firstTMR0.asm

ORG     000H
GOTO    INIT

ORG     004H
GOTO    TMR0ISR

INIT
     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. 
                            ;These 16 locations do not require banking and therefore, make it easier to context save and restore.

     BCF     STATUS,RP1
     BSF     STATUS,RP0     ;move to bank 1 where INTCON and OPTION_REG are

     MOVLW   b'1010 0000'
     MOVWF   INTCON

     MOVLW   b'0000 0110'
     MOVWF   OPTION_REG
     GOTO    MAIN
     
MAIN
     NOP
     NOP
     NOP
     GOTO    MAIN

     BCF     STATUS,RP0
     MOVLW   0B2H
     MOVWF   TMR0
     
TMR0ISR
     MOVWF   WCOPY 
     SWAPF   STATUS,W
     MOVWF   STATCOPY 
     .
     .
     .
     MOVLW   0B2H
     MOVWF   TMR0
     BCF     INTCON,2
     SWAPF   STATCOPY,W    
     MOVWF   STATUS 
     SWAPF   WCOPY,F 
     SWAPF   WCOPY,W
     RETFIE