Simple interrupt

[Art]

I would normally use Steve's solution above, but you won't be able to check button pushes in the
2.5 second COUNT command that way.

Let's hope I remember everything, and I'm assuming registers for 16F877A are the same for your chip.

Near the start of your program, after any defines:

Define  INTHAND _Brake    ' Tell PBP Where the code starts on an interrupt
INTCON.4 = 1                                    'enable portb.0 interrupt
intoccured var byte

Then straight after that:

'****************************************************************
'*  Name    : ASM_INTS.PBP                                      *
'*  Author  : Darrel Taylor                                     *
'*  Notice  : Copyright (c) 2003                                *
'*  Date    : JAN 4, 2003                                       *
'****************************************************************

wsave       var byte    $20     SYSTEM          ' location for W if in bank0

' --- IF any of these three lines cause an error ??  Simply Comment them out to fix the problem ----
wsave1      var byte    $A0     SYSTEM          ' location for W if in bank1
wsave2      var byte    $120    SYSTEM          ' location for W if in bank2
wsave3      var byte    $1A0    SYSTEM          ' location for W if in bank3
' ------------------------------------------------------------------------------

ssave       var byte    BANK0   SYSTEM          ' location for STATUS register
psave       var byte    BANK0   SYSTEM          ' location for PCLATH register
fsave       var byte    BANK0   SYSTEM          ' location for FSR register

Asm
INT_START  macro
    IF (CODE_SIZE <= 2)
        movwf   wsave            ; copy W to wsave register
        swapf   STATUS,W         ; swap status reg to be saved into W
        clrf    STATUS           ; change to bank 0 regardless of current bank
        movwf   ssave            ; save status reg to a bank 0 register
        movf    PCLATH,w         ; move PCLATH reg to be saved into W reg
        movwf   psave            ; save PCLATH reg to a bank 0 register
    EndIF
    movf      FSR,W              ; move FSR reg to be saved into W reg
    movwf     fsave              ; save FSR reg to a bank 0 register
    endm
EndAsm

Asm
INT_RETURN   macro
    MOVF    fsave,W              ; Restore the FSR reg 
    MOVWF   FSR
    Movf    psave,w              ; Restore the PCLATH reg
    Movwf   PCLATH
    swapf   ssave,w              ; Restore the STATUS reg            
    movwf   STATUS
    swapf   wsave,f
    swapf   wsave,w              ; Restore W reg
    Retfie                       ; Exit the interrupt routine    
    endm
EndAsm

Then this:

'*********************** ISR *****************************
Brake:
@ INT_START                    
'
  R0save = R0                     ; Save 2 PBP system vars that are used during
  R1save = R1                     ; the interrupt
'
IF INTCON.1 = 1 THEN        'handle portb.0 interrupt
INTCON.1 = 0            'clear portb.0 interrupt flag
goto overextint            'skip over timer interrupt handler
ENDIF                '
'
overextint:
'
  R1 = R1save                     ; Restore the PBP system vars
  R0 = R0save
@ INT_RETURN                      ; Restore context and return from interrupt
'
'*********************************************************

Now this would usually jump back to the point of execution it left from,
but you want to reset, and need not bother with resoring context,
so I'd create a routine that resets all vars and goes to the start of your program,
name it overextint: and delete the overextint label from this code.

If this works, thank Darrel, if it's broken, blame me!