#include<p18F4550.inc>

CONFIG FOSC = HS ; High-Speed oscillator, HS used by USB
CONFIG WDT = OFF ; Watchdog Timer disabled
CONFIG DEBUG = OFF ; Debugger disabled
CONFIG MCLRE = OFF ; Master Clear Reset enabled
CONFIG CPUDIV = OSC1_PLL2 ; CPU system clock divisor
CONFIG PBADEN = OFF ; PORTB A/D enable/disable (Disabled)

counter_value equ H'04' ; Define constant for counter value

RES_VECTOR CODE 0x0000 ; Reset vector at address 0x0000
GOTO init ; Jump to the initialization code

org 0x0008 ; Interrupt vector at address 0x0008
goto irq_handle ; Go to the interrupt handling function

TMR0_interrupt
    ; Clear the TMR0 interrupt flag
    bcf INTCON , TMR0IF ; Clear the flag
    ; Increment PORTC
    incf counter_value ; Increment counter value
    retfie ; Return from interrupt
    
irq_handle ; Interrupt routine
    ; Check if it is TMR0 interrupt
    btfsc INTCON , TMR0IF
    goto TMR0_interrupt ; Yes, it is TMR0 interrupt, jump to TMR0_interrupt
    retfie ; No, return from interrupt

init
    clrf TRISD ; Set PORTD as output 
    clrf PORTD ; Clear PORTD
    
    clrf TRISC ; Set PORTC as output 
    clrf PORTC ; Clear PORTC
    
    bsf T0CON , TMR0ON ; Turn ON TIMER 0
    bcf T0CON , T08BIT ; Set TIMER 0 to 16 bits mode
    bcf T0CON , T0CS ; Use internal clock source
    bcf T0CON , PSA ; Assign prescaler to TIMER 0
    
    ; Setup the prescaler 
    bsf T0CON, T0PS2 ; Prescaler value 1:256
    bcf T0CON, T0PS1 ; Prescaler value 1:256
    bcf T0CON, T0PS0 ; Prescaler value 1:256
    
    bsf INTCON , GIE ; Enable interrupts
    bsf INTCON , TMR0IE ; Enable TMR0 interrupt
    clrf TMR0 ; Clear the timer
    
    bsf T1CON , TMR1ON ; Enable TIMER 1
    bcf T1CON , TMR1CS ; Use internal clock source
    clrf TMR1L ; Clear TIMER 1 low byte
    clrf TMR1H ; Clear TIMER 1 high byte
    GOTO main_loop ; Jump to the main loop

main_loop
    call seg_set_0 ; Call segment set function for counter_value = 0
    goto main_loop ; Loop indefinitely
    
seg_set_0
    movlw H'00' ; Load value 0 into WREG
    CPFSEQ counter_value ; Compare WREG with counter_value
    goto seg_set_1 ; If equal, jump to seg_set_1
    movlw H'3F' ; Load value 0x3F into WREG (7-segment display pattern for 0)
    movwf PORTD ; Move WREG to PORTD
    bsf PORTC, RC0 ; Set RC0 high
    return ; Return from function
    
seg_set_1
    movlw H'01' ; Load value 1 into WREG
    CPFSEQ counter_value ; Compare WREG with counter_value
    goto seg_set_2 ; If equal, jump to seg_set_2
    movlw H'06' ; Load value 0x06 into WREG (7-segment display pattern for 1)
    movwf PORTD ; Move WREG to PORTD
    bcf PORTC, RC0 ; Set RC0 low
    return ; Return from function
    
; (Similar segments set functions for 2 to 9, with different display patterns)
seg_set_2
    movlw H'02'
    CPFSEQ counter_value
    goto seg_set_3
    movlw H'5B'
    movwf PORTD
    return
    
seg_set_3
    movlw H'03'
    CPFSEQ counter_value
    goto seg_set_4
    movlw H'4F'
    movwf PORTD
    return
    
seg_set_4
    movlw H'04'
    CPFSEQ counter_value
    goto seg_set_5
    movlw H'66'
    movwf PORTD
    return
    
seg_set_5
    movlw H'05'
    CPFSEQ counter_value
    goto seg_set_6
    movlw H'6D'
    movwf PORTD
    return
    
seg_set_6
    movlw H'06'
    CPFSEQ counter_value
    goto seg_set_7
    movlw H'7D'
    movwf PORTD
    return
    
seg_set_7
    movlw H'07'
    CPFSEQ counter_value
    goto seg_set_8
    movlw H'07'
    movwf PORTD
    return
    
seg_set_8
    movlw H'08'
    CPFSEQ counter_value
    goto seg_set_9
    movlw H'7F'
    movwf PORTD
    return
    
seg_set_9
    movlw H'09'
    CPFSEQ counter_value
    goto counter_reset
    movlw H'6F'
    movwf PORTD
    return

counter_reset
    clrf counter_value ; Clear counter_value
    return ; Return from function

END ; End of the code