firstInterrupt.asm

ORG   000H
GOTO  INITIALIZE

ORG   004H
GOTO  INCREMENTER

INITIALIZE
  BCF   STATUS,RP0 
  BCF   STATUS,RP1

  WCOPY     EQU	70H     ;Since the upper 16 bytes of all GPR banks are common in the PIC16F882/883/884/886/887, 
  STATCOPY  EQU	71H     ;temporary holding registers, W_TEMP and STATUS_TEMP, should be placed in here. 
  COUNT     EQU	72H     ;These 16 locations do not require banking and therefore, make it easier to context save and restore.

  BSF   INTCON,GIE
  BSF   INTCON,3

  BSF   STATUS,RP0
  CLRF  TRISB
  COMF  TRISB,1
  CLRF  IOCB
  COMF  IOCB,1

  BSF   STATUS,RP1
  CLRF  ANSEL
  CLRF  ANSELH
  
  GOTO  MAIN
  
MAIN
  NOP
  NOP
  NOP
  GOTO MAIN
 
  
INCREMENTER
  MOVWF WCOPY 
  SWAPF STATUS,W
  MOVWF STATCOPY 
  
  BCF   STATUS,Z
  MOVLW 007H
  XORFW PORTB,0
  BTFSC STATUS,Z
  INCF  COUNT,1
  
  SWAPF STATCOPY,W    ;I don't know how the swap is working here, but I trust the code in the datasheet
  MOVWF STATUS 
  SWAPF WCOPY,F 
  SWAPF WCOPY,W
  RETFIE