have the interrupt working with a toggle on RB1 while main is generating in a loop a pulse on RB0.
During power up both ports are putting out a toggle, but about 5 to 10 seconds after power on the interrupt generated toggle stops. Main still is toggling away. I went through and made sure other peripheral interrupt sources are off...

what am I missing? Would someone please load this code and verify that the interrupt is stopping for some reason?

' This code is for 16F1827 MCU with built in oscillator (Max Osc 32Mhz)
' Code requires PicBasic Pro 2.60 along with MPASM assembler

ASM
    __config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_ON & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_OFF & _FCMEN_OFF
    __config _CONFIG2, _PLLEN_OFF & _LVP_OFF & _LVP_OFF & _STVREN_OFF
        
ENDASM
DEFINE OSC 8  
    
' Define ADCIN parameters
  DEFINE ADC_BITS 8   ' Set number of bits in result
  DEFINE ADC_CLOCK 4   ' Set clock source, look on data sheet for chart
  DEFINE ADC_SAMPLEUS 500   ' Set sampling time in uS 
  
  DEFINE  INTHAND myint                   ' Setup interrupt handler
   
;*******************************************************************************
;*******************************************************************************
; System hardware configuration
;*******************************************************************************
;*******************************************************************************
        OSCCON = %01110000   ' 8MHz internal
        ANSELA = %00000001   ' all digital. A/D disabled
        ANSELB = %00000000
        TRISB = %00000000    ' set port directions 0 = output, 1 = input
        TRISA = %00000001
        ADCON0 = %00000111  ' Set PORTA digital 1, analog 0
        APFCON0.0 = 1        ' CCP1 PWM output on RB0
        APFCON0.3 = 1        ' CCP2 PWM output on RA7
        APFCON1 = 1
        CCPR1L    = 64       ' Set PWM Duty-Cycle to 50%
        CCPR2L    = 64
        PR2 = 49             ' Set PWM frequency 
        CCP1CON = %00000000  ' Mode select = PWM off , to turn on %00001100
        CCP2CON = %00000000  ' Mode select = PWM off, to turn on %00001100
        T2CON = %00000110    ' %00000100 = TMR2 ON 1:1  pre-scale
                             ' %00000101 = TMR2 ON 1:4  pre-scale
                             ' %00000110 = TMR2 ON 1:16 pre-scale
                             ' %00000111 = TMR2 ON 1:64 pre-scale
 
        
;*******************************************************************************
; Program variables 
;*******************************************************************************
        ADCVAL  var byte
      
        
        
;*******************************************************************************        
; Program constants
;*******************************************************************************
        
 

;******************************************************************************* 
; Power on initialization to known port states   
;*******************************************************************************
      
PowerOn_init: 
        PortA = 0             ' force low to avoid glitches 
        POrtB = 0
        PIR1 = 0             ' clear TMR1 int flag
        PIE1 = %00000001     ' TMR1 int enabled
        INTCON = %11000000   ' global & peripheral ints enabled
        T1CON = %00010001    ' TMR1 1:2 prescale, timer1 on

;*******************************************************************************
;*******************************************************************************
 goto mainloop
asm
; Save W, STATUS and PCLATH registers, if not done previously
myint   
        ; retfie auto-restores w, status, bsr, fsr and pclath
  bcf   T1CON,TMR1ON ; stop timer 1
  bcf   PIR1,TMR1IF  ; clear over flow flag
  movlw 0xEF         ; load timer for 16,535 * 2 prescaler interrupt on 16 bit timer
  movwf TMR1H        ; load high byte
  movlw 0xEF         
  movwf TMR1L        ; load low byte
  bsf   T1CON,TMR1ON ; re-enable timer 1
  movlw 0x02
  xorwf PORTB,f      ; toggle RB1
  retfie             ; Return from interrupt
 
        retfie                        ; Return from interrupt
endasm
 
 
mainloop:
    adcin 0, adcval
    
    LATB.0 = 1
    pauseus (4*adcval) + 1000
    LATB.0 = 0 
    pause 15
    
    goto mainloop

[cncmachineguy]

Try adding BSR=0 as the first asm instruction in your ISR. If this works, I will be happy to explain why. But if not the reason will confuse the issue.

[Macgman2000]

Very strange...I did what you suggested but it only prolonged the end result. I am seeing two things when the interrupt crashes....either it hoses the main loop and the interrupt oscillates at a high frequency of 235 Khz or it completely stops and main keeps going with its toggle. This is what I added to the ISR.

asm
; Save W, STATUS and PCLATH registers, if not done previously
myint   
        ; retfie auto-restores w, status, bsr, fsr and pclath
  
  bcf   BSR,0
  bcf   T1CON,TMR1ON ; stop timer 1
  bcf   PIR1,TMR1IF  ; clear over flow flag
  movlw 0xEF         ; load timer for 16,535 * 2 prescaler interrupt on 16 bit timer
  movwf TMR1H        ; load high byte
  movlw 0xEF         
  movwf TMR1L        ; load low byte
  bsf   T1CON,TMR1ON ; re-enable timer 1
  movlw 0x02
  xorwf PORTB,f      ; toggle RB1
  retfie             ; Return from interrupt
        
endasm

[cncmachineguy]

Try bsr=0. There maybe more bank select bit then just 1.Like this:

Myint
Bsr=0
asm
Rest of isr

OR

myint
asm
clrf bsr
rest of isr

[cncmachineguy]

here is what I think is happening:
When the INT is called, the state of the BSR is unknown. If the main program is doing something that requires bsr to be other then 0, when you enter the ISR you can't manipulate the things in the ISR because the wrong bank is selected.

When you added the BCF BSR,0 - This almost fixed it but not quite. When it stays in the ISR that is because you can't clear the flag (acting on wrong reg, NOT PIR) so the INT just fires forever. My guess is when you think the main is running without INT, that may be not true, it may be that you just aren't toggling the output so you think the ISR has not fired.

The easiest way I know of to troubleshoot this is using MPLAB SIM inside of MPLAB. put a breakpoint at the first line of the ISR, then when it fires you can single step through while watching reg's like port b and even better BSR!

[Macgman2000]

Thanks for your help! I will try your suggestion. I did notice one thing before leaving the office last night, when I remove the ADC from main everything works well. When I rerun the test using ADC enabled it screws things up. Do I need to also do something with T1CON like select a bank of memory that it can write to that is common across banks? some how I think writing to values to the timer is somehow not being read out of the correct bank at some point after the interrupt is enabled upon exit....just my guess.

Nick