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;*************  Edge LED timer process  *****************
edge_timer
        bsf     status,rp0      ;Change to Bank1
        movlw   b'00000111'     ;TOCS/PSA=0,PS=111
        movwf   option_reg      ;Set OPTION_REG
        bcf     status,rp0      ;Change to Bank0
        movlw   d'0'            ;Set Hard timer(26msec)
        movwf   tmr0            ;Set TMR0
        movlw   d'255'          ;Set Soft count
        movwf   h_timer         ;Save soft count
        movlw   h'a0'           ;GIE=1,TOIE=1
        movwf   intcon          ;Interruption enable
        return

;---------------  Interruption processing  --------------
int
        movwf   w_save          ;Save W register
        movf    status,w        ;Read STATUS reg
        movwf   s_save          ;Save STATUS reg
        bcf     status,rp0      ;Change to Bank0
        btfsc   intcon,t0if     ;Time out interruption ?
        goto    timer_int       ;Jump to Timer process
 
;------------  END of Interruption Process --------------
int_end
        movf    s_save,w        ;Read saved STATUS reg
        movwf   status          ;Recover STATUS reg
        swapf   w_save,f        ;Read saved W register
        swapf   w_save,w        ;Recover W register
        retfie        

;-----------  Time-out interruption Process  ------------
timer_int
        bcf     intcon,t0if     ;Clear timer int flag
        movlw   d'0'            ;Set Hard timer(26msec)
        movwf   tmr0            ;Set TMR0
        decfsz  h_timer,f       ;Time over ?
        goto    int_end         ;No. Retry
        movlw   d'255'          ;Set Soft count
        movwf   h_timer         ;Save Soft count

;------------------  Switch Process  --------------------
        btfsc   portb,7         ;RB7 = 0(Left) ?
        goto    timer_right     ;RB7 = 1(Right)
        movf    portb,w         ;Read portb
        iorlw   h'80'           ;Set right data
        movwf   portb           ;Output data
        goto    int_end
timer_right
        movf    portb,w         ;Read portb
        andlw   h'7f'           ;Set left data
        movwf   portb           ;Output data
        goto    int_end