' Name        : ASMINT.pbp
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler   : PM or MPASM
' Target PIC  : Any PIC16F types
' Hardware    : Non specific
' Oscillator  : internal or external
' Keywords    : ASSEMBLY INTERRUPTS
' Description : PICBASIC PRO program to demonstrate interrupts in
' assembly language. Turn LED on. Interrupt on PORTB.0 (INTE) turns LED off.
' Program waits .5 seconds and turns LED back on.
'

led    Var   PORTB.7
wsave  Var   byte $20 system
'wsave1  Var  byte $a0 system   ' Necessary for devices with RAM in bank1
'wsave2  Var  byte $120 system  ' Necessary for devices with RAM in bank2
'wsave3  Var  byte $1a0 system  ' Necessary for devices with RAM in bank3
ssave   Var  byte bank0 system
psave   Var  byte bank0 system

   Goto start                   ' Skip around interrupt handler

' Define interrupt handler
define INTHAND myint

' Assembly language interrupt handler
Asm    
; Save W, STATUS and PCLATH registers, if not done previously
myint
   movwf   wsave
   swapf   STATUS, W
   clrf    STATUS
   movwf   ssave
   movf    PCLATH, W
   movwf   psave

; Insert interrupt code here
; Save and restore FSR and any other registers used

   bcf     _led            ; If interrupt, turn off LED
   bcf     INTCON, 1       ; Clear interrupt flag

; Restore saved registers
   movf    psave, W
   movwf   PCLATH
   swapf   ssave, W
   movwf   STATUS
   swapf   wsave, F
   swapf   wsave, W
   retfie                  ; Return from interrupt
Endasm


start:
   TRISB = $7f             ' LED out, rest in
   OPTION_REG = $7f        ' Enable PORTB pullups
   INTCON = $90            ' Enable INTE interrupt
   led = 1                 ' Turn LED on

waitloop:
   If led = 1 Then waitloop ' Wait here while LED is still on
                            ' If we get here, LED is off
   Pause   500              ' Wait .5 seconds
   Goto    start            ' Start over (turn LED back on)

   End